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Biomedical subjects

Z L Lu

Publications and source records attributed to Z L Lu.

At least 19 recordsLinked to original sources
PubMed1995

Attention-generated apparent motion.

Motion perception mechanisms have recently been divided into three categories. First-order mechanisms primarily extract motion from moving objects or features that differ from the background in luminance. Second-order mechanism extract motion from moving properties, such as a moving area of flicker in which there is no difference in mean luminance between target and background. These first- and second-order motion mechanisms are primarily monocular. The existence of purely binocular, interocular and various other unusual kinds of apparent motion has promoted conjectures of a third-order mechanism, but there has been no clear suggestion as to the actual computations that such a mechanism might perform. Here we demonstrate 'alternating feature' stimuli that produce apparent motion only when the observer selectively attends to one of the embedded features in the display. The latent motion in the alternating feature stimuli is invisible to first- or second-order motion mechanisms, and the direction of apparent motion depends on the particular feature attended. These findings suggest the mechanism of third-order motion: the locations of the most significant features are registered in a salience map, and motion is computed directly from this map.

Attention↗
PubMed1995

The functional architecture of human visual motion perception.

UNLABELLED: A powerful paradigm (the pedestal-plus-test display) is combined with several subsidiary paradigms (interocular presentation, stimulus superpositions with varying phases, and attentional manipulations) to determine the functional architecture of visual motion perception: i.e. the nature of the various mechanisms of motion perception and their relations to each other. Three systems are isolated: a first-order system that uses a primitive motion energy computation to extract motion from moving luminance modulations; a second-order system that uses motion energy to extract motion from moving texture-contrast modulations; and a third-order system that tracks features. Pedestal displays exclude feature-tracking and thereby yield pure measures of the first- and second-order systems which are found to be exclusively monocular. Interocular displays exclude the first- and second-order systems and thereby to yield pure measures of feature-tracking. RESULTS: both first- and second-order systems are fast (with temporal frequency cutoff at 12 Hz) and sensitive. Feature tracking operates interocularly almost as well as monocularly. It is slower (cutoff frequency is 3 Hz) and it requires much more stimulus contrast than the first- and second-order systems. Feature tracking is both bottom-up (it computes motion from luminance modulation, texture-contrast modulation, depth modulation, motion modulation, flicker modulation, and from other types of stimuli) and top-down--e.g. attentional instructions can determine the direction of perceived motion.

Attention↗
PubMed1994

Full-wave and half-wave processes in second-order motion and texture.

A theory of human second-order motion perception is proposed and further applied to the discrimination of texture slant. The computational algorithms for deriving the direction of left-right motion from a sequence of images are equivalent to the algorithms for deriving the direction of slant (e.g. from top left to bottom right or top right to bottom left) in a single 2D image. There is a broad range of phenomena for which Fourier analysis of the image plus a few simple rules gives a good account of human perception. The problem with this first-order analysis is that there exists a broad class of 'microbalanced' stimuli in which the motion or slant is completely obvious to human subjects but is invisible to first-order analysis. Microbalanced stimuli require second-order analysis which consists of non-linear preprocessing (spatiotemporal filtering followed by rectification of the input signal) before standard motion or slant analysis. To determine whether the second-order rectification is half-wave or full-wave, we construct two special microbalanced stimulus types: 'half-wave stimuli' whose motion (or texture slant) is interpretable by a half-wave rectifying system but not by full-wave or a first-order (Fourier) analysis and 'full-wave stimuli' which are interpretable only after full-wave rectification. Such experiments show that second-order texture-slant perception utilizes both half-wave and full-wave processes, second-order motion-direction discrimination depends predominantly on full-wave rectification and second-order spatial interactions such as lateral contrast-contrast inhibition and second-order Mach bands are exclusively full-wave.

Algorithms↗
PubMed1994

[Pathological study on thoracic carcinoids accompanied with Cushing's syndrome].

Eight patients with carcinoid tumors (5 from the lungs and 3 from the thymus) associated with Cushing's syndrome were studied. Among them, 5 were male and 3 female with a mean age of 32.5 years. Histologically, all were typical carcinoids. Immunohistochemically, tumor cells were strongly positive of NSE, chromogranin A and ACTH in all 8 cases. Some tumors also positive for S-100, calcitonin, HCG alpha and HCG beta. Various amounts of neurosecretory granules were found in the tumors by electron microscopy and ACTH positive dots were also noticed in some of the neurosecretory granules in the tumor cells by immunoelectron microscopical colloidal gold labelling technique. By in situ hybridization technique, overexpression of chromogranin A mRNA was detected in all of the tumors reported.

Adolescent↗
PubMed1994

[The clinical significance serum N-POMC level in lung cancer patients].

Serum N-POMC level of 103 cases of lung cancer were measured in our hospital. The results were as follows: The lung cancer group, 50.5%, of patienst has an N-PONC level above the normal upper limit. The percentages of the N-POMC levels above the normal limit in lung cancers, such as: squamous-cell carcinoma, adenocarcinoma, SCLC and undifferentiated carcinoma were 52.2%, 50.0%, 47.3% and 57.1%, respectively. There was no statistically significant difference of N-POMC levels among these kinds of lung cancers, Eleven of 18 cases of SCLC patients in stage IIIb or IV, and 3 of 9 cases of SCLC patients in stage IIIa had N-POMC levels above the upper normal limit. Could serum N-POMC be one of the indexes for assisting the diagnosis and prognosis of lung cancer needs further investigation. Cases with carcinoid, thymoma and neurofibroma had higher N-POMC levels too. Six patients had Cushing syndrome.

Adenocarcinoma↗
PubMed1994

Hysteroscopic tubal catheterization and hydrotubation for treatment of infertile women with tubal obstruction.

We reported the efficacy of interval hysteroscopic tubal catherization and hydrotubation for three months in 54 infertile women with tubal obstruction (102 fallopian tubes). By comparison of HSGs before and after treatment, 86 of 102 tubes (84%) showed the improvement of tubal patency (P < 0.01). 56 tubes were patent (54.9%). This method is effective for partially patent tubes (87.5%), intramural tubal obstruction (62.5%), and the obstruction at the distal portion of the fallopian tube (13.3). One -12 month follow-up after treatment, 12 of 35 women whose tubes became completely patent achieved intrauterine pregnancies.

Adult↗
PubMed1992

Behavioral lifetime of human auditory sensory memory predicted by physiological measures.

Noninvasive magnetoencephalography makes it possible to identify the cortical area in the human brain whose activity reflects the decay of passive sensory storage of information about auditory stimuli (echoic memory). The lifetime for decay of the neuronal activation trace in primary auditory cortex was found to predict the psychophysically determined duration of memory for the loudness of a tone. Although memory for the loudness of a specific tone is lost, the remembered loudness decays toward the global mean of all of the loudnesses to which a subject is exposed in a series of trials.

Acoustic Stimulation↗
PubMed1990

Coated amperometric electrode arrays for multicomponent analysis.

This paper describes a sensor array of several amperometric electrodes, each coated with a different permselective film. Coatings with different transport properties, based on size (cellulose acetate), charge (Nafion, poly(vinylpyridine), poly(ester sulfonic acid], and polarity (phospholipid) are employed in connection with a four-electrode thin-layer flow detector. With equipotential operation, the array's response pattern of each analyte provides a unique characterization of the individual components. Multicomponent analysis is obtained by taking advantage of the partial selectivity of the individual sensors and using a pattern recognition (multiple linear regression) method. Additional information is obtained by recording the complete hydrodynamic voltammogram at the individual sensors. The merits of the new array are illustrated for the quantification of neurologically significant catechol compounds.

Electrodes↗
PubMed1990

Highly stable phospholipid/cholesterol electrode coatings for amperometric monitoring of hydrophobic substances in flowing streams.

Composite electrode coatings based on a mixture of phosphatidylcholine and cholesterol offer remarkable mechanical stability under vigorous hydrodynamic conditions. The greatly improved stability (over single-domain phospholipid layers) is attained without compromising the attractive permselective response of lipid electrodes. The enhanced stability is attributed to changes in the fluidity/packing associated with the presence of cholesterol. Due to its high stability, simplicity, and fast and permselective response, the coated electrode seems well-suited for flow measurements of hydrophobic compounds. Parameters affecting the film permeability and the amperometric response are explored in the presence of numerous solutes of biological and pharmaceutical significance. Prevention of surface fouling (in the presence of surfactants) and applicability to selective assays of urine samples are illustrated. Such controlled access to the surface, based on solute polarity, greatly enhances the power of electrochemical flow detectors.

Chemistry, Physical↗
PubMed1989

[Studies on antifertility effect of testosterone undecanoate in combination with danazol in male rats].

Male rats were injected i.m. with 12 mg/kg testosterone undecanoate (TU) twice in the first and once in each of the succeeding 2 months in combination with oral danazol (DZ) of 30 mg/kg/day. Antifertility effects were observed with morphological and functional techniques for half a year. Results showed: reduction of testis weight and seminiferous tubule diameter; decrease of sperm viability and motility in canada epididymidis; and lowering of testosterone levels in testis and phospholipid and protein contents in epididymis. 75 days after treatment spermatogenesis was arrested mainly in the secondary spermatocyte stage with a decrease in sperm count to 0 in the cauda epididymidis. Mating test showed 0% fertility. Testicular testosterone and epididymis phospholipid and protein contents were found to have dropped further. However, all of the above-mentioned changes recovered completely 100 days after cessation of treatment. The authors suggest that TU plus DZ in a suitable dose suppresses spermatogenesis, retards maturation and shortens the survival time of sperm in the epididymis by reducing testosterone levels in the testis.

Animals↗
PubMed1989

[Ectopic ACTH syndrome caused by bronchial carcinoid].

A 35-year male patient with clinical and biochemical manifestations of severe hypercorticism was thought to have Cushing's syndrome of pituitary origin. However, the surgically removed pituitary adenoma was not confirmed by pathological examination. There was no improvement after transsphenoidal microsurgery Chest CT scan showed a small mass located at the upper-lobe of the right lung. This tumor (1.8 x 1.0 x 1.0 cm) was removed and one course of radiotherapy with linear accelerator was given. Remission was achieved clinically and biochemically after these therapies. The diagnosis of bronchial carcinoid was confirmed by pathological findings. Metastasis of a lymph node was also proved. The tumor cells was found to contain ACTH and related peptides with radioimmunoassay, immunocytochemistry and electron microscopy. Gel filtration of the tumor extracts showed molecular heterogeniety of ACTH related peptides and that the big-form were in large percentage.

ACTH Syndrome, Ectopic↗
PubMed1989

[Experimental studies on the role of retinal lipid peroxidation induced by intraocular iron foreign body].

Experimental studies were made to evaluate the role of lipid peroxidation in retinal damage by intraocular iron foreign bodies. It was found that after iron particles were implanted into the vitreous bodies (1) iron concentration in the aqueous humour rose rapidly and significantly (n = 24, P less than 0.01), (2) malondialdehyde (MDA) a degradation metabolite of lipid peroxidation, in the retinas increased significantly (n = 24, P less than 0.05), and (3) superoxide dismutase (SOD) activity decreased (n = 11, P less than 0.05). These findings suggest that lipid peroxidation plays a key role in the retinal damage of siderosis bulbi, and provide a solid basis in studying the pathogenesis and guiding clinical management of the disease.

Animals↗
PubMed1989

[Evaluation of various parameters in the differential diagnosis of Cushing's disease and Cushing's syndrome caused by adrenal adenoma].

Evaluation of the clinical and biochemical parameters for differential diagnosis of two types of Cushing's syndrome, pituitary-dependent Cushing's disease and adrenal adenoma, was studied with analysis of the histories of 79 cases of Cushing's disease and 23 cases of adrenal adenoma. The data show that the symptoms, signs and the routine biochemical analyses were not significantly different between two groups. High-dose dexamethasone suppression test had about 90% coincidence rate in the differential diagnosis with 24-hour urine free cortisol (UFC), which was better than 24-hour urine 17-OHCS. Interestingly, low-dose dexamethasone test was highly valuable and the 24-hour urine 17-KS quite helpful in the differential diagnosis of two types of Cushing's syndrome. Serum N-POMC measurement was the most valuable among the parameters, because there was no overlap between the two groups of Cushing's syndrome.

17-Ketosteroids↗