bluuebunny/crossref_metadata_2025_split huggingface dataset:
THERMODYNAMIC PARAMETERS FOR DISSOLVED GASES
Authors: Hildebrand Joel H. 
Published: May 2006

In 1958 and subsequently we correlated properties of solutions of gases in liquids by using the “force constants,” ε/
k
, and collision diameters, σ, which serve as parameters in equations for molecular pair potential energy such as that of Lennard-Jones or its variants. Unfortunately, however, the figures for these parameters that have been published are so scattered for the same gas as to make it difficult to select “best” values; in 1967, therefore, I substituted for these indirectly determined molecular parameters the directly and accurately known molal energy of vaporization, ΔE
b
v
, and the molal volume, v
b
, of the liquefied gas, both at its boiling point. A plot of values of ΔE
2
v
against the most trustworthy values of ε/
k
reveals direct proportionality. The same is true for V
b
1/3
versus σ.

Recent examples will be shown of excellent linear correlations with these parameters of thermodynamic properties of different gases in the same solvent.
It is no less “scientific” and far more practical to regard molecules of a solute as immersed in the potential energy field of its solvent than it is to split this field into imperfectly known pair potentials of questionable additivity and to try to integrate them over an undetermined distribution function.
COMPARISON OF SOLUBLE HUMAN AND MOUSE TRANSPLANTATION ANTIGENS
Authors: Mann Dean L. , Nathenson Stanley G. 
Published: May 2006

The molecular and chemical characteristics of membrane components bearing the major transplantation antigen systems in mouse (H-2) and man (HL-A) were compared and found to be strikingly similar.
Kinetics of papain solubilization from cell membranes, gel filtration, and electrophoretic patterns of the alloantigenic components were found to be nearly identical. Comparable size heterogeneity of the solubilized materials was also demonstrated. Some differences in amino acid and carbohydrate content of the purified H-2 and HL-A alloantigenic materials were found. The general pattern of distribution of the amino acid residues, however, appears to be quite similar and indicate compositional relatedness in these materials.
These physical and chemical similarities in the characteristics of molecules bearing the transplantation antigens are in accord with biologic studies indicating a comparable functional immunologic role for the mouse H-2 and human HL-A antigen systems. These studies support the view that the genes determining these major transplantation antigen systems may have evolved from a common precursor.
Genetic Transmission of Viruses That Incite Mammary Tumor in Mice
Authors: Bentvelzen P. , Daams J. H. , Hageman Philomena , Calafat Jero 
Published: May 2006

Electron microscopy, immunofluorescence, and bioassay demonstrated the presence of a mammary tumor inciting virus in untreated mice of three different inbred strains, and in irradiated or urethan-treated mice of two other mouse strains, indicating the ubiquitous nature of this group of viruses. In general these viruses are transmitted vertically by the gametes of the mouse strain in which they naturally occur. The virus is present in every cell, although often in an incomplete form. If a mammary tumor inciting virus is introduced into a different mouse strain, only milkborne transmission will take place, after which the virus is found in a limited number of tissues.
It has been speculated that mammary tumor inciting viruses are transmitted as genetic factors of the host strain to which they belong. There is some evidence that a repressor, produced by a regulator gene, controls the rate of release of such a genetically transferred virus. Repression can be abrogated by a carcinogenic treatment. The repressor would also cause resistance to a superinfecting mammary tumor inciting virus by interference with its replication.
Bovine Liver Glutamate Dehydrogenase: Tentative Amino Acid Sequence; Identification of a Reactive Lysine; Nitration of a Specific Tyrosine and Loss of Allosteric Inhibition by Guanosine Triphosphate
Authors: Smith Emil L. , Landon Michael , Piszkiewicz Dennis , Brattin William J. , Langley Trevor J. , Melamed Mark D. 
Published: May 2006

A tentative but almost complete amino acid sequence for the subunit peptide chain of bovine liver glutamate dehydrogenase indicates a minimal size of 506 residues with a molecular weight of 56,100, in accord with the physical size of the subunit of 55,900. Inactivation with pyridoxal 5′-phosphate, followed by reduction with sodium borohydride, has permitted identification of the essential lysine as residue 97. Nitration of tyrosine-412 is accompanied by loss of the allosteric inhibitory effect of guanosine triphosphate.
Comparison of the sequences of glutamate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase has indicated that only two 12-residue sequences are similar in the two enzymes; this sequence includes reactive lysine-97 of the former enzyme.
Isolation and Characterization of Calcifying Matrix Vesicles from Epiphyseal Cartilage
Authors: Ali S. Y. , Sajdera S. W. , Anderson H. C. 
Published: May 2006

Matrix vesicles, associated with initial calcification in cartilage, have been isolated from bovine fetal epiphyseal cartilage. Cartilage was digested with collagenase, then partitioned into seven fractions by differential centrifugation. The cellular fractions contained over 80% of the DNA in the digest. The extracellular fraction that contained matrix vesicles, in which apatite crystals were often seen on electron microscopy, also displayed the highest specific activity for alkaline phosphatase, pyrophosphatase, ATPase, and 5′-AMPase (EC 3.1.3.1., 3.6.1.1, 3.6.1.3, and 3.1.3.5, respectively). Most of the acid phosphatase (EC 3.1.3.2) activity, on the other hand, was found in the cellular fractions, indicating that matrix vesicles are quite distinct from lysosomes. This appears to be the first instance of isolation of membrane-bounded extracellular particles from any normal tissue.
The matrix vesicles possess enzymes that can increase the local concentration of orthophosphate and thus could lead to the formation of hydroxyapatite. The membrane-bounded matrix vesicles may also provide a mechanism for ATP-dependent transport of calcium or phosphate into the lumen of the vesicles with resultant mineralization.
Mutation and Cancer: Statistical Study of Retinoblastoma
Authors: Knudson Alfred G. 
Published: May 2006

Based upon observations on 48 cases of retinoblastoma and published reports, the hypothesis is developed that retinoblastoma is a cancer caused by two mutational events. In the dominantly inherited form, one mutation is inherited via the germinal cells and the second occurs in somatic cells. In the nonhereditary form, both mutations occur in somatic cells.
The second mutation produces an average of three retinoblastomas per individual inheriting the first mutation. Using Poisson statistics, one can calculate that this number (three) can explain the occasional gene carrier who gets no tumor, those who develop only unilateral tumors, and those who develop bilateral tumors, as well as explaining instances of multiple tumors in one eye.
This value for the mean number of tumors occurring in genetic carriers may be used to estimate the mutation rate for each mutation. The germinal and somatic rates for the first, and the somatic rate for the second, mutation, are approximately equal. The germinal mutation may arise in some instances from a delayed mutation.
Spontaneous Precipitation of Brushite in Urine: Evidence that Brushite Is the Nidus of Renal Stones Originating as Calcium Phosphate
Authors: Pak Charles Y. C. , Eanes Edward D. , Ruskin Belle 
Published: May 2006

Further evidence that brushite plays a regulatory role in renal stone formation was provided by the identification of brushite as the first precipitate that appears in supersaturated urine by spontaneous precipitation. Calcium chloride was added to induce supersaturation in urine specimens from twelve subjects with and twelve subjects without nephrolithiasis.
The first precipitate in all specimens with pH below 6.9 was identified as brushite by x-ray diffraction and shown to have a calcium-phosphorus ratio of approximately 1.0.

The activity product of [Ca
2+
] × [HPO
4
2-
] necessary to produce a precipitate ranged from 2.2 to 3.5 times the solubility product of brushite, but the range and mean were the same for both groups of subjects.

The activity product of [Ca
2+
] × [HPO
4
2-
] in the supernatant (after spontaneous precipitation) was not significantly different from that obtained after incubation of the same urine specimen with synthetic brushite.

These results provide conclusive evidence that brushite constitutes the solid phase formed by spontaneous precipitation from acidic urine supersaturated with respect to calcium and phosphorus; they suggest that the nidus for calcium-containing renal stones is brushite as well.
Biological Roles of the Two Components of Crotoxin
Authors: Hendon R. A. , Fraenkel-Conrat H. 
Published: May 2006

Crotoxin, the Brazilian rattlesnake neurotoxin, generally behaves as a homogeneous protein; however, it is a molecular complex of an acidic and a basic protein. These can be separated after alkylation or acylation of the amino groups, or on carboxymethyl cellulose at pH 4, or on DEAE-cellulose in 6 M urea. The two proteins differ greatly in composition, but one or both may exist in the form of closely related variants. Their molecular weights appear to be about 8400 and 13,000.
The acidic protein lacks the hemolytic and neurotoxic activity of crotoxin and the basic protein shows only the high, indirect hemolytic activity; a mixture of the two components shows the high neurotoxicity of crotoxin.
Neurohypophyseal Hormone-Responsive Adenylate Cyclase from Mammalian Kidney
Authors: Douša Thomas , Hechter Oscar , Schwartz Irving L. , Walter Roderich 
Published: May 2006

The investigation was undertaken to evaluate the direct stimulatory effects of neurohypophyseal hormones upon adenylate cyclase activity in a cell-free, particulate fraction derived from the kidney medulla of various mammalian species. The relative affinity of neurohypophyseal hormones for the receptor component of the adenylate cyclase system (as defined by the concentration of hormone required for half-maximal stimulation) had the order [8-arginine]-vasopressin > [8-lysine]-vasopressin ≫ oxytocin (AVP > LVP ≫ OT) for rat, mouse, rabbit, and ox; in the pig, the order was LVP > AVP ≫ OT. The relative affinities of the three hormones in rat and pig cyclase systems were found to correspond with the relative antidiuretic potencies of these hormones in the intact rat and pig. These findings show that the renal receptor for neurohypophyseal hormones in a particular species exhibits the highest affinity for the specific antidiuretic hormone that occurs naturally in that species.
Some of the molecular requirements for the stimulation of rabbit adenylate cyclase were defined by studies of several neurohypophyseal analogs possessing structural changes in positions 1, 2, 3, 4, 5, 8, and 9.

This investigation introduces the particulate preparation of renal medullary adenylate cyclase as a tool for the analysis of neurohypophyseal hormone-receptor interactions and indicates that this preparation can be adapted to serve as an
in vitro
bioassay system for antidiuretic hormonal activity.
Three-dimensional Reconstruction from Radiographs and Electron Micrographs: Application of Convolutions instead of Fourier Transforms
Authors: Ramachandran G. N. , Lakshminarayanan A. V. 
Published: May 2006

A new technique is proposed for the mathematical process of reconstruction of a three-dimensional object from its transmission shadowgraphs; it uses convolutions with functions defined in the real space of the object, without using Fourier transforms. The object is rotated about an axis at right angles to the direction of a parallel beam of radiation, and sections of it normal to the axis are reconstructed from data obtained by scanning the corresponding linear strips in the shadowgraphs at different angular settings.
Since the formulae in the convolution method involve only summations over one variable at a time, while a two-dimensional reconstruction with the Fourier transform technique requires double summations, the convolution method is much faster (typically by a factor of 30); the relative increase in speed is larger where greater resolution is required. Tests of the convolution method with computer-simulated shadowgraphs show that it is also more accurate than the Fourier transform method. It has good potentialities for application in electron microscopy and x-radiography. A new method of reconstructing helical structures by this technique is also suggested.
A Mechanism of Action for Carboxypeptidase A
Authors: Barber Anna K. , Fisher James R. 
Published: May 2006

In an attempt to gain a better understanding of the mechanism of action of carboxypeptidase A (EC 3.4.2.1), many kinetic studies have been undertaken using numerous substrates—both esters and peptides—that have exhibited substrate linearity, inhibition, activation, and sigmoid-shaped rate plots. Numerous interpretations of the kinetic data have been proposed, none of which are fully in accord both with kinetic data and x-ray crystallographic studies. Much of the kinetic data has been interpreted using multisite binding while the x-ray information seems to severely restrict these possibilities.
We have examined the feasibility of a simple model with a single active site, without modifier sites, that allows only one substrate molecule to bind the enzyme at a time. A random-pathway model was identified that simultaneously accounts for the nonlinear kinetic data and meets the restrictions imposed by the x-ray crystallographic studies.
Is There a Discriminator Site in Transfer RNA?
Authors: Crothers D. M. , Seno T. , Söll D. G. 
Published: May 2006

We determined the nature of the fourth nucleotide from the 3′-end of several
Escherichia coli
tRNAs, and tabulated these results with the same data for all known tRNA sequences. We find a striking constancy of the fourth nucleotide in tRNAs specific for a given amino acid. Furthermore, tRNAs specific for chemically related amino acids are very likely to have the same nucleotide at the fourth position.

One possible explanation for these regularities is the “discriminator” hypothesis: The code by which tRNA is recognized by its cognate aminoacyl-tRNA synthetase is logically hierarchical, with the fourth nucleotide serving as a primary “discriminator” site to subdivide the tRNAs into groups for recognition purposes. Each such group could have its own recognition code, or could be further subdivided by a secondary discriminator site. According to this hypothesis, chemically similar amino acids have the same discriminator nucleotide because they evolved from a single set of related amino acids indistinguishable to a primitive system.
There are other possible explanations for the observed regularities at the fourth nucleotide. For example, it is conceivable that the position is used for a direct physical interaction with the amino acid in the charging process, and chemically similar amino acids naturally select the same nucleotide. Further experiments can be expected to clarify this question.
Ribonucleic Acid Components of Murine Sarcoma and Leukemia Viruses
Authors: Maisel J. , Klement V. , Lai M. M-C. , Ostertag W. , Duesberg P. 
Published: May 2006

Defective Kirsten murine sarcoma virus was present as leukemia virus pseudotype [Ki-MSV(MLV)] in a 10- to 100-fold excess over its helper, Kirsten murine leukemia virus (Ki-MLV), when the two viruses were propagated in an NRK rat cell line. The
s
ω,20
of the fastsedimenting RNA complex of Ki-MLV and of Ki-MSV-(MLV) was 62 S and 55 S, respectively. Gel electrophoresis in buffered aqueous or formamide solution of the dissociated 62S RNA complex of Ki-MLV showed a single major peak of molecular weight about 2.5 × 10
6
. Dissociated 55S RNA of Ki-MSV(MLV) was resolved into a major component with a higher electrophoretic mobility than that of Ki-MLV RNA and molecular weight about 2.3 × 10
6
. Occasionally, a minor component with the same electrophoretic mobility as Ki-MLV RNA was observed in Ki-MSV(MLV) RNA; it is thought to be the RNA of Ki-MLV present as helper virus in our stocks of Ki-MSV(MLV). The RNA of an endogenous rat C-type RNA virus was electrophoretically different from both Ki-MLV RNA and Ki-MSV(MLV) RNAs. Oligonucleotide fingerprinting of the RNAs digested with RNase T1 indicated that the RNAs of Ki-MSV(MLV) and Ki-MLV are different. However, the extent of the difference between the two RNAs could not be estimated by this method.

The heat-dissociated 50-70S RNAs of two other defective murine sarcoma-leukemia viruses; Harvey-MSV(MLV) and Moloney-MSV(MLV) and of defective spleen-focus-forming Friend virus were resolved electrophoretically into two components. The larger components had the same electrophoretic mobility as the RNA of Ki-MLV or Moloney MLV. The smaller were not present in leukemia virus. It is suggested that the small RNA components of the two murine viruses and of Friend virus represent specific genetic information of these replication-defective transforming viruses.
Possible relationships between the RNAs of murine leukemia viruses and replication-defective murine sarcoma and Friend viruses are discussed.
Evidence for 30-40S RNA as Precursor of the 60-70S RNA of Rous Sarcoma Virus
Authors: Canaani E. , Helm K. V. D. , Duesberg P. 
Published: May 2006

Rous sarcoma virus harvested from cells at intervals of 3 min has the same density, sedimentation coefficient, and DNA polymerase as virus harvested at hourly intervals. The RNA of the Prague strain-C consists of a minor class of 60-70S RNA, a major class 30-40S RNA, and a 4-12S class of RNA present at variable concentration. The RNA of the Schmidt-Ruppin strain-A contains more 60-70S than 30-40S RNA. Upon incubation of virus harvested at 3-min intervals at 40° in cell growth medium or Tris-saline, most of the 30-40S RNA is converted to 60-70S RNA.
The electrophoretic mobility of the 30-40S RNA of the Rous virus harvested at 3-min intervals is lower than that of the 30-40S subunits of completely dissociated 60-70S RNA; after heating, their mobilities are identical. Heating also releases some small RNAs from 30-40S RNA of virus harvested at 3-min intervals, but five times more 4S RNA is released if the 30-40S RNA is allowed to convert to 60-70S in the virus. The template activity for Rous virus DNA polymerase of the 30-40S RNA of Rous virus harvested at 3-min intervals is about five times lower than that of 60-70S RNA. It is suggested that association of 30-40S RNAs with some RNAs of the 4-12S class may take place simultaneously with their conversion to 60-70S RNA.
A Manyfold Increase in Sister Chromatid Exchanges in Bloom's Syndrome Lymphocytes
Authors: Chaganti R. S. K. , Schonberg S. , German James 
Published: May 2006

Dividing cells from persons with Bloom's syndrome, an autosomal recessive disorder of growth, exhibit increased numbers of chromatid breaks and rearrangements. A highly characteristic feature of the chromosome instability in this syndrome is the tendency for exchanges to occur between
chromatids of homologous chromosomes
at homologous sites. In the present experiments, a cytogenetic technique by which the sister chromatids of a metaphase chromosome are stained differentially has been used to demonstrate a striking and possibly specific, but hitherto unrecognized, increase in the frequency with which
sister chromatids
also exchange segments. The cells were grown in bromodeoxyuridine and stained with 33258 Hoechst and Giemsa. Whereas phytohemagglutinin-stimulated lymphocytes from normal controls had a mean of 6.9 sister chromatid exchanges per metaphase (range 1-14), those from persons with Bloom's syndrome had a mean of 89.0 (range 45-162). Normal frequencies of sister chromatid exchanges were found in cells heterozygous for the Bloom's syndrome gene, and also in cells either homozygous or heterozygous for the genes of the Louis-Bar (ataxia telangiectasia) syndrome and Fanconi's anemia, two other rare disorders characterized by chromosome instability.

In a differentially stained chromatid interchange configuration discovered during the study, it was possible to determine the new distribution of both sister and non-sister-but-homologous chromatids that had resulted from numerous exchanges. By following shifts in the pattern of staining from chromatid to chromatid, visual evidence was obtained that the quadriradial configurations long recognized as characteristic of Bloom's syndrome represent exchanges between homologous chromosomes, apparently at homologous points.
We postulate that the increase in the frequency of exchanges between nonsister-but-homologous chromatids and those between sister chromatids in Bloom's syndrome represents aspects of one and the same disturbance. A study of this phenomenon in relation to the clinical features of Bloom's syndrome may be helpful eventually in understanding the biological significance of chromatid exchange in somatic cells.
Gibberellic Acid Causes Increased Synthesis of RNA Which Contains Poly(A) in Barley Aleurone Tissue
Authors: Jacobsen John V. , Zwar John A. 
Published: May 2006

Incubation of isolated barley aleurone layers with gibberellic acid for 16 hr caused a 50% increase in the synthesis of RNA that contains poly(A) sequences [poly(A)-RNA], but had no measurable effect on the syntheses of the major RNA species. The syntheses of both the poly(A) and the heteropolymeric fractions of the poly(A)-RNA were increased.
The poly(A) sequences were separated into two classes by size, one containing an average of 250 nucleotides and the other about 70 nucleotides. The two classes occurred in a molar ratio of about 1:1. Gibberellic acid increased the syntheses of both sequences to the same extent.
We interpret these results to mean that gibberellic acid increases specifically the synthesis of mRNA in this tissue.
The Primary Structure of High Density Apolipoprotein-Glutamine-I
Authors: Baker H. Nordean , Delahunty Thomas , Gotto Antonio M. , Jackson Richard L. 
Published: May 2006

The major protein constituent of human plasma high density lipoproteins has been isolated and its complete amino-acid sequence determined. The protein, designated apolipoprotein-glutamine-I by the presence of carboxyl-terminal glutamine, is a single polypeptide chain of 245 amino-acid residues, including three residues of methionine. The protein is devoid of cysteine, cystine, and isoleucine. Cleavage of apolipoprotein-glutamine-I with cyanogen bromide yields four fragments with 94, 90, 36, and 25 amino acids. The amino-acid sequence of each fragment was determined by conventional methods, with proteolytic digestion with trypsin, chymotrypsin, and thermolysin. The alignment of the cyanogen bromide fragments was determined by the isolation of the methionine-containing tryptic peptides from apolipoprotein-glutamine-I.
Inspection of the sequence of apolipoprotein-glutamine-I suggests an interesting distribution of amino acids that may account for its helical structure and its ability to bind and transport lipid.