Factors affecting engraftment of allogeneic hematopoietic stem cells after reduced-intensity conditioning

Several factors influence the engraftment of allogeneic hematopoietic stem cells (HSC). Recently, there has been increased utilization of transplant-conditioning regimens that use reduced doses of chemotherapy and radiation that are considered to be non-myeloablative. These non-myeloablative (or reduced-intensity) allogeneic HSC transplants (RIST) decrease early post-transplant complications, but they are associated with higher incidences of mixed chimerism and graft rejection compared with transplantation after myeloablative condition-ing. RIST provides a unique opportunity to study allogeneic HSC engraftment. In particular, host immune status and stem cell graft composition have emerged as important factors affecting engraftment after RIST Based on these observations, it has been hypothesized that conditioning regimens and allograft composition can be tailored to an individual patients immune and disease status prior to transplant.     

Lorentz force electrical impedance tomography

This article describes a method called Lorentz Force Electrical Impedance Tomography. The electrical conductivity of biological tissues can be measured through their sonication in a magnetic field: the vibration of the tissues inside the field induces an electrical current by Lorentz force. This current, detected by electrodes placed around the sample, is proportional to the ultrasonic pressure, to the strength of the magnetic field and to the electrical conductivity gradient along the acoustic axis. By focusing at different places inside the sample, a map of the electrical conductivity gradient can be established. In this study, experiments were conducted on a gelatin phantom and on a beef sample, successively placed in a 300 mT magnetic field and sonicated with an ultrasonic transducer focused at 21 cm emitting 500 kHz bursts. Although all interfaces are not visible, in this exploratory study a good correlation is observed between the electrical conductivity image and the ultrasonic image. This method offers an alternative to detecting pathologies invisible to standard ultrasonography.     

Factors affecting the proliferation and differentiation of clonogenic hematopoietic stem cells in vitro

The characteristics of hematopoietic factors modulating the growth of clonogenic pluripotent stem cells (PSC) in culture (i.e., CFU-GEMM) are examined. The chemical and biologic properties of "burst-promoting activity" (BPA) are compared with those of the lymphokine interleukin-3 (Il-3). The preponderance of the data available suggests that the active moiety of each of these growth factors may be chemically identical since both BPA and purified Il-3 are capable of supporting the growth of PSC in vitro. The effects of hemin on the growth of CFU-GEMM are also examined experimentally. The results show conclusively that, in the absence of exogenous (BPA), hemin is also capable of supporting the growth of CFU-GEMM in culture and to a level that is consistently higher than that of BPA alone. It is therefore suggested that hemin is capable of augmenting the growth of GEMM colonies in vitro in conjunction with BPA/Il-3. However, the in situ role of each of these "candidate" regulators of hemopoiesis remains largely unknown.     

Effect of sow parity on vaginal electrical impedance

The influence of sow parity on the changes of vaginal impedance after weaning was examined. Sows were monitored twice a day for oestrus via exposure to a sexually mature boar. The criterion for confirmation of ovulation was an increase in plasma progesterone levels above 12.5 nmol l(-1) 8 and 12 days after oestrus onset. The impedance measurements were carried out by a four-terminal method. In sows of all parities, the vaginal impedance decreased gradually after weaning (P < 0.01) and increased during oestrus (P < 0.01). No significant impedance changes were observed thereafter. The vaginal impedance was higher in sows above 6 parities than in sows from parities 1 to 5 from the beginning of oestrus to 14 days after oestrus onset. The impedance was also higher in sows of parity 6 than in sows of parity 1 from the beginning of oestrus to 14 days after oestrus onset and in sows from parities 2 to 5 than in sows of parity 1 from 2 to 4 days after oestrus onset. The difference in average impedance values between sows above 6 parities and sows of parity 1 was two-fold in oestrus compared to the luteal phase. In all measured places of the vagina from the cervix to 6 cm from the cervix, a similar significant increase of impedance was observed during oestrus. The results indicate that the parity of sows affects the electrical impedance of vaginal mucosa measured by means of a four-terminal method.     

Studies on the electrical properties of a single plant cell; internodal cell of Nitella flexilis

Impedance changes of single plant cells of Nitella flexilis were studied under different environmental conditions. With the analysis presented changes in resistance of the protoplasmic membrane and of cell sap can be studied independently and simultaneously. Under "transcellular osmosis," the resistance of the protoplasmic membrane and of the cell sap increase at the part of the cell where water enters, while they decrease where water goes out. Ethanol of low concentration (below 8 per cent) first decreases and later increases the resistance of the protoplasmic membrane. Concentrated ethanol (over 10 per cent), however, brings about a large decrease in resistance of the protoplasmic membrane. Its time course is not simple, but undulatory changes occur. When ethanol is applied to one part of the cell, the resistance of the protoplasmic membrane shows a different type of change, which may be attributed to the local osmotic effect of ethanol; injury generally occurs with comparatively low concentration. Methanol, ethanol, and propanol have almost the same effect upon the cell, while butanol is toxic at the same concentration. When the cell dies, the resistance of the protoplasmic membrane decreases greatly, while the resistance of the cell sap increases to a level (several hundred kilo ohms or more), expected when external solution and cell sap are freely mixed with each other.     

Factors affecting flavonoids absorption

In experiments on rats, some of the factors affecting flavonoids absorption (solubility, glycosylation and nutritional status: fasted and not-fasted animals) were examined. Administration of quercetin with different solubilization degree showed no direct correlation between the quercetin absorption extent and solubility, i.e. despite 3 orders of difference in solubilization degree, the extent of absorption varied only about 4-fold. Absorption comparison of genistein and its glycoside genistin showed no difference in the extent of absorption; however, aglycone, in contrast to glycoside, was absorbed already from the rat stomach. Conjugation patterns (sulfation and glucuronization) of genistein metabolites demonstrated that the plasma of animals fasted prior to isoflavone administration contained significantly more sulfates and less glucuronides and mixed sulfates/glucuronides conjugates than the plasma of non-fasted animals.     

Factors affecting microfungal diversity

Species diversity of microfungal communities in decaying oak leaves was analyzed based on the hyphal growth rates of the component species. Dominant species of a low-diversity community had faster hyphal growth rates, while dominant species of a high-diversity community had slower growth rates. These results implies that when the faster growing species became dominant, these species exhausted resources rapidly during the initial stage of fungal colonization. This exclusive utilization of resources made it impossible for other species to invade the substratum and led to a low diversity. Hyphal growth rates played an important role in determining the diversity of microfungal communities.     

Factors affecting PCR-mediated recombination

In the past decade, polymerase chain reaction (PCR) has become an important tool for the identification of previously unknown microorganisms and the analysis of environmental microbial diversity. Several studies published during recent years, however, have demonstrated that products obtained after PCR using Taq or Vent DNA polymerases will contain hybrid molecules when several homologous target sequences such as multigene families, alleles, or RNA viruses are co-amplified. In this report, we examined the recombination frequency and the extent of template switching during PCR using Taq, Pfu and RTth/Vent DNA polymerases. As a test system we constructed a series of plasmids carrying between one and three frame shift mutations in the gene coding for the protease subtilisin or deletions of approximately 100 bp in the lacZ alpha. Highest recombination frequencies were observed when these mutants were co-amplified with Taq followed by RTth/Vent DNA polymerases. Pfu DNA polymerase displayed no discernable recombination activity under normal PCR conditions. Data also suggest that in vivo repair of heteroduplex DNA molecules in Escherichia coli by a RecA-independent mechanism, perhaps the mismatch repair, results in the formation of chimeric molecules. Using Bacillus subtilis as the host, however, can significantly diminish non-PCR RecA-independent in vivo recombination, owing to the fact that transforming DNA molecules enter B. subtilis as single strands. Combined, these results suggest that using Pfu DNA polymerase for amplification and B. subtilis as the host for transformation may significantly reduce chimera formation.     

恶梦的影响因素研究

恶梦是与睡眠相关的常见心理现象.目前,恶梦的概念仍具有争议,但恶梦与心理健康的关系,已经引起了研究者广泛关注.恶梦的病因学研究表明,恶梦与遗传及生理因素有关;恶梦具有人格倾向性,应激与创伤因素是其产生的主要原因,与分裂症等精神疾病高度相关;恶梦与睡眠呼吸相关因素关系不是很明确;恶梦与多巴胺受体激动剂等药物显著相关,恶梦产生的其他因素研究尚待发现.然而这些因素与恶梦的因果关系并不确定,各因素之间的关系及作用机制有待进一步研究.未来的研究可以改进研究方法,扩大研究对象,进行纵向研究等.     

Factors affecting onset of puberty

In humans, foetal and early postnatal growth failure may have persistent consequences for growth and pubertal development in later life. During this period, the developing organs are still plastic to change their function, which may have long-lasting effects. At the time of onset of puberty, acute factors may also interfere with pubertal development. Malnutrition, as seen in anorexic patients, and chronic diseases with malabsorption or diseases with systemic effects result in a delayed onset of puberty. We have observed an earlier onset of puberty in girls with low birth weight; menarcheal age also tended to be earlier. In boys, a low birth weight tended to be associated with a later development. Two rat models with growth failure based on perinatal malnutrition have been examined, one with intrauterine growth retardation (IUGR) by ligation of the uterine arteries and one with postnatal food restriction (FR) by increasing the litter size postnatally. In both models, the rats had a persistent postnatal growth failure. The onset of puberty in female rats, defined by vaginal opening, was delayed only in the IUGR group. Despite a significantly lower weight, there was no difference in the timing of puberty onset in the FR group. In IUGR rats, the ovaries had fewer follicles, while FR rats had a normal number of follicles but an abnormal maturation pattern. In male rats, both models showed a delayed onset of puberty, defined by the balano-preputial separation, as well as impaired testicular function, shown by decreased testosterone levels. These data indicate that early malnutrition during a critical developmental time window may have long-lasting effects on pubertal development, including gonadal maturation in both humans and rats.     

Characterization of three-dimensional tissue cultures using electrical impedance spectroscopy

Electrical impedance spectroscopy was used to characterize the cell environment of multilayered cell cultures (MCCs), a culture system in which cells are grown on a permeable support membrane to form a thick disc of cells with tumor-like properties. Cultures were grown using SiHa tumor cells as well as V79 wild-type cells and V79/DOX cells cultivated to exhibit multidrug resistance. Electrical impedance measurements were made on MCCs over a frequency range of 0. 1 kHz to 1 MHz. Data analysis using a simple electrical model for the cell environment yielded estimates for parameters related to the intra- and extracellular resistance and net membrane capacitance, which were then related to MCC thickness. The extracellular fraction and tortuosity of the MCCs were determined in separate experiments where the rate of diffusion and the equilibrium level of C14-inulin, which does not penetrate the cell membrane, was measured within MCCs. Impedance measurements predicted the barrier to diffusion posed by the extracellular space of MCCs to be roughly two times greater than that inferred from the C14-inulin experiments. However, the relative ranking of the three cell types used to grow MCCs was similar for the two methods. Results indicate that impedance spectroscopy is well suited for use in characterizing the MCC cell environment, offering a fast, nondestructive method for monitoring cell culture growth and integrity.