Guided growth of neurons and glia using microfabricated patterns of parylene-C on a SiO2 background

This paper describes a simple technique for the patterning of glia and neurons. The integration of neuronal patterning to Multi-Electrode Arrays (MEAs), planar patch clamp and silicon based ‘lab on a chip’ technologies necessitates the development of a microfabrication-compatible method, which will be reliable and easy to implement. In this study a highly consistent, straightforward and cost effective cell patterning scheme has been developed. It is based on two common ingredients: the polymer parylene-C and horse serum. Parylene-C is deposited and photo-lithographically patterned on silicon oxide (SiO₂) surfaces. Subsequently, the patterns are activated via immersion in horse serum. Compared to non-activated controls, cells on the treated samples exhibited a significantly higher conformity to underlying parylene stripes. The immersion time of the patterns was reduced from 24 to 3 h without compromising the technique. X-ray photoelectron spectroscopy (XPS) analysis of parylene and SiO₂ surfaces before and after immersion in horse serum and gel based eluant analysis suggests that the quantity and conformation of proteins on the parylene and SiO₂ substrates might be responsible for inducing glial and neuronal patterning.     

A high level of mixed Trypanosoma brucei infections in tsetse flies detected by three hypervariable minisatellites.

The issue of whether genetic exchange occurs at a significant frequency in natural populations of Trypanosoma brucei is controversial and one of the arguments against a high frequency has been the apparent lack of host infections with mixtures of trypanosome genotypes. Three minisatellite markers (MS42, CRAM, 292) within the coding regions of three genes have been identified and PCR based methods developed for detecting variation at these loci using crude lysates of infected blood as templates. Initial PCR analysis, using primers flanking the repeats, of DNA from two cloned stocks of the parasite has shown that two DNA fragments of different size were amplified from each stock. Analysis of the inheritance of these fragments into the F1 progeny of crosses demonstrated that the different size fragments were alleles that segregated in a Mendelian manner. The alleles at each of the three loci segregated independently consistent with their localisation on three different chromosomes. Analysis of a series of cloned isolates from tsetse flies showed that these loci were highly variable giving heterozygosities of 94% and the identification of 12 distinct alleles in a sample of 17 cloned isolates. In order to determine whether isolates are heterogeneous in terms of trypanosome genotype, the allelic variation at these three loci was examined in uncloned samples from tsetse flies isolated in Kiboko, Kenya and Lugala, Uganda. A significant proportion of the isolates (36% in Lugala and 47% in Kiboko) contained more than two alleles at one or more of the loci thus demonstrating that a high proportion of tsetse flies were infected with more than one genotype of trypanosomes. This was established, unequivocally, for two isolates by generating a series of cloned trypanosome lines from each and determining the genotype of each clone; one isolate (927) contained seven different genotypes with a high proportion of the possible combinations of alleles at each locus. These results indicate the possibility of frequent genetic exchange in the field, they imply that a significant proportion of mammalian hosts must contain mixtures of different trypanosome genotypes and they demonstrate the advantages of using minisatellite markers for the analysis of the population structure of T. brucei.     

糖稳态调节细胞定向分化的基因改造方案探讨

目的:探索糖稳态调节细胞定向分化的基因改造方案思路.方法:①研究构建的解除干细胞分化抑制状态的信号传导与转录激活因子-3(STAT-3)基因载体,检测其介导目的基因感染ARIP等细胞基因表达;②研究构建的活化配体DL诱导N信号、在"旁侧抑制"过程中扮演重要角色的Kuzbanian(KUZ)基因载体在转基因小鼠表达后糖稳态调节细胞的分化.结果:在完成的STAT-3腺病毒基因载体生产了腺病毒,用带有目的基因的腺病毒对ARIP靶细胞进行感染,3 d后,荧光显微镜观察时,活细胞、固定液固定细胞均看到了构建基因中绿色荧光蛋白成功、高效的阳性表达报告.在完成的Kuzbanian(KUZ)基因载体构建、转基因、动物模型、小鼠品系鉴定后,用非放射性原位杂交实验对胰腺靶细胞的mRNA进行检测,获得了预期的阳性结果.结论:通过用某些分化抑制性基因的显性失活形式(DN)竞争性预先解除干细胞分化的抑制状态,然后再定向分化诱导使之朝向期望的目标细胞方向分化,可能是糖稳态细胞定向分化的可行途径之一.     

Hyperbilirubinemia, hypocarbia and periventricular leukomalacia in preterm infants: relationship to cerebral palsy

This study comprised 103 preterm infants with a gestational age less than 33 weeks who were born in Tampere University Hospital and who were followed up to two years of age. Sixty-four perinatal variables were compared to ultrasound findings in the neonatal period and neurologic handicap at the age of two years. Duration of hypocarbia (PCO2 < or = 30 mmHg) during the first 72 h and hyperbilirubinemia (the mean level of serum total bilirubin) at three days of age were independently and significantly related to periventricular leukomalacia, but not directly to cerebral palsy. The only perinatal variables related independently and significantly to cerebral palsy at two years of age were periventricular leukomalacia and ventriculomegaly. According to these results, periventricular leukomalacia was the main predictor of cerebral palsy in preterm infants. In addition to hypocarbia, hyperbilirubinemia may also be involved in the pathogenesis of extensive (severe cystic) periventricular leukomalacia.     

Quantifying the contribution of vision to speech perception in noise

The intelligibility of sentences presented in noise improves when the listener can view the talker's face. Our aims were to quantify this benefit, and to relate it to individual differences among subjects in lipreading ability and among sentences in lipreading difficulty. Auditory and audiovisual speech-reception thresholds (SRTs) were measured in 20 listeners with normal hearing. Sixty sentences, selected to range in the difficulty with which they could be lipread (with vision alone) from easy to hard, were presented for identification in white noise. Using the ascending method of limits, the SRT was defined as the lowest signal-to-noise ratio at which all three 'key words' in each sentence could be identified correctly. Measured as the difference in dB between auditory-alone and audiovisual SRTs, 'audiovisual benefit' averaged 11 dB, ranging from 6 to 15 dB among subjects, and from 3 to 22 dB among sentences. As predicted, audiovisual benefit is a measure of lipreading ability. It was highly correlated with visual-alone performance (n = 20, r = 0.86, P less than 0.01). Likewise, those sentences which were easiest to lipread gave a higher measure of benefit from vision in audiovisual conditions than did sentences that were hard to lipread (n = 60, r = 0.92, P less than 0.01). The results establish the basis of an efficient test of speech-reception disability in which measures are freed from the floor and ceiling effects encountered when percentage correct is used as the dependent variable.     

Cloxacillin absorption and disposition in cystic fibrosis

Because of reports of lowered antibiotic serum concentrations in patients with cystic fibrosis (CF), a bioavailability and pharmacokinetic study of cloxacillin was conducted in 12 control and 16 patients with CF after intravenously and orally administered doses of cloxacillin 25 mg/kg. The patients had mild to moderate CF and were in stable condition. Significantly lower serum concentrations in CF were a result of a 78% increase in total body clearance (P less than 0.005) and a 38% increase in the apparent volume of distribution (P less than 0.025). The bioavailability in CF (0.50) was not significantly different than in controls (0.38), but more variability was seen in the group with CF. After the intravenously given dose the fraction of cloxacillin excreted in the urine unchanged was similar in controls (0.644) and patients with CF (0.547). Compared with that in the control subjects, the mean renal clearance in patients with CF was 30% greater (P less than 0.10) and the nonrenal clearance was 144% greater (P less than 0.07). Enhanced nonrenal clearance explains most of the demonstrated difference between serum concentrations in controls and patients with CF after identical weight-adjusted doses. The data suggest enhanced cloxacillin biotransformation in CF.