Presence of brightly fluorescent material in testes of XX males

The case of a phenotypic male with a predominantly 46,XX karyotype is presented. Examination of quinacrine mustard stained frozen sections of testicular tissue revealed that 29% of Sertoli cells contained a brightly fluorescent spot, presumably representing the Y chromosome. Interestingly, these cells were the only X chromatin negative cells observed in the testis. It is concluded that it is hazardous to regard any case as a pure `XX male' without extensive study of all available tissues, including fluorescence of testicular tissue.

On the theory of ion transport across the nerve membrane. VI. Free energy and activation free energies of conformational change

Empirical functions, such as n(infinity)(V) and tau(n)(V) (of the Hodgkin-Huxley type), can be recast in terms of more fundamental functions F(V) (related to a conformational free energy change) and theta(V) (related to the corresponding free energies of activation). Examples of F(V) and theta(V) are given, for squid and frog node. F(V) is essentially a quadratic function of V. The possible molecular origin, for protein-like subunits, of the linear (e.g., net charge) and quadratic (e.g., polarizability) terms in F(V) is discussed. The F(V), theta(V) kind of analysis leads rather automatically to a simple explanation of the well-known approximate coincidence in location (V value) of the maximum in tau(n)(V) (time constant) and the steeply rising part of n(infinity)(V) (also m, 1 - h).

Cooperative effects in models of steady-state transport across membranes. 3. Simulation of potassium ion transport in nerve

An extremely simple membrane transport model simulates qualitatively the observed flux-potential curves for steady-state potassium ion transport across a nerve (squid) membrane in the special case of high external potassium ion concentration. The transporting units (protein molecules) in the model are assumed to exist in two different conformations, which interact cooperatively. The membrane potential induces a transition between the two conformations by virtue, primarily, of a polarizability difference in the two conformations. Differential proton binding may make an important contribution to this effect.

Cooperative effects in models of steady-state transport across membranes. I

Three simple models are discussed which show cooperative effects in the steady-state transport of neutral molecules across a membrane. The Bragg-Williams approximation is employed, and its limitations discussed. In this approximation to cooperative problems, the diagram method for the calculation of steady-state probabilities and fluxes can still be used. This paper is closely related to one by Blumenthal, Changeux, and Lefever, and provides the foundation for sequels on an oscillatory steady-state phase-transition model (part II) and on simple models possibly related to steady-state potassium ion transport across a nerve membrane (part III).

Flow through a collapsible tube. Experimental analysis and mathematical model

Flow through thin-wall axisymmetric tubes has long been of interest to physiologists. Analysis is complicated by the fact that such tubes will collapse when the transmural pressure (internal minus external pressure) is near zero. Because of the absence of any body of related knowledge in other sciences or engineering, previous workers have directed their efforts towards experimental studies of flow in collapsible tubes. More recently, some attention has been given towards analytical studies. Results of an extensive series of experiments show that the significant system parameter is transmural pressure. The cross-sectional area of the tube depends upon the transmural pressure, and changes in cross-section in turn affect the flow geometry. Based on experimental studies, a lumped parameter system model is proposed for the collapsible tube. The mathematical model is simulated on a hybrid computer. Experimental data were used to define the functional relationship between cross-sectional area and transmural pressure as well as the relation between the energy loss coefficient and cross-sectional area. Computer results confirm the validity of the model for both steady and transient flow conditions.