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Biomedical subjects

D Y Yu

Publications and source records attributed to D Y Yu.

At least 55 records · Page 3Linked to original sources
PubMed1990

In vitro characterization of the mechanical properties of canine ophthalmociliary artery.

The form and magnitude of K+ Krebs-induced contractures has been measured for the dog ophthalmociliary artery. Ring segments of the vessel were mounted in a myograph after the method of Hogestatt, Andersson and Edvinsson (1983, Acta Physiol. Scand. 117, 49-61). For low passive tensions the K(-)-induced contractures show both a phasic and tonic component, with the tonic tension component being the smaller. As passive tension is increased, the phasic component grows and plateaus whilst the tonic component continues to increase. For high passive tensions the phasic component disappears and the tonic component reduces in magnitude and the contracture is not fully reversible. Comparison of the length tension curves measured during K+ Krebs-induced contractures and Ca2(+)-free Krebs-induced relaxation shows that the active tension generated by this vessel increases with increasing passive tension until a peak active tension of 3.1 mN mm-1 is reached at an effective radius of 357 microns. For greater values of passive tension the active tension decreases. The calculated transmural pressure required to maintain the vessel at this optimal radius is 51.9 mmHg, which is very similar to the only available measurements of ophthalmic artery pressure, viz. 51.8 mmHg (Grunwald, Sinclair and Riva, 1981, Invest. Ophthalmol. Vis. Sci. 20, 564-6). The optimal passive stretch to apply to these ring segments for further pharmacological or physiological work is discussed.

Animals↗
PubMed1990

Effect of continuous versus multiple intermittent light exposures on rat retina.

The damaging effects of continuous light exposure to the albino rat retina have been well documented. However, the cumulative effects of multiple light exposures are not well defined. We therefore compared the retinal injury induced by a single 24 hour light exposure with that caused by three intermittent exposures of 8 hours each. Eight dark-adapted albino Lewis rats were exposed for 24 hours to green fluorescent light (490-580 nm) at an illuminance level of 175 foot-candles. A second group of 8 rats was exposed under similar conditions in three split doses of 8 hours each at intervals of 7 days between each exposure. Recovery was allowed in total darkness, and the animals were sacrificed 2 weeks following the last exposure. Retinal damage was assessed by morphometry and light and electron microscopy. Mild cumulative retinal injury, mostly in photoreceptor cells with relative sparing of the retinal pigment epithelium, was seen in the split dose group, while extensive damage involving photoreceptor cells and retinal pigment epithelium was noted in the group exposed continuously for 24 hours.

Animals↗
PubMed1990

The response of rat vitreal oxygen tension to stepwise increases in inspired percentage oxygen.

The effect of graded systemic hyperoxia on vitreal PO2 distribution has been determined for the rat eye. Oxygen tension profiles were measured, using oxygen-sensitive microelectrodes, as a function of distance from the internal limiting membrane as the inspired oxygen percentage was increased in 10% steps from 20-100%. Depending on the original touching location of the microelectrode on the retina, there could be substantial PO2 gradients within 500 microns of the retina; at greater distances vitreal PO2 was constant and a function of the inspired oxygen percentage. Whatever the location of the microelectrode in the vitreous, PO2 rose with increasing hyperoxia. The relationship between vitreal PO2 and inspired oxygen was nonlinear with a central relatively flat region between 50-80% inspired oxygen. The ratio between vitreal PO2 during 100% O2 breathing and air breathing was 3.42 +/- 1.08 (standard deviation, n = 7). Possible explanations for the plateau region are the maintenance of a relatively constant PO2 by vascular autoregulation and/or the buffering of capillary PO2 by hemoglobin. The rat eye, therefore, responds to hyperoxia similarly to that of the cat and monkey but differs from that of the miniature pig where there is no rise in preretinal PO2 during hyperoxia.

Animals↗
PubMed1989

Specific binding of a hepatoma nuclear factor to the NF.kappa B/H2TF1 recognition motif found in the C4 promoter, but not in the Slp promoter.

The fourth component of C (C4) and sex-limited protein (Slp) genes of FM strain mice show more than 95% nucleotide identity both in the coding and the about 2 kb of 5' flanking region, but are distinct in their regulation. Although C4 is a constitutive gene, Slp is an androgen-dependent gene and shows negligible basal level expression. We have previously shown that this difference in basal expression is determined by a region of about 400 bp immediately 5' of the transcriptional start site of the C4 and Slp genes. In this report, we demonstrate a specific binding site for a HepG2 nuclear extract in this region of the C4 gene by gel retardation and DNase I footprinting experiments. Nucleotide sequence of this binding site is very similar to the recognition sequence of well characterized transcription factors, NF.kappa B and H2TF1. Synthetic oligonucleotides representing the binding sites of the H-2Kb class I and IL-6 genes for these factors compete with the C4 promoter for the complex formation with a HepG2 nuclear factor. Due to the nucleotide deletion and substitution, the corresponding region of the Slp gene lacks this sequence motif as well as binding activity to the HepG2 nuclear factor.

Animals↗
PubMed1988

Mapping of the transcriptional regulatory domains responsible for the difference in the promoter activity between mouse C4 and Slp (sex-limited protein) genes.

The genes for the fourth complement component (C4) and sex-limited protein (Slp) of the mouse exhibit a high degree of sequence homology and have probably been derived by recent gene duplication from a common ancestor gene, but their mode of expression is greatly different in most standard mouse strains. Although the C4 gene is constitutively expressed, the Slp gene is expressed only under the influence of androgens or not expressed at all. To map the transcriptional regulatory domains that are responsible for the difference in the promoter activity between the mouse C4 and Slp genes, we constructed various hybrid promoters from the 5'-flanking DNA of the C4 and Slp genes of the FM strain and tested for their transcriptional activity. The hybrid promoters were inserted into the HindIII site located immediately upstream of the chloramphenicol acetyl transferase (CAT) gene of the plasmid pSVOcat. The expression of CAT was assayed in transiently transfected HepG2 cells and in permanently transfected Ltk- cells. The transcriptional regulatory region responsible for the difference between the C4 and Slp gene expression was mapped within the 5'-flanking region of about 400 nucleotides near the promoters of the C4 and Slp genes. By S1 mapping analysis, it was shown that the CAT activities expressed in transfected cells were due to the transcripts correctly initiated from the promoter of the C4 or Slp genes in the chimeric constructs.

Animals↗
PubMed1988

Choroidal blood flow measured in the dog eye in vivo and in vitro by local hydrogen clearance polarography: validation of a technique and response to raised intraocular pressure.

Local choroidal flow has been measured using hydrogen (H2) clearance polarography in dog eyes in vivo and in vitro. The accuracy and reproducibility of the method was checked in the eye in vitro by demonstrating a linear relationship between flow measurements obtained by an absolute method and those obtained by the H2 clearance technique. The H2 electrode was placed through a scleral window and its current response to a bolus injection of H2-saturated saline into a proximal artery was measured. The clearance of H2 from the choroidal circulation in vitro was monoexponential and the reproducibility of the measurements at the same site and in the same eye was good. In vivo the technique was used to measure alterations in local choroidal blood flow produced by acute changes of intraocular pressure. A linear relationship between perfusion pressure and choroidal blood flow was obtained. H2 clearance polarography is shown to be an accurate and reproducible method for determining choroidal flow, with the advantage that localized repeated measurements of flow can be made.

Animals↗
PubMed1986

Effect of scleral recording location on ERG amplitude.

The isolated arterially perfused eye preparation has become a valuable tool in the investigation of ocular function. Normal retinal function can be maintained for several hours with the measurement of the gross electroretinogram (ERG) serving as a useful monitor of the electrophysiological condition of the preparation. This paper deals with the manner in which the amplitude of the ERG is affected by the electrode recording locations and describes the characteristic distribution of potentials on the surface of the isolated arterially perfused dog eye. The ERG is recorded between a fixed corneal contact lens electrode and a movable electrode on the uppermost surface of the sclera. The scleral electrode is moved in small increments parallel to the optic axis and lowered onto the uppermost surface of the sclera on a line from the corneal limbus to the optic nerve. The resulting ERG profile is characterised by minimal b-wave amplitude at the corneal limbus and little growth until a point 5 or 6 mm from the corneal limbus is reached, followed by a region of rapidly increasing amplitude up to a maximum at the point where the optic nerve exits from the globe. There follows a region of large but stable signal amplitude along the optic nerve. The ERG profile is largely unaffected by a reorientation of the globe about the optic axis, demonstrating that the potential distribution on the surface of the globe may be described in terms of points equidistant from the limbus being isopotential.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Cyclic combination chemotherapy in advanced adenocarcinoma of the lung: comparison of two FAM schedules.

Forty patients with advanced adenocarcinoma of the lung were treated by two FAM chemotherapy schedules. Group A (20 patients) received Futraful, adriamycin, and mitomycin C, and group B (20 patients) received 5-fluorouracil, adriamycin, and mitomycin C. The response/stabilization rate was greater for group B (4 partial responses + 4 cases of stable disease) than for group A (no responders + 5 cases of stable disease), and the median survival was longer for group B (32 weeks) than for group A (22 weeks), although the differences did not reach statistical significance in either case (P greater than 0.05). Myelotoxicity was mild in both schedules. Further studies of the two FAM schemes at an escalated dose would be worthwhile.

Adenocarcinoma↗
PubMed1984

Guillotine tonsillectomy without anesthesia.

Guillotine tonsillectomy without anesthesia is a new and safe operative procedure. From 1958 to 1973, 11,140 tonsillectomies were performed in our clinic. Being safe, simple, convenient and time-saving, this method gives fairly satisfactory results. Besides, it is less traumatic and has a lower incidence of postoperative hemorrhage. More than 93% of the patients experienced no pain or slight pain during the operation. For assessment of the therapeutic results, we made an analysis of 4,190 cases. There was no much difference in cure rate and size of lymphoid tissue in the tonsillar fossa between guillotine and dissection methods. Guillotine without anesthesia eliminates all the dangers and the unfavourable side-effects of anesthesia. It is distinctly safe and, therefore, is far superior to the procedure under anesthesia.

Adolescent↗
PubMed1983

Clinical features of bronchogenic carcinoma in Hong Kong. Review of 480 patients.

A retrospective study was made of 480 Chinese patients with proven bronchogenic carcinoma, the top cancer in Hong Kong. The male-to-female sex ratio was low (1.9:1) and the female mortality rate ranked amongst the world's highest. The four major histologic types accounted for 87% of the cases: 39% epidermoid, 12% small cell anaplastic, 29% adenocarcinoma, and 7% large cell anaplastic. History of smoking was associated with epidermoid and small cell anaplastic carcinoma only. The commonest symptoms were anorexia and malaise (67%) and cough (51%). Overall our patients presented late and only 30 (6%) had curative surgery. The relatively rare occurrence of deep vein thrombosis (0.7%) is in keeping with the known low incidence of venous thrombosis in Chinese. Adenocarcinoma was a distinct group characterized by its preponderance in females (43%), lack of association with smoking habit (61% female cases being nonsmokers), high frequency of neurologic manifestation (21%) and clinical, roentgenographic, and bronchoscopic features of a predominantly centrally situated tumor. Possible etiologic factors for the high and still increasing incidence of adenocarcinoma are discussed.

Adenocarcinoma↗
PubMed1983

Can hypertransfusion attenuate myelosuppression associated with combination chemotherapy in patients with inoperable bronchogenic carcinoma? A report of a randomised, controlled study.

Based on the concept of "stem-cell competition," hypertransfusion has been shown to attenuate the leucopenia associated with chemotherapy in children with leukemia. We conducted a randomized, controlled study of hypertransfusion in 25 patients with inoperable lung cancer who received combination chemotherapy consisting of methotrexate, adriamycin, cyclophosphamide, and CCNU (Lomustine) (MACC scheme). Twelve patients in the hypertransfusion group were given red cell transfusion to a hemoglobin value greater than or equal to 17 gm/dl prior to each chemotherapy cycle. The two groups of patients were comparable in age, cell type, extent of disease, performance status, and initial hemoglobin level and blood counts. The mean fall in granulocyte count was greater for control group (3.76 X 10(9)/liter) than for hypertransfusion group (3.27 X 10(9)/liter), and the mean fall in platelet count was greater for control group (53.84 X 10(9)/liter) than for hypertransfusion group (35.83 X 10(9)/liter), although the differences did not reach statistical significance (p greater than 0.05) partly because our MACC scheme was probably not sufficiently myelosuppressive to bring about a difference in the two groups. Granulocytopenia-associated infections were infrequent in both groups: two episodes in 37 cycles of chemotherapy in the hypertransfusion group and three episodes in 43 cycles in the control group. Hypertransfusion was simple and safe, and the encouraging trend towards less marked myelosuppression in our hypertransfused group would warrant further studies using more intensive and myelosuppressive combination chemotherapy regimens.

Adult↗
PubMed1983

Response to oral corticosteroids in chronic airflow obstruction.

Sixteen Chinese patients with chronic fixed airflow obstruction (mean age 62.5 years; mean forced expiratory volume in 1 second (FEV1) of 0.85 litres, and mean ratio FEV1/forced vital capacity (FVC) of 0.45) entered a randomized double-blind crossover trial comparing prednisolone 40 mg orally daily for 2 weeks with placebo. Nine of the 16 patients (56%) had an increase in FEV1 of 15% or more after prednisolone. Compared with placebo, prednisolone significantly improved objective measurements (mean FEV1 by 21.4%, mean FVC by 11.9%, mean daily peak expiratory flow rate by 22.6%), subjective measurement (mean dyspnoea score by 16%) and exercise performance assessed by the distance walked in 12 minutes (12MD, by 5.5%). Objective improvements in FEV1 and PEFR were correlated with subjective upgrading of the dyspnoea score, but were not paralleled by an improvement in 12MD. Changes in FVC correlated with neither. FEV1 was thus the best index of objective measurement. The following characteristics were examined for reliability in predicting steroid responsiveness: variability of symptoms, wheezing score, prick skin test positivity, initial bronchodilator response, peripheral blood and sputum eosinophilia, and serum and sputum immunoglobulin E (IgE) level. None was found to be useful. A therapeutic trial of oral corticosteroid should be considered in patients with chronic fixed airflow obstruction on an individual basis.

Administration, Oral↗
PubMed1983

Successful treatment of melioidosis caused by a multiresistant strain in an immunocompromised host with third generation cephalosporins.

A 32-yr-old woman with active systemic lupus erythematosus receiving prednisone and azathioprine developed lung abscesses of the right lower lobe caused by Pseudomonas pseudomallei, which was resistant concomitantly to chloramphenicol, co-trimoxazole, and tetracycline, but highly sensitive to a new cephalosporin, ceftazidime. Melioidosis was treated successfully with lobectomy and parenteral ceftazidime, which was given for 2 months without major side effects. Ceftazidime, being bactericidal, may be more promising for the eradication of P. pseudomallei, especially in immunocompromised hosts. This was also the first reported case of melioidosis in Hong Kong, where the disease might be endemic, as 4 more cases were found later.

Adult↗
PubMed1983

Fibreoptic bronchoscopy in the diagnosis of bronchial cancer: comparison of washings, brushings and biopsies in central and peripheral tumours.

Fibreoptic bronchoscopic cytodiagnosis by washings and brushings and histodiagnosis by forceps biopsy were studied in 484 Chinese patients with bronchial carcinoma. When the tumour was bronchoscopically visible, the yields of the three procedures were: washings 76%, brushings 74% and biopsy 82%, giving a total yield of 94%. For peripheral bronchoscopically non-visible tumour, the yields were 52%, 52% and 61% respectively, making a total yield of 86%. Bronchial washings and brushings were important complementary procedures to biopsy and provided the exclusive diagnosis in 12% of the central and 25% of the peripheral tumours. The cytologic cell typing accuracy is 92% for epidermoid carcinoma, 87% for small cell carcinoma, 83% for adenocarcinoma and only 38% for large cell carcinoma. The accuracy of cell-typing of the two bronchial cytodiagnostic methods was comparable in central tumours, but higher with brushings in peripheral tumours.

Adult↗