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71.
K. Rothfels  R. Nambiar 《Chromosoma》1975,52(3):283-292
Prosimulium multidentatum (Twinn) has three metacentric pairs in its chromosome complement. All six arms are individually identifiably in polytene nuclei. XY1 males are heterozygous for a small basal non-conformity in section 59 of the non-pairing sex differential segments which extends from sextion 58 to section 62 of the IIL arm. XY2 males carry an additional large heterozygous inversion in the center of this same arm. Meiosis is chiasmate in both kinds of male. In XY2 individuals 14.2% of the pachytene nuclei show reverse loop pairing and 12.5% of the anaphase I cells form bridge-fragment configurations. A majority of these bridges persist into second division and 7.1% double sized spermatids are formed. No pachytene loops or anaphase bridges were found in XY1 males. It is concluded therefore that the bridges and fragments of XY2 males result from chiasma formation within the Y2 inversion.  相似文献   
72.
Uptake of Zn65 from dry soil by plants   总被引:1,自引:0,他引:1  
Summary Absorption of Zn65 by plant roots from a layer of dry top soil (suction > 15 bar) was measured using a technique that obviated water stress in the plant.Roots growing through the dry layer absorbed significant amounts of Zn65 provided they absorbed water from lower depths. Mucilage accumulated around the roots in the dry soil and may have facilitated ion transfer in the immediate vicinity of the root. The ability of roots to grow in dry soil and to absorb Zn65 varied between plant species.  相似文献   
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The establishment of the vertebrate body plan involves patterning of the ectoderm, mesoderm, and endoderm along the dorsoventral and antero-posterior axes. Interactions among numerous signaling molecules from several multigene families, including Wnts, have been implicated in regulating these processes. Here we provide evidence that the zebrafish colgate(b382) (col) mutation results in increased Wnt signaling that leads to defects in dorsal and anterior development. col mutants display early defects in dorsoventral patterning manifested by a decrease in the expression of dorsal shield-specific markers and ectopic expression of ventrolaterally expressed genes during gastrulation. In addition to these early patterning defects, col mutants display a striking regional posteriorization within the neuroectoderm, resulting in a reduction in anterior fates and an expansion of posterior fates within the forebrain and midbrain-hindbrain regions. We are able to correlate these phenotypes to the overactivation of Wnt signaling in col mutants. The early dorsal and anterior patterning phenotypes of the col mutant embryos are selectively rescued by inactivation of Wnt8 function by morpholino translational interference. In contrast, the regionalized neuroectoderm posterioriorization phenotype is selectively rescued by morpholino-mediated inactivation of Wnt8b. These results suggest that col-mediated antagonism of early and late Wnt-signaling activity during gastrulation is normally required sequentially for both early dorsoventral patterning and the specification and patterning of regional fates within the anterior neuroectoderm.  相似文献   
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We report the development of a multichannel microscopy for whole‐slide multiplane, multispectral and phase imaging. We use trinocular heads to split the beam path into 6 independent channels and employ a camera array for parallel data acquisition, achieving a maximum data throughput of approximately 1 gigapixel per second. To perform single‐frame rapid autofocusing, we place 2 near‐infrared light‐emitting diodes (LEDs) at the back focal plane of the condenser lens to illuminate the sample from 2 different incident angles. A hot mirror is used to direct the near‐infrared light to an autofocusing camera. For multiplane whole‐slide imaging (WSI), we acquire 6 different focal planes of a thick specimen simultaneously. For multispectral WSI, we relay the 6 independent image planes to the same focal position and simultaneously acquire information at 6 spectral bands. For whole‐slide phase imaging, we acquire images at 3 focal positions simultaneously and use the transport‐of‐intensity equation to recover the phase information. We also provide an open‐source design to further increase the number of channels from 6 to 15. The reported platform provides a simple solution for multiplexed fluorescence imaging and multimodal WSI. Acquiring an instant focal stack without z‐scanning may also enable fast 3‐dimensional dynamic tracking of various biological samples.   相似文献   
78.
The ability of several chemical soil N availability indexes to predict the N supplying capability (NSC) of soils to maize in the field was evaluated in 49 field experiments over 3 years in Pennsylvania. Two recently proposed indexes based on the amount of NH4 + released by treating soil with 2 M KCl at 100°C for 4 hr or with a pH 11.2 phosphate-borate buffer for 8 min were not good predictors of NSC (r=0.484 and 0.254, respectively). The absorbance of a 0.01 M NaHCO3 extract at 260 nm was also poorly correlated with field-measured NSC (r=0.412). The pre-sidedress soil NO3 test (PSNT), the soil NO3 concertration in the surface 20 cm of soil at planting, and the UV absorbance at 200 nm of a 0.01 M NaHCO3 extract of at planting soils were all moderately well correlated with NSC (r=0.672, 0.750, and 0.737, respectively). The latter two indexes are very simple, rapid, and inexpensive to perform and offer the possibility of improving the prediction of NSC in heavily manured fields. Paper No 8211 of the Journal series of The Pennsylvania Agricultural Experimental Station.  相似文献   
79.
Background  Seizures were observed in a 16-year old male Guyanese squirrel monkey with a history of inappetence and weakness.
Methods and results  Complete blood count, biochemical profile, and urinalysis indicated systemic disease. Nematode larvae were detected in the feces. Cerebrospinal fluid (CSF) analysis revealed leukocytes and gram-positive cocci. Staphylococcus aureus was isolated from the CSF. Histopathological evaluation revealed systemic lesions with inflammation and nematodes in the small and large intestine.
Conclusion  This is the first report describing spontaneous staphylococcal CNS infection in a squirrel monkey.  相似文献   
80.
Paraoxonase 1 (PON1) has been described as an efficient catalytic bioscavenger due to its ability to hydrolyze organophosphates (OPs) and chemical warfare nerve agents (CWNAs). It is the future most promising candidate as prophylactic medical countermeasure against highly toxic OPs and CWNAs. Most of the studies conducted so far have been focused on the hydrolyzing potential of PON1 against nerve agents, sarin, soman, and VX. Here, we investigated the hydrolysis of tabun by PON1 with the objective of comparing the hydrolysis potential of human and rabbit serum purified and recombinant human PON1. The hydrolysis potential of PON1 against tabun, sarin, and soman was evaluated by using an acetylcholinesterase (AChE) back-titration Ellman method. Efficient hydrolysis of tabun (100 nM) was observed with ∼25-40 mU of PON1, while higher concentration (80-250 mU) of the enzyme was required for the complete hydrolysis of sarin (11 nM) and soman (3 nM). Our data indicate that tabun hydrolysis with PON1 was ∼30-60 times and ∼200-260 times more efficient than that with sarin and soman, respectively. Moreover, the catalytic activity of PON1 varies from source to source, which also reflects their efficiency of hydrolyzing different types of nerve agents. Thus, efficient hydrolysis of tabun by PON1 suggests its promising potential as a prophylactic treatment against tabun exposure.  相似文献   
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