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Liesbeth Vossaert Imen Chakchouk Roni Zemet Ignatia B. Van den Veyver 《黑龙江环境通报》2021,41(10):1202-1214
Investigators have long been interested in the natural phenomenon of fetal and placental cell trafficking into the maternal circulation. The scarcity of these circulating cells makes their detection and isolation technically challenging. However, as a DNA source of fetal origin not mixed with maternal DNA, they have the potential of considerable benefit over circulating cell-free DNA-based noninvasive prenatal genetic testing (NIPT). Endocervical trophoblasts, which are less rare but more challenging to recover are also being investigated as an approach for cell-based NIPT. We review published studies from around the world describing both forms of cell-based NIPT and highlight the different approaches’ advantages and drawbacks. We also offer guidance for developing a sound cell-based NIPT protocol. 相似文献
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877.
The extent to which exposure to environmental hypoxia (PO2=8, 6, and 4 kPa, approximately 40%, 30%, and 20% saturation, respectively) resulted in an increase in the concentration of the respiratory pigment haemocyanin ([Hc]) in individuals of the Norway lobster Nephrops norvegicus depended crucially on the initial [Hc] as well as the intensity of the hypoxia itself. While mean [Hc] did increase with decreasing PO2 (and the variation decreased), for individuals with relatively high initial [Hc] there was no change or even a decrease observed. The greatest hypoxia-related increases in [Hc] were observed in the individuals with the lowest initial [Hc]. Consequently the notion of an 'optimum' [Hc] for a given level of oxygenation was postulated. The changes in [Hc] recorded took place over a considerably shorter time scale (hours rather than days) than has been observed in previous studies. It was not possible to correlate environmental PO2 and median [Hc] in the field. However, it was interesting that the [Hc] frequency distribution curve for lobsters collected from a site that had been markedly hypoxic (PO2=8.0 kPa, approximately 40% saturation) until a few days before sampling was almost exactly the same shape (i.e. leptokurtic) and position (i.e. similar median) to that obtained when lobsters were exposed to PO2=8.0 kPa in the laboratory. Although it would have been desirable to investigate the effect of hypoxia on the frequency distribution of a physiological trait, in this case [Hc], it was not possible due to insufficient sample size, even though the sample sizes employed were considerably larger than those normally used in physiological investigations. 相似文献
878.
G. Pecl 《Marine Biology》2001,138(1):93-101
A major difficulty confronting the determination of cephalopod reproductive life history is assessing over what portion of
the life span an individual is reproductively mature and actively depositing eggs. This paper assesses the potential of the
tropical Sepioteuthis lessoniana and two genetic types of the temperate Sepioteuthis australis, to spawn multiple batches of eggs at discrete times throughout the adult life span. This is achieved by histological examination
of the ovarian gametogenic cycle and detailed morphological assessments of the reproductive system, in conjunction with other
biological information. The genetic type of S. australis found at the northern limits of its Australian distribution showed evidence of a high correlation between body size and quantity
of mature eggs, suggesting that eggs may be accumulating to be laid in a single batch. Although maturation was also a size-related
process in S. lessoniana and Tasmanian S. australis, oviduct size was not correlated with body weight in mature females, which is indicative of multiple spawning. Further supporting
evidence includes relatively low gonadosomatic indices, the heavier weight of the ovary relative to the oviduct, and the feeding
activity of mature animals. Mature S. lessoniana and S. australis individuals were present at each location over very wide age and size ranges. In Tasmanian waters, there were distinct seasonal
differences in the reproductive biology of S. australis. Summer-caught individuals had much higher gonadosomatic indices and may have been laying larger batches of eggs compared
with winter-caught individuals. Summer-caught females also showed a negative correlation between egg size and egg number within
the oviduct, suggesting that some individuals were producing fewer, larger eggs and others many smaller eggs. Evidence suggests
that considerable flexibility is inherent in the reproductive strategy of both S. lessoniana and S. australis.
Received: 11 May 2000 / Accepted: 12 September 2000 相似文献
879.
The use of transparency as camouflage in the epipelagic realm is complicated by the presence of ultraviolet radiation, because
the presence of UV-protective pigments decreases UV transparency and may reveal transparent zooplankton to predators and prey
with UV vision. During July 1999, September 1999, and June 2000, transparency measurements (from 280 to 500 nm) were made
on living specimens of 15 epipelagic (collection depth: 0–20 m, average: 11 ± 1 m) and 19 mesopelagic (collection depth: 150–790 m,
average: 370 ± 40 m) species of transparent zooplankton from Oceanographer Canyon and Wilkinson Basin in the Northwest Atlantic
Ocean. In addition, measurements of downwelling irradiance (from 330 to 500 nm) versus depth were made. The tissues from epipelagic
zooplankton had lower UV transparency than those from mesopelagic zooplankton, while the average visible transparency (at
480 nm) of the two groups was not significantly different. Percent transparency was positively correlated with wavelength
over most of the measured range, with a rapid decrease below a certain cutoff wavelength. In mesopelagic tissues, the cutoff
wavelength was generally 300 nm. In epipelagic tissues, the cutoff wavelength was between 300 and 400 nm. Twelve out of 19
epipelagic tissues had transparencies at 320 nm that were half or less than their 480 nm transparency values, versus only
4 out of 21 mesopelagic tissues. The effects of UV absorption on UV visibility and minimum attainable depth were modeled using
contrast theory and the physics of light attenuation. Because UV absorption was generally significantly greater in the UVB
than in the UVA spectrum (where UV vision occurs), and because the highest UV absorption was often found in less transparent
individuals, its modeled effects on visibility were slight compared to its effects on minimum attainable depth.
Received: 14 April 2000 / Accepted: 16 November 2000 相似文献
880.
Effects of environmental parameters on the oxygen consumption of four marine invertebrates: a comparative factorial study 总被引:1,自引:0,他引:1
The oxygen consumption curves of two decapod crustaceans (Palaemon serratus, Penaeus monodon) and two prosobranch molluscs (Trunculariopsis trunculus, Nassarius mutabilis) have been detected in the entire pO2 interval from 0 to 160 mmHg, under different conditions of temperature and salinity. From the experimental curves, physiological
parameters such as the initial oxygen consumption velocity, the Q
10 values and the oxygen independence indices have been measured. The latter parameters have been obtained using normalised
plots which allow their better evaluation. The effects of temperature, salinity and oxygen partial pressure on the oxygen-consumption
features have been studied using a factorial experimental plan which allows measurement of the effects of each experimental
variable as well as the effects of synergistic interactions between different variables.
Received: 27 March 2000 / Accepted: 13 November 2000 相似文献