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T Chang

Publications and source records attributed to T Chang.

At least 109 records · Page 6Linked to original sources
PubMed1994

Fluctuations of excitability in the monosynaptic reflex pathway to lumbar motoneurons in the cat.

1. It is well known that the amplitude of successive monosynaptic reflexes (MSR), elicited by afferent stimuli of constant strength, fluctuate from trial to trial. Previous evidence suggests that such excitability fluctuations within the motor pool can be introduced either pre- and/or postsynaptically. Using unanesthetized decerebrate or decerebrate/spinal cats, we attempted to evaluate the relative importance of pre- and postsynaptic mechanisms to MSR variability and the potential contribution of changes in the identities of responding motoneurons to such variability. 2. Comparisons between the MSR amplitude, measured in a severed ventral root, and the probability of firing of up to three individual motoneurons in fine filaments teased from the same root, confirmed that both correlated and uncorrelated fluctuations of motoneuron excitability are involved in MSR variability. Linear regression analysis from concurrent intracellular recordings from homonymous motoneurons showed that the MSR fluctuations were correlated with the variations in membrane potential baseline, as well as with the fluctuations in the monosynaptic excitatory postsynaptic potential peak amplitude. In all 11 cases tested, the former correlation was stronger than the latter. 3. Stimulation of the caudal cutaneous sural nerve (CCS) was used to alter the postsynaptic potential background on which triceps surae (GS) MSRs were generated. The interval chosen between CCS conditioning and the GS stimulation excluded the involvement of presynaptic inhibition. When conditioned by preceding CCS stimulation, GS population MSRs generally (8/9 cases tested) increased in amplitude without much change in their overall variance. However, the individual motoneurons that contributed to the population responses did show changes in both relative excitability and in the uncorrelated component of their response variance. About half of the concurrently recorded motoneurons (6/13) showed a decrease in relative excitability after CCS conditioning, 5/13 showed an increase, and 2/13 were unchanged. Comparison of unit and population responses indicated that the identities of the motoneurons that responded at any given level of population response were quite different with and without CCS conditioning. 4. High-frequency stimulation of Ia fibers was used to alter the state of presynaptic Group Ia-afferents that produced population MSRs. Post tetanic potentiation following high-frequency stimulation did not greatly alter the variance of population MSRs or ratio of correlated and uncorrelated fluctuations in MSR responses among individual motoneurons within the responding population. However, intratetanic depression and posttetanic potentiation of population MSRs were accompanied by marked shifts in individual motoneuron excitability relative to the population response, again indicated that changes in the identities of responding motoneurons contributes to population response fluctuations.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1994

Soft tissue anchor systems.

The concept of soft tissue attachment and reattachment has been addressed over the years through a variety of surgical techniques. This includes tendons and ligaments that have been detached both surgically and traumatically from their osseous origins or insertions. This study is designed to provide the reader with a comprehensive overview of current commercially available devices. Detailed descriptions of the various devices are provided along with a discussion of the advantages and disadvantages of each. Their application and use in reconstructive foot and ankle surgery are also discussed.

Ankle↗
PubMed1994

Duplex ultrasound of extracranial carotid artery in a male patient of Takayasu's arteritis: a case report.

Takayasu's arteritis is a chronic inflammatory disease of artery. Its etiology is still uncertain. The disease mostly involves aorta and its major branches. We recently examined a young male patient using duplex Doppler ultrasound (DUS). High resolution real-time ultrasound revealed long-segment stenosis over common carotid arteries on both sides and internal carotid arteries, mostly due to adventitia thickening. Doppler ultrasound showed increased blood velocity of bilateral common carotid arteries with spectral broadening. B-mode findings correlated well with those of Doppler's, and all the information obtained from DUS was compatible with those of angiography. DUS is helpful in diagnosis of Takayasu's arteritis and provides hemodynamic data of the diseased carotid arteries. It can also be used as an effective tool for follow-up in patients with Takayasu's arteritis.

Adult↗
PubMed1994

Percutaneous transluminal angioplasty of neck vessels.

BACKGROUND: Although surgical endarterectomy or bypass is regarded as the treatment-of-choice for extracranial cerebral vascular stenosis, percutaneous transluminal angioplasty (PTA) has its role as an alternative procedure for symptomatic patients refractory to medical therapy and/or for whom surgical treatment is contraindicated. METHODS: Occlusive blood vessels were first identified by neurologic, ultrasonic and angiographic studies. Patients were premedicated with heparin and corticosteroid. From a transfemoral approach, double lumen balloon dilatation catheter was guided across the area of stenosis, and inflated two or three times to produce dilatation. Following PTA, patients received anticoagulants and corticosteroid for a period, and were followed by clinical examination, Doppler blood-flow and angiographic studies. RESULTS: Seventeen patients undergoing 26 procedures were included in this study. The lesions involved subclavian artery in nine cases, common carotid artery in seven, internal carotid artery in five and proximal vertebral artery in five. Digital subtraction angiography (DSA) was done immediately after PTA and showed improvement of stenotic segment (residual stenosis < 30%) in 22 vessels. Restenosis occurred in two cases of subclavian artery PTA six months later. There were three complications, including TIA in two cases and hematoma at the puncture site in one case. Clinically, symptomatic improvement was obtained in 13 cases. CONCLUSIONS: In patients with significant atherosclerotic stenosis of neck vessels, PTA is a beneficial procedure for improving blood flow to brain circulation and for alleviating symptoms.

Aged↗
PubMed1994

Computed tomography evaluation of chronic paranasal sinusitis.

BACKGROUND: Although chronic paranasal sinusitis has been recognized and diagnosed more frequently in recent years, it is still one of the most frequently overlooked disease and a significant source of morbidity and economic loss. Therefore, a further detailed analysis of its clinical pictures and computed tomographic (CT) presentations is necessary for better understanding. METHODS: We collected 230 cases in recent two years and studied their CT manifestations. RESULTS: The pathological changes of sinusitis on CT were classified into four groups: mucosal thickening, mucosal thickening combined with fluid level, fluid level only, and total sinus opacification, in increasing frequency. Maxillary sinus was the most commonly involved sinus. Focal high density areas were noted in 17 sinuses. Ten of them were operated and revealed only thick mucous without evidence of calcification or fungal infection. There was no correlation between the disease duration and the number of sinuses involved. CONCLUSIONS: CT is the image modality of choice in evaluating patients with chronic paranasal sinusitis.

Adolescent↗
PubMed1993

The sequence of the mouse phosducin-encoding gene and its 5'-flanking region.

Phosducin (Pd), a principal protein of retinal photoreceptor cells, modulates the phototransduction cascade by interacting with transducin. A recent report indicated that Pd and the G-protein-inhibitor protein (GIP) in brain are virtually identical. Here, we have sequenced the complete mouse clone (P1-AT) carrying the Pd gene, 3026 bp of its 5'-flanking region, and cDNAs generated from the retinal mRNAs. Gene Pd is 15 kb in length and has four exons. The splice sites for donor and acceptor were in good agreement with the GT/AG rule. Deduced Pd amino acid sequences were highly homologous to those of human, bovine and rat. In addition, we found more than one similar Pd gene and two different mRNAs. The P1-AT clone encodes one of the Pd mRNAs. These results open the possibility that the multiple Pd genes encode multiple Pd.

Animals↗
PubMed1993

Measurement of CI-979 (a candidate drug for the treatment of age-related disorders of cognition) in human plasma by capillary gas chromatography with nitrogen-selective detection.

A specific and highly sensitive method for the measurement of CI-979 in human plasma is described. The compound and internal standard were extracted from alkalinized plasma with methyl tert.-butyl ether and analyzed by capillary gas chromatography with nitrogen-selective detection. The method was demonstrated to be accurate and precise. Since the limit of quantitation was 0.10 ng/ml, this method was suitable for clinical pharmacokinetic studies in which subjects received repeated administration of 0.5-2.5 mg CI-979 every 6 h.

Chromatography, Gas↗
PubMed1993

Coexistence of calcific tendinitis and rotator cuff tear: an arthrographic study.

A prospective evaluation of the coexistence of calcific tendinitis and tear of the rotator cuff demonstrated by arthrography was made in patients presenting with shoulder pain. Patients were X-rayed using conventional views and impingement views. Eighty-one patients (mean age 61.2 years) with calcific tendinitis underwent arthrography. Arthrography showed 22 partial or complete tears of the rotator cuff. A small rather than a large amount of calcification was more likely to be associated with a rotator cuff tear (p = 0.005). The coexistence of calcific tendinitis with rotator cuff tear is not uncommon, especially in older age groups.

Calcinosis↗
PubMed1993

Posterior cranial fossa tumours in childhood.

We reviewed clinical and CT findings in 133 posterior cranial fossa tumours in children. All had histological diagnosis, apart from 20 cases of brain stem glioma. The majority were intra-axial tumours, including 53 medulloblastomas (40%), 31 cerebellar astrocytomas (23%), 28 brain stem gliomas (21%), 14 ependymomas (11%), and single cases of ganglioglioma, haemangioblastoma and teratoma. Extra-axial tumours formed only 3%, including 2 chordomas and 2 schwannomas. The clinical data and CT findings are reviewed. Cerebellar astrocytoma involved the sexes equally, while medulloblastoma, brain stem glioma, and ependymoma were more common in males. Most cerebellar astrocytomas were in the midline, and presumably arose from the vermis. The frequency of calcification was similar to that in previous reports, being highest in ependymoma (69%), followed my medulloblastoma (29%), cerebellar astrocytoma (17%), and brain stem glioma (8%).

Astrocytoma↗
PubMed1993

Obstructive intestinal herniation due to improper use of a seat belt: a case report.

The term "seat belt syndrome" has been used to describe injuries to the abdominal viscera caused by seat belts during car accidents. These injuries are usually sustained as a result of the rapid deceleration that occurs in front-end collisions, with the consequent compression of the abdominal viscera. The spectrum of injuries includes intestinal perforation or stenosis, mesenteric disruption, and lumbar fracture-dislocation. We present an uncommon case of obstructive herniation in a 2-year-old girl which we believe was due to improper use of a seat belt.

Child, Preschool↗
PubMed1993

Pharmacokinetics, mass balance, and induction potential of a novel GABA uptake inhibitor, CI-966 HCl, in laboratory animals.

CI-966 exhibits anticonvulsant properties in various animal models. The drug acts by inhibiting synaptic uptake of gamma-aminobutyric acid (GABA). Oral absorption of CI-966 in dogs given 1.39 mg/kg is rapid with a tmax of 0.7 hr. In rats given 5 mg/kg oral, a mean tmax of 4.0 hr was observed. Following iv administration of the same respective doses, elimination t1/2 in dogs and rats averaged 1.2 and 4.5 hr. Absolute oral bioavailability of CI-966 was 100% in both species. Following oral dosing of [14C]CI-966 HCl to dogs, fecal, and urinary excretion accounted for 89% and 2.3% of the 14C dose, respectively. In bile-duct cannulated rats, biliary excretion is the major elimination pathway of radioactivity (75%). Urinary and fecal excretion accounted for 4.1 and 12%, respectively. CI-966 does not induce or inhibit mouse hepatic mixed function oxidases, as determined by hexobarbital sleeping time.

Administration, Oral↗
PubMed1993

Spontaneous contraction of leukodermic patches in Waardenburg syndrome.

Waardenburg Syndrome is an autosomal dominantly inherited disorder with variable penetrance. It is a rare disorder with an estimated frequency of 1:20,000 in Kenya (East Africa) and 1:40,000, in the Netherlands presenting with or without deafness. The frequency with deafness is lower, estimated at 1:50,000 to 1:212,000. The major characteristic features are as follows, with reported incidences in parenthesis: 1) Dystopia canthorum (99%); 2) synophrys (17%-69%); 3) broad nasal root (78%); 4) depigmentation of hair, skin, or both (17%-58% with white forelock); 5) heterochromic or hypochromic irides (greater than 20%); 6) congenital deafness (9%-38%). Genetic heterogeneity has led to classification of affected families as type I, with dystopia canthorum, or type II, without dystopia canthorum (2, 6). Piebaldism and Woolf's Syndrome can present with pigmentary changes which are similar to Waardenburg Syndrome. Woolf's Syndrome also includes deafness. However, the distinguishing structural ophthomologic abnormalities of dystopia canthorum, broad nasal root, and synophrys are not found in either piebaldism or Woolf's Syndrome. The congenital patterns of leukoderma in both piebaldism and Waardenburg Syndrome has been believed to be stable throughout the lifetime of the affected individuals. We report an otherwise typical family with Waardenburg Syndrome, type I, in which 2 members atypically demonstrate spontaneous pigmentation and contraction of congenital leukodermic patches. To our knowledge, this has not been previously reported in Waardenburg Syndrome.

Female↗
PubMed1993

Ultrastructural study of two patients with both piebaldism and neurofibromatosis 1.

Piebaldism was associated with neurofibromatosis 1 (NF-1) in two patients, an association not previously reported. Dopa staining (tyrosinase) and electron microscopy were performed: no melanocytes or melanosomes were found in hypomelanotic skin of patient 2 and in the white forelock skin of patient 1; in patient 2, normal melanocytes and melanosomes were present in the white forelock epidermis but absent from the cortex, cuticles, and inner root sheath of the white forelock hair. Because these structures receive melanosomes from melanocytes in the hair bulb, it was assumed that there were no melanocytes in the hair matrix. Melanocytes and melanosomes were normal by ultrastructural criteria and in terms of their distribution in a normally pigmented macule within a hypomelanotic patch of patient 2. These and earlier report findings led to three conclusions: subtypes of piebaldism exist, including our patients showing a combination of piebaldism and NF-1; the most commonly reported subtype has no melanocytes in the white forelock and hypomelanotic skin, although microscopic islands of melanocytes may exist within hypomelanotic skin; and the ultrastructure of white forelock skin and hair of patient 2 is consistent with a mouse model of piebaldism, in which the hair follicle has no active melanocytes, but the interfollicular epidermis is normally melanized.

Adolescent↗
PubMed1993

A case of acute renal artery thrombosis caused by blunt trauma: computed tomographic and Doppler ultrasonic findings.

A 16-year-old girl who was involved in a traffic accident subsequently received emergency surgery for facial lacerations and an exploratory laparotomy. She had gross hematuria which was ignored initially. A left renal infarction, detected by computed tomography on the 12th post-operative day, showed no enhancement of the left renal artery with the cortical rim sign. Further study by color and pulsed Doppler ultrasound revealed the absence of normal renal arterial flow with only venous flow detected, confirming the diagnosis of acute renal artery thrombosis.

Acute Disease↗
PubMed1993

Articular manifestations of renal osteodystrophy.

The relationship between hyperparathyroid bone disorders and chronic renal diseases has been studied extensively for a long period of time. Zvaifler and Bywaters are the first to emphasize articular manifestations in hyperparathyroidism. Sundaram has found 30% in 80 hemodialysis patients presenting with articular disorders in hands. We reviewed routine radiographs of 258 uremia patients retrospectively and found that 36 patients had typical X-ray presentations of renal osteodystrophy. Sixteen among them (44.44%) were noted with articular involvement. Fourteen patients involved axial joints including sacroiliac, acromio-clavicular, sternoclavicular and symphysis pubis in decreasing order. Appendicular joints involvement were found in 6 patients, patellofemoral joints and small joints of hands involvement in 4 patients respectively and hip and shoulder joints in each one patient. None of the 16 patients complained joint pain. Diagnosis is easy because of the uncommon presentations of joint disorders in uremic patients. However, more knowledge about articular manifestations of renal osteodystrophy may eliminate the unnecessary investigations.

Adolescent↗
PubMed1993

Staging of bladder cancer by transabdominal real-time ultrasound.

In the past six years, there were 726 cases of proved bladder cancer in our hospital. Among these, 376 cases received transabdominal ultrasonographic examination of the urinary bladder for evaluation of the bladder tumor. Two hundred and fourteen cases of them were newly diagnosed as bladder cancer and had adequate pathological specimens for staging of the tumor. The retrospective comparison between preoperative local staging of the bladder tumor by ultrasound and final pathological report showed 78.5% of total accuracy, 9.8% of overstaging, and 11.7% of understaging. The accuracy is 87% for stage A tumor; 60.5% for stage B; 41.2% for stage C; 83.3% for stage D. Strong echogenic foci on the surface or in the tumor were detected in 39.3% (84/214) of cases, which may indicate encrusted stones on the surface of the tumor or intratumoral dystrophic calcification. There was no strong correlation between tumor grading and staging, except that most of the grade I lesions were at stage A (30/31, 97%). The preoperative local staging of urinary bladder cancer by real-time ultrasound might be of great value to determine the management planning and prognosis of the patients.

Adolescent↗