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Biomedical subjects

C Y Chang

Publications and source records attributed to C Y Chang.

At least 19 recordsLinked to original sources
PubMed1992

Mice deficient for Rb are nonviable and show defects in neurogenesis and haematopoiesis.

The retinoblastoma gene, a prototypic tumour-suppressor gene, encodes a nuclear phosphoprotein (Rb). To understand better the role of Rb in development and in tumorigenesis, mice with an insertional mutation in exon 20 of the Rb-1 locus were generated. Homozygous mutants die before the 16th embryonic day with multiple defects. The haematopoietic system is abnormal; there is a significant increase in the number of immature nucleated erythrocytes. In the nervous system, ectopic mitoses and massive cell death are found, particularly in the hindbrain. All spinal ganglion cells die, but the neural retina is unaffected. Transfer of the human retinoblastoma (RB) mini-transgene into the mutant mice corrects the developmental defects. Thus, Rb is essential for normal mouse development.

Abnormalities, Multiple↗
PubMed1992

Shoulder impingement syndrome: impingement view and arthrography study based on 100 cases.

A prospective evaluation combining the shoulder impingement view and arthrography was made in patients presenting with chronic shoulder pain. Five hundred and twenty-three patients with chronic shoulder pain were X-rayed using conventional views and impingement views. One hundred of these patients (mean age 62 years) had subacromial bony spurs on the impingement view; these underwent arthrography. They were divided into two groups according to the degree of spur formation--whether or not the size of the spur exceeded one half of the acromial width as measured from the outer margin to the acromioclavicular joint. Of the 100 subacromial spurs demonstrated on the impingement view, only 18 were visible on the conventional view as assessed by an independent radiologist. Arthrography showed 35 cases of rotator cuff tear. The size of the bony spur was strongly associated with the incidence of rotator cuff tear (P < 0.02).

Acromion↗
PubMed1992

Differential expression of Hz-1 baculovirus genes during productive and persistent viral infections.

Hz-1 viral RNA transcription was studied during productive and persistent infections. The RNAs were localized to 10- to 30-kb regions within the viral genome, and the timing of their expression was determined. During productive infections, we detected 101 virus-specific transcripts that could be grouped into three categories by time of appearance. At 2 h postinoculation (p.i.), a total of 34 virus-specific transcripts were detected. An additional 51 and 16 virus-specific transcripts appeared between 4 and 6 h p.i. and at 8 h p.i., respectively. After 8 h, no new transcripts were found. Under conditions of persistent infection, we detected only one viral persistency-associated transcript (PAT1). The region of the viral DNA which encodes PAT1 was cloned. During productive infections, three transcripts were derived from this region. Each had the same polarity as PAT1. One of them was of the same size as PAT1 and had similar, if not identical, 3' and 5' ends. This report provides detailed and very useful information concerning sequentially expressed transcripts of the Hz-1 baculovirus.

Animals↗
PubMed1992

Transcription of the human ferredoxin gene through a single promoter which contains the 3',5'-cyclic adenosine monophosphate-responsive sequence and Sp 1-binding site.

We have investigated the functional elements involved in cAMP-stimulated transcription of the human ferredoxin gene. Unlike the bovine gene, the human gene lacked a second upstream RNA initiation site as demonstrated by sequence analysis of the exon boundary, lack of upstream RNA, and analysis of the promoter. The presence of a single promoter was determined by testing the ability of various gene segments to drive the expression of the chloramphenicol acetyltransferase gene after transfection into a mouse adrenal cell line Y1. Full promoter activity was conferred by a DNA fragment spanning -209 to +55, although the -94 to +55 fragment already provided some promoter activity. Transcription from the -94 to +55 segment was stimulated by 2-fold when 8-bromo-cAMP was added to the cell. Footprinting analyses showed two GC boxes at -50 to -70 and -87 to -108 were protected by proteins from both Y1 and HeLa cells. Competition experiments showed that a protein with a recognition sequence indistinguishable from Sp1 bound to these sites. When connected to a heterologous TATA box, the sequence at -76 to -42, which contained the proximal GC box, was able to confer a high level of basal transcription and cAMP stimulation. This sequence does not show sequence homology with the known cAMP-responsive element. Mutations or deletion of the Sp 1-binding site showed diminished basal transcription and defined the cAMP responsive sequence to be from -76 to -62. Therefore the cAMP-responsive sequence of the human ferredoxin gene was located at -76 to -62, which was adjacent to the Sp 1-binding site.

Amino Acid Sequence↗
PubMed1992

Afferent and efferent connections of the paramedian reticular nucleus in the brain stem of cats.

Anatomical connections of the paramedian reticular nucleus (PRN) of the caudal medulla were investigated using a bi-directional tracer, horseradish peroxidase (HRP). The followings were observed when the tracer was microinjected to PRN: A. Both labelled neurons and terminals were found in the areas of the mesencephalic cardioinhibitory mechanism (CIM), the gigantocellular reticular nucleus (GRN), the ambiguus nucleus (AN) and the contralateral PRN. B. Only labelled terminals were demonstrated in the area of the nucleus of solitary tract (NTS) and the intermedial lateral cell column (IML) of the spinal cord. C. Only retrogradely labelled neurons were observed in the areas of the dorsal and dorsomedial medulla (DM) and ventrolateral medulla (VLM). A few labelled neurons were observed in the periaqueductal gray, the cuneiform nucleus and superior colliculus of the mesencephalon as well as the alamina spinal trigeminal nucleus. When HRP was applied to the CIM, GRN or AN structures, respectively, both labelled cells and terminals were found in the PRN area. HRP injection in the VLM showed only labelled terminals in the PRN. However, injection of HRP to DM showed neither labelling neurons nor terminals in PRN. Results suggest that PRN projects to the pressor area of DM/NTS and IML through which PRN could exert its inhibitory functions on the sympathetic pressor actions. In addition, PRN may suppress the vagal bradycardiac action through its reciprocal connections with CIM, GRN and AN. No lateralization in the PRN pathway was evident.

Afferent Pathways↗
PubMed1992

Shoulder computed arthrotomography: role of internal and external rotation.

Computed arthrotomography of the shoulder is the best investigation for instability of the glenohumeral joint. The purpose of this paper is to evaluate the role of internal rotation and external rotation in detecting glenoid and capsular lesions. From October 1989 to December 1991, 74 double-contrast CT arthrograms of the shoulder were performed with both internal and external rotation. Most of these patients were referred for instability problems or shoulder pain of vague origin. Of the 49 abnormalities of the anterior portion of glenoid labrum, 44 (89.8%) were identified on the scans with internal rotation; however, 5 (10.2%) was seen only in external rotation view. Most of the anterior capsular abnormalities occurred on the internal rotation. Only one of 74 examination was evidenced solely on external rotation. There were relatively few posterior labral or capsule abnormalities. Of the five, two were seen solely on external rotation. The results suggest that internal rotation scans detect most of the lesions; however, with the help of external rotation view, 10% increase in diagnostic yield can be expected for anterior labral abnormalities. Although few posterior labral or capsule lesions occur, external rotation examination does play an important role in this respect.

Adolescent↗
PubMed1992

Solitary metastasis of renal cell carcinoma to the ovaries: a case report.

Though renal cell carcinoma may metastasize to unusual sites via hematogenous spread, ovarian metastasis is very uncommon. This is explained by atrophy of the ovaries with decreased blood perfusion in most postmenopausal patients who are at the age of peak incidence of renal cell carcinoma. We report a 28-year-old woman with metastatic renal cell carcinoma to the ovaries. Special attention to the differential diagnosis and the management should be taken.

Adult↗
PubMed1992

Diffuse panbronchiolitis: report of a case.

A 33-year-old male presented with a productive cough of yellowish sputum which he had had for several years and progressive dyspnea on exertion that had been present for one year. Physical examination on admission disclosed clubbing of the fingers, diffuse inspiratory crackles and some rhonchi on auscultation. Plain chest film showed diffuse fine nodular lesions in both lungs. Pulmonary function tests demonstrated obstructive ventilatory impairment with a positive bronchodilator response. A CT scan of the chest showed diffuse fine nodular infiltrations in both lung fields. Arterial blood gas analysis of the patient, while breathing room air, revealed mild hypoxemia. The histologic findings of an open lung biopsy specimen were compatible with a diagnosis of diffuse panbronchiolitis. The patient was treated with erythromycin and a bronchodilator, and was regularly followed at the outpatient department. In this report, clinical manifestations, diagnostic criteria and recent advances in the treatment of diffuse panbronchiolitis are discussed.

Adult↗
PubMed1992

Magnetic resonance image of internal derangement of the temporomandibular joint.

Sixteen temporomandibular joints (TMJ) were examined by a high resolution magnetic resonance (MR) imager. Multisection 3.5 mm thick sagittal and coronal images were obtained by 1.0-T MR system and spin-echo sequence (TR = 800 msec, TE = 20 msec). MR provided useful information about meniscal position, morphology and histology. In our study, the MR of the 16 TMJ showed normal finding in two cases and abnormal findings could be differentiated into anterior disc displacement with reduction (8 cases), anterior disc displacement without reduction (3 cases) and bony change (3 cases). MR imaging can produce high-quality tomographic images with good demonstration of the internal structures of TMJ. As it is a noninvasive technique involving no ionizing radiation, MR imaging has been shown to be a useful tool for the demonstration of internal changes in TMJ.

Adult↗
PubMed1991

Characterization of Alu repeats surrounding the human ferredoxin-encoding gene.

Three Alu sequences have been identified surrounding the human ferredoxin-encoding genes. Among them, one is located about 1000 bp upstream from the active gene, whereas two others flank the ferredoxin pseudogene, psi FDX3. All these Alu sequences contain poly(A) tails and are flanked by direct repeats, indicating that they arose by RNA-mediated transposition events.

Base Sequence↗
PubMed1991

Organization and stability of a polytopic membrane protein: deletion analysis of the lactose permease of Escherichia coli.

The overall topology of polytopic membrane proteins is thought to result from either the oriented insertion of the N-terminal alpha-helical domain followed by passive insertion of subsequent helices or from the function of independent topogenic determinants dispersed throughout the molecules. By using the lactose permease of Escherichia coli, a well-characterized membrane protein with 12 transmembrane domains and the N and C termini on the cytoplasmic surface of the membrane, we have studied the insertion and stability of in-frame deletion mutants. So long as the first N-terminal and the last four C-terminal putative alpha-helical domains are retained, stable polypeptides are inserted into the membrane, even when an odd number of helical domains is deleted. Moreover, even when an odd number of helices is deleted, the C terminus remains on the cytoplasmic surface of the membrane, as judged by lacY-phoA fusion analysis. In addition, permease molecules devoid of even or odd numbers of putative transmembrane helices retain a specific pathway for downhill lactose translocation. The findings imply that relatively short C-terminal domains of the permease contain topological information sufficient for insertion in the native orientation regardless of the orientation of the N terminus.

Alkaline Phosphatase↗
PubMed1991

Evolution of Alu repeats surrounding the human ferredoxin gene.

Ferredoxin is an iron-sulfur protein that serves as an electron carrier for the mitochondrial oxidation/reduction system. During the characterization of the human ferredoxin gene, we have identified three Alu sequences surrounding it. When these Alu sequences were compared with others, all three of them are more related to the consensus Alu than the 7SL gene, the progenitor of the Alu family. It suggests that they are members of the modern Alu family. Their sequences differ from the Alu consensus sequence by about 5%, indicating that they were inserted into the chromosome about 35 million years ago.

Base Sequence↗
PubMed1991

Ostrich crystallins. Structural characterization of delta-crystallin with enzymic activity.

Lens crystallins from the African ostrich (Struthio camelus) were isolated and characterized. Four crystallin fractions corresponding to alpha-, delta/beta- and beta-crystallins similar to those of duck crystallins were isolated, but epsilon-crystallin was found to be absent. The native molecular masses and subunit structures of the purified fractions were analysed by gel filtration. SDS/PAGE and isoelectric focusing, revealing various extents of heterogeneity in each orthologous crystallin class. An ion-exchange chromatographic method was used for the large-scale preparation of delta-crystallin suitable for structural and enzymic studies. It was unexpectedly found that the purified native delta-crystallin of ostrich lens possessed high argininosuccinate lyase activity, in contrast with chicken delta-crystallin. The c.d. spectra indicated a predominant beta-sheet structure in alpha- and beta-crystallins, and a significant contribution of alpha-helical structure in the delta-crystallin fraction. The estimate of secondary structures from c.d. spectroscopy for each crystallin class bears a resemblance to that of duck crystallins, except that ostrich delta-crystallin possesses much less helical content than duck delta-crystallin. Comparison of crystallin compositions and structures from aquatic and terrestrial birds revealed distinct differences.

Amino Acids↗
PubMed1991

Traumatic sinus of Valsalva fistula.

Two rare cases of nonpenetrating trauma-induced fistula from the right sinus of Valsalva to the right heart chambers are reported. Both were diagnosed preoperatively and operated on successfully. A transverse tear was found in the right sinus of Valsalva, just below the right coronary ostium, in both patients. The ragged inlet and a rough fistula tract were noted during operation. The tears were closed with direct sutures or with a Dacron patch. Coronary artery bypass grafting was needed in 1 patient. The results of operation were excellent.

Adult↗
PubMed1991

Fluid levels in aneurysmal bone cysts.

Aneurysmal bone cysts are benign, expansile, osteolytic lesions of the bone. All the aneurysmal bone cysts studied in this case report were observed during the 2 year period, 1989 to 1991. The patients involved had received radiographic examination: plain and magnetic resonance (MR) image; one of the patients also received a computed tomography (CT). The plain radiograph generally showed a well-defined, expansile, osteolytic lesion associated with a pathologic fracture; the CT and MR images showed a fluid-fluid level within the lesion. This paper will report the findings of fluid-fluid levels, using radiographic images, in aneurysmal bone cysts.

Adult↗