bluuebunny/crossref_metadata_2025 huggingface dataset:
NUTRITIONAL CONTROL OF SEXUALITY IN CHLAMYDOMONAS REINHARDI
Authors: Sager Ruth , Granick S.
Published: May 2004

1. Cells of Chlamydomonas reinhardi grown in the light or dark on standard medium require an additional exposure to light in the absence of a nitrogen source, in order to become sexually active. As the culture ages, the light requirement decreases.

2. This light requirement is a function of nitrogen depletion, as shown by the observation that cells from cultures grown to maturity on a low nitrogen medium in the light or in the dark, have no additional light requirement for zygote formation. The withholding of no other component of the medium has this effect.

3. In cells requiring light for zygote formation, the light can be supplied before the mating types are mixed, indicating that light is required, not for mating per se, but for the conversion of vegetative cells to gametes.

4. Gametes can be dedifferentiated to the vegetative state by any nitrogen compound which the cells can use for growth; and by further exposure to light in the absence of a nitrogen source, these vegetative cells can again become gametic.

5. Cells grown at different nitrogen levels become gametic at widely different cell concentrations of nitrogen and carbon and C/N ratios.

6. It is postulated that the role of light in gametic differentiation is indirect, providing by photosynthesis, energy for the mating process and carbohydrates to tie up excess nitrogenous reserves; and that the concentration of some particular nitrogen fraction or compound determines whether or not gametic differentiation is initiated.
USE OF A GLASS ELECTRODE FOR MEASURING RAPID CHANGES IN PHOTOSYNTHETIC RATES
Authors: Rosenberg Jerome L.
Published: May 2004

1. A continuously recording glass electrode apparatus has been described for measuring carbon dioxide concentration changes in solution. The limits of applicability of the apparatus have been analyzed.

2. The glass electrode apparatus has been used for the measurement of transient rates of photosynthesis by algal suspensions.

3. The decline of the photosynthetic rate in high light at carbon dioxide partial pressures less than 0.5 per cent atmosphere, observed in the glass electrode apparatus, has been confirmed by steady state experiments in which flowing gas streams were analyzed.
THE POSITION OF THE CELL NUCLEUS IN PATHWAYS OF HYDROGEN TRANSFER: CYTOCHROME C, FLAVOPROTEINS, GLUTATHIONE, AND ASCORBIC ACID
Authors: Stern Herbert , Timonen S.
Published: May 2004

A study has been made of calf thymus and liver tissue to ascertain the position of the nucleus with respect to mechanisms capable of hydrogen transfer. Although previous work had shown that reduced pyridine nucleotide coenzymes are produced in the course of nuclear metabolism, it has now been established that the flavoprotein system of cytochrome c reductase, cytochrome c, and most, if not all, of other flavoproteins are absent from nuclei. Metabolites capable of cytochrome c reduction, notably ascorbic acid and glutathione, have been demonstrated in the nuclei. Glutathione reductase has been found present in nuclei only to a minor extent, suggesting that nuclear glutathione might function largely in a capacity other than that of hydrogen carrier in the nucleus. Although no enzymatic relation could be established between ascorbic acid and hydrogen transfer in nuclei) it was possible to demonstrate a close association between ascorbic acid concentration and the mitotic process in lily anthers. The significance of the anaerobic character of nuclear metabolism to chromosome function is discussed.
THE INACTIVATION OF DILUTE SOLUTIONS OF CRYSTALLINE TRYPSIN BY X-RADIATION
Authors: McDonald Margaret R.
Published: May 2004

The activity of dilute solutions of crystalline trypsin is destroyed by x-rays. The inactivation is an exponential function of the radiation dose. The reaction yield of inactivation is independent of the intensity at which the radiation is delivered or the quality of the x-rays. The reaction yield increases with increasing concentration of trypsin, varying from 0.06 to 0.7 micromoles per liter per 1000 r for trypsin solutions ranging from 1 x 10–7 to 2 x 10–4 M.
CONSERVATION OF NUCLEIC ACIDS DURING BACTERIAL GROWTH
Authors: Hershey A. D.
Published: May 2004

In experiments of 6 hours duration, no replacement of phosphorus or purine and pyrimidine carbon in DNA, nor flow of these atoms from RNA to DNA, could be detected in rapidly growing cultures of E. coli. The slow replacement that has been demonstrated for many substances in non-proliferating tissues of other organisms, though it may occur also in bacteria, is not greatly accelerated under conditions of rapid cellular growth, and therefore cannot be a characteristic feature of synthetic processes.
REVERSAL OF THE STREPTOMYCIN INJURY OF ESCHERICHIA COLI
Authors: Wasserman Aaron E. , Lessner James M. , West Margaret K.
Published: May 2004

The number of viable Escherichia coli in a young, actively growing culture is decreased approximately 99.9 per cent by a 30 second exposure to 25 ϕg. streptomycin/ml. The injury induced by the antibiotic is only potentially lethal, however, and may be reversed by subculture within 5 minutes into fresh culture medium, NH4NO3, NH4Cl, (NH4)2HPO4, NH4 citrate, and NH4 tartrate. Subculturing into water, glucose, or MgSO4 results in a more marked decrease in the number of viable organisms. In KNO3, NaNO3, K2HPO4, and Na2SO4 solutions reversal occurs first, followed by a rapid decrease in viability.

True reversal of the streptomycin injury takes place, as demonstrated by the rapid rate of recovery to the viable count of the original culture. Development of resistance has been eliminated as the cause of regrowth since the streptomycin sensitivity of recovered cultures remained the same as that of the original culture.

The use of water as diluent for viability determinations potentiates the lethal effect of streptomycin activity. Several compounds, at various dilutions, substituted for water as the diluent gave rise to four types of responses, group I, NH4NO3, NH4Cl, KNO3, NaNO3, Ca(NO3)2, showed complete reversal of the streptomycin injury at all levels of the salts tested, from 0.01 to 0.5 M concentrations. Group II, NaCl and K2HPO4 showed complete reversal at 0.03 and 0.1 M. Group III, glucose and urea allowed complete reversal at 0.5 M. Group IV, glycerol and glycerine showed no reversal at 0.5 M concentration.

The reversal of the streptomycin injury to young actively growing bacteria is suggested as a tool for studying the pathology of the injury to the cells.
KINETICS OF AMINO ACID INCORPORATION INTO SERUM PROTEINS
Authors: Green H. , Anker H. S.
Published: May 2004

1. The effect of varying body temperature on the rate of amino acid incorporation into serum protein does not give support to the idea that the rate of this process is adjusted in vivo to restore those protein molecules destroyed by thermal denaturation. The experimentally observed Q10 was about 3.9.

2. When amino acids are injected into the blood of animals in a steady state of serum protein turnover, a period of time elapses before these amino acids can be found in the serum proteins. This has been called transit time. At a given temperature (31°) it is the same in rabbits, turtles, and Limulus (1 hour). In rabbits and turtles it has a Q10 of 3.2. It appears to be specifically related to the process of synthesis (or release) of serum proteins.

3. It was not possible to affect the transit time or the incorporation rate by the administration of amino acid analogues.
ACTIVE SODIUM UPTAKE BY THE TOAD AND ITS RESPONSE TO THE ANTIDIURETIC HORMONE
Authors: Kalman Sumner M. , Ussing Hans H.
Published: May 2004

A method has been described in which sodium uptake may be studied in the intact, anesthetized toad. Sodium uptake is determined by "counting" the whole animal in a special chamber after suspending it in a frog Ringer bath containing radioactive Na24. The effects of subcutaneous injection of the neurohypophyseal antidiuretic factor were studied with these results:

1. There was a pronounced increase in sodium influx following treatment with the hormone.

2. Sodium outflux was small in both experimental and control animals.

3. There was an increase in water uptake in both experimental and control animals after 1 hour in the bathing solution. This increase was greater in the experimental toads in which it is believed to be related, at least in part, to sodium transport.

4. Potentiometric measurements were made on the skin membrane potential of the whole animal while suspended in bathing solutions. These results were in essential agreement with those found for isolated frog skin. However, there was no apparent influence of the antidiuretic factor on the skin potential.
POTASSIUM TRANSPORT IN HUMAN ERYTHROCYTES: EVIDENCE FOR A THREE COMPARTMENT SYSTEM
Authors: Solomon A. K. , Gold G. Lennard
Published: May 2004

Whole human blood is incubated for periods of ½ to 3 hours with K42 at 37°C. At the close of this period, called pre-incubation, the plasma is removed from the cells and the cells, now become radioactive, are again incubated in a mixture of plasma and buffer for periods of up to 10 additional hours. The time course of the K42 activity of the incubating medium is followed. Characteristically, after 2 hours of pre-incubation, the activity in the medium rises to a peak about 1 and ½ hours after resuspension, and then falls slowly until at 10 hours it is very close to its initial value at the beginning of the resuspension interval. This transient rise in K42 activity in the medium is taken to indicate that the red cell does not consist of a single uniform K compartment, but contains at least two compartments. Thus one cellular compartment contains a reservoir of high specific activity K which provides the specific activity gradient necessary to drive the K42 content of the medium to its transient peak. Experiments with Na indicate that its behavior in this respect is unlike that of K.

The experimental data are matched to a simple model system which is capable of theoretical analysis with the aid of an analogue computer. The model system, whose characteristics agree fairly well with those observed experimentally on red cell suspensions, comprises two intracellular compartments, one containing 2.35 m.eq. K/liter blood, and the other 44.1 m.eq. K/liter blood. The plasma K content is 2.64 m.eq./liter blood. The flux between plasma and the smaller intracellular compartment is 0.65 m.eq. K/liter blood hour; that between the smaller and the larger intracellular compartment, 1.77 m.eq. K/liter blood hour; and that between the larger intracellular compartment and the plasma is 0.34 m.eq. K/liter blood hour.
SOME OBSERVATIONS ON PROTEIN METABOLISM IN CHROMOSOMES OF NON-DIVIDING CELLS
Authors: Allfrey V. G. , Daly M. M. , Mirsky A. E.
Published: May 2004

1. The metabolism of chromosomal proteins has been studied in the pancreas, liver, and kidney of adult mice (a) by measuring the rates of glycine-N15 incorporation into histones and residual chromosome fractions, and (b) by measuring the extent to which N15, once incorporated into chromosomal proteins, is retained.

2. The uptake of isotopic nitrogen by these nuclear constituents was compared with that of protein fractions prepared from the cytoplasm by differential centrifugation in sucrose solutions. One such fraction, which comprises the bulk of the ribosenucleoprotein of the cell sediments as a pellet on high speed centrifugation. The supernatant remaining after this centrifugation is a fraction which, in the pancreas, is rich in the secretory enzymes synthesized by the cell.

3. A comparison of the rates of glycine-N15 uptake shows that cytoplasmic ribonucleoprotein is the most active of the protein fractions analyzed. In the pancreas it meets the conditions required of a precursor for the secretory enzymes of the supernate.

4. In all tissues considered the rates of glycine-N15 uptake into histone and residual chromosome fractions are lower, that for histone being the lowest of any of the protein components considered and that for residual protein approximating the over-all rate for cytoplasmic protein.

5. The effects of feeding and fasting upon glycine-N15 incorporation have been studied. In the pancreas, feeding causes a sharp increase in N15 uptake by the mixed tissue proteins and by the nucleoprotein and supernatant protein of the cytoplasm. There is a parallel increase in N15 uptake by the chromosomal constituents—histone and residual protein.

6. A parallelism between N15 uptake in cytoplasmic and chromosomal proteins is also observed in the liver and kidney when over-all protein metabolism is altered by feeding and fasting.

7. The responsiveness of the histones and residual proteins to changes in the environment has also been demonstrated in N15 retention experiments. The loss of isotope once incorporated into chromosomal proteins is much more rapid in fed than in fasted animals.
A STUDY OF THE PROPERTIES OF THE FREE AMINO ACID POOL AND ENZYME SYNTHESIS IN YEAST
Authors: Halvorson Harlyn , Fry William , Schwemmin Donald
Published: May 2004

A study has been made of the distribution and properties of the free amino acid pool in yeast. The depletion of the pool was found to depend upon the energy source used, conditions of growth, and the nature of the exogenous nitrogen source. Pool levels could be restored either by an internal replenishment mechanism or by various nitrogen sources. In the absence of internal replenishment a strong positive correlation was established between the ability of nitrogen compounds to support free glutamic add synthesis and enzyme-synthesizing capacity. Amino acid assimilation by nitrogen-starved yeast was studied and compared with that in other organisms. The significance of these results for the problem of enzyme and protein synthesis in yeast is discussed.
THE SPECIFIC HEAT AND THE HEAT OF COMPRESSION OF HUMAN RED CELLS, SICKLED RED CELLS, AND PARACRYSTALLINE RAT RED CELLS
Authors: Ponder Eric
Published: May 2004

The investigation of two thermal properties of red cells throws some light on whether sickling is a process involving the crystallization of a relatively insoluble hemoglobin. These properties are the specific heat and the heat of compression, both of which would be expected to become numerically less if the hemoglobin of the red cell were to crystallize. In the case of paracrystalline rat red cells, which give spacings at 45 A and 58 A by x-ray diffraction, the specific heat is reduced to 85 per cent of that of the normal red cells, and the heat of compression is only about 75 per cent of that found for the normal red cell. In the case of the red cell sickled by a reduction of the O2 tension, the specific heat and the heat of compression are substantially the same as found for the normal red cell. This is an argument against sickling being the result of a crystallization process, and supports the observation that sickled cells do not give x-ray spacings. The result is compatible, on the other hand, with sickling being the result of the formation of an oriented and birefringent gel.
RELATIONSHIP BETWEEN THE ACTIVITY OF THE SUCCINOXIDASE SYSTEM AND THE RATE OF OXYGEN CONSUMPTION DURING THE EMBRYONIC DEVELOPMENT OF THE MEALWORM, TENEBRIO MOLITOR LINNAEUS
Authors: Ludwig Daniel , Barsa Mary C.
Published: May 2004

1. Readings were made on the rates of oxygen consumption and on the activities of the succinoxidase system of eggs of the mealworm for each day of embryonic development at 30°C.

2. The rate of oxygen consumption, expressed as microliters/50 eggs/hour, was low (4.89) in newly laid eggs. It rose to 7.41 during the next 24 hours, remained at this level for the next 2 days, and then increased during the remainder of the embryonic period reaching a high value of 14.79 at the time of hatching.

3. The activity of cytochrome oxidase in eggs from newly emerged beetles, expressed as Δ log [Cy Fe++]/minute, remained at a value of 0.042 during the first half of the embryonic period, increasing to 0.233 during the latter half of this period.

4. The activity of succinic dehydrogenase showed the same series of changes except at much lower values. Expressed as Δ log [Cy Fe+++]/minute, they ranged from 0.010 in the newly laid egg to 0.034 at the end of the embryonic period.

5. The activity of cytochrome oxidase of the egg was found to decrease with parental age. Eggs from newly emerged beetles had activity values considerably higher than those of beetles 6 or 8 weeks after emergence. However, no comparable changes were noted in the activity of succinic dehydrogenase or in the rate of oxygen consumption. These observations suggest that cytochrome oxidase is not a rate-limiting enzyme in the respiratory metabolism of the mealworm egg.
MONOSYNAPTIC REFLEX RESPONSE OF SPINAL MOTONEURONS TO GRADED AFFERENT STIMULATION
Authors: Hunt Carlton C.
Published: May 2004

Monosynaptic reflex response of spinal motoneurons to graded afferent volleys has been studied in natural populations and in a representative sample of individual motoneurons. By analysis of input-response relations certain of the requirements for initiation of reflex discharge have been defined.

Initation of motoneuron discharge by monosynaptic afferent excitatory volleys results from the development of transmitter potentiality among members of a pool. Transmitter potentiality is considered to have the following characteristics:

1. It is a function of the number of active excitatory synaptic knobs, the degree to which such knobs are aggregated on the motoneuron soma, and the intensity of action per knob.

2. It has an appreciable spatial decrement and rapid temporal decay.

3. While transmitter potentiality has considerable dependence on number of active excitatory knobs, proximity of such knobs is an important variable. Total activation of a discrete zone does not appear to be necessary for initiation of discharge.

In addition to initiation of discharge, volleys in monosynaptic afferent excitatory fibers facilitate response otherwise engendered. Such facilitation depends upon the production of an increment in transmitter potentiality. Facilitator potentiality has the following characteristics:

1. It depends principally on number of active excitatory synaptic knobs and intensity of action per knob.

2. Facilitatory action may result from synchronous activity in knobs interspersed among aggregations of knobs otherwise activated, thus fulfilling spatial requirements for transmitter potentiality. Alternatively a residual facilitation may result from a generalized action.

3. Residual facilitation has a slow temporal decay in comparison with transmitter potentiality.
ELECTROLYTE DISTRIBUTION AND ACTIVE SALT UPTAKE IN FROG SKIN
Authors: Huf Ernst G. , Wills Joyce P. , Arrighi Mary F.
Published: May 2004

1. The "chloride space" in frog skin was determined and found to be 69.7 per cent by weight of wet skin. The chloride space occupies about 94 per cent of the total water space of skin. From this and other information, it appears that the "non-chloride space" measures only a part of the space occupied by the structural elements of skin. This space is referred to here as the intracellular compartment and the remainder as the extracellular compartment of frog skin. On this basis, potassium and sodium in skin are distributed as follows: total sodium, 60 to 75 µeq./gm. of wet skin; all sodium is probably extracellular; total potassium, 39 to 49 µeq./gm.; intracellular potassium, 37 to 47 µeq./gm.

2. Skins were immersed in solutions differing from each other in their sodium and potassium concentrations. Three levels of NaCl were studied: 48, 119, and 169 µeq./ml. For each of these solutions (referred to below as diluted, physiological, and concentrated saline), the potassium levels were varied from 0.1 to 20 µeq./ml. For skins in solutions low in potassium and high in sodium, it was found that an exchange of intracellular potassium against extracellular sodium occurs. The ratio for the number of potassium ions lost/number of sodium ions gained was 4:1,4:6, and 4:8 for skin in K+-free diluted, physiological, and concentrated saline, respectively.

3. Uptake of NaCl by the epithelium of frog skin is dependent on the potassium concentration of the environment. For skins in physiological saline, net uptake of NaCl was optimal (0.90 µeq. x cm.–2 x hr.–1) at 1 to 5 µeq. K+/ml. For skins in diluted and concentrated saline optimal NaCl uptake was seen at potassium concentrations of approximately 5 and 10 µeq. K+/ml., respectively. Net uptake of NaCl by the skin is also discussed, with relation to the potassium balance of skin.

4. Skin potentials decreased with increasing extracellular potassium concentration when diluted saline solutions were used. The opposite of this was found for skins in concentrated saline. For skins in physiological saline, skin potentials rose sharply from rather low values, when placed in solutions very low in potassium, to relatively high values, when immersed in solutions containing 1 to 5 µeq. K+/ml. Further increase in potassium concentration of the bath led to slight reductions in skin potentials. The highest potentials observed were of the order of 40 mv. In all cases studied, the inside was positive with relation to the outside.

5. It can be shown that values for intracellular potassium concentration as a function of extracellular potassium concentration satisfy, at a first but good approximation, Freundlich's isotherm. A modification of Freundlich's isotherm, recently introduced by Sips, may also be used to correlate the experimental data quantitatively. Since the latter isotherm has a rational interpretation, it is suggested that this be used, rather than Freundlich's isotherm, to express quantitatively the dependence of intracellular on extracellular potassium in frog skin.
RELATIONS BETWEEN PIGMENT CONTENT AND PHOTOSYNTHETIC CHARACTERISTICS IN A BLUE-GREEN ALGA
Authors: Myers Jack , Kratz W. A.
Published: May 2004

1. The blue-green alga Anacystis nidulans was cultured under steady state conditions at 25 and 39°C. and under several different light intensities to give five different types of cells.

2. Cells were submitted to pigment analysis based upon acetone extracts and aqueous extracts obtained by sonic disintegration. The different cell types show a threefold range of chlorophyll content and a fourfold range of phycocyanin content with only minor changes in the chlorophyll/phycocyanin ratio. Cells of highest pigment content were estimated to contain 2.8 per cent chlorophyll a and 24 per cent phycocyanin, the latter on a total chromoproteid basis.

3. Light intensity curves of photosynthesis were obtained for each of the cell types at 25 and at 39°C. The slopes of the light-limited regions of the curves are approximately linear functions of chlorophyll and phycocyanin contents. Maximum light-saturated rates of photosynthesis at 25 and 39° show no simple relation to pigment content.
A DEVICE FOR GROWING BACTERIAL POPULATIONS UNDER STEADY STATE CONDITIONS
Authors: Fox Maurice S. , Szilard Leo
Published: May 2004

A device for maintaining an exponentially growing population of bacteria in the steady state at maximal growth rates is described.
MUTATION RATES OF BACTERIA IN STEADY STATE POPULATIONS
Authors: Fox Maurice S.
Published: May 2004

The breeder and the chemostat have been used to measure mutation rates for two mutations under a variety of steady state growth conditions. These rates have been found to be higher in complex medium than in minimal (F) medium. The effects of changes in nutritional conditions on these high rates have been described. In addition, the mutation rates at short generation times, in complex medium, have been shown to decrease with increasing generation time.
DELAYED LIGHT PRODUCTION BY BLUE-GREEN ALGAE, RED ALGAE, AND PURPLE BACTERIA
Authors: Arnold William , Thompson Jane
Published: May 2004

1. Blue-green algae, red algae, and purple bacteria all show the emission of delayed light.

2. The action spectra for the production of delayed light by three species of blue-green algae have one broad band with a peak at 620 mµ.

3. The action spectrum for production of delayed light by the red algae has one peak at 550 mµ with a shoulder from 600 to 660 mµ.

4. The emission spectra of the delayed light from both the blue-green and red algae were the same as from the green algae, Chlorella.

5. The action spectra for the production of delayed light by the different species of purple bacteria tested consisted of one or more bands not resolved between 800 and 900 mµ.

6. The emission spectrum of the delayed light from the purple bacteria was largely at wave lengths longer than 900 mµ.
OSMOTIC DIURESIS AND ITS EFFECT ON TOTAL ELECTROLYTE DISTRIBUTION IN PLASMA AND URINE OF THE AGLOMERULAR TELEOST, LOPHIUS AMERICANUS
Authors: Forster Roy P. , Berglund Fredrik
Published: May 2004

Quantitative evaluations have been made of the chief anions and cations in plasma, urine, and pericardial fluid taken both from freshly captured goosefish and from those undergoing "laboratory diuresis." Measurements included: Na, K, Ca, Mg, Cl, SO4, PO4, protein, HCO3, NH3, pH, titratable acidity, freezing point depression, creatine, trimethylamine oxide, and plasma volume. The total patterns of electrolyte distribution in these body fluids are presented.

The morphologically undifferentiated aglomerular tubule acts as a barrier to the free diffusion of monovalent electrolytes, while transporting actively the divalent ions, especially Mg.

Urine taken from freshly captured fish is hypotonic to plasma, low in electrolyte, and as much as 50 per cent of its total osmolarity is accounted for by nitrogenous components. Of these creatine is transported most actively by the renal tubule cells.

With the onset of diuresis immediately after capture, plasma osmolarity slowly rises and urine suddenly becomes isotonic with plasma as chloride floods into the urine. The active movement of Mg continues during diuresis and urine/plasma concentration ratios of 100 or more are sustained for days while the animals are kept in the laboratory. Na follows chloride and never reaches 50 per cent of plasma values, and K never appears in urine in more than mere traces.

Electrolytes in this system are viewed as not being in true equilibrium but rather as constituting a biological steady state with the distribution across renal cells being maintained against passive diffusion by the expenditure of cellular energy.
NORTHROP'S PHENOMENON
Authors: Castañeda-Agulló M.
Published: May 2004

1. Evidence has been found that Northrop's phenomenon (so called by us) is produced in the digestion of casein or hemoglobin brought about by trypsin, papain, and pepsin either crude or crystalline in the presence of gelatin.

2. Anson's and Kunitz' methods permit the measure of proteolytic activity of any protease on casein or hemoglobin substrate in the presence of gelatin, even in very small quantities and with prolonged digestion time.
STUDIES ON THE BIOSYNTHESIS OF EXTRACELLULAR PROTEASES BY BACTERIA
Authors: Castañeda-Agulló M.
Published: May 2004

Apparently the extracellular protease of S. marcescens is present in protein- or protein derivative-free media only when the conditions favor an abundant growth and bacterial conglomerates are formed, which possibly could be explained by assuming that the proteins of dead bacteria or proteic metabolic products act as inducers of protease formation.

Dilute solutions of gelatin induce the production of proteolytic activity after a short period of time and its rapid increase before the initial number of bacteria has been duplicated.

Calcium is necessary to preserve the activity of the enzyme formed in synthetic media but not that produced in gelatin.
MITOCHONDRIA IN THE FLIGHT MUSCLES OF INSECTS
Authors: Levenbook Leo , Williams Carroll M.
Published: May 2004

1. In the present study a correlation has been sought between aging, flight muscle mitochrondria (sarcosomes), cytochrome c, and flight ability in the blowfly, Phormia regina.

2. During the 1st week of adult life, individual sarcosomes increase in mass from 2.7 x 10–7 µg. dry weight at the time of emergence, to 8.5 x 10–7 µg. by the 7th day. During this period of growth, the number of sarcosomes per fly (6.7 x 108) remains constant. When mature, the sarcosomes account for 32.6 per cent of the total muscle dry weight, or close to 40 per cent on a wet weight basis.

3. It appears probable that the high content of flight muscle cytochromes is entirely localized in the sarcosomes. The cytochromes continue to be synthesized and increase in titer within the sarcosomes for 7 days after adult emergence.

4. As determined spectroscopically, the various cytochrome components at all times maintain a constant ratio both to one another and to the sarcosomal dry weight. This suggests the possibility that the cytochrome system may be synthesized as a single entity.

5. The wing-beat frequency of Drosophila funebris and Phormia varies with the age of these flies, being lowest at the time of emergence and maximum after the 6th day.

6. The relations between wing-beat frequency, respiration during flight, and sarcosomal cytochrome c content are discussed. On the basis of some likely assumptions it is calculated that the cytrochrome c turnover number is over 5,000, and that the cytochrome c turns over once for every two wing-beat cycles.
THE EFFECT OF CHLORAMPHENICOL ON DEOXYRIBONUCLEIC ACID SYNTHESIS AND THE DEVELOPMENT OF RESISTANCE TO ULTRAVIOLET IRRADIATION IN E. COLI INFECTED WITH BACTERIOPHAGE T2
Authors: Tomizawa Jun-ichi , Sunakawa Sumiko
Published: May 2004

To elucidate the role of protein synthesis in DNA formation, E. coli R2 infected with phage T2 was studied as a model, employing chloramphenicol to inhibit protein synthesis. The following results were obtained.

1. Chloramphenicol inhibited protein synthesis but not synthesis of nucleic acids in uninfected bacteria.

2. Studies of the effect of chloramphenicol on phage maturation indicated a delay of 2 minutes between time of addition and cessation of phage growth.

3. The increase of DNA in phage-infected bacteria was completely suppressed by the addition of chloramphenicol within 2 minutes following infection. Addition at later times showed progressively less inhibitory action depending upon the time interval, and addition after the 10th or 12th minute showed no appreciable effect on DNA synthesis despite the cessation of intracellular phage formation and protein synthesis.

4. When chloramphenicol was added to infected cells the increase of resistance to UV stopped within 2 minutes, whether or not DNA synthesis continued. Thus evolution of resistance paralleled the rate of DNA synthesis achieved, but not the amount of DNA accumulated.

5. We conclude that in infected bacteria, protein synthesis is necessary to initiate DNA synthesis but is not essential for its continuation. The resistance to UV that characterizes infected cells near the midpoint of the latent period is not due to accumulation of DNA, but depends on some chloramphenicol-sensitive process (probably protein synthesis) completed at about the time the rate of DNA synthesis becomes maximal.
SULFHYDRYL GROUPS AND THE STRUCTURE OF HEMOGLOBIN
Authors: Riggs Austen F. , Wolbach Robert A.
Published: May 2004

1. Addition of 2 moles of mersalyl, mercuric chloride, p-chloromercuribenzoate (PCMB), or methyl mercury hydroxide per mole of hemoglobin greatly reduces heme-heme interactions (n), yet these substances have quite different effects on the oxygen affinity (-log p50). Mersalyl and mercuric chloride at this concentration each increase the oxygen affinity, while PCMB and methyl mercury have little or no effect on the oxygen affinity. These effects are primarily associated with the binding of —SH groups, and are largely reversed on the addition of glutathione. —SH groups do not appear to be responsible for the Bohr effect.

2. Evidence is presented for the belief that the two hemes of each half-molecule of horse hemoglobin are situated on either side of a cluster of—SH groups.

3. The mechanism of interaction between the hemes is discussed. It is concluded that the reorganization of the protein architecture which accompanies oxygenation plays a central role in this interaction, in agreement with the views of Pauling and Wyman.
THE UPTAKE OF RADIOCOLLOIDS BY MACROPHAGES IN VITRO
Authors: Gosselin Robert E.
Published: May 2004

Macrophages isolated from the rabbit peritoneal cavity extract radioactive colloidal gold from solutions in vitro. This reaction (ultraphagocytosis) involves two phases: the reversible adsorption of gold on the cell surface and the subsequent irreversible removal of surface-bound colloid into the cell. The latter process (called ingestion) appears to proceed at a rate which is proportional at any moment to the amount of gold attached to the cell surface; the latter in turn can be related to the concentration in extracellular fluid by a simple adsorption isotherm. In terms of rate, therefore, ingestion is related to the extracellular gold concentration in the same way that many enzyme reactions are related to the substrate concentration. Although enzyme kinetics are useful in describing rates of ultraphagocytosis, there is no evidence that enzymes participate in either adsorption or ingestion or that metabolic energy is required of the macrophage. Exudative leucocytes of the heterophilic series show little or no interaction with these finely dispersed gold sols (mean particle diameter 6 to 9 millimicrons).

37°C. three parameters are sufficient to characterize the reaction between gold and a suspension of macrophages, namely an affinity constant (1/Ks), an adsorption maximum (L), and a rate constant of ingestion (k3). Although numerical values differed markedly among cells of different exudates, all three parameters were estimated in three instances. In these suspensions between 2 and 20 per cent of the surface-bound gold was ingested each minute (37°C., pH 7.4). Under conditions of surface saturation, it was estimated that tens of thousands of gold particles were attached to the surface of an average macrophage; this amount of colloid, however, occupied less than 1 per cent of the geometric area of the cell surface. Although surface saturation imposed an upper limit on the rate of ingestion, no practical limit was noted in the capacity of macrophages to continue the reaction. Optical measurements imply that within the cell agglutination of colloidal gold began promptly after its ingestion.

These data are compared with published kinetic studies on the phagocytosis of microscopic particulates and on the parasitism of bacteria by virus.
OXIDATIVE ENZYME SYSTEMS OF THE HONEY BEE, APIS MELLIFERA L
Authors: Hoskins Dale D. , Cheldelin Vernon H. , Newburgh R. W.
Published: May 2004

1. Oxidative dissimilation has been studied in enzymes from the honey bee. Using mitochondria isolated from the thoraces, complete oxidation of most of the TCA cycle members has been shown.

2. The presence of the acetate-activating enzyme, citrate-condensing enzyme, isocitric dehydrogenase, α-ketoglutarate dehydrogenase, glucose-6-phosphate, and 6-phosphogluconic dehydrogenase has been demonstrated and the cofactor requirements established.

3. The oxidation of isocitric acid has been shown to be either non-specific for the D- or L-isomer, or the presence of a racemase is indicated.

4. The presence of the pentose cycle is indicated in the soluble portion of the thoracic homogenate.
VAGAL AND SYMPATHETIC EFFECTS ON THE PACEMAKER FIBERS IN THE SINUS VENOSUS OF THE HEART
Authors: Hutter Otto F. , Trautwein Wolfgang
Published: May 2004

1. Action potentials from sinus venosus and auricle fibers of spontaneously beating frog hearts have been recorded with intracellular electrodes.

2. Sinus fibers show a slow depolarization, the pacemaker potential, during diastole. The amplitude of this potential varies in different parts of the sinus. In some fibers the membrane potential falls by 11 to 15 mv. during diastole and the transition to the upstroke of the action potential is comparatively gradual. In other regions the depolarization develops more slowly and the action potential takes off more abruptly from a higher membrane potential. It is proposed that the fibers showing the largest fall in membrane potential during diastole are the pacemaker fibers of the heart, and that the rest of the preparation is excited by conduction. In auricle fibers the membrane potential is constant during diastole.

3. The maximum diastolic membrane potential and the overshoot of the action potential vary inversely with the amplitude of the pacemaker potential. The highest values were measured in auricle fibers.

4. Stimulation of vagi suppresses the pacemaker potentials. While the heart is arrested the membrane potential of the sinus fibers rises to a level above the maximum diastolic value reached in previous beats. In 28 experiments vagal stimulation increased the membrane potential from an average maximal diastolic value of 55 mv. to a "resting" level of 65.4 mv. The biggest vagal polarization was 23 mv.

5. In contrast to the sinus fibers vagal inhibition does not change the diastolic membrane potential of frog auricle fibers.

6. Vagal stimulation greatly accelerates the repolarization of the action potential and reduces its amplitude. These changes were seen both in the sinus and in auricle fibers stimulated by direct shocks during vagal arrest.

7. The conduction velocity in the sinus venosus of the tortoise is reduced by vagal stimulation. Block of conduction often occurs.

8. In the frog sinus venosus sympathetic stimulation increases the rate of rise of the pacemaker potential, accelerating the beat. The threshold remains unchanged. The rate of rise of the upstroke and the amplitude of the overshoot are increased.

9. The analogies between the vagal inhibition of the heart and the nervous inhibition of other preparations are discussed.
STUDIES ON THE EFFECTS OF SUBZERO TEMPERATURES ON THE VIABILITY OF SPORES OF ASPERGILLUS FLAVUS
Authors: Mazur Peter
Published: May 2004

1. The survival of spores of Aspergillus flavus suspended in distilled water and cooled rapidly to –70 to –75°C. was found to depend primarily on the rate of subsequent warming of the frozen suspension. Only 7 per cent of the spores germinated following slow warming at 0.9°C. per minute, whereas about 75 per cent germinated following rapid warming at 700°C. per minute.

2. Viability was dependent on the rate at which the suspensions warmed from –70 to 0°C. (subzero warming), but was not dependent on the rate of thawing of the frozen water in which the spores were suspended.

3. The logarithm of the percentage of germination appeared to be a linear function of the logarithm of the rate of subzero warming when spores were warmed at rates ranging from 0.12 to 1000°C. per minute.

4. The lethal effects of slow warming from –70 to 0°C. were more pronounced between about –20 and 0°C. than between –70 and –20°C. In the former range of temperatures, the percentage of germination decreased sharply as slow warming progressed towards 0°C.

5. Slow warming from –70 to 0°C. was more harmful to the spores than was a 1 or 2 hour exposure to constant temperatures between –70 and 0°C.

6. Slow warming was found to be more harmful than rapid warming when spores were suspended in horse serum, 0.16 molal sodium chloride, or 0.29 molal sucrose as well as in distilled water.
OLFACTORY PERCEPTION IN MIGRATING SALMON
Authors: Idler D. R. , Fagerlund U. H. M. , Mayoh Helen
Published: May 2004

The properties of a repellent for migrating salmon present in mammalian skin are discussed. l-Serine which is present in the washings of human skin has been shown to have repellent activity at extremely high dilution.
ACID-BASE PROPERTIES OF RHODOPSIN AND OPSIN
Authors: Radding Charles M. , Wald George
Published: May 2004

Purified preparations of cattle rhodopsin have been titrated to various pH, irradiated, and the pH changes followed thereafter until completed. In this way we have obtained the titration curves of rhodopsin, of the immediate product of irradiation, measured within 30 seconds; and of the final product of irradiation (opsin).

The rhodopsin preparations display about 54 titratable groups per mole of pigment: about 34 base-binding and 20 acid-binding groups. In default of an absolute purification, one cannot be sure that all of these go with rhodopsin itself.

Exposure to light induces an immediate rise of pH between pH 2 and 8, maximal at about pH 5. This—followed by its slow partial or complete reversal—is the only change of pH in the physiological range (6–7). It involves the exposure of 1 new acid-binding group per mole of rhodopsin with pK about 6.6, close therefore to that of the imidazole group of histidine.

At acid and alkaline pH this immediate change is followed by slower changes, occupying up to 40 minutes at 20°C. These changes are always in the direction of neutrality. They involve increases of 5 to 6 moles acid bound at acid pH, and 7 moles base bound at alkaline pH. They are associated with the irreversible denaturation of opsin in acid and alkaline solution, as evidenced by loss of its capacity to regenerate rhodopsin. Such frank denaturation procedures as the exposure of rhodopsin to alkali or heat in the dark result in comparable acid-base changes.
THE NON-CORRELATION OF BIOELECTRIC POTENTIALS WITH IONIC GRADIENTS
Authors: Shaw F. H. , Simon Shirley E. , Johnstone B. M.
Published: May 2004

The sartorius muscles of 320 toads have been analyzed for Na+ and K+. There is a wide variation in the Na+ content which when calculated intracellularly varied from 0 m.eq./kg. to 58 m.eq./kg. In particular it was found that the distribution of internal Na+ in the intact animal was such that only 17 per cent of the muscles should give from the Nernst equation the observed overshoot of 37 mv.

In contrast to this wide variation the K+ content is comparatively constant, the range being 71 to 112 m.eq./kg. The mean observed resting potential of 87 mv. agreed well with the potential calculated from the mean intracellular K+ by the Nernst equation.

Analyses of plasma show that the Na+ content is constant at 130 m.eq./liter, and the K+ is 3.0 m.eq./liter.

The resting and action potentials of 77 muscles have been recorded and then the muscles have been analyzed. The results have shown that there is no correlation between the level of intracellular Na+ and the overshoot. Furthermore the apparent correlation between the average K+ content and the average resting potential has been shown to be fortuitous, when the correlation in individual muscles is considered.

When a muscle is soaked in Ringer solution for several hours there is a gain of Na+ and a loss of K+. These shifts should result in changes in the respective potentials, but such changes were not found.

The above findings have been discussed in the light of the present theories that the resting potential and the action potential are directly related to the ionic ratio across the membrane. Our results very definitely do not support the theory that the overshoot is related to the Na+ gradient, and this also applies with respect to the K+ gradient and the resting potential.
CHANGES IN MEMBRANE CHARACTERISTICS OF HEART MUSCLE DURING INHIBITION
Authors: Trautwein W. , Kuffler S. W. , Edwards C.
Published: May 2004

Membrane characteristics were studied in isolated muscle strands from auricles of frogs using the "square pulse" technique. Changes in the time course and spatial spread of subthreshold electrotonic potentials were measured. If acetylcholine is applied in concentrations which cause slowing or stoppage of the heart beat, the following changes are produced: (a) the length constant (λ) of the membrane is reduced, (b) the time constant is shortened. The effects are reversible and increase with acetylcholine concentration. The membrane changes caused by acetylcholine dimmish with time.

It is concluded that during acetylcholine inhibition, as well as during vagal inhibition, the conductance of the muscle membrane is increased. Appreciable changes in the resting membrane potential need not accompany inhibition.
SOME PERMEABILITY PROPERTIES OF ISOLATED RAT LIVER CELL MITOCHONDRIA
Authors: Jackson Kenneth L. , Pace Nello
Published: May 2004

The rates of penetration of various solutes into isolated rat liver mitochondria have been studied.

Sodium, potassium, and sucrose were observed to enter the mitochondria until an equilibrium concentration was reached. The diffusion of these solutes, after the first few minutes, followed the predicted diffusion curve for solutes entering a particle with a rate-limiting membrane and instantaneous mixing in the interior. Reasons for deviations from the predicted equation during the first few minutes of diffusion are suggested.

The data show that at pH 7.4 sodium and potassium enter more rapidly than sucrose. I131-labelled albumin was found to enter very slowly, if at all. Increasing the pH from 7.4 reduced the rate at which sodium ion penetrated the mitochondria. The rate of diffusion of sucrose into mitochondria was considerably slower than diffusion of sucrose into a sphere of water of the same size.

Sodium ion was not found to be concentrated in vitro against an external concentration gradient as has been reported by other investigators.

It is concluded that the rate of diffusion of solutes between the external medium and the interior of mitochondria is probably restricted and controlled by a mitochondrial membrane exhibiting passive permeability characteristics.
STUDIES OF FLUID EXCHANGES BETWEEN RAT LIVER SLICES AND SIMPLE MEDIA
Authors: Itoh Shinji , Schwartz Irving L.
Published: May 2004

1. The exchange of fluid between slices of rat liver and solutions of monosaccharides, disaccharides, and sodium chloride has been studied in relation to the temperature of incubation. The point of apparent isotonicity (P.A.I.) of the tissue was defined as the concentration of the solution in which the slices neither gained nor lost weight after immersion for a period of 10 minutes.

2. In solutions of glucose, the P.A.I. of the slices was significantly lower at 4°C. than at 20°C. but similar at 20°C. and 37°C. Upon immersion for 15 to 60 minutes in 0.66 molar glucose the slices always swelled more at 37°C. than at 20°C. In solutions of sucrose change in the temperature of incubation was without effect on the hydration of the tissues.

3. In solutions of sodium chloride, the P.A.I. and the content of water, chloride, and sodium plus potassium were lower at 37°C. than at 20°C.

4. These findings emphasize the role of translocation of solute in providing an osmotic gradient for the movement of water between the tissue slices and the media.
THE EXCITABLE PROPERTIES OF THREE TYPES OF MOTOR AXONS
Authors: Adelman William J.
Published: May 2004

1. Three anatomically different types of lobster motor axons have been shown to possess different excitabilities under identical conditions.

2. The type, openers, which fired the longest trains of repetitive responses also had the lowest rheobase values, the longest utilization times, and the least accommodation.

3. A relationship between the time course of the local potential and the time course of the excitatory state has been disclosed.

4. The characterization of the excitatory state by simple two factor equations has been discussed and found to be only approximate since both the excitatory state and the local response tend to be somewhat oscillatory.