bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhancement of Dopamine Release In Vivo from the Rat Striatum by Dialytic Perfusion of 6R‐l‐erythro‐5,6,7,8‐Tetrahydrobiopterin
Authors: Koshimura Kunio , Miwa Soichi , Lee Ken , Fujiwara Motohatsu , Watanabe Yasuyoshi 
Published: October 2006

Abstract:We have previously reported that intracerebroventricular administration of 6R‐L‐erythro‐5,6,7,8‐tetrahydrobiopterin (6R‐BH4), a cofactor for tyrosine hydroxylase, enhances biosynthesis of 3,4‐dihydroxyphenylethylamine (dopamine) in the rat brain. In the present study, we have more precisely examined the effects of 6R‐BH4 on dopamine release in vivo from the rat striatum using brain microdialysis. The amount of dopamine collected in striatal dialysates was determined using HPLC with electrochemical detection after purification with an alumina batch method. When the striatum was dialyzed with Ringer solution containing various concentrations of 6R‐BH4 (0.25,0.5, and 1.0 mM), dopamine levels in striatal dialysates increased in a concentration‐dependent manner. Biopterin had little effect on dopamine levels in dialysates. The 6R‐BH4‐induced increase in dopamine levels in dialysates was abolished after pretreatment with tetrodotoxin (50 μM) added to the perfusion fluid, but after pretreatment with nomifensine (100 mg/kg, intraperitoneal injection), an inhibitor of dopamine uptake mechanism, a larger increase was observed. After inhibition of tyrosine hydroxylase by pretreatment with α‐methyl‐p‐tyrosine (250 mg/kg, intraperitoneal injection), most of the increase persisted. These results suggest that 6R‐BH4 has a dopamine‐releasing action, which is not dependent on biosynthesis of dopamine.
Evidence for δ‐Opioid Binding and GTP‐Regulatory Proteins in 5‐Day‐Old Rat Brain Membranes
Authors: Szücs Maria , Coscia Carmine J. 
Published: October 2006

Abstract:The availability of the bispenicillamine enkephalin [3H][d‐Pen2,d‐Pen5]enkephalin ([3H]DPDPE) a highly selective ligand for δ‐opioid receptors, has made possible a more definitive examination of the ontogeny of this receptor subtype. In this report, the binding characteristics of [3H]DPDPE in 5‐day‐old neonatal (P‐5) and adult rat brain are compared. Analysis of saturation curves as well as homologous displacement data revealed no significant difference in the binding affinity of [3H]DPDPE between P‐5 animals and adults. Conversely, the binding capacity increased fivefold during this period. The δ‐specificity of the sites was further proven by competition experiments with μ‐ and δ‐selective ligands. Mn2+ (0.5 mM) elevated [3H]DPDPE specific binding by lowering the Kd, whereas 50 μM 5′‐guanylylimidodiphosphate inhibited it by decreasing the total number of high‐affinity binding sites in both P‐5 animals and adults. Pertussis toxincatalyzed ADP ribosylation experiments revealed the presence of 40‐kDa proteins, with a molecular mass corresponding to G protein subunits αi/αo, as early as 1 h after birth. There was a low, but detectable, basal low‐Km GTPase activity in P‐5 animals, which increased fivefold during postnatal development. The present report establishes the existence of high‐affinity [3H]DPDPE binding as well as GTP‐regulatory proteins 5 days after birth. Yet, heterologous competition studies and ionic effects suggest that neonatal binding sites differ from adult receptors. Whether the neonatal sites are newly synthesized, incompletely processed sites or a developmentally programmed isoform remains to be determined.
Theory of Photochemical Reactions
Authors: Salem L. 
Published: October 2006

Although the great number of electronic states available to an excited molecule might seem to preclude a coherent picture of photochemical reaction mechanisms, it is possible to bring out some basic features common to a great many reactions. The electronic states of the primary diradical intermediates, surface crossings, topicity, and avoided surface crossings have been shown to be essential components of the electronic theory of photochemical reactions.
Diradicals have four important electronic states. Knowing these states, and making a simple electron count, it is possible to draw state correlation diagrams. Some diagrams show a typical surface crossing of the ground singlet state with the lowest (singlet, triplet) pair of excited states, with clear-cut consequences for quantum yields under various conditions. In other reactions the surfaces stay apart. The critical discriminating feature that determines the type of correlation diagram is the topicity. Photochemical reactions can be classified according to topicity, which is useful in interpreting their mechanisms. Avoided surface crossings can also be classified into different types. Figure 7, which illustrates the interplay of a covalent and an ionic surface responsible for photochemical electron transfer, is a typical multidimensional representation of a photochemical reaction.

The chemical behavior of the excited zwitterionic states of common intermediates, such as twisted ethylene or diallyl, reflects the quantum mechanical nature of photochemical processes. In these states, for perfectly symmetric systems, charge oscillates back and forth between two symmetry-equivalent sites. Slight geometric perturbations can create a sudden polarization of the excited molecule, with localization of almost a full charge at one end of the molecule. A photon is transformed into an electrical signal thanks to an appropriate molecular distortion. Nature may have used this simple process in the
N
-retinylidene visual chromophore to trigger an electrical response to vision.
Radiation Dose Rate and Mutation Frequency
Authors: Russell W. L. , Russell Liane Brauch , Kelly Elizabeth M. 
Published: October 2006

New data have clearly confirmed the earlier finding that specific locus mutation rates obtained with chronic gamma irradiation of spermatogonia are lower than those obtained with acute x-rays. Since this result is in contrast to classical findings for
Drosophila
spermatozoa, and apparently contradicts one of the basic tenets of radiation genetics, it was important to determine what factors were responsible for it.

Experiments undertaken for this purpose reveal the following: (i) the lower mutation frequency is due mainly to difference in dose rate of radiation, rather than quality; (ii) a dose-rate effect is not obtained in experiments with mouse spermatozoa, confirming classical findings for spermatozoa, and indicating that the explanation for intensity dependence in spermatogonia resides in some characteristic of gametogenic stage; and (iii) a dose-rate effect is found not only in spermatogonia but also in oocytes, where cell selection is improbable, indicating that the radiation intensity effect is on the mutation process itself.
A threshold response for all mutations in spermatogonia and oocytes is not a necessary consequence of the findings. Plausible hypotheses consistent with the present results can lead to other predictions.
From a practical point of view, the results indicate that the genetic hazards, at least under some radiation conditions, may not be as great as those estimated from the mutation rates obtained with acute irradiation. However, it should not be forgotten that even the lower mutation rates obtained with the present intensity levels are still appreciable.
Fluted Projectile Points: Their Age and Dispersion
Authors: Haynes C. Vance 
Published: October 2006

The stratigraphic record shows Clovis projectile points to be restricted to sediments between 11,000 and 11,500 years old. Underlying deposits dating back 11,600 to 13,000 years are without evidence of human occupation. In the High Plains, overlying deposits dating back 10,000 to 11,000 years contain Folsom and Hell Gap artifacts and are without mammoth remains. The glacial history of Alaska, Canada, and the Great Lakes region indicates that, for the first time in at least 15,000 years, an ice-free, trans-Canadian corridor opened up approximately 12,000 years ago. Since Clovis points are distributed from coast to coast south of the Valders ice border, the abrupt appearance of Clovis artifacts in the stratigraphic record of the High Plains some 700 years later suggests that Clovis progenitors passed through Canada during Two Creeks time. If eastern fluted points (for example, Enterline) are older than Clovis points, the difference may be on the order of only a hundred or so years, not thousands.
The change from Clovis points to Folsom points in the High Plains may be related to a marked decline in the mammoth population after 11,000 years ago, but whether or not man was a prime factor in the extinction of Pleistocene megafauna is a moot question.
On the basis of new data and critical geological evaluation of dates obtained by the radiocarbon method a hypothesis has been offered to explain (i) the abrupt appearance of Clovis points in the stratigraphic record of the United States around 11,500 years ago, and (ii) the lack of a cultural continuum in the United States leading to fluted projectile points. Llano hunters, like the game they pursued, may have persisted longer in some areas of the continent (for example, Bull Brook) than in others, but if a Clovis site can be found for which good stratigraphic evidence supports a date earlier than the Two Creeks interstade, then correlation of this event to the opening of the trans-Canadian ice-free corridor is incorrect. Such a misinterpretation of timing would not affect the explanation for the lack of Clovis progenitors in the United States. We must continue to look for an indigenous cultural continuum leading to Clovis points, but if such cannot be demonstrated in the conterminous United States, then it would appear that fluted projectile points were developed elsewhere. Clovis progenitors might best be sought in northern Alaska or the Mackenzie Valley.
The interpretations offered here are based on new data and critical geological evaluation of dates previously obtained by the radiocarbon method. How valid these interpretations are can be ascertained only through careful scrutiny of all man-mammoth associations found in the future, to assure precise relating of dates, fossils, and ar tifacts to the stratigraphic framework. We must pay closer attention to stratigraphic detail if we are to make the fullest use of radiocarbon dating.
Lemur Social Behavior and Primate Intelligence
Authors: Jolly Alison 
Published: October 2006

Our human intellect has resulted from an enormous leap in capacity above the level of monkeys and apes. Earlier, though, Old and New World monkeys' intelligence outdistanced that of other mammals, including the prosimian primates. This first great advance in intelligence probably was selected through interspecific competition on the large continents. However, even at this early stage, primate social life provided the evolutionary context of primate intelligence.
Two arguments support this conclusion. One is ontogenetic: modern monkeys learn so much of their social behavior, and learn their behavior toward food and toward other species through social example. The second is phylogenetic: some prosimians, the social lemurs, have evolved the usual primate type of society and social learning without the capacity to manipulate objects as monkeys do. It thus seems likely that the rudiments of primate society preceded the growth of primate intelligence, made it possible, and determined its nature.
Growth-Rings of Trees: Their Correlation with Climate
Authors: Fritts Harold C. 
Published: October 2006

Many differences in the ring-width growth within a tree may be attributed to changing supplies of food and hormones. In moist sites or during periods of favorable climate, there may be sufficient food for the production of wide rings throughout the tree. But in dry sites or during years of low moisture and high temperatures, food competition within the tree is likely to be greater and the cambium at the base of the stem is likely to receive a limited food supply and may produce narrow rings. The cambium at the stem base depends upon the entire crown for food, hence ring growth reflects the tree's ambient climate. But, the cambium in the top of the tree or in the upper branches depends upon a more restricted portion of the crown for its food and hormone supplies. The rings produced by the cambium vary greatly from branch to branch and are less reliable indicators of the climate surrounding the entire tree than rings at the tree base. Therefore, ring series at the base of trees in semiarid sites provide the most reliable, as well as the longest, record of macroclimatic variation.
Tree-ring widths in certain coniferous species growing in semiarid sites appear to represent the integrated effect of climate on food-making and food accumulation in the crown throughout the 14 to 15 months previous to and including the period of growth. Trees in warm, low-elevation sites may utilize winter moisture most efficiently; trees in cool, high-elevation or more northern sites may utilize early summer and early autumn moisture most efficiently. But even with these differences, a significant amount of variance is found to be common among tree-ring series from a wide range of sites, species, and geographical areas in western North America, emphasizing a common dependence of ring widths on the gross regional patterns of precipitation and temperature. The remaining variance, which is not correlated among sites, may be attributed to local environmental and climatic differences, to variability among and within trees, and to compounding effects of occasional fires, insect or other infestations, and recurring years of high seed production.
It is evident that a large portion of the variability in ring-width patterns from semiarid sites in western North America does reflect differences in climate from year to year. If ring chronologies are derived from a number of trees in semiarid sites and if adequate corrections for age and trend are made, these chronologies may be used to reconstruct a first approximation of annual, or somewhat longer period, climatic fluctuations in the past.
Molecular Aspects of Lens Cell Differentiation
Authors: Papaconstantinou John 
Published: October 2006

I have presented a series of observations on macromolecular interactions which occur during the terminal stages of lens cell differentiation. These are summarized in Fig. 2. Other cell types that undergo similar changes are the erythrocyte and skin cells (epidermis) during the process of keratinization. These other cells are also involved in the synthesis of highly specific proteins, and there are indications that molecular alterations similar to those described for the lens may also occur in these cells (26). Thus, elucidation of a specific series of macromolecular interactions such as those described may provide a basis for the biochemical definition of the terminal stages of cellular differentiation. Differentiation of the reticulocyte, for example, involves inactivation of the nucleus, stabilization of mRNA, and possibly a ribosomal breakdown such as I have described here (26). Furthermore, elucidation of the mechanisms of reactions involving the initiation of tissue-specific protein synthesis and subsequent nuclear inactivation, stabilization of mRNA, and breakdown of the ribosomes may provide a basis for defining the mechanisms of terminal cellular differentiation.
The lens cell has reached its highest form of cellular differentiation when it has formed the fiber cell. With respect to the mechanism of lens fiber cell formation, we would like to know whether specific biochemical changes such as γ-crystallin synthesis are intimately linked to fiber cell formation—that is, whether γ-crystallins are required to bring about the formation of a fiber cell. The potential for synthesizing γ-crystallins is inherent in the genome of the cell. This part of the genome is nonfunctional in the epithelial cell. Can these genes be activated without bringing about a simultaneous cellular elongation, nuclear inactivation and loss of cellular replication, stabilization of mRNA, and breakdown of the ribosomes? The degree of coupling or uncoupling of tissue-specific-protein synthesis to morphogenesis is an important part of the mechanism of cellular differentiation. We feel that we have now reached the stage where we can begin to answer these questions.
Water Balance in Desert Arthropods
Authors: Edney E. B. 
Published: October 2006

As judged by the number of species, or of individuals, arthropods are an extremely successful group of desert inhabitants. There is very great structural and physiological diversity within the group, and since adaptations to desert life open to one are not open to all. we should not expect to find the maximum possible development of adaptive features in any arthropod simply because it lives in a desert. Most adult insects fly; their larvae and all other arthropods do not, and their adaptations will differ accordingly. Desert beetles have very impermeable cuticles and tolerate high body temperatures, while desert cockroaches live below the sand. have more permeable cuticles, and absorb water vapor. There is probably no single respect in which all desert arthropods differ from insects of other environments. Perhaps a profitable way of viewing desert animals is to recognize that each is a whole organism with a specific collection of adaptations that must be consistent within themselves and which are associated with a specific mode of life and a specific evolutionary history.
The arthropod organization is capable of producing highly efficient desert species. There is, however, a converse way of looking at the situation, which is often neglected but which may be of general biological interest: does the evolution of adaptations to desert environments necessarily involve loss of viability in more mesic habitats? If so, then what are these disadvantages— what, for example, is the disadvantage of a highly impermeable cuticle? In some cases the answer is clear: sandroaches need sand dunes to live in because they are morphologically and behaviorly specialized for this habitat. More often the answer is not obvious.
Leaf Epicuticular Waxes
Authors: Eglinton Geoffrey , Hamilton Richard J. 
Published: October 2006

The external surface of the higher plants comprises a cuticular layer covered by a waxy deposit. This deposit is believed to play a major part in such phenomena as the water balance of plants and the behavior of agricultural sprays. The wax contains a wide range of organic compounds. These complex mixtures are amenable to modern microchromatographic and microspectrometric analytical procedures. The few surveys which have been made of the species distribution of certain classes of constituents indicate that such distribution may be of limited taxonomic value; however, the wax composition of a species may differ for different parts of the same plant and may vary with season, locale, and the age of the plant.
This fascinating subject, in which the disciplines of botany, biochemistry, chemistry, and physics overlap and interact, is still in a very active state. Much remains to be learned about the composition and fine structure of the wax deposits, and, for this, experimental study of wax crystallization and permeation through artificial membranes will be required. Enzymic studies, radiolabeling, and electron microscopy will be needed to reveal the mode of biogenesis of the wax constituents and their site of formation and subsequent pathway through the cuticle to the leaf surface.
Intelligence Has Three Facets
Authors: Guilford J. P. 
Published: October 2006

In this limited space I have attempted to convey information regarding progress in discovering the nature of human intelligence. By intensive factor-analytic investigation, mostly within the past 20 years, the multifactor picture of intelligence has grown far beyond the expectations of those who have been most concerned. A comprehensive, systematic theoretical model known as the "structure of intellect" has been developed to put rationality into the picture.
The model is a cubical affair, its three dimensions representing ways in which the abilities differ from one another. Represented are: five basic kinds of operation, four substantive kinds of information or "contents," and six formal kinds of information or "products," respectively. Each intellectual ability involves a unique conjunction of one kind of operation, one kind of content, and one kind of product, all abilities being relatively independent in a population, but with common joint involvement in intellectual activity.
This taxonomic model has led to the discovery of many abilities not suspected before. Although the number of abilities is large, the 15 category constructs provide much parsimony. They also provide a systematic basis for viewing mental operations in general, thus suggesting new general psychological theory.
The implications for future intelligence testing and for education are numerous. Assessment of intellectual qualities should go much beyond present standard intelligence tests, which seriously neglect important abilities that contribute to problem-solving and creative performance in general. Educational philosophy, curriculum-building, teaching procedures, and examination methods should all be improved by giving attention to the structure of intellect as the basic frame of reference. There is much basis for expecting that various intellectual abilities can be improved in individuals, and the procedures needed for doing this should be clear.
Songs of Humpback Whales
Authors: Payne Roger S. , McVay Scott 
Published: October 2006

1) Humpback whales (
Megaptera novaeangliae
) produce a series of beautiful and varied sounds for a period of 7 to 30 minutes and then repeat the same series with considerable precision. We call such a performance "singing" and each repeated series of sounds a "song."

2) All prolonged sound patterns (recorded so far) of this species are in song form, and each individual adheres to its own song type.
3) There seem to be several song types around which whales construct their songs, but individual variations are pronounced (there is only a very rough species-specific song pattern).
4) Songs are repeated without any obvious pause between them; thus song sessions may continue for several hours.
5) The sequence of themes in successive songs by the same individual is the same. Although the number of phrases per theme varies, no theme is ever completely omitted in our sample.
6) Loud sounds in the ocean, for example dynamite blasts, do not seem to affect the whale's songs.
7) The sex of the performer of any of the songs we have studied is unknown.
8) The function of the songs is unknown.
Perception of Changes in Certain Exteroceptive Stimuli
Authors: Notterman J. M. , Filion R. D. L. , Mandriota F. J. 
Published: October 2006

Although cybernetic models of one sort or another have become quite common in behavioral research, and although these models theoretically require a capacity for system detection of changes in error, no general psychophysical description of the individual human being's ability to discriminate different rates of stimulation is available. An initial survey of this type has been attempted and is reported here.
For reasons which appear to be related to the biological mechanisms underlying sensory information processing, it is concluded, first, that ancillary cues of rate-related final magnitude are more valuable than cues of stimulus duration; second, that direct attention to on-going change is less precise than attention to final values only; and third, that differences in isochronal stimulus rates occurring in place or extent are more readily perceived than differences in isochronal rate of change in energy content, at least for the stimuli and ranges examined.