Development of germ cell transplants in mice

Development of spermatogonial transplants was studied by using 5- to 6-wk-old histocompatible mice as cell donors and sterile (W-locus) mice as recipients. Groups of animals transplanted with germ cell suspensions were killed at 10 min, 9 h, 24 h, 1 wk, 1 mo, 2 mo, and 3 mo along with age-matched "start" and "end" W-locus controls. Weight of testes increased significantly at 24 h through 3 mo after germ cell transplantation, suggesting that the infused cells quickly stimulated organ function. Small clones of young spermatocytes were evident at 1 mo and sperm at 2 mo. The percentage of tubular profiles containing active spermatogenesis originating from spermatogonia increased with time (0.8% at 1 mo, 8.9% at 2 mo, and 28.2% at 3 mo). Most transplanted germ cells were eliminated from the seminiferous epithelium through phagocytosis by Sertoli cells that occurred primarily before 1 wk, although some pachytene cells were able to proceed through meiosis by 1 wk. A variety of abnormal features are described that characterize developing spermatogenesis in the transplanted testis. Spermatogenesis improved quantitatively and qualitatively with time although released sperm were frequently engulfed by intratubular macrophages and Sertoli cells. A quantitative analysis of spermatogenesis from transplanted germ cells will serve as a basis for improving spermatogonial transplant efficiency.     

Duration of Borrelia burgdorferi infectivity in white-footed mice for the tick vector Ixodes scapularis under laboratory and field conditions in Ontario

The duration of Borrelia burgdorferi infectivity in white-footed mice (Peromyscus leucopus) experimentally inoculated or infested with infected Ixodes scapularis nymphs was evaluated. Infectivity was assessed by infesting these mice with unfed I. scapularis larvae at 7, 21, 35 and 49 days post-inoculation (DPI) or post-infestation (PI). At 7 DPI, B. burgdorferi was transmitted from 18 of 24 syringe-inoculated mice and all three tick-infected mice to I. scapularis larvae which fed upon them. However, at 21, 35 and 49 DPI, significantly fewer mice were infective. Borrelia burgdorferi was isolated from tissues of 14 of 22 syringe-inoculated mice about 56 DPI, and from all three tick-infected mice. However, the level of agreement between xenodiagnosis and bacterial culture was no greater than would be expected by chance alone. We also determined if B. burgdorferi infectivity of mice varied in relation to periods of tick feeding in the field. White-footed mice were trapped during April, July and August 1993 from two habitats on Long Point peninsula (Ontario, Canada), where B. burgdorferi is endemic. Mice from each habitat were infested with laboratory-reared I. scapularis larvae. Ticks from each mouse were subsequently examined by immunofluorescent assay for B. burgdorferi infection and mice were cultured for B. burgdorferi. None of 3577 I. scapularis larvae fed on 62 mice captured within the cottonwood dune habitat were infected with B. burgdorferi, although it was isolated from six of these mice. Within the maple forest habitat, 0/24, 8/21 (38%) and 1/21 (5%) mice transmitted B. burgdorferi to I. scapularis larvae during April, July and August, respectively. Most mice from the maple forest with B. burgdorferi-positive tissues (14/21) were collected during July, although the level of agreement between xenodiagnosis and tissue culture was poor. Because B. burgdorferi infectivity in mice appears to be of short duration, overwintered I. scapularis larvae and nymphs may have to feed upon infected hosts at the same time of year in order for a cycle of B. burgdorferi infection to be maintained on Long Point. Infected I. scapularis nymphs, rather than persistently infected vertebrate hosts, likely serve as the overwintering "reservoir" for B. burgdorferi on Long Point.     

Fast spatial autocorrelation

Knowledge and Information Systems - Physical or geographic location proves to be an important feature in many data science models, because many diverse natural and social phenomenon have a spatial...     

End Group Tuning in Acceptor–Donor–Acceptor Nonfullerene Small Molecules for High Fill Factor Organic Solar Cells

High fill factors have only recently become commonplace in nonfullerene‐based organic solar cells, with the balance of charge carrier mobilities often cited as the contributing factor. Here an end‐group modification to a commonly used nonfullerene acceptor (O‐IDTBR) is reported, in which the rhodanine end groups are replaced with dicyano moieties, resulting in the acceptor O‐IDTBCN. This new acceptor affords significant improvement in the fill factor (73%) and photocurrent (19.8 mA cm^?2) in organic solar cells with the low bandgap polymer PTB7‐Th. A narrowing of the bandgap, as a result of greater push–pull hybridization, allows complementary absorption to the donor and thus improved photon harvesting. Additionally, the measurement of charge carrier mobilities and lifetimes in both systems reveal that the PTB7‐Th:O‐IDTBCN blend possesses more balanced charge carrier mobilities, and longer lifetimes. Morphology studies reveal a slightly greater degree of molecular mixing of the O‐IDTBCN when blended with PTB7‐Th, despite the greater and more balanced charge carrier mobilities in this blend.     

Gastrointestinal immune responses in HIV infected subjects

Biliary atresia (BA) is characterized by luminal obstruction of the extrahepatic bile duct with fibrous remnants. The authors reviewed ultrasonographic examinations of the fibrous tissue in the bifurcation of the portal vein at the porta hepatis and identified the triangular- or tubular-shaped echogenic density, the so-called "triangular cord" (TC), in the vicinity of the portal vein on a transverse or longitudinal scan. In this prospective study, the authors investigated whether TC was useful in the noninvasive diagnosis of biliary atresia in 18 infants who had persistent neonatal jaundice. This was done by comparing the ultrasonographic examination with the histopathologic examination (HPE) of liver specimens obtained from a needle biopsy. The TC was identified in nine patients, all of whom were confirmed to have BA by HPE. The TC was not observed in the other nine patients, who had neonatal hepatitis (NH). The mean size of the TC was 13 mm (wide) x 6 mm (thick) (width range, 5 to 21 mm; thickness range, 4 to 12 mm). The diagnosis of BA was confirmed at the time of Kasai hepatoportojejunostomy in eight of the nine patients whose TC was noted by ultrasonography (US). The other patient was discharged because his parents refused the operation; he died of liver failure at 15 months of age. The nine patients with absent TC were treated medically for NH. Eight of them improved clinically. The other, diagnosed to have NH by needle and wedge liver biopsies, was reexamined 40 days after the initial examination because of worsening jaundice. A 18 x 12-mm TC was visualized ultrasonographically. Additionally, a percutaneous liver biopsy specimen showed BA with severe portal fibrosis and ductal proliferation. The patient underwent a Kasai hepatoportoenterostomy. On the basis of these results, the authors conclude that TC is a very specific ultrasonographic finding, representing the fibrous cone at the porta hepatis, and is a useful tool in the noninvasive diagnosis of BA. However, early exploration or close US follow-up is recommended for any patient suspected of having BA clinically, even if a liver biopsy confirms the NH.     

Parameters Influencing Charge Separation in Solid‐State Dye‐Sensitized Solar Cells Using Novel Hole Conductors

Solid‐state dye‐sensitized solar cells employing a solid organic hole‐transport material (HTM) are currently under intensive investigation, since they offer a number of practical advantages over liquid‐electrolyte junction devices. Of particular importance to the design of such devices is the control of interfacial charge transfer. In this paper, the factors that determine the yield of hole transfer at the dye/HTM interface and its correlation with solid‐state‐cell performance are identified. To this end, a series of novel triarylamine type oligomers, varying in molecular weight and mobility, are studied. Transient absorption spectroscopy is used to determine hole‐transfer yields and pore‐penetration characteristics. No correlation between hole mobility and cell performance is observed. However, it is found that the photocurrent is directly proportional to the hole‐transfer yield. This hole‐transfer yield depends on the extent of pore penetration in the dye‐sensitized film as well as on the thermodynamic driving force ΔG_dye–HTM for interfacial charge transfer. Future design of alternative solid‐state HTMs should focus on the optimization of pore‐filling properties and the control of interfacial energetics rather than on increasing material hole mobilities.     

Chernobyl accident: reconstruction of thyroid dose for inhabitants of the Republic of Belarus

The Chernobyl accident in April 1986 resulted in widespread contamination of the environment with radioactive materials, including (131)I and other radioiodines. This environmental contamination led to substantial radiation doses in the thyroids of many inhabitants of the Republic of Belarus. The reconstruction of thyroid doses received by Belarussians is based primarily on exposure rates measured against the neck of more than 200,000 people in the more contaminated territories; these measurements were carried out within a few weeks after the accident and before the decay of (131)I to negligible levels. Preliminary estimates of thyroid dose have been divided into 3 classes: Class 1 ("measured" doses), Class 2 (doses "derived by affinity"), and Class 3 ("empirically-derived" doses). Class 1 doses are estimated directly from the measured thyroidal (131)I content of the person considered, plus information on lifestyle and dietary habits. Such estimates are available for about 130,000 individuals from the contaminated areas of the Gomel and Mogilev Oblasts and from the city of Minsk. Maximum individual doses are estimated to range up to about 60 Gy. For every village with a sufficient number of residents with Class 1 doses, individual thyroid dose distributions are determined for several age groups and levels of milk consumption. These data are used to derive Class 2 thyroid dose estimates for unmeasured inhabitants of these villages. For any village where the number of residents with Class 1 thyroid doses is small or equal to zero, individual thyroid doses of Class 3 are derived from the relationship obtained between the mean adult thyroid dose and the deposition density of (131)I or 137Cs in villages with Class 2 thyroid doses presenting characteristics similar to those of the village considered. In order to improve the reliability of the Class 3 thyroid doses, an extensive program of measurement of (129)I in soils is envisaged.     

Fluorinated polymer films from r.f. plasmas containing benzene and sulfur hexafluorine

Mixtures of C₆H₆ and SF₆ were polymerized in an r.f. discharge. Actinometry (quantitative optical emission spectroscopy) was used to determine trends in the plasma concentrations of the species F, H and CH as a function of the proportion of SF₆ in the feed. Infrared spectroscopy and electron spectroscopy for chemical analysis were employed to characterize the deposited material. Increasing proportions of SF₆ in the feed produced increased fragmentation of the benzene molecules and greater fluorination of the deposited material. The deposition rate, as determined by optical interferometry, was found to be enhanced about 4 times by the presence of 10–20% SF₆ in the feed. At 50% SF₆ in the feed, deposition rates were greater than in pure C₆H₆ plasmas despite the (probably large) etching effect of atomic fluorine from the discharge. Relationships between the plasma composition, electron density and temperature, film composition and growth rate are discussed.     

Photophysical Study of DPPTT‐T/PC70BM Blends and Solar Devices as a Function of Fullerene Loading: An Insight into EQE Limitations of DPP‐Based Polymers

Diketopyrrolopyrrole (DPP)‐based polymers have been consistently used for the fabrication of solar cell devices and transistors due to the existence of intermolecular short contacts, resulting in high electron and hole mobilities. However, they also often show limited external quantum efficiencies (EQEs). In this contribution, the authors analyze the limitations on EQE by a combined study of exciton dissociation efficiency, charge separation, and recombination kinetics in thin films and solar devices of a DPP‐based donor polymer, DPPTT‐T (thieno[3,2‐b]thiophene‐diketopyrrolopyrrole copolymer) blended with varying weight fractions of the fullerene acceptor PC₇₀BM. From the correlations between photoluminescence quenching, transient absorption studies, and EQE measurements, it is concluded that the main limitation of photon‐to‐charge conversion in DPPTT‐T/PC₇₀BM devices is poor exciton dissociation. This exciton quenching limit is related not only to the low affinity/miscibility of the materials, as confirmed by wide angle X‐ray diffraction diffraction and transmission electron microscopy data, but also to the relatively short DPPTT‐T singlet exciton lifetime, possibly associated with high nonradiative losses. A further strategy to improve EQE in this class of polymers without sacrificing the good extraction properties in optimized blends is therefore to limit those nonradiative decay processes.