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1.
A trophic effect of epidermal growth factor (EGF) on rat colonic mucosa in organ culture 总被引:1,自引:0,他引:1
The development of an organ-culture system for rat colonic mucosa has enabled a direct assessment of the effect of epidermal growth factor (EGF) on cell division. An augmented mitotic index (AIm) has been employed to identify changes in cell proliferation. Explants of colonic mucosa from four animals were maintained in a medium containing serum for five days. On the fifth day of culture, half of the explants received fresh medium containing EGF (40 ng/ml) and the remainder (controls) fresh medium only. At 6, 12, 24 and 48 hr thereafter groups of both experimental and control explants received the metaphase-arresting drug vincristine (4 micrograms/ml) for 3 hr prior to fixation. The proportions of vincristine-arrested metaphases within the explants were determined. Analysis of the data indicates that when serum is present exogenous EGF exerts a trophic effect which increases with time (P less than 0.001). In a second experiment colonic explants from four animals were maintained for five days in a serum-free medium and were then divided into groups, each of which received one of a range of concentrations of EGF. The AIm was determined for each group after 36 hr. It was found that increasing concentrations of EGF produce a small but significant increase in cell proliferation (P less than 0.01). This effect, however, was less pronounced than that seen when serum was present. These results suggest that EGF has a trophic action on the colon and interacts with additional factors found in serum. 相似文献
2.
Trimethyloxonium modification of single batrachotoxin-activated sodium channels in planar bilayers. Changes in unit conductance and in block by saxitoxin and calcium 总被引:13,自引:9,他引:4 下载免费PDF全文
Single batrachotoxin-activated sodium channels from rat brain were modified by trimethyloxonium (TMO) after incorporation in planar lipid bilayers. TMO modification eliminated saxitoxin (STX) sensitivity, reduced the single channel conductance by 37%, and reduced calcium block of inward sodium currents. These effects always occurred concomitantly, in an all-or-none fashion. Calcium and STX protected sodium channels from TMO modification with potencies similar to their affinities for block. Calcium inhibited STX binding to rat brain membrane vesicles and relieved toxin block of channels in bilayers, apparently by competing with STX for the toxin binding site. These results suggest that toxins, permeant cations, and blocking cations can interact with a common site on the sodium channel near the extracellular surface. It is likely that permeant cations transiently bind to this superficial site, as the first of several steps in passing inward through the channel. 相似文献
3.
C Bartholomew W Charles C Saxinger W Blattner M Robert-Guroff C Raju P Ratan W Ince D Quamina K Basdeo-Maharaj et al. 《BMJ (Clinical research ed.)》1985,290(6477):1243-1246
Adult T cell leukaemia/lymphoma was first recognised as a clinical entity in southwest Japan. Subsequently the Caribbean has been found to be another area where the disease is endemic, and sporadic cases have been identified in different parts of the world. The human T cell leukaemia/lymphoma virus (HTLV-I) is causally related to adult T cell leukaemia/lymphoma. A subgroup of HTLV, designated HTLV-III, has recently been isolated from many patients with the acquired immunodeficiency syndrome (AIDS) and preAIDS, and there is now evidence that this variant is the primary cause of AIDS. This is the first report from Trinidad to describe 12 cases of adult T cell leukaemia/lymphoma and 14 of AIDS. All were in patients of African descent. No cases were seen in subjects of East Indian descent, who, like those of African descent, comprise as much as 40% of the population. West Indians of African descent may have increased susceptibility to infection with both HTLV-I and HTLV-III. 相似文献
4.
B. W. Ince 《Journal of fish biology》1983,22(3):259-263
Plasma insulin and glucose responses to a secretin-like factor, extracted from pike intestines, have been investigated in vivo in European eels, Anguilla anguilla L. Intra-arterial injection of pike secretin elicited a dose-related, significant increase of plasma insulin after 30 min at 100 and 250 μgkg-1 body weight, but was without effect at 40μgkg-1 . Plasma glucose levels, however, remained unchanged over this dose range. These results suggest that hormonal factors of gastrointestinal origin may modify pancreatic endocrine function in teleost fish. 相似文献
5.
M. Moorghen P. Ince Karen J. Finney A. J. Watson A. L. Harris 《In vitro cellular & developmental biology. Animal》1991,27(11):873-877
Summary The in-vitro effects of hydroxyurea 5-FU and 5-FUdR have been extensively studied in experimental systems employing cell-line
techniques. In this study we investigated the effects of these drugs on the levels of incorporation of labeled nucleosides
into DNA in explants of intact rat colonic mucosa maintained in organ culture. The effects of the nucleoside transport inhibitors
nitrobenzylthioinosine (NBMPR) and dipyridamole—which are modulators of antimetabolite cytotoxicity—on the incorporation of
tritiated thymidine [(3H]TdR) into DNA were also studied. The incorporation of tritiated TdR into DNA was reduced by hydroxyurea but was not altered
by either 5-FU or 5-FUdR. The levels of tritiated deoxyuridine were reduced by 5-FU and 5-FUdR in separate experiments; this
is in keeping with thymidylate synthase inhibition. NBMPR and dipyridamole also reduced 3H-TdR incorporation into DNA. These
results can be explained in terms of the known mechanisms of action of these drugs. This experimental model is therefore useful
in assessing the effects of antimetabolites and nucleoside transport inhibitors in intact colonic mucosa. 相似文献
6.
We present a mathematical method for acceleration workspace analysis of cooperating multi-finger robot systems using a model of point-contact with friction. A new unified formulation from dynamic equations of cooperating multi-finger robots is derived considering the force and acceleration relationships between the fingers and the object to be handled. From the dynamic equation, maximum translational and rotational acceleration bounds of an object are calculated under given constraints of contact conditions, configurations of fingers, and bounds on the torques of joint actuators for each finger. Here, the rotational acceleration bounds can be applied as an important manipulability index when the multi-finger robot grasps an object. To verify the proposed method, we used a set of case studies with a simple multi-finger mechanism system. The achievable acceleration boundary in task space can be obtained successfully with the proposed method and the acceleration boundary depends on the configurations of fingers. 相似文献
7.
Intracellular microelectrode measurements in small cells evaluated with the patch clamp technique. 总被引:4,自引:0,他引:4 下载免费PDF全文
C Ince E van Bavel B van Duijn K Donkersloot A Coremans D L Ypey A A Verveen 《Biophysical journal》1986,50(6):1203-1209
Microelectrode penetration of small cells leads to a sustained depolarization of the resting membrane potential due to a transmembrane shunt resistance (Rs) introduced by the microelectrode. This has led to underestimation of the resting membrane potential of various cell types. However, measurement of the fast potential transient occurring within the first few milliseconds after microelectrode penetration can provide information about pre-impalement membrane electrophysiological properties. We have analyzed an equivalent circuit of a microelectrode measurement to establish the conditions under which the peak of the impalement transients (Ep) approaches the pre-impalement resting membrane potential (Em) of small cells most closely. The simulation studies showed that this is the case when the capacitance of the microelectrode is low and the membrane capacitance of the cell high. In experiments performed to assess the reliability of Ep as a measure of Em, whole-cell patch clamp measurements were performed in the current clamp mode to monitor, free from the effects of Rs, Em in cultured human monocytes. Microelectrode impalement of such patch clamped cells and measurement of Ep made it possible to detect correlation between Ep and Em and showed that for small cells such as human monocytes Ep is on average 6 mV less negative than the resting membrane potential. 相似文献
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