PubMed · 14323282
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I KOSMAK, O SKRANC, V HAVEL. 1965. [A SIMPLE PULSE COUNTING DEVICE].. https://pubmed.ncbi.nlm.nih.gov/14323282/
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The instantaneous frequency (IF) of cardiovascular time series is used to describe the time-varying spectral contents of the characteristic frequency bands that are of interest for psychophysiological and cardiovascular research. Four methods to compute IF of band-limited, monocomponent, and analytical cardiovascular time series were compared by means of simulated time series contaminated with additive noise. These four methods are: the method using the inverse Fourier transform of uncorrelated time-slices of the Wigner-Ville distribution, the discrete time-frequency transform, the circular mean direction of the time-slices of the Wigner-Ville distribution, and the central finite difference of the phase. The time resolution of the estimates is optimal and is inversely related to the bandwidth of the frequency components, as given by the uncertainty principle of Gabor. At periods in time where the signal fulfills the requirements of the model signal, the four estimates of IF are numerically equal; only the circular mean direction showed a slight deviation from the other estimates. Although the estimates of IF differ at sudden phase shifts at low amplitude, i.e. at points where the signal locally does not comply with the requirements of the model signal, overall the four methods produce comparable estimates of IF of a cardiovascular time series at an optimal time resolution.
Vasculogenesis, angiogenesis and vascular remodelling are complex processes where the fate of several cell types is determined by different signalling networks. Many of these networks ultimately function by changing the abundance of RNA transcripts within the cells which constitute blood vessel walls. Researchers can now map these transcript abundance changes using gene array technology. In this review, we describe the design, production and use of a gene array specifically tailored to investigate vascular biology. We describe the advantages of tailored gene arrays, and give detailed protocols based on our experience to allow the reader to use such gene arrays to generate meaningful data. We list the issues to consider when choosing and verifying the genes and splice variants included in an array, and describe our use of Arabidopsis sp. RNA spikes for quality control. We present data that illustrates the absolute necessity for both technical and biological replicates to be incorporated in the design of gene array experiments using primary cells such as HUVECS. Finally, we describe methods for the normalisation and interpretation of the data that gene arrays produce. The approach to gene array technology described here is easily within reach of the budget and expertise of most academic research groups.