Investigating metabolism

Calorimetry together with special dietary regimes, exp erimental (timing) schedules and treatments can be used to obtain insight into specific parts of the metabolism. Using indirect calorimetry this can be expanded to more specific insights into substrate metabolism. 

The same method could also be applied to the net substrate oxidation rates. Due to the - at least partial - mutual exchangeability of the substrates as source of energy, this approach was not fully functional for the substrates. In [29] a diet containing 37 % of protein, 4 % of fat and 51 % of CHO (The remainder consists of dietary fiber, water, minerals, etc.) was used. In this case by increasing the protein intake by 1 g the CHO intake was automatically increased by 1.4 g. And in energy metabolism CHO is preferred, as long as there is enough CHO from both intake and body stores available. So the relation of the substrates as fuel differed at different levels of diet intake. This resulted in a fat utilisation factor of up to 800 % and CHO utilisation factors of as low as 33 %. The CD s, however, remained at levels of 92 - 99 %. Only for carbohydrate and 

Some parameters of direct and indirect chambers are given in Table 2 to simplify a comparison of both methods. 

The chemical energy in the diet is distributed into different pools. Some energy is maintained in the faeces or is used to synthesise urea. The remaining metaboliseable energy is used for three purposes. Some energy is used to maintain the dynamic equilibrium of the subject s body and to perform all the 

The industrial motion detectors commonly used in human experiments are often modified to fit this application. This alteration decreases the threshold of motions being detectable to assess even small movements. Standard detectors activate a switch for a given period of about some seconds to minutes with every motion they have detected. This period is dramatically decreased to parts 

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A key feature of apoptosis is that, similar to the cell cycle, the duration of apoptosis is variable and the process is asynchronous in most cell populations. Consequently, there are variable proportions of cells in distinct phases of apoptosis and a sample, collected from a culture in which apoptosis has been induced, will contain cells in all the phases of apoptosis. This could represent a major technical problem in the investigation of apoptosis and requires measurement of metabolic apoptotic changes concomitantly with established markers of apoptosis progression. Using the same cellular model described above, we investigated metabolic alterations induced by X-rays using flow cytometry and a panel of fluorochromes... 

Bakris GL, Fonseca V, Katholi RE, McGill JB, Messerli FH, Phillips RA, Raskin P, Wright JT, Oakes R, Lukas MA, Anderson KM, Bell DSH, for the GEMINI Investigators. Metabolic effects of carvedilol vs metoprolol in patients with type 2 diabetes mellitus and hypertension. A randomized controlled trial. JAMA 2004 292 2227-36. 

In the current context, we will use the term alcohol not in its chemical sense in which there are many different alcohols with various (often poorly investigated) metabolic fates. This overview will be confined to the variable elements of ethanol metabolism. 

In another study PET was used to investigate metabolic abnormalities in 20 recently abstinent metamfetamine abusers and 22 controls (13). The mood disturbances in these individuals were also compared with their cerebral metabolism. Metamfetamine abusers were tested after 4-7 days of abstinence. All gave self-ratings on depression, anxiety, and craving for metamfetamine. PET images were acquired... 

Investigating metabolism or stability of prostanoids, radiolabeled precursors or analytes are often used. The tritiated or -labeled compounds can easily be detected without any further derivatization using online or off-line liquid scintillation, which is not impaired by any interferences derived from matrix components. Efficient but less sensitive PG analysis is possible by UV detection (190-210 nm) of underivatized substances demanding the remove of interfering contaminants or simple sample matrices like buffers or some cell supernatants. 

The route of exposure is a consideration for metabolism studies and is generally via the oral route. Few studies are conducted to investigate metabolism of compounds from dermal and inhalation routes of exposure. Therefore, the techniques which have been developed to study each of the routes are relatively new, and to our knowledge, have never been standardized. A major problem is to reduce the exposure to a single route. For example, a whole body exposure of an animal to an aerosol, smoke, gas, etc., could represent all three inhalation, dermal, and oral. Inhalation toxicity studies now represent significant efforts, and metabolism studies from inhalation exposure are still relatively few in number. 

Yang, J. Y, Karr, J. R., Watrous, J. D., Dorrestein, P. C. (2011). Integrating -omics and natural product discovery platforms to investigate metabolic exchange in microbiomes. Current Opinion in Chemical Biology, 75(1), 79-87. 

NMR studies of isolated organs have been widely used to investigate metabolic processes in vivo and their responses to various experimental interventions. In particular, the perfused isolated heart has... 

Crockford et al. utilized tfre freterospectroscopic methodology to investigate metabolic mixtures [52,53]. They concatenated spectral data from NMR and ultra high-performance liquid chromatography (UPLC) coupled to MS to obtain NMR—MS covariance maps. The approach was baptized SHY as an acronym of statistical heterospectroscopy. 

Animal studies of skeletal muscle often employ direct stimulation of the sciatic nerve to induce contraction and associated metabolic response. Basic metabolic control can be investigated using such a model, as can a wide range of disease-related processes. Genetically abnormal animals provide models of diseases such as muscular dystrophy and NMR spectroscopy provides a tool for investigating metabolism, pH regulation and possible therapeutic interventions. 

Microcalorimetry has been applied in a few studies to investigate metabolism, in the resting or stimulated state, of those cells who play an important role in the field of immunology lymphocytes, macrophages and granulocytes. 

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