CARRIERS IN COMMUNICATION AND IN PHYSIOLOGY.

Abstract

CARRIERS IN COMMUNICATION AND IN PHYSIOLOGY STANFORD GOLDMAN* I. Carriers and Selectivity Communicationengineers employ carriers to dealwith diverseproblems met in the transmission ofinformation. It may be that analogous carriers transmit biochemical "information." The experience ofengineers may be useful in understanding biological phenomena and suggesting experiments to get new biological knowledge. Conversely, biological knowledge may help toward a better understanding ofthe ultimate significance ofcarriers. When a man speaks into a microphone at a broadcasting studio, his speech is translated from a sound signal into an electrical signal. If this electrical signal, even greatly amplified, were sent into a transmitting antenna , the amount ofradiated signal power would be negligible because an antenna of reasonable size is an ineffective radiator of radio waves at speech frequencies. In order to get effective radiation ofthe speech information , the audio (speech) signal is used to modulate a high-frequency carrier—of, say.i.ooo kilocycles (one million cycles) per second. One can build a practical antenna which is an efficient radiator at such a frequency. Figure ? illustrates the wave form ofthe speech signal and ofthe modulated carrier. Using such carriers has other advantages also. Carriers improve the uniformity of transmission, so that, for example, a steady signal is available for automatic gain control. But the most important advantage of all is that carriers, when used in conjunctionwith properly tuned circuits, allow great selectivity. Consequently, a listener in his home can receive the programhe wants and eliminate allthe other programs being broadcastsimultaneously . Let us see whether these facts are instructive when we consider carriers of biochemical information. * Department ofElectrical Engineering, Syracuse University. The writer has benefited from discussion with Drs. B. F. Argyris, Scott Swisher, andJay Tepperman in the preparation ofthis paper. This work has been sponsored by the Information Systems Branch ofthe Office ofNaval Research. 159 First, what do we mean by the term "biochemical information?" In information theory1 it is pointed out that when a message is translated from one language into another or, even more generally, when an idea is translated into words, there is something which does not change in the translation and which may be considered the "information" in the message . This "information" is the specification or selection ofone particular (a) Speech signal (b) Modulated carrier bearing the same speech information Fig. t.—A speech signal shown in its original audio waveform and as a modulated carrier message out ofall the possible messages which could have been sent.2 If every particular message in one language can be translated into an equivalentparticular message in another language, then translation can take place between the two languages without a loss ofinformation. In conformity with the foregoing ideas, ifa specific biochemical substance when put into a particular situation will cause a specific event to occur, we say that in 1 Information theory is a recently developed branch ofcommunication engineering which deals quantitatively with theamount ofinformation in messagesand with what happens to this information in the process oftransmission [l]. * In the simplest cases the quantity ofinformation in a particular message is equal to the logarithm ofthe total number ofmessages in the set from which the particular message was chosen. 1 60 Stanford Goldman · Carriers in Communication and in Physiology Perspectives in Biology and Medicine · Winter 1964 this context the substance may be considered to be a message ofbiochemical information which can be translated into the event. In this sense hormones may be considered messages carrying endocrinologicalinformation . Manyhormones are known to be transported through the circulatory systemwith the aid of "carriers." Let us examine this situation to see whether these carriers have properties analogous to those of the carriers used by communication engineers. It is interesting to note that the name "carrier" has beenused by bothengineer and physiologist for the vehicle associated with transport ofa message. II. Thyroid-binding Proteins Thyroid-binding proteins in the blood act as a carrier for thyroxin. It is generally believed that these proteins improve the efficiency and uniformity of the transmission of thyroxin. In their absence, most of the thyroxin in the blood would probably be precipitated; with their aid, not only can sufficient thyroxin enter the blood stream, but it is believed that they act as a storage and buffering...