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Male rodents were studied before and after undergoing one of three treatment conditions for 9 days: 1) cage control (n = 15, CON), 2) horizontal suspension (n = 15, HOZ), and 3) head-down suspension (n = 18, HDT). Testing included measurements of maximal O2 uptake (VO2 max) and select cardiovascular responses to graded treadmill exercise. VO2 max expressed on an absolute basis (ml/min) was significantly decreased after HOZ (-14.1 +/- 2.5%) and HDT (-14.3 +/- 2.0%), while being essentially unchanged in CON (-1.0 +/- 3.3%). Significant reductions in body weight were observed after both HOZ (-10.1 +/- 4.2 g) and HDT (-22.5 +/- 3.3 g), whereas CON animals exhibited a significant increase in weight (10.4 +/- 3.8 g). As a result, when VO2 max was normalized for body weight, all groups exhibited similar significant reductions of 6-7%. Although no differences in heart rate and blood pressure response to graded exercise were observed, the HDT group exhibited greater increases in mesenteric resistance at the same absolute exercise intensity. Furthermore, both suspended groups had higher iliac resistance values during exercise at similar relative exercise conditions, suggesting that muscle blood flow during treadmill running may have been reduced after suspension. In general, the decrements associated with the HOZ and HDT conditions were similar. It was concluded that reduction in exercise capacity and altered cardiovascular responses to exercise observed after 6-9 days of suspension were attributable to a combination of hypokinesia, lack of hindlimb weight bearing, or restraint, rather than to hydrostatic influences associated with HDT. 相似文献
3.
Various aspects of the breeding of three gulls, Larus thayeri, glaucoides and hyperboreus, which nested in colonies both on cliff ledges and on level ground in the eastern Canadian Arctic, were compared with those of the ground-nesting L. argentatus and the cliff-nesting Rissa tridactyla. As the result of adaptation to cliff ledge nesting, many aspects of the breeding biology of R. tridactyla were strikingly different from those of the ground-nesting European L. argentatus, but the behaviour of L. thayeri, glaucoides and hyperboreus clearly spanned these differences. Cliff-nesting individuals of thayeri and glaucoides were most like Rissa; ground-nesting individuals of these species were most like argentatus. L. thayeri was more like Rissa than was glaucoides. With but few exceptions, both cliff- and ground-nesting individuals of hyperboreus were most like argentatus. The factors responsible for the intra-specific differences between cliff- and ground-nesters of thayeri and glaucoides are not clear. Limited gene exchange between cliff and ground colonies occurs. Because of physical features of the nest, first-laid eggs were more liable to fall from ledges than second or third eggs. L. thayeri and glaucoides have evolved separate mechanisms to cope with this problem. Egg shape was multimodal in thayeri and glaucoides. Long pyriform eggs were less liable to fall from ledges than eggs of other shapes. L. thayeri laid more long pyriform eggs as first eggs than did glaucoides. L. thayeri lost fewer eggs than did glaucoides, but glaucoides replaced all lost eggs while thayeri did not. Delayed follicular atresia provided glaucoides with insurance of egg replacement. In thayeri, accessory follicles were reabsorbed after the first egg was laid; in argentatus, after the second egg, and in glaucoides after the third egg. At the approach of a predator, it was advantageous for cliff-dwelling chicks to remain motionless but for ground-dwelling chicks to flee their nests and to hide. Among the cliff-nesters, the “freezing in place” reaction of chicks was best developed in thayeri, to a lesser extent in glaucoides, and least in hyperboreus. Among the ground-nesters, chicks of glaucoides and hyperboreus behaved like those of argentatus and fled their nests when disturbed, but chicks of thayeri froze like their cliff-dwelling siblings. Reciprocal transfers of eggs and chicks between cliff and ground colonies indicated that in argentatus, glaucoides and hyperboreus, the factors determining a chick's reaction to disturbance came into play between hatching and the eighth day. In thayeri, the reaction appeared to be effectively innate. Chicks of glaucoides showed a greater predisposition to this behaviour than chicks of argentatus after both had received identical experience on cliff ledges. In thayeri, stereotypy of the freezing reaction has probably been a factor limiting the colonisation of areas where cliffs are scarce but predators present. In argentatus, lack of perfection of this behaviour (compared to glaucoides and thayeri) has probably been a factor preventing argentatus from attaining cliff ledges. L. hyperboreus, although nowhere abundant, is a widespread species nesting on level ground and on cliff ledges but lacking the modifications observed in glaucoides and thayeri; this is due to its size and aggressiveness, the fact that it picks nest-sites before glaucoides and thayeri arrive in the colonies, and that on cliffs it chooses the largest and most level ledges. 相似文献
4.
Nicholas Cianciotto Terry Serwold-Davis Neal Groman Giulio Ratti Rino Rappuoli 《FEMS microbiology letters》1990,66(1-3):299-301
Chromosomal restriction fragments of Corynebacterium ulcerans and C. diphtheriae, containing an integration site for corynephages of the beta family, show homology on Southern blots. Homologous DNA in also found in the soil isolate C. glutamicum, although this strain is not susceptible to beta-corynephages. Three of these DNA fragments, one for each bacterial strain, and a fragment of gamma-corynephage DNA previously shown to contain the phage integration site, were cloned and sequenced. Alignment of the 3 bacterial sequences shows a very high degree of homology in a stretch of ca 120 nucleotides, whereas the rest of the sequences is generally non-homologous. Within this common bacterial portion, a segment of ca. 96 nucleotides (core sequence) is also highly homologous to the phage sequence. The first half (ca. 50 bp) of the core sequence is identical in all aligned sequences whereas the second half, which is largely occupied by a stem-and-loop structure, contains point mutations peculiar to each clone. The described sequences are likely to be involved in phage integration/excision processes. 相似文献
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Blood glucose and glucose tolerance tests demonstrated that many male MM mice are diabetic. Serial urine sampling showed that the diabetes occurred only in mature MM males and consisted of a single self-limiting episode. Histological examination of the pancreas, together with measurements of body weight, glycosylated haemoglobin and plasma insulin, revealed that the diabetes was of the maturity-onset insulin-resistant type. Bacteriological examination of the urine samples showed that urinary tract infection, a known feature of male MM mice, occurred in the diabetics but only after the onset of hyperglucosuria. It was concluded that the high urinary glucose levels of diabetic MM males are of prime importance in the aetiology of the renal infection which occurs rarely in non-diabetic MM males or in other strains in the colony. An infectious aetiology for the diabetes per se was excluded by the existence of diabetes in germfree MM males. 相似文献
8.
The effects of TGF1 on cell cycle events in a rat liver derived epithelial cell line (BL9) and in two in vitro transformants of this line were studied by flow cytometry. Using either ethidium bromide staining or the incorporation of bromodeoxyuridine to evaluate DNA synthesis it was shown that TGF1 prevented the entry of G0/G1 phase BL9 cells into S phase. TGF1 did not exert its inhibitory effect(s) on DNA synthesis by the modulation of early events in the cell cycle. The tumorigenic transformed BL9 cell lines gave contrasting responses to the effects of TGF1. DNA synthesis in a BL9 cell line derived by transfection with an active N-ras oncogene was unaffected by TFG1 and thus appeared refractory to its growth controlling effects. On the other hand cells from a BL9 cell line derived by in vitro transformation with activated aflatoxin B1 retained their sensitivity to the effects of TGF1. Thus the loss of the inhibitory effect of TGF1 on DNA synthesis is not obligatory for the malignant transformation of rat liver epithelial cells.Abbreviations TGF1
transforming growth factor 1
- BSA
bovine serum albumin
- FBS
foetal bovine serum
- BrdUrd
bromodeoxyuridine
- PI
propidium iodide
- PBS
phosphate buffered saline 相似文献
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10.
Richard C. Woodman John T. Curnutte Bernard M. Babior 《Free radical biology & medicine》1988,5(5-6):355-361
We examined the effects of the recombinant human colony stimulating factors GM-CSF and G-CSF, cycloheximide (a protein synthesis inhibitor) and dihydrocytochalasin B (a microfilament disrupting agent) upon FMLP (N-formyl-methionyl-leucylphenylalanine)-stimulated O2 − production by neutrophils. We confirmed a time dependent augmentation of O2 − production following preincubation of neutrophils either alone or with colony stimulating factors. Furthermore, we found that GM-CSF, but not G-CSF, increased O2 − production at some concentrations of the stimulus. Preincubation of neutrophils with cycloheximide in the absence of CSF caused a marked fall in O2−-production that was first evident at 2 hours. The fall in O2−-forming capacity caused by cycloheximide was much less pronounced if dihydrocytochalasin B was also included in the preincubation buffer. These findings suggest a previously unrecognized role for de novo protein synthesis in maintaining the ability of neutrophils to manufacture O2−, and support earlier studies indicating that the cycling of FMLP receptors between the cell membrane and an intracellular compartment is important in determining the magnitude of the respiratory burst in FMLP-stimulated neutrophils. 相似文献