Influence of the growth rate calculation on the relationship between growth rate and temperature

Three calculations of the growth rate (e.g. slope of a plot of the log10 of cfu ml-1 vs time, mum of the Gompertz equation and the reciprocal of time to obtain 108 cfu ml-1) were compared for Escherichia coli TG1 growing in tryptone soy broth medium at temperatures ranging from 14 to 39 degrees C. Up to now, the influence of using such different definitions on the relationship between microbial growth rate and temperature has never been investigated. In order to compare these calculation procedures, a dimensionless analysis based on the following normalized variables, mudim = mu/muopt and Tdim = [T-Tmin]/[Topt-Tmin], was used (Dantigny 1998). The influence of suboptimal temperatures on the growth rate was represented by means of a Belehràdek-type model based on a power function law: [mudim] = [Tdim]alpha. The influence of the different growth rate calculations on the model constants was assessed. Despite the great dependence of the raw growth rate values on the calculation procedure, the dimensionless analysis demonstrated that the alpha-value is independent of the growth rate definition. This result suggests that any definition for the growth rate can be utilized in studies aimed at determining the influence of temperature on microbial growth and highlights the interest of using dimensionless variables to overcome differences in the order of magnitude of the growth rate data and to avoid confusion between definitions.     

Effect of mammalian growth hormone and prolactin on the growth of hypophysectomized chickens

Body weight gain and shank-toe growth during a 26-day treatment period following hypophysectomy were 55 and 46%, respectively, of control values, but the body weight gain was unaffected and bone growth only slightly reduced when the hypophysectomized chickens were fed a low dose of corticosterone (5 ppm). Bovine growth hormone (0.5 mg GH/kg body wt/day for 18 days) enhanced body weight gain and shank-toe length increase (an estimate of bone growth) by 46 and 33%, respectively, compared to the growth of hypophysectomized chickens receiving only corticosterone. These same endpoints were increased approximately 24% after ovine growth hormone treatment in hypophysectomized chickens not receiving corticosterone. Body weight gain during 18 days of treatment with bovine prolactin (0.5 mg PRL/kg/day) was 27% greater than the value for corticosterone-treated hypophysectomized chickens, but bone growth was unaffected. The mammalian GH preparations increased heart weight of the hypophysectomized chickens (25-29%), but pectoralis muscle weight was unaffected. GH treatment enhanced thymal weights by 71% in corticosterone-treated hypophysectomized chickens, and by 93% in hypophysectomized animals not receiving corticosterone. GH had no significant effect on bursal weights, and PRL had no effect on either of these lymphoid organ weights in corticosterone-treated hypophysectomized chickens. GH increased liver and adipose tissue weights considerably more than the large increases that followed treatment of hypophysectomized chickens with corticosterone alone (69 and 126% greater, respectively), but had no effect on these endpoints in hypophysectomized chickens not receiving corticosterone. PRL also greatly increased liver and adipose tissue weights in corticosterone-treated hypophysectomized chickens (79 and 75%, respectively). These results provide evidence that mammalian GH enhances body weight gain, bone growth, and the growth of several organs in the hypophysectomized chicken. Mammalian PRL increased body weight gain, liver weight, and adipose tissue weight in corticosterone-treated hypophysectomized chickens, but did not influence bone growth or the weights of the heart, pectoralis, thymi, or bursa.     

Structural-proliferative units and organ growth: effects of insulin-like growth factor 2 on the growth of colon and skin

Many epithelial renewal tissues in vertebrates are organised into structural-proliferative units. We have examined the effect of IGF2 dose on the structure of structural-proliferative units in skin and colon. The mouse strains used were the Igf2 knockout, wild type and K:Igf2, a transgenic in which Igf2 is overexpressed under control of a keratin promoter. For both skin and colon, the histological organisation of structural-proliferative units was unaltered with increasing IGF2 dose, although there was a higher fraction of dividing cells in the proliferative compartment. In the colon an increase in IGF2 dose increases the overall area of the epithelium. This is due to an increase in the number of crypts with no change of cell size or of crypt area. Growth stimulation appears to be due to a reduction in the duration of crypt fission. The conclusion is that the IGF2 pathway can stimulate the multiplication of colonic crypts independently of stimulating increased cell proliferation. The results for the skin are consistent with this. An increase of IGF2 dose increases the proportion of dividing cells in the basal layer, the thickness of the epidermis and the total area of the epidermis. By comparison with Drosophila, these results show no effects on cell size, but do show the possibility of inducing disproportionate growth. These differences may represent properties of the SPU organisation that is characteristic of vertebrate tissues.     

Influence of herbicides and growth regulators on the growth and essential oil content of sage

Foliar application of a wide range of herbicides provided suggestive evidence for a direct correlation between growth and essential oil production in sage (Salvia officinalis) grown under controlled environmental conditions. Conversely, foliar application of the growth regulators AMO-1618 and DCPA indicated that moderate stunting of growth was associated with an increase in essential oil yield. Quantitative changes in the principle monoterpenes of sage oil, β-pinene, 1,8-cineole, 3-isothujone and camphor, were also observed in response to the various treatments. However, attempts to correlate the changes in oil composition with alteration in growth or oil yield also failed to establish any definitive relationships. Since the four monoterpene components examined arise by independent routes from a common precursor, the changes in oil composition observed indicate that the applied bioregulators exert a direct effect on terpene metabolism by a means independent of growth or development.     

Reevaluation of the effects of growth hormone and prolactin on anuran tadpole growth and development

The effects of ovine prolactin (oPRL) and ovine (o) or porcine (p) growth hormone (GH) on growth of anuran larvae were compared. In grass frog tadpoles (Rana pipiens), injections of oPRL (10 micrograms/gm/day) increased tail growth and body weight but had no effect on hindlimb growth or development. The same dose of oGH did not significantly affect the tail or body weight but it caused a striking increase in limb length and development. In bullfrog tadpoles (Rana catesbeiana) given an ergot drug (bromocriptine) to induce metamorphic changes, significant tail regression and loss of body weight occurred. Treatment with oPRL reversed these effects but had no effect on hindlimb growth or development. The pGH was much less effective than the oPRL in blocking tail regression and body weight loss but it significantly increased limb growth and development. These results show that GH and PRL can differentially regulate growth and development of structures in larval anurans. The effects of GH on limb growth and development can not be explained simply by a thyrotropic effect.     

Influence of plant growth hormones on the growth of Mucor rouxii and chitosan production

Supplementation of molasses-salt medium with plant growth hormones, viz., indoleacetic acid, indolebutyric acid, kinetin and gibberellic acid, increased chitosan production by Mucor rouxii as well as its growth at different optimum concentrations. The increase in yield of chitosan was found to range from 34% to 69% and mycelial growth from 12% to 17.4%. Gibberellic acid was the most potent in this respect. Sixty-nine percent more chitosan over the control could be obtained from 1l of the medium supplemented with 3mg gibberellic acid. Degree of acetylation of chitosan ( approximately 13%) was not changed due to addition of hormone in the medium but weight average molecular weight of chitosan increased by more than 50%. Thus, the plant growth hormones add a value to chitosan by increasing its molecular weight.     

High diversity of the chicken growth hormone gene and effects on growth and carcass traits

The chicken growth hormone (cGH) gene plays a crucial role in controlling growth and metabolism, leading to potential correlations between cGH polymorphisms and economic traits. In this study, DNA from four divergent chicken breeds were screened for single nucleotide polymorphisms (SNPs) in the cGH gene using denaturing high-performance liquid chromatography and sequencing. A total of 46 SNPs were identified, of which 4 were in the 5' untranslated region, 1 in the 3' untranslated region, 5 in exons (two of which are nonsynonymous), with the remaining 36 in introns. The nucleotide diversity in the cGH gene ( theta = 2.7 x 10(-3)) was higher than that reported for other chicken genes, even within the same breeds. The associations of five of these SNPs and their haplotypes with chicken growth and carcass traits were determined using polymerase chain reaction-restriction fragment length polymorphism analysis in a F2 resource population cross of two of the four chicken breeds (White Recessive Rock and Xinghua). This analysis shows that, among other correlations, G+1705A was significantly associated with body weight at all ages measured, shank length at three of four ages measured, and average daily gain within weeks 0 to 4. Thus, this cGH polymorphism, or another polymorphism that is in linkage disequilibrium with G+1705A, appears to correspond to a significant growth-related quantitative trait locus difference between the two breeds used to construct the resource population.     

氮素和植物生长促进剂对羊草生长及竞争力的影响

选取羊草、斜茎黄芪、克氏针茅3种内蒙古典型草原常见植物,通过不同植物物种组合(单独种植或者羊草与其他两种混合种植)、施加不同剂量的氮素(0、0.1、0.2、0.4、0.8mg·g^-1)和植物生长促进剂——油菜素内酯(0.005 mg·g^-1)的温室盆栽试验,分析氮素和油菜素内酯对羊草生长及其与其他植物竞争力关系的影响.结果表明:添加氮素对羊草、斜茎黄芪的生物量影响显著,对克氏针茅的生物量影响较弱,并且氮素的影响因其伴生植物的不同而改变.氮素添加显著增加了羊草在单独种植和与斜茎黄芪混合种植时的地上生物量,但显著降低了与克氏针茅混合种植时的地下生物量.由于土壤可利用氮增加,羊草的地上与地下分配发生变化,表现为单独种植、与克氏针茅混合种植时,根冠比下降;与斜茎黄芪混合种植时,氮素添加对羊草根冠比的影响则不显著.油菜素内酯对植物生长的显著影响不普遍,仅显著降低了斜茎黄芪单独种植时的地下生物量;在羊草与斜茎黄芪混合种植时,显著增加了羊草地上生物量.油菜素内酯和氮适量联用可有效增加特定物种组合的生物量,从而在退化草地恢复中具有一定的应用前景.     

Studies on the growth of the fetal guinea pig. The effects of nutritional manipulation on prenatal growth and plasma somatomedin activity and insulin-like growth factor concentrations

In guinea pigs between days 41-46 of pregnancy prenatal growth has been manipulated by alteration of nutritional state. Three methods were used. Uterine artery ligation at day 30 of pregnancy depressed fetal growth rate by greater than 50% and was associated with falls in plasma insulin, IGF-1, cortisol, thyroid hormone, glucose, acetate and free fatty acid concentrations and rises in that of IGF-2, glucagon and amino acids. Fetal plasma was inhibitory to sulphate incorporation into pig costal cartilage. Complete food withdrawal from pregnant guinea pigs for 2 days at days 43-44 of pregnancy caused mild fetal growth retardation and similar changes in plasma constituents, except in that plasma IGF-2 concentrations were now depressed and plasma was not inhibitory to sulphate incorporation into pig costal cartilage. Production of hypoglycaemia by 4-times-daily maternal injections of glucose between days 41-46 of pregnancy accelerated fetal growth rate. It also elevated fetal plasma concentrations of insulin, IGF-1, IGF-2, sulphation-promoting activity, thyroid hormones, glucose and free fatty acids and depressed that of glucagon and amino acids. Fetal growth rate during the experimental period showed a good correlation with plasma glucose, insulin and IGF-1 and, to a certain extent, with sulphation-promoting activity. It did not correlate closely with fetal plasma IGF-2 concentration. Hepatic glycogen concentrations showed a good correlation with plasma IGF-2 levels.     

Studies on the growth and development of Oxalis latifolia

The growth and development of Oxalis latifolia was assessed on outdoor-grown potted plants raised from bulbs. Three main phases of growth appeared to be correlated with major physiological developments in the aerial and subterranean organs. Establishment (weeks 1 – 5) was characterised by a slow gain in plant dry weight accompanied by high relative growth rate (RGR) values for individual plant organs. The second phase of growth (weeks 6 – 12) was reproductive, as stolons grew and initiated bulbils at the apices. Bulbils had the capacity to produce their own shoot system and ultimately some primary bulbils supported secondary bulbils. Dry matter accumulation was in the order: bulbils > peduncles > leaves > petioles > stolons = roots > parent bulb. The RGR of individual plant organs declined together with the net assimilation (NAR) rates and the leaf area ratio of the shoots during the reproductive phase and beyond into the senescence phase (week 13 onwards). The results are discussed in relation to the problem of achieving weed control via cultural and herbicide treatments.     

Effects of geminivirus infection and growth irradiance on the vegetative growth and photosynthetic production of Eupatorium makinoi

Eupatorium makinoi plants with or without geminivirus infection were grown in shading frames with 70, 15 and 5.5% sunlight. Growth characteristics of these plants in the early vegetative phase were compared by means of growth analysis. We also measured leaf photosynthetic gas exchange rates and examined relationships between leaf photosynthesis and whole-plant growth. Relative growth rate (RGR=(1/W)×(dW/dt), where W is plant dry mass) of virus-infected plants was lower than that of uninfected plants under all three light conditions. The reduction of RGR by infection was increased with irradiance. The net assimilation rate (NAR=(1/A)×(dW/dt), where A is total leaf area of the plant) was also reduced both by infection and shading. NARs that were estimated from light-response curves of leaf photosynthesis, in situ measurements of irradiance, and respiration rates of leaves, stems and below-ground parts, agreed very well with the values obtained by conventional growth analysis techniques. Decreases in the estimated NAR value from infection and shading were mostly explained by the decreases in leaf photosynthesis. These results clearly showed that lowered RGR in virus-infected plants was attributed mainly to impaired photosynthesis in virus-infected leaves.