Biomedical subjects

Y F Tan

Publications and source records attributed to Y F Tan.

10 recordsLinked to original sources

PubMed2006

The influence of surface bioactivated modification on titanium percutaneous implants anchored in bone.

In order to achieve biological sealing and resist mechanical damage of load-bearing percutaneous devices, Ti with excellent mechanical properties was anodic-oxidized to be endowed with bioactivity, with plasma-sprayed hydroxyapatite coated Ti as control. Similar to previous works, hydroxyapatite coating could bond tightly with living tissues, resulting in implant stability for whole implantation periods. Meanwhile, when anodic-oxidized bioactivated Ti was implanted percutaneously in vivo, it could induce a layer of calcium phosphate at the interface of tissues/implant. This layer of Ca-P not only induced the fibrous tissue or collagen ingrowth in its structure, but also improved the osteointegration between the bone and the implant. There was no significant biological response difference for the anodic-oxidized Ti and HA coated Ti at different implantation period with histological statistical analysis (p>0.05). Accordingly, suitable bioactivated modified surface of Ti by anodic-oxidized method could not only obtain the same results as the HA coating, but also might avoid some drawbacks of plasma-sprayed HA coatings to achieve biological sealing for a long period in vivo.

Animals↗

PubMed2003

Global gene profiling analysis of mouse uterus during the oestrous cycle.

Many genes related to the cyclic changes of the uterus during the oestrous cycle have been identified using a one-by-one approach. In the present study, cDNA microarray technology was applied to investigate the global profile of gene expression of mouse uterus at the oestrous and dioestrous stages. At a certain stage of the oestrous cycle, the uteri of mature CD-1 mice (n=10) were removed, pooled and snap-frozen in liquid nitrogen. Total RNA was extracted to synthesize cDNA probes for microarray assay. By screening 8192 mouse genes and expressed sequence tags (ESTs), 51 upregulated and 51 downregulated genes were identified in oestrous uterus, of which 62 are well characterized and 40 are ESTs. The known genes were assigned to various gene categories according to their main function. The microarray was performed three times with three independent sets of uterine tissue pools. The results of northern blot analysis for small proline-rich protein 2 (Sprr2), 17beta-hydroxysteroid dehydrogenase type 2 (17betaHSD-2), high mobility group 2 (Hmg2), mitotic checkpoint component 2 (Mad2) and an EST AW555366 mRNA were consistent with that of microarray analysis. In situ hybridization was performed to localize the transcript of the EST AW555366. Most of the upregulated genes encode secreted immune-related proteins, proteinases and their inhibitors, indicating their potential involvement in sperm viability as well as capacitation. The downregulated genes mainly encode cell cycle-related factors, implying the active proliferation of uterus at dioestrus.

Animals↗

PubMed2002

Simultaneous improvement for four quality traits of Zhenshan 97, an elite parent of hybrid rice, by molecular marker-assisted selection.

"Zhenshan 97" is the female parent of a number of widely used hybrids for rice production in China. However, this line is of poor quality because of a high amylose content (AC), a hard gel consistency (GC) and a low gelatinization temperature (GT), together with a chalky endosperm. It had been determined that the three traits for cooking and eating quality, AC, GC and GT, are controlled by the Waxy locus and/or the tightly linked genomic region. In this study we improved the eating and cooking quality of Zhenshan 97 by introgressing the Waxy gene region from Minghui 63 (wx-MH), a restorer line, that has medium AC, soft GC and high GT. The wx-MH fragment was transferred to Zhenshan 97B by three backcrosses and one selfing, then from Zhenshan 97B to Zhenshan 97A by a cross and a backcross. Molecular marker-assisted selection was applied in the series to select for individuals carrying wx-MH, to identify recombination between the Waxy and flanking markers, and also to recover the genetic background of the recurrent parent. According to the marker genotypes, the improved versions of Zhenshan 97B and Zhenshan 97A, or Zhenshan 97B(wx-MH) and Zhenshan 97A(wx-MH), were the same as the originals except for the Waxy region of less than 6.1 cM in length. The selected lines and their hybrids with Minghui 63, or Shanyou 63(wx-MH), showed a reduced AC and an increased GC and GT, coupled with a reduced grain opacity. Field examinations of agronomic performance revealed that Zhenshan 97B(wx-MH) and Shanyou 63(wx-MH) were essentially the same as the originals except for a significant decrease in grain weight. The simultaneous improvement of AC, GA, GT and opacity, indicated that the Waxy region had major effects on the four quality traits. The improved versions of Zhenshan 97 A and B should be immediately useful in hybrid rice production.

Amylose↗

PubMed2001

Comparative computations of spike synchronization in visual cortex of cats.

In recent years it has been proposed that synchronous activity between neurons is a putative mechanism to bind together various trigger features of an image. Thus the measure of synchronization becomes an important issue since it may be an electrophysiological sign of visual perception. This paper describes and compares six techniques of computing synchronization strength, that is, the central peak of a cross-correlogram. Data were obtained in anesthetized cats prepared for electrophysiological recordings in a conventional fashion. Results indicate that: (1) eye fits are misleading. Visual inspection of cross-correlograms, may be interesting if one needs to estimate approximately synchronization strength and the presence of oscillations in the cross-correlograms, however it may be misleading if one wants to compare different cross-correlograms; (2) regression analysis to compare one method against the others yields a relatively poor correlation suggesting that methods are not directly comparable; (3) the sensitivity of each computational method is unequal. The results may indicate that some functional connections are either under- or over-evaluated depending upon the strategy employed to measure synchronization.

Animals↗

PubMed2001

Modulation of the synchronization between cells in visual cortex by contextual targets.

It has been suggested that synchronization of action potentials encodes diverse features of a single image. However, properties of the synchronization, which occurs on a time scale of approximately 1-5 ms, are still poorly understood. We have tested the modulation of synchronization by manipulating the contextual targets introduced in the surround of the receptive field. Experiments were carried out on anaesthetized cats prepared for multiunit and single-cell recordings in area 17. Initially, a patch of sine-wave drifting grating was positioned over the overlapping receptive fields of several neurons. If this coherent motion produced a significant synchronization in cross-correlograms, contextual targets were added. The first contextual stimuli were two sine-wave patches placed above and below the central compound receptive field. Only the contrast of contextual targets changed. Results show that the larger the differential contrast the higher the synchronization. The second contextual stimulus was a lateral shift of a sine-wave patch. Data show that the wider the distance between the central and peripheral patches the better the synchronization. Furthermore, results suggest that the synchrony pattern computed by cross correlating multiunit recordings from two sites differs when the cross correlation is carried out between individual units belonging to each multiunit recording. Together with our previous results it appears that synchronization is stimulus dependent and its strength increases with larger disparities included in the whole stimulating image.

Action Potentials↗

PubMed2001

[Analysis of QTL x environment interaction for rice panicle characteristics].

The development of molecular genetic linkage map has accelerated the identification and mapping of genomics regions controlling quantitative trait loci. A recombinant inbred line population derived from Zhenshan 97/Minghui 63 was grown in two years. Mixed linear model approach was used to jointly identify QTLs and QTL x environment interactions for five panicle characteristics. Ten, three, six, eight and seven QTLs were detected for spiketets per panicle, grains per panicle, seed setting, panicle length and panicle setting density, respectively. They collectively explained 29.13%, 19.2%, 29.46%, 26.39% and 35.76% of phenotypic variations for these traits, respectively. For the five traits, QTLs with increasing effects and decreasing effects could be simultaneously identified in high value parent and low value parent. QTLs for correlative traits clustering located in the similar regions. One QTL for panicle length, two QTLs for spikelets per panicle and three QTLs for seed setting performed significant interactions with environment. The contributions from interactions were slightly larger than that from the QTLs involved in the interactions. No QTL x environment interaction was detected for traits with high heritabilities such as grains per panicle and panicle setting density.

Chromosome Mapping↗

PubMed2001

[Studies of the correlation between fragile sites and giant panda's breeding problem].

An unique culture system has been established which can effectively indicate fragile sites induced by BrdU on giant panda chromosomes. After we cultured the lymphocytes of giant panda for 96 hours and treated it with low concentration of BrdU (10 micrograms/ml) for only a short time (4 hours), the areas of high-frequency-expressed fragile sites were successfully located on the centromeres of No. 2 and No. 12 chromosomes. After statistic analysis, we found that the frequency of fragile sites on No. 2 and No. 12 chromosomes are notably different among pandas. What is more important, the former is relative to giant pandas' breeding conditions and correlation coefficiency (r equals to -0.772). The result indicates that high frequency of fragile sites on No. 2 chromosome is unfavorable to giant panda's breeding and survival of filial generation.

Animals↗

PubMed2000

Stimuli outside the classical receptive field modulate the synchronization of action potentials between cells in visual cortex of cats.

It is proposed that various attributes of an image are bound neuronally when responsive units fire in synchrony. Our investigations describe the influences of the contextual stimuli upon the occurrence of synchronization, in anaesthetized cats. Once a significant synchronization was recorded in the cross-correlogram (XCRG) between evoked action potentials of two groups of neurons in response to a drifting sine-wave grating, additional gratings were positioned outside the compound receptive field. The synchronization strength was then measured in relation to the difference between the orientations of the central and peripheral gratings. In the majority of cases results indicate that the synchronization is facilitated with larger orientation disparities. Thus, our data support the notion that contrasting features of images facilitate synchrony of activity between neurons.

Action Potentials↗

PubMed1997

Importance of epistasis as the genetic basis of heterosis in an elite rice hybrid.

The genetic basis of heterosis was investigated in an elite rice hybrid by using a molecular linkage map with 150 segregating loci covering the entire rice genome. Data for yield and three traits that were components of yield were collected over 2 years from replicated field trials of 250 F(2:3) families. Genotypic variations explained from about 50% to more than 80% of the total variation. Interactions between genotypes and years were small compared with the main effects. A total of 32 quantitative trait loci (QTLs) were detected for the four traits; 12 were observed in both years and the remaining 20 were detected in only one year. Overdominance was observed for most of the QTLs for yield and also for a few QTLs for the component traits. Correlations between marker heterozygosity and trait expression were low, indicating that the overall heterozygosity made little contribution to heterosis. Digenic interactions, including additive by additive, additive by dominance, and dominance by dominance, were frequent and widespread in this population. The interactions involved large numbers of marker loci, most of which individually were not detectable on single-locus basis; many interactions among loci were detected in both years. The results provide strong evidence that epistasis plays a major role as the genetic basis of heterosis.

Journal Article↗

PubMed1997

[A study on the etiology and epidemiology of familial aggregation in arteriosclerotic cerebral infarction].

A case-control study including 214 pedigrees (109 cases and 105 controls) was carried out to explore the etiology of family aggregation of arteriosclerotic cerebral infarction in Yi-Xing city, March 1997. The results showed that the family member in both cases and control groups were comparable. The total prevalence rate of the first-degree relatives in cases was 5.12%, significantly higher than (1.63%) that noticed in controls, with chi 2 = 16.40 (P < 0.01). The same results was also found in their parents and siblings. Results from binominal distribution analysis showed that the number of cases in the families of arteriosclerotic cerebral infarction was significantly higher than the theortical range which indicated that there was significant familial aggregation in the occurance of arteriosclerotic cerebral infarction. Logistic regression model also showed that genetic factor was one of the most important risk factors in Xi-xing, Jiangsu. Dose-response was observed in this model. The heritability and the segregation ratio of arteriosclerotic cerebral infarction were the same as seen in other chronic diseases, such as coronary heart disease and esophageal cancer.

Adult↗