bluuebunny/crossref_metadata_2025_split huggingface dataset:
TIME COURSE AND QUANTUM EFFICIENCY OF PHOTOSYNTHESIS IN CHLORELLA
Authors: Brackett Frederick S. , Olson Rodney A. , Crickard Robert G. 
Published: May 2004

1. Though the quantum yield remains constant for different samples of the same culture despite great changes in respiration due to dark adaptation, the quantum requirement for different cultures varies from 6.1 to 13.5 quanta per molecule of oxygen evolved (q/m).
2. This variation from one culture to another appears to depend upon chlorophyll concentration, though other paralleling factors cannot be ruled out.
3. Both chlorophyll concentration and quantum requirement show a random distribution. A statistical median for 50 cultures and 99 determinations gives q/m = 8.5 with a systematic uncertainty of perhaps 10 per cent. Since the variations are real, the median is regarded as less important than the lower limit approached (about q/m = 6).
4. Dark adaptation under aerobic conditions produces an initial photosynthetic rate of nearly zero. The immediate rise to steady state is somewhat logarithmic in character and may require over 3 minutes.
5. In intermittent light (of periods from 1 to 6 minutes) the induction observed in subsequent light periods starts from a finite initial rate and occupies a shorter time, often as little as 30 seconds.
6. The theoretical importance of aerobic induction is discussed. A chlorophyll cycle of two photochemical steps is found to satisfy most of the observed characteristics and to be compatible with an efficiency independent of intensity.
AFTER-POTENTIAL OF SPINAL AXONS IN VIVO
Authors: Rudin Donald O. , Eisenman George 
Published: May 2004

A method is evolved whereby the after-potential sequence intrinsic to longitudinal dorsal column myelinated fibers may be studied in isolation from those events occurring in intact spinal cord subjected to an afferent volley.
The recovery sequence intrinsic to dorsal column fibers, after refractoriness is over, is characterized by supernormality approximately four to five times greater than that seen in peripheral nerve. This supemormality averages 15.7 ± 4 per cent (current calibration) at peak and decays exponentially with a half-time of 7.5 msecs. It is not followed by subnormality unless conditioning is repeated more than three times at frequencies greater than 100/sec.
Characterization of the recovery curve of dorsal column fibers permits by exclusion, the allocation of the origin of DRV to structures more centrally located.
DCV (the dorsal column counterpart of DRV) is seen to exist equally developed in active and passive dorsal column fibers.
THE KINETICS OF PROGRESSIVE REACTIONS IN SYSTEMS CONTAINING SAPONIN, DIGITONIN, AND SODIUM TAUROCHOLATE
Authors: Ponder Eric 
Published: May 2004

The relations between lysin concentration, percentage hemolysis at the moment at which the lysin concentration is reduced by dilution, and the amount of hemolysis which follows the dilution as a result of the reaction being "progressive" point to there being an "internal" phase at the red cell surfaces, in which the lysin is less affected by the dilution than in the system as a whole. A second possibility, i.e. that the combination of lysin molecules with certain components of the cell surface has an ultimate effect on neighboring components which depend on the former for their stability cannot, however, be ruled out.
In systems containing digitonin or sodium taurocholate, this internal phase, once formed, seems to be almost unaffected by the dilution of the system; i.e., these lysins are very firmly held at the cell surfaces. In systems containing saponin the lysin is less firmly attached, so that dilution of the system affects its concentration appreciably.
NUCLEIC ACID ECONOMY IN BACTERIA INFECTED WITH BACTERIOPHAGE T2
Authors: Hershey A. D. , Dixon June , Chase Martha 
Published: May 2004

1. The phosphorus content per infective particle of isolated bacteriophage T2 has been redetermined. It does not exceed 1.8 to 2.2 x 10–11 µg. The equivalent amount of DNA has been defined in terms of several analytical methods and taken as a unit of measurement of intrabacterial DNA.
2. The DNA of E. coli contains guanine, adenine, cytosine, and thymine in approximately equal amounts, but no hydroxymethylcytosine. One bacterial cell contains 40 to 150 units of DNA, depending on the conditions of growth and the method of measurement.
3. The DNA of phage T2 (one unit per particle by definition) contains guanine, 5-hydroxymethylcytosine, and relatively large amounts of adenine and thymine, but no cytosine.
4. Infected bacteria contain DNA of a composition that varies systematically during the course of viral growth. At all times it resembles a mixture of bacterial and viral DNA.
5. The characteristic bacterial DNA is decomposed after infection, measuring about one-third its initial amount at 20 minutes. The characteristic viral DNA increases in amount, after a short delay, reaching a level of 100 to 400 units per bacterium 30 minutes after infection. At 10 minutes after infection, the two kinds of DNA are approximately equal in amount.
6. The characteristic viral DNA present in infected cells exists in two forms, one consisting of infective particles and one not. The portion not contained in infective particles builds up to 40 to 80 units per cell during the first 10 minutes after infection and afterwards remains roughly constant in amount. Infective particles begin to appear at 10 minutes and account for all or most of the increase thereafter.
THE EFFECTS OF TOBACCO MOSAIC VIRUS SYNTHESIS ON THE FREE AMINO ACID AND AMIDE COMPOSITION OF THE HOST
Authors: Commoner Barry , Nehari Varda 
Published: May 2004

1. Changes in concentrations of free amino acids and amides have been determined in TMV-infected tobacco leaf discs and in comparable uninfected discs during the time of virus formation.
2. During the period of rapid virus formation the infected discs show a transitory deficiency (as compared to uninfected discs) in glutamine, asparagine, aspartic acid, glutamic acid, serine, and to a lesser extent in valine, threonine, and proline. About 100 hours before this time smaller deficiencies in the concentrations of these components also occur. The latter effect is probably associated with the early synthesis of a non-virus protein in infected tissue.
3. Comparison of the above effects with the known amino acid composition of TMV indicates that it is unlikely that the virus protein is synthesized by condensation of appropriate free amino acids. Rather, the deficiencies observed appear to result from removal of ammonia from the nitrogen pool during synthesis of new proteins in infected tissue. Equilibrium shifts resulting from ammonia withdrawal probably account for the observed deficiencies in amides and free amino acids. TMV protein, therefore, appears to be synthesized de novo, from non-protein nitrogen, probably ammonia.
4. It is suggested that the changes in free amino acid concentrations induced by virus formation may account for some of the symptoms observed in infected plants.
INHIBITION OF LACTIC STREPTOCOCCUS BACTERIOPHAGE BY CRYSTAL VIOLET AND OTHER AGENTS
Authors: Graham D. M. , Nelson F. E. 
Published: May 2004

Ninety-nine selected compounds and eleven antibiotic-producing organisms were tested for antiphage activity and host toxicity. A paper disc-agar diffusion method was used for primary screening and quantitative methods were employed for confirmatory investigation. Most of the agents tested, although previously reported as inhibitory to one or more other virus-host systems, did not selectively prevent multiplication of lactic streptococcus bacteriophage. Several compounds which prevented mass lysis were extremely toxic to host bacteria.
Crystal violet suppressed growth of two phage strains at a level (1.0 x 10–7 M) which permitted normal growth of the host cells. Failure of crystal violet to prevent multiplication of many phage strains suggested possible variations in the multiplication mechanisms of different strains of virus. Virustatic levels of crystal violet did not destroy unadsorbed virus, reduce adsorption, or prevent invasion; increase of virus was reduced in one-step growth experiments; mass lysis was prevented or delayed in long time experiments. Addition and removal of crystal violet at various intervals during the latent period resulted in virus yields directly related to the portion of the latent period during which no dye was present. Duration of the latent period was unaffected. Single burst experiments indicated that the yield of plaque-forming particles per infected bacterium was reduced; the proportion of infected bacteria giving rise to active progeny did not appear to be influenced to a significant degree. Crystal violet apparently interferes with intracellular multiplication of the virus, possibly by combination of the dye with phage DNA or fractions thereof at some critical stage in the incorporation of DNA into the virus particle.
MITOCHONDRIA IN THE FLIGHT MUSCLES OF INSECTS
Authors: Watanabe Mary Ishimoto , Williams Carroll M. 
Published: May 2004

1. The sarcosomes of Drosophila and the blowfly, Phormia, are dense, spherical, homogeneous bodies when isolated from flight muscle and promptly examined under the phase contrast, oil immersion objective.
2. Their average diameter in newly emerged flies is about 1 µ. This value increases rapidly during the 1st week of adult life and then becomes constant at approximately 2.5 µ. At each age the variation in sarcosome diameter conforms approximately to a normal distribution.
3. The degree to which isolated sarcosomes retain their initial size and organization is remarkably conditioned by the composition and the hydrogen ion concentration of the medium in which they are teased and suspended. In suboptimal media three major categories of change were encountered: (1) swelling, with or without compaction of the contents (as in distilled water and salt solutions); (2) shrinkage to rod-like, pleomorphic forms (as in blood serum); and (3) fuzzy degeneration (as in sugar solutions).
4. The membrane that surrounds each sarcosome becomes plainly visible in swollen sarcosomes. A continuation of swelling is accompanied by the escape of the sarcosomal contents, the vacated membrane persisting as a spherical, optically empty ghost.
5. Sarcosomes appear to behave like osmometers when suspended in various aqueous solutions. Solutes which penetrate the membrane show only transient effects in preventing the osmotic entry of water.
6. Under this analysis we find the membrane to be more or less freely permeable to the ions of sodium, potassium, calcium, magnesium, chloride, and phosphate, to non-electrolytes smaller than hexoses, to phosphorylated hexoses, and to several intermediates of the citric acid cycle.
7. The sarcosomal membrane appears to be less permeable to non-electrolytes larger than pentoses, provided that such molecules are not phosphorylated.
8. The membrane shows a higher permeability to ATP than to ADP. The significance of this observation is considered with respect to the ADP-ATP shuttle between sarcosomes and muscle fibrils.
9. Simple solutions of electrolytes or non-electrolytes cause more or less conspicuous changes in the microscopic appearance of sarcosomes. Prolonged preservation was achieved only in more complicated media containing protein. It is concluded that the Donnan equilibrium is the source of the principal osmotic forces regulating the movement of water through the sarcosomal membrane.
10. The optimal medium for the preservation of isolated sarcosomes was an intracellular Ringer solution containing 2.5 per cent crystalline bovine albumin in 0.16 M potassium phosphate buffer at pH 7.0.
MECHANISMS OF BIOELECTRIC ACTIVITY IN ELECTRIC TISSUE
Authors: Altamirano Mario , Coates Christopher W. , Grundfest Harry , Nachmansohn David 
Published: May 2004

1. A preparation is described consisting of one or several layers of innervated cells of the electric organ of Electrophorus electricus.
2. Each plaque is multiply innervated and only at its caudal face. The nerve fibers may derive from two or more different nerve trunks.
3. During activity the innervated face becomes negative relative to the non-innervated.
4. The first electrical response of the cell to an increasing neural volley is graded and has the character of a prepotential. At a critical size of the prepotential the cell discharges with an all-or-nothing spike.
5. Both responses have durations of about 2 msec.
6. A neural volley which does not cause the spike discharge facilitates the discharge of the cell by a second subsequent volley in the same nerve (temporal facilitation).
7. The period of facilitation lasts ca. 900 msec. During the first 100 msec., the facilitation is large enough to cause a spike. In the later portion only the prepotential is facilitated. No electrical concomitant has been detected.
8. Neural volleys reaching the plaque from different trunks interact at the cell to produce a period of facilitation lasting only about 2 msec. This interaction is interpreted as spatial summation.
9. In a population of cells, simultaneous stimulation of 2 nerves causes a smaller discharge than the sum of the two isolated responses (occlusion).
10. Cells denervated for 7 weeks or more can be excited directly, but only by a current flow outward through the caudal face.
11. Weak direct stimulation causes a prepotential in the denervated plaque. On increasing the stimulus the prepotential increases to a critical size when a spike develops. The duration of both responses is about 2 msec.
12. The absolutely refractory period of the denervated cell is about 1.5 msec. and relative refractoriness lasts about 15 msec.
13. Direct stimulation causes slight facilitation lasting as long as 200 msec.
14. Repetitive stimulation of the nerve at low frequencies (2 to 3 per second) causes rapid "fatigue" of transmission. The denervated plaque, however, responds for several minutes to repetitive direct stimulation at high frequencies (25 per second).
QUANTUM RELATIONS IN PHOTOREACTIVATION OF COLPIDIUM
Authors: Giese A. C. , Iverson R. M. , Shepard D. C. , Jacobson C. , Brandt C. L. 
Published: May 2004

1. The amount of visible or long ultraviolet light (UV) required to photoreactivate Colpidium colpoda injured with known dosages of short UV (2654 A) was determined.
2. The effect of the short UV was tested by the delay in division of exposed animals compared to controls. Photoreactivation was tested by the effect of postillumination on the delay of division of treated colpidia compared to controls.
3. Colpidia were used in two physiological states: well fed and starved in balanced medium for 48 hours. The latter are much more sensitive to short UV although less susceptible of photoreactivation.
4. Photoreactivation occurred over the entire span from 3350 A to 4350 A for the well fed colpidia, from 3130 A to 5490 (green) for starved colpidia.
5. The photoreactivating effect of a single quantum of blue (4350 A) or long UV (3660 A) delivered per quantum of 2654 A used to injure colpidia was too slight to be considered significant. The effect of 10 quanta was usually more pronounced, but only after 100 quanta had been delivered was the photoreactivation nearly maximal for well fed colpidia.
6. The quantum requirement for maximal photoreactivation of the starved animals was greater at all wave lengths tried: 3660, 4050, 4350, and 5460 A being of the order of 800 incident quanta per incident quantum of 2654 A.
7. The transmission of UV(2654 A), blue, yellow, and red light by a suspension of colpidia was determined.
8. Large dosages of blue, violet, or long UV were slightly injurious to starved colpidia. In a few cases large dosages of 3660 A killed starved colpidia, especially after a non-lethal dose of short UV(2654 A).
9. Photoreactivation seems to be a balance between the slight injurious effect produced by the visible light or UV of long wave lengths and the injury produced by short wave length UV.
10. Possible reasons for the large number of quanta of photoreactivating light required per quantum of short UV are discussed.
SOME PROPERTIES OF A PHOTODYNAMIC PIGMENT FROM BLEPHARISMA
Authors: Giese Arthur C. 
Published: May 2004

1. A pigment can be extracted from Blepharisma undulans by heat treatment of a concentrated suspension of the deeply pigmented animals.
2. In the presence of this pigment, various colorless protozoans are sensitized to light and killed if exposed long enough. The protozoans show a differential sensitivity, some being much more sensitive than others.
3. Bleached colorless blepharismas are not sensitized to their own pigment even after prolonged exposure in the most concentrated solutions available.
4. Blepharisma is also less sensitive than any of the protozoans tested to such photodynamic dyes as rose bengal.
5. The pigment is not extracted from wet blepharismas by non-polar solvents, but is readily extracted into such polar organic solvents as the alcohols.
6. When the alcohol extract is dried, the amorphous residue is readily soluble in a variety of organic solvents, but not in the most non-polar.
7. The pigment is highly stable in alcohol extract and has been kept in the dark for years.
8. The pigment is bleached by light in a photooxidation.
9. Absorption maxima are found at wave lengths 5800, 5400, 4800, and 3300 A, the latter being the largest. Similar peaks are found in alcohol and water solutions, although the heights are not exactly the same. In both alcoholic and aqueous solutions pH had an effect on the absorption spectrum. Heat has little effect but illumination with intense visible light or exposure to ultraviolet light bleaches the pigment with decreases in the characteristic peaks.
10. Preliminary absorption column experiments indicate a single pigment in the alcohol extract.
11. Experiments on the migration of zoopurpurin in agar and gelatin gels indicate that it diffuses at about the same rate as eosin and is therefore probably not a large molecule.
THE ODOROUS ATTRACTANT OF THE AMERICAN COCKROACH, PERIPLANETA AMERICANA (L.)
Authors: Wharton D. R. A. , Miller Gail Lorenz , Wharton Martha L. 
Published: May 2004

1. Procedures have been developed for studying quantitatively the response of the male American cockroach to the odorous attractant of the female.
2. The percentage of male roaches responding to extracts of the attractant of the female has been found to vary with the log of the concentration of the attractant throughout a wide range.
3. Adaptation to the olfactory stimulus has been demonstrated.
4. A theory of adaptation is offered.
FURTHER STUDIES ON THE FUNCTIONAL PROPERTIES OF SPINAL AXONS IN VIVO
Authors: Eisenman George , Rudin Donald O. 
Published: May 2004

Mammalian spinal tracts in situ demonstrate a phase of marked hyperexcitability during hypoxia or on the application of an excess of potassium or citrate ion. This is in keeping with the fact that they also show post-spike supernormality as well as hyperexcitability under cathodal polarization (17). Behavior of this kind indicates that central axons carry a well developed L fraction of membrane properties.
The rhythmic state in central axons in situ, unlike peripheral nerve or spinal root, is not induced by the action of excess potassium ion. This appears to be related to the absence of a positive after-potential in dorsal columns (17).
However, sodium citrate can elicit autonomous firing in central axons. When synchronized by an applied stimulus the resulting periodic oscillations have a fundamental frequency (340 to 400 C.P.S.) which is significantly greater than that of peripheral nerve.
THE ACTION POTENTIAL OF SPINAL AXONS IN VITRO
Authors: Rudin Donald O. , Eisenman George 
Published: May 2004

Despite the trauma of dissection and special metabolic requirements, the physiological properties of funiculi of the mammalian spinal cord can be studied in vitro. They are adequately oxygenated by diffusion at 0.88 atm. pO2 and remain in a functionally normal state for over 12 hours.
The internal consistency of several kinds of data presented in this and the foregoing papers (5, 38) serves to characterize certain properties of central myelinated axons whether excised or in situ. (1) Spinal tracts support a large spike potential in vitro whose form, duration, and velocity are comparable to those of alpha fibers in vitro and spinal tracts in vivo. (2) Properties consistent with a large L fraction are found in central axons whether excised or in situ. (3) Following conduction there has been identified post-spike supernormality with exponential time course (7.5 msecs. half-time) which is the result of activity intrinsic to parent fibers of dorsal columns. The supernormality is similar in form and magnitude both in excised and intact funiculi. (4) In excised funiculi the action potential of parent axons includes a large negative after-potential whose form and duration correspond satisfactorily with this supernormality. This potential appears not to result from activity arising in broken collaterals. (5) Central axons, excised or intact, fire spontaneously in the presence of citrate ion, and when synchronized by stimulation develop periodic oscillations at about 400 C.P.S. but show no such behavior in the presence of excess potassium ion.
Certain characteristics peculiar to central axons indicate that they occupy an extreme position in the spectrum of properties encountered in conducting tissues. Dorsal column myelinated axons differ from their peripheral counterparts, even though they are parts of the same cell, in the following ways. The maintenance of the column spike potential is more critically dependent on CO2 and the entire tissue mass has a higher oxygen consumption. The negative after-potential is much larger and the positive after-potential, non-existent following a single volley, is more difficult to develop by repetitive stimulation. Unlike peripheral nerve, central axons are not incited to spontaneous activity by manipulation of certain constituents normally present in their environment. However, when induced by the application of citrate the resulting rhythmic behavior has twice the frequency of that in peripheral nerve. In general, the recovery process in central axons is more invariant than that in peripheral axons when they are subjected to similar changes in their artificial environments.
IMMUNOLOGICAL STUDIES OF INSECT METAMORPHOSIS
Authors: Telfer William H. 
Published: May 2004

1. In the pupal stage of the cecropia silkworm, antigen 7, a protein with the solubility characteristics of an albumin, is present in female blood in approximately a thousand times higher concentration than in the blood of males. Antigen 7 is undetectable in the blood of larvae of either sex. It first appears in the blood after the larva has spun its cocoon, and is present throughout all subsequent stages of metamorphosis. Late in the pupal-adult transformation, when the eggs are produced, the concentration of antigen 7 in female blood decreases significantly.
2. An antigen which could not be distinguished from antigen 7 immunologically is present in solution in the yolk of unfertilized eggs.
3. In females which, by ovariectomy, were prevented from forming eggs, the concentration of antigen 7 in the blood increased during the usual period of egg formation rather than undergoing the normal decrease. Ovaries transferred to the hemocoel of males produced eggs but were unable to incorporate antigen 7 in the yolk unless a detectable amount of the protein was present in the blood. The ovaries of polyphemus females which had been transfused with cecropia blood incorporated cecropia antigen 7 into the eggs they produced. These lines of evidence indicate that antigen 7 is secreted into the blood by some tissue other than the ovaries, and that it is subsequently drawn from the blood and deposited in the yolk.
4. The concentration of antigen 7 in the clear, liquid fraction of the yolk is four times higher than the maximum concentration attained in the blood during metamorphosis, and twenty times higher than that of the blood at the conclusion of egg formation. The protein thus appears to be transferred from blood to yolk against a concentration gradient.