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101.
M. Chakravarty P. M. Amin H. D. Singh J. N. Baruah M. S. Iyengar 《Biotechnology and bioengineering》1972,14(1):61-73
A kinetic model has been presented to explain the growth of microorganism on solid hydrocarbons. The model is based on the assumption that metabolite produced by the growing cells helps the dissolution of the solid substrate in the aqueous medium. The linear behavior of the growth curve predicted by the model is verified experimentally. 相似文献
102.
Abstract. 1. Female Utetheisa ornatrix (Lepidoptera: Arctiidae) mate selectively with large males able to transmit sizeable quantities of nutrient and defensive pyrrolizidine alkaloid with the spermatophore. The female gauges male size indirectly by assessment of the male's courtship pheromone.
2. Male Utetheisa invest upward of 10% of body mass in spermatophore production, and could therefore have been expected to be choosy; however, when offered females differing in alkaloid content, body mass, or mating status, males showed disregard of these parameters, both in their choice of partner and in their allocation of resources to the spermatophore.
3. It is concluded that Utetheisa males do not have the option to select females by comparison shopping . Females broadcast their attractant pheromone for less than an hour per day. Given this time constraint and the potentially high cost of mate localisation, males may have no choice but to mate on an opportunistic basis. 相似文献
2. Male Utetheisa invest upward of 10% of body mass in spermatophore production, and could therefore have been expected to be choosy; however, when offered females differing in alkaloid content, body mass, or mating status, males showed disregard of these parameters, both in their choice of partner and in their allocation of resources to the spermatophore.
3. It is concluded that Utetheisa males do not have the option to select females by comparison shopping . Females broadcast their attractant pheromone for less than an hour per day. Given this time constraint and the potentially high cost of mate localisation, males may have no choice but to mate on an opportunistic basis. 相似文献
103.
Iyengar V 《Biological trace element research》2007,116(1):1-4
The association of physics and chemistry with metrology (the science of measurements) is well documented. For practical purposes, basic metrological measurements in physics are governed by two components, namely, the measure (i.e., the unit of measurement) and the measurand (i.e., the entity measured), which fully account for the integrity of a measurement process. In simple words, in the case of measuring the length of a room (the measurand), the SI unit meter (the measure) provides a direct answer sustained by metrological concepts. Metrology in chemistry, as observed through physical chemistry (measures used to express molar relationships, volume, pressure, temperature, surface tension, among others) follows the same principles of metrology as in physics. The same basis percolates to classical analytical chemistry (gravimetry for preparing high-purity standards, related definitive analytical techniques, among others). However, certain transition takes place in extending the metrological principles to chemical measurements in complex chemical matrices (e.g., food samples), as it adds a third component, namely, indirect measurements (e.g., AAS determination of Zn in foods). This is a practice frequently used in field assays, and calls for additional steps to account for traceability of such chemical measurements for safeguarding reliability concerns. Hence, the assessment that chemical metrology is still evolving. 相似文献
104.
Biological phenomena at the cellular level can be represented by various types of mathematical formulations. Such representations
allow us to carry out numerical simulations that provide mechanistic insights into complex behaviours of biological systems
and also generate hypotheses that can be experimentally tested. Currently, we are particularly interested in spatio-temporal
representations of dynamic cellular phenomena and how such models can be used to understand biological specificity in functional
responses. This review describes the capability and limitations of the approaches used to study spatio-temporal dynamics of
cell signalling components. 相似文献
105.
106.
Duration of ERK1/2 phosphorylation induced by FGF or ocular media determines lens cell fate 总被引:4,自引:0,他引:4
Iyengar L Wang Q Rasko JE McAvoy JW Lovicu FJ 《Differentiation; research in biological diversity》2007,75(7):662-668
The ocular environment is important for the establishment and maintenance of lens growth patterns and polarity. In the anterior chamber of the eye, the aqueous humour regulates lens epithelial cell proliferation whereas in the posterior, the vitreous humour regulates the differentiation of the lens cells into fiber cells. Members of the fibroblast growth factor (FGF) growth factor family have been shown to induce lens epithelial cells to undergo cell division and differentiate into fibers, with a low dose of FGF able to induce cell proliferation (but not fiber differentiation), and higher doses required to induce fiber differentiation. Both these cellular events have been shown to be regulated by the MAPK/ERK1/2 signalling pathway. In the present study, to better understand the contribution of ERK1/2 signalling in regulating lens cell proliferation and differentiation, we characterized the ERK1/2 signalling profiles induced by different doses of FGF, and compared these to those induced by the different ocular media. Here, we show that FGF induced a dose-dependent sustained activation of ERK1/2, with both a high (fiber differentiating) dose of FGF and vitreous, stimulating and maintaining a prolonged (up to 18 hr) ERK1/2 phosphorylation profile. In contrast, a lower (proliferating) dose of FGF, and aqueous, stimulated ERK1/2 phosphorylation for only up to 6 hr. If we selectively reduce the 18 hr ERK1/2 phosphorylation profile induced by vitreous to 6 hr, by specifically blocking FGF receptor signalling, the vitreous now fails to induce lens fiber differentiation but retains the ability to induce lens cell proliferation. These findings not only provide insights into the important role that FGF plays in the different ocular media that bathe the lens, but enlighten us on some of the putative molecular mechanisms by which one specific growth factor, in this case FGF, can elicit a different cellular response in the same cell type. 相似文献
107.
Iyengar RR Lynch JK Mulhern MM Judd AS Freeman JC Gao J Souers AJ Zhao G Wodka D Doug Falls H Brodjian S Dayton BD Reilly RM Swanson S Su Z Martin RL Leitza ST Houseman KA Diaz G Collins CA Sham HL Kym PR 《Bioorganic & medicinal chemistry letters》2007,17(4):874-878
The optimization of potent MCHr1 antagonist 1 with respect to improving its in vitro profile by replacement of the 3,4-methylenedioxy phenyl (piperonyl) moiety led to the discovery of 19, a compound that showed excellent MCHr1 binding and functional potencies in addition to possessing superior hERG separation, CYP3A4 profile, and receptor cross-reactivity profiles. 相似文献
108.
Compartment-specific feedback loop and regulated trafficking can result in sustained activation of Ras at the Golgi 总被引:1,自引:0,他引:1 下载免费PDF全文
Imaging experiments have shown that cell signaling components such as Ras can be activated by growth factors at distinct subcellular locations. Trafficking between these subcellular locations is a regulated dynamic process. The effects of trafficking and the molecular mechanisms underlying compartment-specific Ras activation were studied using numerical simulations of an ordinary differential equation-based multi-compartment model. The simulations show that interplay between two distinct mechanisms, a palmitoylation cycle that controls Ras trafficking and a phospholipase C-epsilon (PLC-epsilon) driven feedback loop, can convert a transient calcium signal into prolonged Ras activation at the Golgi. Detailed analysis of the network identified PLC-epsilon as a key determinant of "compartment switching". Modulation of PLC-epsilon activity switches the location of activated Ras between the plasma membrane and Golgi through a new mechanism termed "kinetic scaffolding". These simulations indicate that multiple biochemical mechanisms, when appropriately coupled, can give rise to an intracellular compartment-specific sustained Ras activation in response to stimulation of growth factor receptors at the plasma membrane. 相似文献
109.
110.
Kamlesh Kumar Yadav Leela Iyengar Nils-Kåre Birkeland Gurunath Ramanathan 《World journal of microbiology & biotechnology》2005,21(8-9):1529-1534
Summary Activated sludge from a sewage treatment plant in Kanpur, India, was screened for bacterial strains metabolizing p-cresol exclusively under aerobic conditions. One such isolate was identified to be belonging to the genus Pseudomonas based on morphological and physiological criteria as well as 16S ribosomal RNA gene sequence analysis. Two intermediates
were identified from the culture medium during the growth phase of Pseudomonas sp. strain A that indicated that the strain degraded p-cresol via the protocatechuate (PCA) pathway. p-Cresol was rapidly converted into p-hydroxybenzaldehyde (PHB) during early growth phase, which was later utilized after p-cresol depletion. p-Hydroxybenzoate (PHBA) accumulation was observed during the later stages of exponential growth phase. Kinetic constants for
the degradation of p-cresol were determined using Haldane’s model. High μmax and inhibitory constant (KI) values along with the observed accumulation of significant amounts of PHB in culture filtrates seem to indicate that the
isolated Pseudomonas sp. strain A may be of potential use in biotransformations. 相似文献