Slice Spacing Research Articles

The wave equation in asymptotically retarded time coordinates: Waves as simple, regular functions on a compact manifold

The Minkowski‐space scalar wave equation is represented on a spatially compact manifold with an asymptotically retarded time. In this coordinate system, with hyperbolic space slices and space coordinates generated by a conformal map, the wave equation takes a simple time‐independent form which may form a model for numerical integration calculations with nonlinear wave equations.

4.リング型エミッションCT(I.RI画像構成とその評価)(第37回総会)

Emission computed tomograph (ECT) consists of detector system, mechanism for scanning, electronics for data access and control, and computer system. ECT images have to be reconstructed carefully to correct for tissue absorption, to reduce scattered radiation and so on. These were described in detail. Also here mentioned basic design and performance of HEADTOME system developed in our institute as a first dual purpose emission computed tomograph for positron and single photon emission imaging. The system has shown the resolution of 10 and 11 mm FWHM at center (of field of view) with ^<99m>Tc and ^<68>Ga, respectively, and the sensitivity of 20 Kcps/μCi/ml (with 20 mm slice spacing). The HEADTOME is routinely used in clinical study.

Amino Acid Uptake by Bovine Mammary Slices

A method which measures amino acid uptake by bovine mammary slices is described. Slices of approximately 200mg were preincubated for 1h in a modified Krebs-Ringers bicarbonate buffer containing a physiological mixture of amino acids. After preincubation, slices were incubated with radioactive amino acid for 10min. Slices then were homogenized in perchloric acid, centrifuged, and a sample of the supernate was counted for radioactivity. In parallel experiments, the percent tissue water was determined by drying slices to constant weight. Extracellular space of slices was measured with inulin. These measurements allowed uptake to be expressed in terms of amino acid concentration in the cell water. The in vitro uptake pattern of nine essential amino acids was compared to the known in vivo uptake pattern of these amino acids by the cow udder. The correlation between in vitro, and in vivo uptake patterns was .91, suggesting that the tissue slice technique can be useful in further study of bovine mammary amino acid transport.

Effects of polyvalent cations on electrolyte transport and inulin space of rat kidney cortical slices.

Effects of polyvalent cations on electrolyte transport and inulin space of rat kidney cortical slices.

EVOLUTION OF THE RECREATIONAL FUNCTIONS OF A TERRITORY

Space-time models, using a two-dimensional space system and time coordinate, are devised to analyze recreational development patterns in the Soviet Union, both around large cities and in specialized resort districts. A series of time and space slices of the three-dimensional models are considered to trace recreational development in its spatial and temporal dimensions around two major metropolitan centers–Moscow and Khar'kov–and in the resort district of Greater Sochi on the Black Sea. Discrepancies between idealized and real-life models of recreational development are noted and explained. [The paper is part of a program of research in recreational geography at the Institute of Geography, Moscow. A previous paper appeared in Soviet Geography, May 1977.]

&lt;i&gt;In vitro&lt;/i&gt; Use of Polyethylene-(1,2-&lt;sup&gt;14&lt;/sup&gt;C)-Glycol to Measure Extracellular Space in Renal Cortex Slices from Neonatal, Immature and Adult Mammals

Polyethylene-(1, 2-&lt;sup&gt;14&lt;/sup&gt;C)-glycol is a reliable probe of the extracellular space in renal cortex slices. The PEG distribution volume is similar to that measured with inulin (24–25% of wet slice weight at 30 min). Comparable values were found using PEG and inulin in slices from newborn, 4-week-old and adult animals. Contamination of PEG with low molecular polymers did not occur, in contrast with our experience with stored inulin.

Note on the spacetimes of Szekeres

We find that the "quasispherical" spacetimes of Szekeres have conformally flat space slices in comoving coordinates. These spacetimes can represent pressureless nonspherical gravitational collapse with no gravitational radiation. We give a restriction on general-relativistic exact solutions for matter with pressure which admit flat comoving slices.

Transmembrane Fluxes of Potassium in Dog Kidney Slices

The effect of warm ischemia on the transmembrane transport of potassium in dog kidney slices was studied by measurement of the uptake of 42K. The requirement for steady-state conditions concerning the intracellular potassium concentration was thereby studied. The total potassium content in the slices was found to be constant between 120 and 180 min incubation at both 25 and 37 degrees C. The cell water calculated from the total tissue water and 14C-inulin space in the dog kidney slices amounted to 38 ml-100 g wet weight-1 at 37 degrees C and 45 ml-100 g wet weight-1 at 25 degrees C and was found to remain constant for the incubation interval 120--180 min. The major part of the tissue uptake of 42K could be described by one single mono-exponential function under these conditions. The transmembrane influx at 37 degrees C calculated by using a modified Keynes formula amounted to 1.70 mmol K+-kg wet weight-1-min-1 after no warm ischemia and to 0.89 mmol K+-kg wet weight-1-min-1 after 2 h warm ischemia. The corresponding values for incubation at 25 degrees C were 1.26 and 0.77 mmol K+-kg wet weight-1-min-1, respectively. In the slices incubated at 25 degrees C, the potassium content was higher and the sodium content lower than in slices incubated at 37 degrees C.

Factors Influencing the Insulin Space in Cerebral Cortex Slices from Adult and 7‐Day‐Old Rats

The inulin spaces and swelling of brain cortex slices from adult and 7-day-old rats were measured under differing experimental conditions. At 37 degrees C inulin penetrated into larger compartments than at 0 degrees C in both age groups. At 37 degrees C the inulin space increased with decreasing concentration of inulin in the medium. At 0 degrees C the inulin space did not depend on the inulin concentration. The swelling of the slices at 37 degrees C diminished with increasing concentrations of inulin. Anaerobic conditions, 0.2, and 1.0 mmol/l sodium cyanide and 0.1 mmol/l dinitrophenol reduced the inulin space and caused increased swelling of the slices. 1.0 mmol/l sodium iodoacetate was ineffective. In anaerobic conditions the inulin space did not change significantly as a function of the inulin concentration. A serious disadvantage of the inulin space as an indicator of extracellular space is that its size depends on the inulin concentration used. The inulin itself may influence the size of the space to be measured. Inulin also in osmotically inactive concentrations considerably reduces the swelling of brain cortex slices.

Experimental myocardial ischemic injury. II. Effect of In vivo ischemia on dog heart slice function In vitro

The capacity of myocardium, acutely injured in vivo by ischemia, to maintain cell volume regulation in vitro was studied in dogs with posterior papillary muscle infarcts of 60 and 120 min duration. Non-ischemic control tissue maintained mean K + concentrations of about two thirds of the K + found in left ventricular myocardium in vivo and had tissue H 2O volumes which were virtually identical to those observed in vivo. The extracellular space of the control slices was greater than that estimated to be present in vivo. The slices of irreversibly-injured ischemic tissue were greatly swollen, showed low K + and Mg 2+ and often exhibited structural defects in the plasma membrane of the sarcolemma. In addition, damaged tissue showed a significantly increased inulin diffusible space after 60 and a greater diffusible space after 120 min of ischemia. These findings are new evidence indicating that increased myocardial cell membrane permeability is an early feature of irreversible ischemic injury.

The inulin space, solute concentrations, and weight changes in rat renal medullary slices incubated in iso-osmolal media, and their modification during anoxia and hypothermia.

1. The volume of distribution of [14-C]carboxyl inulin has been studied in slices of outer and inner medulla from rat kidney incubated in Krebs phosphate-bicarbonate Ringer, modified to render it iso-osmolal with the tissue fluids in these zones, under three conditions, (a) aerobically at 37 degrees C (control), (b) anoxically at 37 degrees C, and (c) aerobically at 0 degrees C. 2. Under control conditions near steady-state volumes of approximately 24 and 42 mul./100 mg wet weight slice were obtained for outer and inner medulla respectively during the period 10-30 min from the start of incubation. In the outer medulla the volumes of distribution in anoxic and hypothermic slices exceeded that in control slices during this time, but control values increased from 30 to 100 min so that after 100 min the distribution volumes were approximately 30 mul./100 mg under each set of conditions. 3. In the inner medulla control and anoxic slices had inulin distribution volumes of approximately 42 mul./100 mg during 10-30 min, rising to over 50 mul./u99 mg by 100 min. Slices incubated hypothermically reached a steady-state value of approximately 40 mul./100 mg by 30 min, which did not increase further for up to 100 min. 4. All slices lost about 10% of their initial weight during the first 3 min of incubation. Thereafter control slices maintained weight constancy for at least 30 min (outer medulla) or 100 min (inner medulla); slices incubated anoxically or hypothermically gained weight, the gains being greatest in anoxic outer and hypothermic inner medulla. 5. The K concentration within control slices (both zones), hypothermic outer and anoxic inner medulla attained equilibrium when slice [K] was approximately 8 times medium [K] (5-9 mM). In anoxic outer and hypothermic inner medullary slices [K] fell to a significantly greater extent, but interpretation of these findings in terms of slice K loss is subject to modification in respect of the increases in slice weight (water content) accompanying the [K] decreases. 6. There was a transient (1-3 min) rise in [Na] in all slices. This was followed by a [Na] decrease, which was most apparent in control slices, and finally a gradual increase towards medium [Na] (141 and 180 mM for outer and inner medulla respectively).

Norepinephrine uptake by the mycoardium of the senescent mouse in vitro.

Age-related delays in the uptake of norepinephrine (NE) by the rat myocardium were observed after subcutaneous injection of NE (Gey, Burkard, and Pletscher, 1965). We report here that in vitro uptake of 3H-NE by myocardial slices from healthy C57BL/6J male mice is not impaired by aging (8-28 mo.) at 0.1 ng/ml, 2.0 ng/ml, 1000 ng/ml of NE. Additionally, no age-related changes of inulin space in myocardial slices were observed. Hence, the delayed uptake observed in vivo by Gey et al. may be attributed to age-related changes in the absorption from the subcutaneous site.

The Free Space of Citrus Leaf Slices

Measurements of 36Cl and 22Na efflux have been used to estimate water free space and Donnan free space in Citrus (orange) leaf slices. The water free space within the slices amounts to about 0.025 ml/g fresh weight, suggesting that there is little infiltration of bathing solution into intercellular air spaces. The exchangeable cations of the Donnan free space within the slices total 20-25 μ-equiv/g fresh weight, and these values appear to reflect the exchange properties of the cell walls. The role of the free space as a 'reservoir' for ions in the intact leaf is discussed.

The contribution of adherent films of liquid on the cut surfaces of mouse brain slices to tissue water and "extracellular" marker space.

1. Equations for surface film thicknesses and “surface” spaces are derived from a simple geometric model of a tissue slice. 2. In agreement with this model, the tissue water, inulin space, and sucrose space of slices of mouse cerebrum exposed briefly to the incubation medium or to the marker substance increase linearly with slice thinness (I/thickness). 3. The adherent film of medium on the cut surfaces of brain slices has an effective thickness of 0.0056 mm at 0°C, and 0.0085 mm at 37°C. 4. On cut surfaces of unicubated tissue, the effective film thickness measured with inulin is 0.0080 mm at 0°C, and 0.015 mm at 37°C because of superficial penetration into damaged tissue. After incubation for 60 min these thicknesses become 0.014 mm at 0°C, and 0.022 mm at 37°C. The effective film thickness measured with sucrose is even larger because of greater penetration. 5. The adherent film of medium on cut surfaces contributes appreciably to the fluid content of slices. At 0°C it adds 0.27 ml/g of dry tissue or 7% to the fluid content of a fresh unincubated 0.2-mm thick slice, and 0.14 ml/g of dry tissue or 3.5% to the fluid content of a 0.4-mm slice; at 37°C it adds 0.41 ml/g of dry tissue or 11%, and 0.21 ml/g of dry tissue or 5% respectively.

Extracellular and intracellular distribution of inulin in rat brain cortex slices

The wash-out of car☐yl-[ 14C]inulin from brain cortex slices was found to follow a course, which in a semilogarithmic plot can be resolved into 3 monoexponentials, i.e. a fast, an intermediate and a slow component. The fast component follows diffusion kinetics and represents extracellularly located inulin in a space of 29.0 μl/100 mg initial wet wt. The intermediate component can be interpreted as representing either extracellularly or intracellularly located inulin, and amounts to 4–5 μl/100 initial wet wt. The slow component represents inulin located in a cellular compartment, the total volume of which can be calculated to 40–50 μl/100 mg initial wet wt. After 60 min of incubation with inulin in a balanced medium this cellular compartment is, however, only partly (1/7) filled; this intracellularly located amount of inulin, equivalent to 6 μl/100 mg initial wet wt., constitutes at least 15% of the ‘total inulin space’. It is concluded that the traditionally defined inulin space is not a measure of the extracellular space in brain cortex slices.

On the measurement of extracellular space in slices prepared from different rat brain areas

Extracellular space values were determined with either 14C-sucrose or 14C-inulin at different incubation time intervals (30 and 60 min) in rat brain slices prepared from the cerebellum, cortex, striatum and hypothalamus. At both time intervals and in all brain area slices, 14C-sucrose spaces were larger than 14C-inulin spaces. Efflux of 14C-sucrose but not of inulin could be resolved into two linear components with half-times of 1.6 and 15.0 min. Efflux of 22Na from each of the different brain areas also could be separated into two distinct components, the slower of which was increased by ouabain. Similarities between 22Na and 14C-sucrose movements indicate that there is a cellular accumulation of sucrose but not of inulin. An accurate estimation of functional extracellular space in brain slices could be derived from either the 14C-inulin space or the 14C-sucrose space corrected for cellular uptake. Values obtained range from approximately 12 ml/100 g (cortex) to 20 ml/100 g (cerebellum).

Kinetics of inulin penetration in cortex and medullary kidney slices.

The inulin space of dog kidney slices obtained from cortex and outer and inner medulla was evaluated by incubating the tissue at different time intervals in inulin Ringer. When the kidney was cut normal to the major axis of Henle's loops and collecting ducts, inulin uptake appeared to follow a single exponential time function in each renal region.When the organ was cut parallel to the major axis of Henle's loops the inulin space was greater and inulin uptake appeared to follow two exponential functions of time in each of the three renal regions. This would indicate that the plane of section can influence the apparent size of the extracellular space of kidney slices, as measured by the distribution of inulin.

A New Theory of Gravity

A new relativistic theory of gravity is presented. This theory agrees with all experiments to date. It is a metric theory; it is Lagrangian-based; and it possesses a preferred frame with conformally flat space slices. With an appropriate choice of certain adjustable functions and parameters and of the cosmological model, this theory possesses precisely the same post-Newtonian limit as general relativity.

Theoretical Frameworks for Testing Relativistic Gravity.IV. a Compendium of Metric Theories of Gravity and Their POST Newtonian Limits

Metric theories of gravity are compiled and classified according to the types of gravitational fields they contain, and the modes of interaction among those fields. The gravitation theories considered are classified as (1) general relativity, (2) scalar-tensor theories, (3) conformally flat theories, and (4) stratified theories with conformally flat space slices. The post-Newtonian limit of each theory is constructed and its Parametrized Post-Newtonian (PPN) values are obtained by comparing it with Will's version of the formalism. Results obtained here, when combined with experimental data and with recent work by Nordtvedt and Will and by Ni, show that, of all theories thus far examined by our group, the only currently viable ones are general relativity, the Bergmann-Wagoner scalar-tensor theory and its special cases (Nordtvedt; Brans-Dicke-Jordan), and a recent, new vector-tensor theory by Nordtvedt, Hellings, and Will.

Developmental changes in Na + , K + and ATP and in the levels and transport of amino acids in incubated slices of rat brain.

Abstract— Upon incubation, slices of brain tissue took up fluid; the degree of swelling increased with increasing age. No sweiling occurred in slices from foetal brain. Since this swelling was associated with increases in the inulin space, the percentage of inulin space in slices at the end of incubation increased during brain development. Most of the capacity for ion transport seemed to be absent from foetal brain. In vivo and in slices, Na+ was very high and K+ was very low in comparison to levels at other ages. There was a rapid change around birth, but no significant change at later ages. Upon incubation, Na+ levels increased in other slices, but not in slices of foetal brain. Upon incubation of the slices, ATP levels were restored to levels close to those in the living brain; there were no significant alterations in available energy during development to explain changes in amino acid transport. The composition of the free pool of cerebral amino acids in vivo changed with development, with some compounds (glutamic acid and related compounds) increasing, others (mostly‘essential’amino acids) decreasing, with age. These changes were not linear with time, and the level of a compound might exhibit several peaks during development. The uptake (influx) of taurine, glutamate and glycine into brain slices increased rapidly during the foetal and early neonatal periods, reached a maximum between 2 and 3 weeks of postnatal age and then declined to adult levels. The levels of steady‐state uptake with glycine also exhibited a maximal peak at 2‐3 weeks of postnatal age. Steady‐state uptake of taurine and glutamate reached adult levels by about 3 weeks of age. The pattern of inhibition of amino acid transport by two specific amino acid analogues changed during development for some amino acids (GABA, glycine and glutamate), indicating an alteration in substrate specificity. The results demonstrate complex changes in cerebral amino acid transport during development, with several maxima or minima and with changes in specificity for at least some compounds.