Difference equation model of the entrainment of myocardial pacemaker cells based on the phase response curve

As a method for investigating entrainment phenomena found in biological oscillations, a model is presented which is formulated as a set of difference equations on the basis of "phase response curves" of biological oscillators. Properties of the model are discussed and synchronization of cardiac pacemaker cells to the external periodic stimuli is analyzed by use of the model. It is shown that the model is reducible to an equivalent system to the mathematical neuron model of Nagumo et al. under a specific parametric condition of the phase response curve. As an application to the cardiac arrhythmias, the model of ventricular parasystoles studied by Moe et al. is described mathematically in terms of a system of difference equations. In addition, a more comprehensive model of ventricular parasystoles is proposed.

Granule formation in rat mast cells. Study with serial ultrathin sections

The process of granule formation in mast cells was investigated with young mast cells in the milky spot of adult rats, seven days after an intraperitoneal injection of distilled water. Serial ultrathin sections were made and examined with an electron microscope to reveal the following results. The early step of granule formation is observed as a complex which consists of an irregularly shaped narrow vestibular space and several primary aggregate granules which are bowl-like in form, attached to the vestibular space and contain a few subgranules. The vestibular space has microvilli. The precursor materials seem to be secreted from the microvilli and transported through the vestibular space into the primary aggregate granules, being coagulated to become subgranules. As the subgranules increase in number, the primary aggregate granules become aggregate granules which grow further to their maximum size. With further addition of the materials, the aggregate granules become, through a step of ropy cord granule, mature dense homogeneous granules. The complex seems to remain as a unit after the maturation of granules and to react as a whole to any stimulus.

[Non-destructive neutron activation analysis of dental porcelain powders (author's transl)]

Determination of 15 elements in the dental porcelain powders (Vita VMK 68) marketed in Japan was done by means of non-destructive neutron activation analysis. The potassium and sodium contents showed less variations from powder to powder, and the uranium contents varied from a few ppm to 1090 ppm in a wide range. The high contents of uranium (345--1090 ppm) were detected in the powders of Enamel, Dentin, Effect, Color and Gum which were used for the superficial parts of a porcelain crown, while the low contents of uranium (1.6--2.7 ppm) were detected in those of Opaque and Translucent which were used for the core part and the top of the crown. Cerium and samarium were also detected in each powder in the amounts similar to those of uranium. The main radionuclides present in the porcelain powders were 238U, 235U, 234U, 234mPa, 234Th, 231Th and 40K. The activities of these nuclides were calculated and discussed.

Hemodynamic parameters of the isolated dog kidney as determined by a frequency response method

The isolated kidney of the dog was perfused with autologous blood through an oxygenator. Responses of arterial input pressure (PI), venous pressure (PV), and venous flow (UV) were measured during sinusoidal forcing of arterial inflow (UA) at 5 to 1,000 cpm superimposed on a steady-state flow level. Pre- (RA) and postglomerular (REV) resistances, and compliances of artery (CA) and glomeruli (CG) were estimated based on a network model and using the Bode diagram of gains PI/UA, UV/UA. The data were evaluated by the least square method with a digital computer. The mean values of the parameters normalized for the average weight of the kidney (64.5g) were: CA = 0.0027 ml/mmHg, CG = 0.088, RA = 0.45 mmHg . min/ml, and REV = 0.35. Mean arterial pressure (PA) and glomerular pressure (PG) were 111 and 50 mmHg, respectively. The regression lines of PG against PA were significantly different at high and low PA, this being taken as a manifestation of autoregulation of the renal circulation. PG values were less than those given by the classical study of Winton but close to those recently obtained on mutants rats with a direct puncture method by Brenner et al. It is concluded that the present study has given an experimental background with which we may continuously estimate, under more intact conditions, circulatory parameter values by monitoring pressures and flows which respond to external perturbations.

Estimation of body water and salt contents from plasma sodium, protein concentrations, and hematocrit

New formulae for the estimation of change in water (delta W) and salt (delta NaCl) contents of the body from hematocrit, plasma Na, and protein concentrations were proposed based on a compartment model of body fluid regulation: delta W = 0.4(delta Vi/Vi0) + 0.2(delta Ve/Ve0) litres/Kg of body weight; delta NaCl = 1.64[delta Ve/Ve0 + 1)/(delta Vi/Vi0 + 1) - 1)-1] Gms/Kg of body weight; where delta Vi/Vi0, and delta Ve/Ve0 are relative increment of intra and extracellular fluid volume. delta Vi/Vi0 is considered equal to ([Na]0/[Na]-1) under the condition of normal cell membrane, whereas delta Ve/Ve0 may be a nonlinear function of relative increment of plasma volume and hematocrit or sodium concentration. Thus a nomograph was presented to obtain delta W and delta NaCl simultaneously. This nomograph could predict delta W and delta NaCl with satisfactory accuracy in the experiments with the dogs to which fluid of various osmolarity was given intravenously. It was also confirmed in a case of mixed water depletion in which the clinical estimation agreed with that of the present method. The conventional formulae of calculation based on either pure dehydration or purse salt loss proved not to be applicable in the usual cases of body fluid disturbances.

Neutron activation analysis of the rare earth elements in Nasu hot springs

Eleven rare earth elements (lanthanum, cerium, neodymium, samarium, europium, gadolinium, terbium, holmium, thulium, ytterbium and lutetium) in hot spring waters and sinter deposits in the Nasu area were determined by the neutron activation method. The rare earth elements in hot spring water were pre-concentrated in ferric hydroxide precipitate and neutron-irradiated. The rare earth elements were chemically separated into lighter and heavier groups and the activity of each group was measured with a Ge(Li) detector. Distribution of the rare earth elements between the hot spring water and the sinter deposit was also discussed.

Determination of uranium in human teeth, bones and tissues by the fission track method

The uranium content of several human tooth, bone and soft tissue samples was determined by the fission tract method. The average uranium content in teeth, bones and soft tissues were 6.7, 8.4 and 64 ppb ash, respectively. The distribution of uranium in bones is less uniform than that of teeth, and the uranium content of soft tissues is generally higher than that of teeth and bone. The presence of thorium does not interfere with the uranium determination in most cases.

Congenital dilatation of the biliary tract; new classification and study with particular reference to anomalous arrangement of the pancreaticobiliary ducts

Yotsuyanagi's theory is often quoted in the discussion of the etiology of congenital dilatation of the biliary duct (CDBD), but there has been no established etiology as yet. With particular reference to the relationship between anomalous arrangement of the pancreaticobiliary ducts and CDBD, Babbit collected 19 cases of CDBD. The authors also observed the anomalous arrangement in 10 of 24 cases of CDBD (42 percent). Analysis of 570 CDBD cases collected in Japan disclosed that the anomalous arrangement was present in 183 of them (33 percent), dilation of the intraheptic bile ducts in 236 (42 percent), and narrowing and malformation of the bile duct in the hepatic hilum in 58 (10 percent). The authors have proposed a new classification, including these morphologic anomalies of the whole pancreaticobiliary ductal system. This classification provides useful indices in selecting the surgical procedures. The effect of the anomalous arrangement was pathophysiologically studied on dogs. The static internal pressure of the dog pancreatic duct was 14.6 + or - 5.5 cm H2O, and that of the dog bile duct, 8.9 + or - 3.4 cm H2O. Puppies were then operated on by shunting the pancreaticobiliary ducts. As the result, the biliary tract was devastated by pancreatic juice, giving rise to similar pathologic changes to those clinically observed.