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PubMed1977

[New method of determination of carboxyhemoglobin by the conductometric method of extraction of carbon monoxide from the blood].

The newly elaborated method consists in the gasometric CO determination in the blood. The extraction of CO from the blood sample (0,1-1,0 ml) is performed by means of a simple device designed by the authors. The extracted CO is determined by gas analyser ANKO-3 or Ultragas 5. The comparison between the new method and iodometric method showed very high correlation (r greater than 0,9). A discussion follows on the advantages of the new method (quick, easy, high-sensitive and precise), its use can be suggested to laboratories which are equipped with a gas analyser ANKO-3 for other purposes. The new method can be used for numerous routine analyses as well as for scientific studies.

Carbon Monoxide↗
PubMedDate not supplied

[Demonstration of three protonated forms of poly(A): potentiometric and conductometric study of isoionic solutions].

It is shown that there are three parts on the potentiometric titration curves of isoionic solutions of poly(A) ascribed to the three protonated structures. Double-helical protonated structures are especially stable in isoionic solution. These parts on potentiometric curves are attributed to the single-stranded poly(A), to the completely protonated double-stranded poly(A+).poly(A+), and to the semiprotonated poly(A+).poly(A) structures: D, A, B forms of poly(A), respectively. pK0 values of these forms are calculated. The D form portion is found to be about 18% in isoionic solution, 40% in KCl solution (from 0.01 to 1.0 M), 40% in solution, containing 1.2 X 10(-3) M MgCl2 and 70% in 8 X 10(-4) M MgCl2 solution. The increase of MgCl2 concentration up to 8 X 10(-4) M leads to complete degradation of the double-helical structure. Only single-stranded D form exists in 5 X 10(-3) M MgCl2 solution. About 5-7% of all protons become inaccessible for titration in all solutions containing KCl and in the presence of small amounts of MgCl2. This phenomenon can not be explained by aggregation of poly(A), because all protons become accessible for titration in more concentrated MgCl2 solution when aggregation of poly(A) is significant and accompanied by the precipitation of sediment insoluble in NaOH. The supposition is made, that unprotonated double-stranded poly(A) can exist in salt-free solution at neutral pH. It is this form that is protonated with decrease of pH.

Chemical Phenomena↗
PubMed1982

Blood flow an intestinal absorption.

Intestinal blood flow interacts with intestinal absorption at several levels and affects absorption through several mechanisms. The precise relationships are difficult to define because, at present, there is not an adequate technique available for measuring blood flow to the absorptive site. The absorption of certain nutrients requires O2 delivered through the blood for maintenance of carrier-mediated transcellular transport. Both altered capillary pressure, which may or may not accompany altered blood flow because of myogenic autoregulation, and changes in absorption can influence tissue hydrostatic and colloid osmotic pressure and also epithelial and interstitial space conductance. These latter, in turn, can change the rate of passive ultrafiltration for a constant driving force. Changes in blood flow can also influence the rate of washout of absorbed substances. Countercurrent exchange in the villous vasculature can buffer the rate of absorption of some substances and may also facilitate the absorption of water. Regulatory agents such as hormones or neurotransmitters can affect blood flow and absorption both independently and interactively. Agents that cause active intestinal secretion may have their effects modified by consequent changes in blood flow.

Animals↗