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1.
Karen F. Greif Mark G. Erlander Niranjala J. K. Tillakaratne Allan J. Tobin 《Neurochemical research》1991,16(3):235-242
The recent identification of two genes encoding distinct forms of the GABA synthetic enzyme, glutamate decarboxylase (GAD), raises the possibility that varying expression of the two genes may contribute to the regulation of GABA production in individual neurons. We investigated the postnatal development the two forms of GAD in the rat cerebellum. The mRNA for GAD67, the form which is less dependent on the presence of the cofactor, pyridoxal phosphate (PLP), is present at birth in presumptive Purkinje cells and increases during postnatal development. GAD67 mRNA predominates in the cerebellum. The mRNA for GAD65, which displays marked PLP-dependence for enzyme activity, cannot be detected in cerebellar cortex by in situ hybridization until P7 in Purkinje cells, and later in other GABA neurons. In deep cerebellar nuclei, which mature prenatally, both forms of GAD mRNA can be detected at birth. The amounts of immunoreactice GAD and GAD enzyme activity parallel changes in mRNA levels. We suggest that the delayed appearance of GAD65 is coincident with synapse formation between GABA neurons and their targets during the second postnatal week. GAD67 mRNA may be present prior to synaptogenesis to produce GABA for trophic and metabolic functions.Special issue dedicated to Dr. Eugene Roberts. 相似文献
2.
To follow growth of rats, in which growth hormone secretion has been chronically stimulated, L-Dopa (5 mg/kg) was injected subcutaneously twice daily for 70 days to growing rats. A control group, matched for sex and sibship, pair fed with the treatment group was given saline injections. At 10-day intervals, the rats were weighed and measured. At 90 days of age the rats were ether anesthesized, bled for growth hormone determination, and internal viscera weighed. Weight gain and length in the L-Dopa-treated group was found to be significantly greater. A mean weight gain of 6% and 12% in the male and female rats, respectively, and a mean length gain of 5% in both male and female rats was observed at 90 days of age. The thymus, thyroid, adrenals, uterus, and gonads all tended to be heavier in the L-Dopa-treated group. Significantly heavier kidneys were found in the L-Dopa group. Serum growth hormone was found to be 8.44 +/- 1.4(SE) ng/ml in the L-Dopa group and 4.6 +/- 0.9 ng/ml in the control group. It is concluded that the continuous administration of L-Dopa produces an increase of circulating serum growth hormone levels, and this in turn enhances growth. 相似文献
3.
H Kersten K H Averkamp W Braatz P Greif W Kersten B Hess 《Hoppe-Seyler's Zeitschrift für physiologische Chemie》1969,350(12):1619-1634
4.
5.
Christian C. Voigt B.-Markus Schuller Stefan Greif Björn M. Siemers 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2010,180(7):1079-1088
Foraging behaviour of bats is supposedly largely influenced by the high costs of flapping flight. Yet our understanding of
flight energetics focuses mostly on continuous horizontal forward flight at intermediate speeds. Many bats, however, perform
manoeuvring flights at suboptimal speeds when foraging. For example, members of the genus Rhinolophus hunt insects during short sallying flights from a perch. Such flights include many descents and ascents below minimum power
speed and are therefore considered energetically more expensive than flying at intermediate speed. To test this idea, we quantified
the energy costs of short manoeuvring flights (<2 min) using the Na-bicarbonate technique in two Rhinolophus species that differ in body mass but have similar wing shapes. First, we hypothesized that, similar to birds, energy costs
of short flights should be higher than predicted by an equation derived for bats at intermediate speeds. Second, we predicted
that R. mehelyi encounters higher flight costs than R. euryale, because of its higher wing loading. Although wing loading of R. mehelyi was only 20% larger than that of R. euryale, its flight costs (2.61 ± 0.75 W; mean ± 1 SD) exceeded that of R. euryale (1.71 ± 0.37 W) by 50%. Measured flight costs were higher than predicted for R. mehelyi, but not for R. euryale. We conclude that R. mehelyi face elevated energy costs during short manoeuvring flights due to high wing loading and thus may optimize foraging efficiency
by energy-conserving perch-hunting. 相似文献
6.
The idea that copulation might increase predation risk is a classic suggestion [1-3], but empirical evidence to support it is surprisingly scarce. While some early work found decreased vulnerability to predation during mating [2], two lab and one very recent field study documented increased predation during mating in freshwater amphipods [4], water striders [5] and locusts [6]. Decreased vigilance, less efficient escape responses, and increased conspicuousness of mating pairs have been suggested as mechanisms that might underpin elevated predation risk during copulation [2]. However, these putative mechanisms have never been investigated empirically. Here we describe a bat-insect system within which copulation greatly increases predation risk. We experimentally demonstrate that wild Natterer's bats (Myotis nattereri) 'eavesdrop' on acoustic cues emanating from copulating flies (Musca domestica) in a cowshed (Figure 1). With this evidence, we pinpoint increased conspicuousness as a relevant mechanism for elevated predation risk during mating. 相似文献
7.
DM Greif M Kumar JK Lighthouse J Hum A An L Ding K Red-Horse FH Espinoza L Olson S Offermanns MA Krasnow 《Developmental cell》2012,23(3):482-493
Some of the most serious diseases involve altered size and structure of the arterial wall. Elucidating how arterial walls are built could aid understanding of these diseases, but little is known about how concentric layers of muscle cells and the outer adventitial layer are assembled and patterned around endothelial tubes. Using histochemical, clonal, and genetic analysis in mice, here we show that the pulmonary artery wall is constructed radially, from the inside out, by two separate but coordinated processes. One is sequential induction of successive cell layers from surrounding mesenchyme. The other is controlled invasion of outer layers by inner layer cells through developmentally regulated cell reorientation and radial migration. We propose that a radial signal gradient controls these processes and provide?evidence that PDGF-B and at least one other signal contribute. Modulation of such radial signaling pathways may underlie vessel-specific differences and pathological changes in arterial wall size and structure. VIDEO ABSTRACT: 相似文献
8.
Frankenberg D Greif KD Beverung W Langner F Giesen U 《Radiation and environmental biophysics》2008,47(4):431-438
We have studied the dependence of clonogenic bystander effects on defects in the pathways of DNA double-strand break (DSB)
repair and on linear energy transfer (LET). The single-ion microbeam of the Physikalisch-Technische Bundesanstalt (PTB) was
used to irradiate parental Chinese hamster ovary cells or derivatives deficient in nonhomologous end joining (NHEJ) or homologous
recombination (HR) in the G1-phase of the cell cycle. Cell nuclei were targeted with 10 MeV protons (LET = 4.7 keV/μm) or
4.5 MeV α-particles (LET = 100 keV/μm). During exposure, the cells were confluent, allowing signal transfer through both gap
junctions and diffusion. When all cell nuclei were targeted with 10 MeV protons, approximately exponential survival curves
were obtained for all three cell lines. When only 10% of all cell nuclei were targeted, a significant bystander effect was
observed for parental and HR-deficient cells, but not for NHEJ-deficient cells. For all three cell lines, the survival data
after exposure of all cell nuclei to 4.5 MeV α-particles could be fitted by exponential curves. When only 10% of all cell
nuclei were targeted, significant bystander effects were obtained for parental and HR-deficient cells, whereas for NHEJ-deficient
cells a small, but significant, bystander effect was observed only at higher doses. The data suggest that bystander cell killing
is a consequence of un- or misrejoined DSB which occur in bystander cells during the S-phase as a result of the processing
of oxidative bistranded DNA lesions. The relative contributions of NHEJ and HR to the repairing of DSB in the late S/G2-phase
may affect clonogenic bystander effects. 相似文献
9.
Alkaline ribonuclease inhibitor in rat thyroid 总被引:1,自引:0,他引:1
10.