Strict Proportionality Research Articles

Pharmacokinetics of Orally Administered Pentoxifylline in Humans

The pharmacokinetics of pentoxifylline was studied in healthy male volunteers following single oral doses of 100, 200 and 400mg of the drug in solution. Concentrations of the drug and three of its metabolites were determined in plasma. The major urinary metabolite was also determined for 24hours after dosing. Pentoxifylline was rapidly and extensively absorbed at all doses. Peak plasma concentrations of pentoxifylline occurred between 0.29 and 0.41hours after dosing. Its metabolites, a secondary alcohol and two homologous carboxylic acids showed tmax values from 0.72 to 1.15hours. Cmax and AUC values increased in a dose-dependent manner for pentoxifylline and its metabolites over the three dose levels though strict dose proportionality could only be demonstrated for the principal carboxylic acid metabolite. The apparent plasma half-life of pentoxifylline varied between 0.39 and 0.84hours for the various doses while the apparent is half-lives of the metabolites were in the range of 0.96 to 1.61hours. The major circulating metabolites, the secondary alcohol and carboxypropyl derivative, were at consistently higher plasma concentrations than the parent drug. Two major pathways account for the circulating metabolites of pentoxifylline though oxidation of the parent drug to a carboxylic acid accounts for the formation of the principal urinary elimination product. Because of the pharmacological activities of pentoxifylline, studies are proposed of the pharmacokinetic-pharmacodynamic correlations of pentoxifylline and its metabolites. The present pharmacokinetic results further support the use of a controlled-release dosage form of pentoxifylline for therapy.

Mechanical Limits to Size in Wave‐Swept Organisms

Plants and animals that inhabit the intertidal zone of wave—swept shores are generally small relative to terrestrial or subtidal organisms. Various biological mechanisms have been proposed to account for this observation (competition, size—specific predation, food—limitation, etc.). However, these biological mechanisms are constrained to operate within the mechanical limitations imposed by the physical environment, and these limitations have never been thoroughly explored. We investigated the possibility that the observed limits to size in wave—swept organisms are due solely or in part to mechanical, rather than biological, factors. The total force imposed on an organism by breaking waves and postbreaking flows is due to both the water's velocity and its acceleration. The force due to velocity (a combined effect of drag and lift) increases in strict proportion to the organism's structural strength as the organism increases in size, and therefore cannot act as a mechanical limit to size. In contrast, the force due to the water's acceleration increases faster than the organism's structural strength as the organism grows, and thus constitutes a potential mechanical limit to its size. We incorporated this fact into a model that predicts the probability that an organism will be destroyed (by breakage or dislodgement) as a function of five parameters that can be measured empirically: (1) the organism's size, (2) the organism's structural strength, (3) the maximum water acceleration in each wave, (4) the maximum water velocity at the time of maximum acceleration in each wave, and (5) the probability of encountering waves with given flow parameters. The model was tested using a variety of organisms. For each, parameters 1—4 were measured or calculated; the probability of destruction, and the size—specific increment in this probability, were then predicted. For the limpets Collisella pelta and Notoacmaea scutum, the urchin Strongylocentrotus purpuratus, the mussel Mytilus californianus (when solitary), and the hydrocoral Millepora complanata, both the probability of destruction and the size—specific increase in the risk of destruction were determined to be substantial. It is conjectured that the size of individuals of these species may be limited as a result of mechanical factors, though the case of M. complanata is complicated by the possibility that breakage may act as a dispersal mechanism. In other cases (the snails Thais canaliculata, T. emarginata, and Littorina scutulata; the barnacle Semibalanus cariosus), the size—specific increment in the risk of destruction is small and the size limits imposed on these organisms are conjectured to be due to biological factors. Our model also provides an approach to examining many potential effects of environmental stress caused by flowing water. For example, these methods may be applied to studies of: (1) life—history parameters (e.g., size at first reproduction, age at first reproduction, timing of reproductive cycles, length of possible reproductive lifetime), (2) the effects of gregarious settlement on the flow encountered, (3) the physical basis for patterns of disturbance, (4) the optimum (as opposed to the maximum) size of organisms, and (5) the energetic cost of maintaining a skeleton with an appropriate safety factor. A definitive answer regarding the possibility of mechanical limits to size depends both upon an accurate measurement of the probability of encountering a wave of specific flow parameters and upon factors that are external to the model considered (e.g., life—history parameters). Further, due to their ability to move with the flow, organisms that are sufficiently flexible can escape the size limits imposed on more rigid organisms. Thus, some macroalgae attain large sizes (2—3 m in maximum dimension). The precise role of these factors awaits further research.

Use of the Hammett equation in substituted thiophenes

The application of multivariate statistics to linear free-energy relationships in the thiophene series increases the understanding of the Hammett equation. Principal components analysis shows that α-substituted thiophenes require the σ constants used for para-substituted benzene derivatives, owing to a strict proportionality of the substituent effects in the heterocyclic and homocyclic systems. Partial least-squares analysis indicates that two independent effects are linearly transferred from benzenes to thiophenes.

On the kinetics of isothermal crystallization of branched polyethylene

Isothermal crystallization of branched polyethylene was studied by time-dependent small-angle X-ray scattering experiments and dilatometry. A strict proportionality between scattering intensities and density changes was found for all times. This result indicates complete absence of crystal thickening and perfectioning processes. Isotherms directly reflect the increase in specific inner surface resulting from nucleation and lateral growth of lamellae. The shape of isotherms suggests a time-dependent non-uniform internal structure of spherulites with a decrease in specific inner surface with increasing distance from centre.

Specific-heat measurements and critical exponents of the ferroelastic phase transition inPb3(PO4)2andPb3(P1−xAsxO4)2

The ferroelastic phase transitions in ${\mathrm{Pb}}_{3}$${(\mathrm{P}{\mathrm{O}}_{4})}_{2}$ and ${\mathrm{Pb}}_{3}{({\mathrm{P}}_{1\ensuremath{-}x}{\mathrm{As}}_{x}{\mathrm{O}}_{4})}_{2}$ are accompanied by large excess specific heats in a wide temperature range above ${T}_{c}$ and critical crossover above and below ${T}_{c}$. Critical exponents of the specific heat ${\ensuremath{\alpha}}^{\ensuremath{'}}=0.363(4), 0.360(5), \mathrm{and} 0.36(1)$ for ${\mathrm{Pb}}_{3}$(${\mathrm{P}{\mathrm{O}}_{4})}_{2}$, ${\mathrm{Pb}}_{3}$${({\mathrm{P}}_{0.97}{\mathrm{As}}_{0.03}{\mathrm{O}}_{4})}_{2}$, and ${\mathrm{Pb}}_{3}$${{(\mathrm{P}}_{0.2}{\mathrm{As}}_{0.8}{\mathrm{O}}_{4})}_{2}$, respectively, agree with theoretical predictions of a $q=3$, $d=2$, Potts model. Along with other experimental results of neutron and Raman scattering, the specific-heat behavior above ${T}_{c}$ indicates dynamical fluctuations in ${\mathrm{Pb}}_{3}$${(\mathrm{P}{\mathrm{O}}_{4})}_{2}$ and a static intermediate phase in the mixed crystals. A strict proportionality between the transition entropy $\ensuremath{\Delta}S$ and the spontaneous birefringence $\ensuremath{\Delta}{n}_{\mathrm{bc}}$ was observed in ${\mathrm{Pb}}_{3}$(${\mathrm{P}{\mathrm{O}}_{4})}_{2}$ at temperatures up to 415 K. Nonlinear behavior was found close to the transition point (453.6 K), which is interpreted in terms of a multicomponent order-parameter theory.

Regulation of the pattern of basal bodies within the oral apparatus of Tetrahymena thermophila

The number and arrangement of basal bodies included in the four compound ciliary organelles making up the mature oral apparatus of Tetrahymena thermophila ordinarily vary only slightly. Severe starvation brings about formation of oral structures with a reduced number of basal bodies within these organelles, and sometimes with a complete loss of one of the component organelles. Such reductions are stringently specified in spatial terms, but they do not represent simple and proportional shrinkage of the organelle complex. Instead, certain spatial features remain essentially unaltered, while others undergo major quantitative reductions, resulting in large changes in the internal proportions of the structures. This selective regulation can be explained in terms of the different parallel and sequential processes taking place during the development of this organelle complex. There is also no strict proportionality between the size of the oral apparatus and that of the cell; instead, oral apparatuses become relatively larger as cells become smaller. This is due in part to the inherent temporal discontinuity of oral development, but there is probably also a real change in the oral/body size relation at the time of oral development. The 'French flag' rule fails when applied to the relative sizes and internal proportions of organelle systems in this and in other ciliates.

Ion induced electron emission from metal surfaces

The total electron emission yield γ of sputter-cleaned Al, Cu, Ag, W, and Au surfaces has been measured under bombardment with H +, H 2 +, H 3 +, He +, Ne +, and Ar + ions in the energy range from 80 keV to 1 MeV. The yield γ is found to be proportional to the electronic stopping power in the case of proton impact. Deviations from a strict proportionality are reported for the heavier ions. The yields induced by the molecular ions H 2 + and H 3 + are compared with the proton yields. It is found that the additional electron(s) of the molecular ions directly contribute to the secondary electron yield at the highest velocities of this experiment.

Probing and imaging techniques for surface studies

Recent progress in high resolution surface analytical techniques is reviewed with special emphasis on secondary ion mass spectrometry. Improvements in ion optics have made it possible to combine an element sensitivity in the 1000 ppm range with a surface resolution of the order of 0.3 μm. In stigmatic imaging of element distributions over areas of diameter 60 μm, a mass resolution better than 3000 has been achieved by transfer optics. The sensitivity of detection of negative ions has been greatly improved by caesium flooding which in many cases offers the added advantage of strict proportionality between ion yield and concentration. Depth profiling techniques and their limitations and prospects are discussed in detail. Examples include the evaluation of sputter-induced surface roughness from composition profiles. A new technique involving thermal dissociation and ionization of the particles sputtered from the surface provides strict proportionality of ion yields to concentrations in non-dilute systems. Non-destructive analysis of depth profiles using electron microprobes is possible by matching the observed dependence of X-ray emission signals on beam voltage against calculations for assumed concentration-depth distributions. Examples of this technique are given.

Positronium formation in xenon gas near the critical point

The amount of positronium formation in xenon gas has been determined from the intensity of the long lived component, I 3, in the positron decay spectrum. I 3 remains essentially constant for temperatures T > T c + 1 along the critical isochore. It decreases from the constant value for T < T c + Δ T where δ T ∼ 1 K, while for T < T c, I 3 of the vapor phase is found to be proportional to the vapor density of xenon. I 3 also decreases from strict proportionality at T > T c − Δ T. These variations of the positron formation are interpreted as due to scattering of the slowing down positrons by the increasing critical fluctuations which occur when T is near T c.

The decarboxylation of S-adenosylmethionine by detergent-treated extracts of rat liver.

1. The production of (14)CO(2) from S-adenosyl[carboxyl-(14)C]methionine by rat liver extracts was investigated. It was found that, in addition to the well-known cytosolic putrescine-activated S-adenosylmethionine decarboxylase, an activity carrying out the production of (14)CO(2) could be extracted from a latent, particulate or membrane-bound form by treatment with buffer containing 1% (v/v) Triton X-100 [confirming the report of Sturman (1976) Biochim. Biophys. Acta428, 56-69]. 2. The formation of (14)CO(2) by such detergent-solubilized extracts differed from that by cytosolic S-adenosylmethionine decarboxylase in a number of ways. The reaction by the solubilized extracts did not require putrescine and was not directly proportional to time of incubation or the amount of protein added. Instead, activity a showed a distinct lag period and was much greater when high concentrations of the extracts were used. The cytosolic S-adenosylmethionine decarboxylase was activated by putrescine, showed strict proportionality to protein added and the reaction proceeded at a constant rate. Cytosolic activity was not inhibited by homoserine or by S-adenosylhomocysteine, whereas the Triton-solubilized activity was strongly inhibited. 3. By using an acetone precipitate of Triton-treated homogenates as a source of the activity, it was found that decarboxylated S-adenosylmethionine was not present among the products of the reaction, although 5'-methylthioadenosine and 5-methylthioribose were found. Such extracts were able to produce (14)CO(2) when incubated with [U-(14)C]-homoserine, and (14)CO(2) production was greater when S-adenosyl[carboxyl-(14)C]methionine that had been degraded by heating at pH6 at 100 degrees C for 30min (a procedure known to produce mainly 5'-methylthioadenosine and homoserine lactone) was used as a substrate than when S-adenosyl[carboxyl-(14)C]methionine was used. 4. These results indicate that the Triton-solubilized activity is not a real S-adenosylmethionine decarboxylase, but that (14)CO(2) is produced via a series of reactions involving degradation of the S-adenosyl-[carboxyl-(14)C]methionine. It is probable that this degradation can occur via several pathways. Our results would suggest that part of the reaction occurs via the production of S-adenosylhomocysteine, which can then be converted into 2-oxobutyrate via the transsulphuration pathway, and that part occurs via the production of homoserine by an enzyme converting S-adenosylmethionine into 5'-methylthioadenosine and homoserine lactone.

Quantitative auger electron spectroscopy: Modulating the spectrometer

AbstractAs part of an on‐going programme at the National Physical Laboratory on the quantification of surface spectroscopies, it is shown that, in using the modulation technique for quantitative Auger electron spectroscopic analysis in the differential mode, care must be taken in applying the modulation. With the complex electron spectrometers now being employed for combined X‐ray photoelectron and Auger spectroscopic work, error signals can be added into the spectra by several of the proposed systems of modulation. The error signals are analysed quantitatively and are shown to be important at energies below 200 eV. Similar error signals can be found in the case of the cylindrical mirror analyzer. To obtain the correct derivative spectrum care must be taken to modulate the whole electron spectrometer with AC levels in strict proportionality to the incremental DC changes appropriate to each of the electrodes.

Influence of Temperature Between Floral Initiation and Flag Leaf Emergence on Grain Number in Wheat

Plants of Kalyansona, Condor and Janak semidwarf wheats, grown at a density of 130 plants m-2, were transferred every 4 days after floral initiation of the main shoot from temperature regimes of 27/22°C and 21/16°C to a regime of 15/10°C to determine if specific developmental stages of the ear are particularly important to the establishment of grain number. No stages between the appearance of double ridges and flag leaf emergence were significantly more sensitive to temperature changes than others, there being a progressive reduction in grain number per ear for every day that plants of Kalyansona and Condor remained at a higher temperature. Grain number of the main ear was closely correlated with the amount of dry matter in the stem, in the ear structure (chaff), and in the four uppermost leaves of the main shoot; the partial correlation coefficients demonstrated that leaf weight was best related to grain number. Thus large shoots with heavy ear structures had many grains and vice versa. It can be inferred from these results that the distribution of dry matter to the various plant organs before anthesis is in a strict proportionality irrespective of the availability of assimilates.

The Hubble diagram for supernovae

view Abstract Citations (52) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Hubble diagram for supernovae. Branch, D. ; Bettis, C. Abstract The distribution of 47 type I and 13 type II supernovae (SN) in the Hubble diagram is presented and evaluated. Values of the parameter Mpg(100) and the dispersion are determined by least-squares fits to various data subsets, and the results are compared with those of previous studies. Sources of scatter are considered, specifically inaccurate corrections for interstellar extinction in the Galaxy, systematic and random departure from a strict proportionality between velocity and distance, errors in estimates of apparent magnitudes at maximum brightness, and interstellar extinction in the parent galaxies. It is found that: (1) the observed dispersion among type I SN in elliptical galaxies is comparable to that expected from the first three sources of scatter; (2) only two of the type I SN occurred in irregular galaxies; (3) the distribution of type I SN in spirals shows a steeper slope than would be expected in the absence of scatter; and (4) the best value for the mean absolute magnitude should be that obtained for SN in ellipticals, corresponding to Mpg(100) = -18.70, provided the intrinsic properties of type I SN do not depend on parent-galaxy type Publication: The Astronomical Journal Pub Date: March 1978 DOI: 10.1086/112196 Bibcode: 1978AJ.....83..224B Keywords: Hubble Diagram; Supernovae; Elliptical Galaxies; Interstellar Extinction; Least Squares Method; Spiral Galaxies; Astronomy; Hubble Diagram:Supernovae; Luminosities:Supernovae full text sources ADS | data products SIMBAD (60) NED (60)

Precision half-life measurements using Ge(Li) detectors

Three correction methods for counting losses - a constant pulser, a proportional feed-back pulser and a pile-up rejector technique - have been examined in conjunction with a Ge(Li) detector and a slow electronic system. Computer simulations of multi-component, multi-sample half-live data indicate that the rejector method should be preferred over the pulser feed-back method for precision measurements. The latter technique is comparable if strict pulser proportionality to the half-life under investigation is maintained. Maximum accuracy is always obtained if each data sample is corrected for losses before summation to other data. Summing of several data sets before counting loss correction always introduces an error, unless the samples contain only one half-life component. The improper statistical analysis of accumulated data has been found to give rise to errors comparable in size to counting loss correction errors. It is found that a weighted mean anomaly must be considered, distinct from the logarithmic weighting effect described by Robinson 4). This effect is found to shift the apparent half-life a few standard deviations from the true half-life. Precision half-life measurements are reported for 10 C: (19.28 ± 0.02) s, 14 O: (70.43 ± 0.18) s, and 23 Mg: (11.26 ± 0.08) s .

Quantitative zytochemische Untersuchungen der Veränderungen des Nukleoproteins von Spermien bei Fertilitätsstörungen des Mannes

Introduction There is some evidence that fluctuations of the Feulgen-DNA content of spermatozoa associated with male infertility do not represent true differences in DNA content. It is rather the changes of the nuclear proteins modifying the stoichiometry of the Feulgen reaction which seem to be responsible for these facts ( Gledhill et al., 1966 ). These phenomena should be more precisely defined, as proposed by Sandritter et al. (1965) by investigating the kinetics of the “Feulgen hydrolysis curve” of the spermatozoa. Material and Methods Ejaculated spermatozoa were fixed immediately in 96% ethanol, hydrolyzed, as proposed by Bachmann (1968) at 39.5°C in 0.75 N HCL for 2, 3.5 and 5 hours, and stained with Schiff's reagent ( Graumann, 1953 ) according to the Feulgen procedure. The total dye content of the stained spermatozoa was determined using a type GN 2 scanning integrating microdensitometer (Barr & Stroud, Glasgow, Scotland). The nuclei of 50 sperm heads of each slide were measured at 570 nm, the mean value and the variation of the measurements calculated. The significance of this variation between the spermatozoa of fertile and infertile men was checked by an F-test. Furthermore, the hydrolysis curves of spermatozoa of fertiles and infertiles were compared. Fertility and infertility were identified by standard andrological examinations. Results and Discussion The hydrolysis curve of spermatozoa shows a fertility-linked significant difference as can be demonstrated by Figure 1. The mean values of dye content in arbitrary units (AE) of the spermatozoa of fertile male are lower and the curve does not reach a maximum after 5 hours of hydrolysis, indicating a different stoichiometry of the Feulgen reaction. The variations (s 2) of our cytophotometric measurements also show a difference between the populations of fertile and infertiles spermatozoa. The latter show a significant higher scattering of the cytophotometrically determined dye content after different hydrolysis times. The results of these calculations are summarized in Figure 2 and Table 1, insignificant values being drawn with heavy-faced typs. All these findings are considered as fertility-linked disturbances in synthesis and structure of acid nuclear proteins and the so-called (acid-insoluble) “residual proteins” of the sperm heads. Considering data of Bahr and Wied (1971) this control of protein synthesis seems to be lax under physiological conditions with respect to quantity but not to quality. This means that the macromolecular components of sperm cells are assembled without regard to strict proportionality. It now seems obvious that under pathological conditions linked to infertility, which is expressed by the abnormal histological pattern of spermiogenesis (Fig. 3), the lack of control of protein synthesis may increase. This simple investigation of the structure of nucleoproteins of the sperm head enables us to investigate the complex problems of male infertility.

Polyploidy in the human nervous system: Part 2. Studies of the glial cell populations of the purkinje cell layer of the human cerebellum

We have been able to confirm and extend previous findings reporting the presence of polyploid classes of glia within the Purkinje cell layer of the human cerebellum. This polyploidy is not age-dependent, and a strict numerical proportionality exists between these glial types and the Purkinje cell. For each Purkinje neurone there are 250 diploid, 50 tetraploid and 1 octoploid glial cells. We speculate as to the function of these glial types in relation both to the Purkinje cell itself and the cerebellum as a whole, and suggest that they may be producers of specific RNA species involved in cerebellar memory.

Early response of a tall, one-, two- and three-gene dwarf wheat varieties to increasing levels of nitrogen

Summary The fertilizer-N tolerance during germination and early growth of C 306, Sonalika, Kalyan Sona and U.P. 301—tall, one-, two- and three-gene dwarf wheat varieties respectively, have been determined. On equal N-basis, U.P. 301 (3-gene dwarf) well tolerated NH 4 Cl (up to 0.5% N, w/v) and C 306 (tall wheat) tolerated (NH 4 ) 2 SO 4 more than any other variety during germination. Except ammonium sulphate the remaining three forms of the fertilizers were less tolerated by the tall Indian wheat as against the dwarf Mexican wheat varieties. In general, the dwarf Mexican wheats tolerated higher doses of ammonium nitrate and ammonium sulphate nitrate and were susceptible to chloride in comparison to the tall Indian wheat variety. The inhibitory effect of different fertilizers on shoot and root elongation was in the order NH 4 NO 3 (NH 4 ) 2 SO 4 . NH 4 NO 3 (NH 4 ) 2 SO 4 NH 4 Cl which is in strict proportionality of the osmotic pressure developed. Germination seems to be more affected by ionic whereas elongation by osmotic effects and the tolerance limits for germination and shoot or root elongation are different.

Biosynthèse des acides gras dans les mitochondries végétales isolées

Mitochondria with good respiratory activities, as judged from polarographic studies of oxygen consumption, measurement of ADP/O and respiratory controls, have been isolated from cauliflower florets and potato tubers. Examination of the centrifugation pellets by means of electron microscopy have shown well‐preserved organelles, with a condensed matrix and a minimal contamination by other membranes. Additional mitochondria pellets have been prepared from germination roots of Vicia faba and Lupinus albus. In these mitochondria, the phosphorylations were not tightly coupled to oxidations. Total fatty acid compositions of the mitochondria isolated from the four different species were not identical: linoleic acid was predominant in potato and Vicia faba root mitochondria; linolenic acid was predominant in cauliflower or Lupinus albus root mitochondria. When isolated mitochondria, from any species, are incubated under aerobic conditions in a suitable solution containing various cofactors (ATP, NADPH, CoASH, Mg2+) and a respiratory substrate (succinate), any one of the following labelled precursors: [1‐14C]acetate, [2‐14C] acetate, [1‐14C]acetyl‐CoA, [2‐14C]malonate or [2‐14C]malonyl‐CoA is incorporated into the mitochondrial fatty acids. The labelled fatty acids are the same, starting from any one of the four precursors, in the same conditions. With tightly coupled mitochondria, the incorporation of the labelled precursor into the mitochondria fatty acids is linear during 60 min, provided the mitochondria are furnished with a respiratory substrate. This is not true with uncoupled mitochondria. The amount of labelled acetate incorporated into the mitochondrial fatty acids increases with increasing quantities of mitochondrial proteins put in the incubation medium. With cauliflower mitochondria, a strict proportionality has been found between the biosynthesis intensities and the quantities of mitochondrial proteins; with the mitochondria of the other species, the incorporation intensities reach a plateau for high protein concentrations. The isolated mitochondria of the four species synthesize the same fatty acids under aerobic conditions, i.e. palmitic, hexadecenoic, stearic and octadecenoic acids. (These newly synthesized fatty acids are analyzed by radio‐gas chromatography.) No significant quantities of polyunsaturated fatty acids are formed. Mono‐unsaturated fatty acids are not synthesized under anaerobic conditions. Dilute mitochondrial suspensions synthesize predominantly palmitic (50%) and octadecenoic acid (40%); concentrated mitochondrial suspensions synthesize predominantly palmitic (50%) and stearic acid (30%). Dilute mitochondrial suspensions synthesize during the first 5 min of incubation exclusively palmitic and palmitoleic (9‐hexadecenoic) acid (identified by radio‐gas chromatography of the products of oxidative cleavage). With longer incubation times, newly synthesized oleic (9‐octadecenoic) acid and cis‐vaccenic (11‐octadecenoic) acid appear in great quantities in the isolated mitochondria, with only trace amounts of stearic acid.

Myrmekite and muscovite developed by retrograde metamorphism at Broken Hill, New South Wales

SummaryRetrograde metamorphism of gneisses and pegmatites leads in part to the destruction of feldspar and its replacement by late-stage lobate myrmekite and muscovite. Reactions promoted by retrogression suggest a range in volume of quartz production that may supplement that developed by exsolution and lead to deviations from the strict proportionality relationship suggested by previous workers. There is no need, however, to propose that quartz in myrmekite originates by constriction of pre-existing quartz within exsolved albite.

Cell wall components of various species of yeasts

Cell walls were obtained from three species of yeasts, Torulopsis aeris, Oospora suaveolens and Geotrichum lactis, and their components were analysed. The monosaccharide constituents found were glucose and mannose in T. aeris, and the same, plus galactose, in O. suaveolens and G. lactis. The only amino sugar in all three cases is glucosamine. An increase in total nitrogen and hexosamine was observed, together with a decrease in total sugars, as the morphological characteristics approached those of filamentous fungi. The mannan content of the wall of O. suaveolens was directly related to the age of the culture. Three polysaccharide-protein complexes were isolated from each species. Glucose, mannose and galactose were present in quantities which varied from fraction to fraction in each case, but not in the strict proportions which have been found by other authors. There is no qualitative difference to be observed in the amino acid content of each fraction, the twelve most common in protein being present. Our analyses do not suggest that these fractions represent, as such, structural units in the cell wall. Examination of one fraction revealed that the original form of the cell remains in some cases. In these cases a large amount of hexosamine was present, which suggests that the fraction concerned contains the chitin of the original cell wall.