bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of intake of L-ascorbic acid on the incidence of dermal neoplasms induced in mice by ultraviolet light.
Authors: Dunham W B , Zuckerkandl E , Reynolds R , Willoughby R , Marcuson R , Barth R , Pauling L
Published: May 2006

We have carried out a study of large malignant skin tumors (squamous cell carcinomas) and other lesions in hairless mice (groups of 38-45) intermittently exposed to ultraviolet light over a period of 15 weeks, beginning when the mice were about 10 weeks old. The several groups were given a standard diet with 0%, 0.3%, 5%, and 10% added L-ascorbic acid (vitamin C) throughout the study. No lesions developed in unirradiated control groups. The lesions were counted every 14 days for 4 months, beginning 4 weeks before the end of the period of irradiation. The observed incidence of lesions of several sizes during successive time periods was analyzed by the statistical method recommended by a committee of the International Agency for Research on Cancer. A pronounced effect of vitamin C in decreasing the incidence and delaying the onset of the malignant lesions was observed with high statistical significance.
Quantitative determination of dopamine receptor subtypes not linked to activation of adenylate cyclase in rat striatum.
Authors: Huff R M , Molinoff P B
Published: May 2006

The binding of [3H]domperidone and [3H]spiroperidol was examined in membranes prepared from rat striatum. Scatchard analysis of the binding of [3H]domperidone resulted in curvilinear plots consistent with the presence of multiple classes of binding sites. Nonlinear regression analysis of untransformed data showed that the curvature was best explained by the presence of two populations of binding sites. Scatchard plots of the binding of [3H]spiroperidol were linear, suggesting that this radioligand binds to a single class of receptors. However, results obtained in studies of the inhibition of [3H]spiroperidol binding by a number of competing ligands were not consistent with the interaction of these agents with a single class of binding sites. Computer-assisted analysis of the Hofstee plots of six competing ligands gave the same relative proportion for two classes of sites as determined by analysis of the binding of [3H]domperidone. The two classes of receptors labeled with [3H]spiroperidol had affinities for domperidone that were similar to those of the two populations of binding sites for [3H]domperidone. Furthermore, the number of binding sites for [3H]spiroperidol was equal to the total number of binding sites for [3H]domperidone. These findings suggest that the two radioligands bind to the same two classes of binding sites. It is unlikely that either of the two classes of striatal sites are receptors for serotonin. The approach described will make it possible to assess the effects of physiological or pharmacological manipulations on the densities or properties of subtypes of dopamine receptors.
Human copper-containing superoxide dismutase of high molecular weight.
Authors: Marklund S L
Published: May 2006

A superoxide dismutase (superoxide:superoxide oxidoreductase, EC 1.15.1.1), distinct from previously known superoxide dismutases, has been isolated from human lung tissue. It is probably of the same nature as a previously demonstrated high molecular weight superoxide dismutating factor in human extracellular fluids. The enzyme has a molecular weight around 135,000 and is composed of four equal noncovalently bound subunits. Each molecule appears to have four copper atoms. No iron or manganese was found in the enzyme. Cyanide inhibits the enzyme efficiently. The enzyme brings about a first-order dismutation of the superoxide radical, the rate constant for the catalyzed reaction being about 1 X 10(9) M-1 s-1 per copper atom. The enzyme has hydrophobic properties. Affinity for various lectins indicates the presence of carbohydrate. Upon chromatography on heparin-Sepharose it is divided into three fractions, one with no, one with weak, and one with strong affinity for heparin.
Isolation of a nonmitogenic angiogenesis factor from wound fluid.
Authors: Banda M J , Knighton D R , Hunt T K , Werb Z
Published: May 2006

Angiogenesis, or new capillary growth, is essential to normal growth and wound healing. It is also active in several pathologic states, including the growth of malignant tumors. An extracellular, nonneoplastic angiogenesis factor has been isolated from cell-free rabbit wound fluid by pore-limit dialysis and chromatography on a size-exclusion HPLC column. The isolated angiogenesis factor was purified 9,600-fold with a yield of 81% and has a molecular weight between 2,000 and 14,000. Wound fluid angiogenesis factor was completely separated from the mitogenic activity of wound fluid; it did not increase the number of capillary endothelial cells in vitro or stimulate [3H]thymidine uptake by these cells. The isolated angiogenesis factor stimulated endothelial cell migration in vitro, and less than 200 ng of the factor stimulated angiogenesis in vivo in the corneal implant assay.
Serum and epidermal growth factor transiently depolarize quiescent BSC-1 epithelial cells.
Authors: Rothenberg P , Reuss L , Glaser L
Published: May 2006

Continuous intracellular recording of membrane potential with microelectrodes in BSC-1 epithelial cells has been used to study the early ionic effects of the interaction of mitogens with cell surface receptors. Initial results show that (i) there is no significant difference in membrane potential between growing and quiescent cells, (ii) addition of epidermal growth factor or serum to quiescent BSC-1 cells induces a brief and transient depolarization, (iii) the mitogenic response of BSC-1 cells to epidermal growth factor and the transient depolarization show similar concentration dependences, and (iv) serum addition to quiescent BSC-1 cells induces a sustained increase in Na+ influx that is electroneutral and amiloride sensitive. Intracellular pH changes may be a primary event triggering the response of quiescent cells to mitogenic polypeptides.
Event-related brain potentials are different in individuals at high and low risk for developing alcoholism.
Authors: Elmasian R , Neville H , Woods D , Schuckit M , Bloom F
Published: May 2006

Event-related brain potentials (ERPs) from normal drinkers with and without a family history of alcoholism were compared. Three separate groups of 10 subjects each (5 with and 5 without a family history of alcoholism) ingested either a placebo or ethanol at 0.56 or 0.94 g/kg. In each comparison, ERP components elicited in conjunction with subjects' decisions about task-relevant stimuli were of significantly reduced amplitude in individuals with a family history of alcoholism. Additionally, both the latency of the positive component and reaction times to correctly detected targets were significantly later in individuals with a positive history of alcoholism than in those without such a history. These group differences were apparent both with and without a challenge of alcohol. The data suggest that brain functions are different in individuals at high and low risk for the development of alcoholism (i.e., those with and without a family history of alcoholism, respectively).
Regulation of intracellular pH by human peripheral blood lymphocytes as measured by 19F NMR.
Authors: Deutsch C , Taylor J S , Wilson D F
Published: May 2006

We have measured the intracellular pH of human peripheral blood lymphocytes by means of high-resolution 19F NMR spectroscopy using D,L-2-amino-3,3-difluoro-2-methylpropanoic acid (F2MeAla) as a probe. Lymphocytes readily took up the methyl ester of F2MeAla, and endogenous esterase hydrolyzed the ester to the free amino acid inside the cell. This alpha-methyl amino acid is not metabolized by the cell, and its 19F NMR spectrum exhibits large pH-dependent shifts as the alpha-amino group is protonated. The size of the 19F shifts, the high sensitivity of 19F NMR, and the favorable pKa of the alpha-amino group of F2MeAla (pKa = 7.3) allowed us to measure intracellular pH of lymphocytes at 25-30 degrees C with approximately 5-min acquisition times. Measurements at various external pH values demonstrated that human peripheral blood lymphocytes regulate their internal pH, a process requiring expenditure of metabolic energy. In the pH range between 6.8 and 7.4, lymphocytes maintain a constant internal pH of 7.17 +/- 0.06 pH unit. Outside this range, intracellular pH changes with extracellular pH. The accuracy of this 19F pH probe has been confirmed by independent measurements of intracellular pH using equilibrium distributions of 5,5-dimethyloxazolidine-2,4-dione.
Modification of age-related immune decline in mice dietarily restricted from or after midadulthood.
Authors: Weindruch R , Gottesman S R , Walford R L
Published: May 2006

Although weaning-initiated dietary restriction of rodents is known to increase maximum survivorship and inhibit spontaneous late-life disease and immunologic aging, restriction begun in adulthood has been much less thoroughly evaluated. In the present studies, male mice of a long-lived F1 hybrid strain were gradually restricted dietarily beginning at 12 mo or older until their body weights stabilized at 60-70% of controls. Underfeeding decreased the number of nucleated cells per spleen but increased the percentage of T cells. For mice restricted at 12, 17, or 22 mo and tested at various ages thereafter, the [3H]thymidine uptake of spleen cells after phytohemagglutinin stimulation significantly exceeded values for age-matched unrestricted controls. Restriction did not, however, alter either splenocyte responses to concanavalin A or to B-cell mitogens or phytohemagglutinin responses of peripheral lymph node cells. In the splenic plaque-forming cell response to injected sheep erythrocytes, restricted and control mice differed more clearly in response kinetics than in peak levels. The splenic cell-mediated lymphocytotoxic response to alloantigens was comparable in old mice (27-29 mo) restricted since 12 mo of age with that of young (5- to 6-mo) controls and was greater than that of age-matched old controls. Spontaneous tumors were observed less frequently in 19- to 25-mo-old mice restricted at 12 mo of age than in mice restricted at 17 mo or in controls. Our results indicate that appropriate food restriction initiated in adulthood influences immunosenescence and spontaneous tumor incidence in a fashion not unlike its weaning-initiated counterpart.
Abnormal polyunsaturated fatty acid patterns of serum lipids in Reye's syndrome.
Authors: Ogburn P L , Sharp H , Lloyd-Still J D , Johnson S B , Holman R T
Published: May 2006

Fatty acid patterns of the serum lipids were measured in 17 children with Reye's syndrome (RS). Serial measurements of total serum free fatty acids (FFA) showed that levels were increased during RS and, after recovery, were significantly lower in the patients who survived. Fatty acid patterns of serum FFA, triglycerides, and phospholipids in patients with RS were significantly different from those in controls. In RS the polyunsaturated fatty acid content of phospholipids was less than control values; in the FFA, it was higher. This was consistent with the possible involvement of increased phospholipase activity. The increase in polyunsaturated fatty acids in FFA, the precursors of prostaglandins, suggests that a grossly disturbed prostaglandin pattern may occur in RS. These changes in lipid metabolism may be related to the abnormal hepatic and neurological functions observed in RS.
Ca-mediated activation of a K current at fertilization of golden hamster eggs.
Authors: Miyazaki S , Igusa Y
Published: May 2006

Golden hamster eggs respond to fertilization with recurring hyperpolarizations [Miyazaki, S. & Igusa, Y. (1981) Nature (London) 290, 703-705]. We analyzed the ionic mechanism of the fertilization potential and examined whether the fertilization potential plays a role in polyspermy block. Each hyperpolarizing response (HR) during fertilization is found to be caused by an increase in the K conductance activated by an increase in the intracellular Ca2+ concentration. This conclusion is based on the following: (i) The reversal potential of the HR shifted with the Nernstian slope for K ions when the external K concentration was changed, whereas it was unaltered by the removal of Cl ions. (ii) The HR was blocked by the intracellular injection of EGTA. (iii) Injection of Ca2+ into an egg induced a hyperpolarization of the membrane similar to the HR. The Ca-activated K conductance shows an apparent outward rectification, which could be explained by an asymmetric distribution of K ions across the membrane. The HR associated with sperm entry into the egg occurred at any membrane potential between -160 and +50 mV. Therefore, a potential-dependent block of sperm entry does not occur in the hamster egg.
Third component of human complement: Localization of the internal thiolester bond
Authors: Thomas Matthew L. , Janatova Jarmila , Gray William R. , Tack Brian F.
Published: May 2006

Human complement protein C3 was inactivated by using methylamine and thereby generating a SH group from the internal thiol ester. The protein was coupled via this SH group to activated thiol-Sepharose and digested with elastase. Fragment C3d remained attached to the thiol-Sepharose and was subsequently eluted with L-cysteine. Concomitantly, the original SH group was regenerated, and it was then labeled with iodo[2-
3
H]acetic acid. Partial sequence analysis of the radiolabeled C3d fragment showed that both components of the thiol ester are located close to the amino terminus (residues 23 and 26). Specific chemical cleavage of the α-chain was achieved after
S
-cyanylation of the thiol. The two fragments obtained corresponded to the amino-terminal section (
M
r
≈46,000) and the carboxy-terminal section (
M
r
≈70,000). These results together indicate that fragment C3d occupies approximately positions 345-610 of the α-chain. The partial sequence of C3d was extended by completion of the sequence of a previously described tryptic peptide. Comparison of residues 1-49 of C3d with a peptide from α
2
-macroglobulin [Swenson, R. P. & Howard, J. B. (1980)
J. Biol. Chem.
255, 8087-8091] shows a previously recognized identity of seven residues around the thiol ester site and a second region of identity around a known glycosylation site of α
2
-macroglobulin. The relationships among these proteins and protein C4 are discussed. An overall outline of the structure of C3 is presented, showing the locations of various fragments and cleavage sites. The thiol ester group places constraints on the local folding of the peptide chain; a possible conformation is suggested and discussed in relation to the mechanism of activation.
Growth of hybridoma cells in serum-free medium: ethanolamine is an essential component.
Authors: Murakami H , Masui H , Sato G H , Sueoka N , Chow T P , Kano-Sueoka T
Published: May 2006

A serum-free medium supplemented with a few growth factors was devised to grow lymphocyte hybridomas. The medium was developed with the hybridoma line MPC11-BL, a fusion product between a mouse plasmacytoma cell line (MPC11TG70na3) and mouse (BALB/c) spleen cells. In the process of developing the medium, ethanolamine was found to be an essential growth factor for the hybridoma. Phosphoethanolamine at 10-fold higher concentration could substitute for ethanolamine. Long-term cultivation of the cells was achieved in the defined medium supplemented with insulin, transferrin, ethanolamine, and selenium. The defined medium supported the growth of various other mouse hybridoma cell lines, mostly at a rate comparable to that observed in a serum-containing medium. After one-step ammonium sulfate precipitation of the spent medium, more than 95% of the protein recovered was immunoglobulin as shown by NaDodSO4/polyacrylamide gel electrophoresis.
Monoclonal antibody to transferrin receptor blocks transferrin binding and inhibits human tumor cell growth in vitro.
Authors: Trowbridge I S , Lopez F
Published: May 2006

A murine hybridoma has been obtained that produces a monoclonal antibody against the human transferrin receptor. In contrast to previously characterized monoclonal antibodies that recognize the transferrin receptor, this antibody, designated 42/6, blocks the binding of transferrin to its receptor and inhibits the growth of the human T leukemic cell line, CCRF-CEM, in vitro. Inhibition of cell growth was dose dependent, and as little as 2.5 micrograms of purified antibody per ml had a detectable effect, even though transferrin was present in the tissue culture medium in large molar excess. Cells grown in the presence of antibody for 7 days accumulated in S phase of the cell cycle. The addition of iron to antibody-treated cultures in the form of ferric complexes or ferrous sulfate did not overcome the growth inhibitory effects of the anti-transferrin-receptor antibodies. This result suggests that either transferrin is the only means by which CCRF-CEM leukemic cells can be provided with sufficient iron in vitro or that other factors in addition to iron starvation are involved in the antibody-mediated growth inhibition. The inhibition of cell growth by 42/6 monoclonal antibody suggests that monoclonal antibodies against proliferation-associated cell surface antigens, such as the transferrin receptor, may be useful pharmacological reagents to modify cell growth in vitro.
Mapping of the vaccinia virus thymidine kinase gene by marker rescue and by cell-free translation of selected mRNA
Authors: Weir Jerry P. , Bajszár Gyorgy , Moss Bernard
Published: May 2006

A selective plaque assay that uses thymidine kinase (TK)-deficient human 143 cells was developed to titer mixtures of TK
+
and TK
-
vaccinia virus. With this assay it could be shown that methotrexate-resistant TK
+
virus was formed in cells coinfected with TK
-
virus and wild-type virus DNA. By substituting vaccinia DNA fragments cloned in plasmids for virion DNA, this marker rescue system provided the basis for mapping the TK gene. Of the 15
Hin
dIII fragments, only J could rescue five independently derived TK
-
mutants. This 5000-base-pair (bp) fragment maps approximately 80,000 bp from the left-end of the 180,000-bp vaccinia genome. Marker rescue could be detected with 18 ng or less of plasmid and was proportionate to DNA concentration. The resistance to methotrexate of the TK
+
recombinants was shown to be due to TK synthesis. Evidence that the
Hin
dIII J fragment contains the structural TK gene and not a regulatory element was demonstrated by the synthesis of active TK in a cell-free system programmed with mRNA selected by hybridization to the plasmid. Previous studies [Belle-Isle, H., Venkatesan, S. & Moss, B. (1981)
Virology
112, 306-317] indicated that mRNAs coding for three immediate early polypeptides with molecular weights of 41,000, 21,000, and 17,000 map within
Hin
dIII J. The mapping of the easily selectable vaccinia virus TK gene now opens the way to genetic manipulations that should increase our understanding of vaccinia virus gene expression and facilitate the use of vaccinia virus as an efficient cloning vector for foreign genes.
Somatic mutation in a cultured mouse myeloma cell affects antigen binding.
Authors: Cook W D , Rudikoff S , Giusti A M , Scharff M D
Published: May 2006

The S107 mouse myeloma cell line synthesizes an IgA antibody that binds the hapten phosphocholine and is similar if not identical in its heavy and light chain variable region sequence to the predominant antibody produced by BALB/c mice in response to immunization with phosphocholine. This cell line frequently and spontaneously generates somatic variants producing immunoglobulins with decreased ability to bind antigen. One such variant, S 107.U1, is described here. This variant has a decreased ability to bind phosphocholine when it is attached to a carrier, although its affinity for free hapten is the same as that of the parent. This decrease in antigen binding is associated with a single amino acid substitution at the fifth residue in the JH segment.
High-resolution solid-state NMR of quadrupolar nuclei
Authors: Meadows Michael D. , Smith Karen A. , Kinsey Robert A. , Rothgeb T. Michael , Skarjune Robert P. , Oldfield Eric
Published: May 2006

We report the observation of high-resolution solid-state NMR spectra of
23
Na (
I
= [unk]),
27
Al (
I
= [unk]) and
51
V (
I
= [unk]) in various inorganic systems. We show that, contrary to popular belief, relatively high-resolution (≈10 ppm linewidth) spectra may be obtained from quadrupolar systems, in which electric quadrupole coupling constants (
e
2
qQ/h
) are in the range ≈1-5 MHz, by means of observation of the (½, -½) spin transition. The (½, -½) transition for all nonintegral spin quadrupolar nuclei (
I
= [unk], [unk], [unk], or [unk]) is only normally broadened by dipolar, chemical shift (or Knight shift) anisotropy or second-order quadrupolar effects, all of which are to a greater or lesser extent averaged under fast magic-angle sample rotation. In the case of
23
Na and
27
Al, high-resolution spectra of
23
NaNO
3
(
e
2
qQ/h
≈300 kHz) and α-
27
Al
2
O
3
(
e
2
qQ/h
≈2-3 MHz) are presented; in the case of
51
V
2
O
5
(
e
2
qQ/h
≈800 kHz), rotational echo decays are observed due to the presence of a ≈10
3
-ppm chemical shift anisotropy. The observation of high-resolution solid-state spectra of systems having spins
I
= [unk], [unk], and [unk] in asymmetric environments opens up the possibility of examining about two out of three nuclei by solid-state NMR that were previously thought of as “inaccessible” due to the presence of large (a few megahertz) quadrupole coupling constants. Preliminary results for an
I
= [unk] system,
93
Nb, having
e
2
qQ/h
≈19.5 MHz, are also reported.
Angiotensin increases Na+ entry and Na+/K+ pump activity in cultures of smooth muscle from rat aorta.
Authors: Brock T A , Lewis L J , Smith J B
Published: May 2006

Angiotensin markedly altered the Na+ permeability of smooth muscle cells cultured from explants of rat aorta. The rate of net Na+ uptake was followed in the presence of ouabain in order to block Na+ efflux via the Na+/K+ pump. Angiotensin II (AII) or angiotensin III (AIII) increased net Na+ uptake by about 3-fold. Maximal stimulation of Na+ uptake was produced by about 10 nM AII. Bradykinin and the angiotensin antagonist [Sar1, Ileu5, Ala8]AII had no significant effect on net Na+ uptake. Angiotensin also enhanced the activity of the Na+/K+ pump, which was assayed by following the rate of ouabain-sensitive 86Rb+ uptake by the cells. AII and AIII nearly doubled ouabain-sensitive 86Rb+ uptake, but bradykinin, norepinephrine, and [Sar1, Ileu5, Ala8]AII had no effect. In the presence of ouabain, 86Rb+ uptake was not significantly affected by AII or AIII, indicating that angiotensin did not alter passive permeability to Rb+. Loading the cells with Na+, either by incubation in K+-free medium or exposure to the Na+-selective ionophore monensin, markedly increased ouabain-sensitive 86RB+ uptake. This result indicates that the activity of the Na+/K+ pump is limited by the low level of Na+ that is normally in the cells. AII had no effect on the activity of the Na+/K+ pump in Na+-loaded cells. These results suggest that AII or AIII stimulates the Na+/K+ pump in cultured aortic muscle cells by increasing its Na+ supply.
Tumor growth inhibition in patients with prostatic carcinoma treated with luteinizing hormone-releasing hormone agonists.
Authors: Tolis G , Ackman D , Stellos A , Mehta A , Labrie F , Fazekas A T , Comaru-Schally A M , Schally A V
Published: May 2006

Ten patients with prostatic carcinoma--six with stage C and four with stage D disease--were treated for 6 weeks to 12 months with agonistic analogues of luteinizing hormone-releasing hormone (LH-RH). [D-Trp6]LH-RH was given subcutaneously once daily at a dose of 100 microgram and [D-Ser(But)6]des-GlyNH2(10)-LH-RH ethylamide (HOE 766) was given subcutaneously (50 microgram once daily) or intranasally (500 microgram twice daily). In all patients, mean plasma testosterone levels showed a 75% suppression by the third week of treatment and remained low thereafter. This was followed by a decrease or normalization of plasma acid phosphatase levels by the second month of treatment and a 47% decrease in serum alkaline phosphatase by the 10th week of treatment in all but one patient. In patients with stage C disease presenting with prostatism or urinary outflow obstruction, there was a noticeable clinical improvement. In two such patients, a decrease in the size of the prostate was confirmed by ultrasonography. In patients with stage D disease manifested by diffuse bone metastases, there was relief of bone pain, and in one patient treated for greater than 12 months the improvement was documented by radioisotope bone imaging. It is concluded that superactive agonistic LH-RH analogues hold promise as therapeutic agents in patients with androgen-sensitive prostatic adenocarcinoma. Furthermore, the analogous of LH-RH may be used to assess the responsiveness of patients to surgical castration. Long-term administration of LH-RH analogues could become an alternative to surgical castration and estrogen therapy for the treatment of hormone-dependent prostatic carcinoma.
Thymosins beta 8 and beta 9: two new peptides isolated from calf thymus homologous to thymosin beta 4.
Authors: Hannappel E , Davoust S , Horecker B L
Published: May 2006

Two new peptides, designated thymosin beta 8 and thymosin beta 9, respectively, have been isolated and their amino acid sequences established. Thymosin beta 8, isolated from calf thymus fraction 5, has a mass of 4518 daltons and contains 39 amino acid residues, of which 31 are identical to the corresponding amino acid residues in thymosin beta 4 isolated from the same source. The NH2 terminus of thymosin beta 8 is acetylalanine, compared with acetylserine in thymosin beta 4. Thymosin beta 9, isolated from fresh-frozen calf thymus by a procedure that minimizes proteolysis, is identical to thymosin beta 8 except for the presence of an additional dipeptide, -Ala-LysOH, at the COOH terminus. It has a mass of 4717 daltons and 32 of its 41 amino acids are identical to those of thymosin beta 4. The similarity in structures of thymosin beta 4 and thymosin beta 9 suggests that they may have related functions.
Dietary fat affects immune response, production of antiviral factors, and immune complex disease in NZB/NZW mice.
Authors: Levy J A , Ibrahim A B , Shirai T , Ohta K , Nagasawa R , Yoshida H , Estes J , Gardner M
Published: May 2006

Autoimmune-prone (NZB x NZW)F1 (B/W) mice fed three nearly isocaloric diets with varied fat content showed a marked difference in their spontaneous development of immune complex disease and their immune response. Those animals received the diets high in either unsaturated or saturated fats had more severe immune complex nephritis and died earlier than mice on the low-fat diet. Endogenous production of the mouse xenotropic virus was unaffected by dietary fats, but the serum lipoproteins associated with antiviral activity were increased to levels as high as 1:600,000 in the B/W mice on the high-fat diets. These lipoproteins may be partially responsible for the decreased mitogenic response of spleen cells from mice fed the two high-fat diets. The mice receiving a diet high in saturated fats produced substantially higher titers of natural thymocytotoxic autoantibody, an IgM class of antibody, than did the mice maintained either on the high-unsaturated-fat or low-fat diet. In contrast, the mice receiving the diet high in unsaturated fats made significantly greater levels of antibodies to double-stranded DNA, an IgG, than did the mice kept on the two other diets. These results suggest that the type of fat in the diet could affect the serum level of different immunoglobulin classes. The data provide further evidence that the amount of dietary lipids alone can influence cellular and humoral immune responses and the spontaneous development of immune complex disease.
Thymosin beta 4: a ubiquitous peptide in rat and mouse tissues.
Authors: Hannappel E , Xu G J , Morgan J , Hempstead J , Horecker B L
Published: May 2006

Thymosin beta 4, recently isolated from calf thymus, is present in a number of rat and mouse tissues, including spleen, thymus, brain, lung, liver, and heart muscle. High concentrations are found in peritoneal macrophages, suggesting that its occurrence in other tissues may be related to the presence of macrophages or macrophage-like cells in these tissues. The conclusion that "thymosin" beta 4 does not originate solely in the thymus gland is supported by the high concentrations found in tissues of athymic (nu/nu) mice.
Differential expression of the amv gene in human hematopoietic cells.
Authors: Westin E H , Gallo R C , Arya S K , Eva A , Souza L M , Baluda M A , Aaronson S A , Wong-Staal F
Published: May 2006

Total cellular RNAs from a variety of fresh and culture-derived human hematopoietic neoplastic cell types at various stages of differentiation and human sarcoma, carcinoma, melanoma, and glioblastoma cell lines were enriched for poly(A)- containing sequences, fractionated by gel electrophoresis, and blot hybridized to a cloned DNA probe containing the transforming sequences (v-amv) of avian myeloblastosis virus (AMV), a virus known to cause myeloid leukemias in chickens. Expression of RNA sequences homologous to AMV was detected in all immature myeloid and lymphoid T cells in addition to the single erythroid cell line examined, but not in mature T cells or in B cells, including lymphoblast cell lines derived from patients with Burkitt lymphoma. In addition, induction of the cell line HL60, a promyelocytic leukemia line, to differentiate with dimethyl sulfoxide or retinoic acid resulted in a reduction of the level of expression of the human cellular gene c-amv homologous to v-amv. There was no detectable c-amv mRNA in any of the solid tumor cell lines examined. Thus, expression of the human c-amv gene could be correlated with the stage of differentiation of different hematopoietic cell types determined by morphologic and marker studies. Expression of c-amv could not be correlated with the extent of methylation in HL60 and in HL60 induced to differentiate with dimethyl sulfoxide.
Complete sequence analyses show that two defective interfering influenza viral RNAs contain a single internal deletion of a polymerase gene.
Authors: Nayak D P , Sivasubramanian N , Davis A R , Cortini R , Sung J
Published: May 2006

Defective interfering (DI) influenza viral RNAs arise by internal deletion of progenitor RNAs. By using recombinant DNA cloning and DNA sequence analysis techniques, we have deduced the complete sequence of two such RNAs (L2b and L3), both arising from the same polymerase (P1) gene of WSN influenza virus. We have also partially determined the sequence of the P1 polymerase gene, including the sequence at the point of deletion and the flanking regions. Our sequence study shows the following. (i) Both L2b and L3 arise by a simple deletion in the P1 gene. (ii) L2b and L3 are 683 and 441 nucleotides long, respectively. (iii) The first 413 and 244 nucleotides of the 5' ends of L2b and L3, respectively, are identical to those of the 5' end of the P1 gene. (iv) The last 270 nucleotides of L2b and 197 nucleotides of L3 are the same as those of the 3' end of the P1 gene. (v) The entire sequence of L3 is present in the sequence of L2b. (vi) Both the 5' and the 3' termini, including the transcription stop and poly(A) addition signals of the progenitor P1 gene, are present in both L2b and L3. (vii) The sequences at the deletion point and the flanking region of the P1 gene do not resemble the consensus splicing sequence of spliced mRNA suggesting that a replicational event rather than splicing is involved in the formation of influenza defective interfering RNAs.
Immunochemical detection of metallothionein in specific epithelial cells of rat organs.
Authors: Danielson K G , Ohi S , Huang P C
Published: May 2006

The distribution of a heavy metal binding protein, metallothionein, was studied immunocytochemically by using antimetallothionein antibody and the immunoperoxidase staining technique on histological sections of liver, kidney, intestine, lung, and testis from cadmium-treated rats. These tissues either accumulate heavy metals (e.g., liver, kidney, and testis) or are exposed to metal by ingestion or inhalation (intestine and lung). Staining for metallothionein was observed intracellularly in epithelial parenchymal cells of the liver and kidney; all hepatocytes and most renal tubular cells stained for the protein. Accumulation of metallothionein was not seen in connective tissue cells surrounding either blood vessels or renal tubules. Extracellular localization of metallothionein was also observed in the liver sinusoids and within the lumina of the renal tubules, suggesting a metal transport or excretory function for this protein. Surface columnar epithelial cells of the intestinal villi indicated the presence of metallothionein but connective tissue cells of the lamina propria were negative for the protein. The granular secretory Paneth cells of the small intestine also stained strongly for metallothionein as did respiratory epithelial cells of the lung. In the testis, metallothionein was detected in the Sertoli cells and interstitial cells but not within the spermatogonia. Sertoli cells are closely associated with the developing spermatogonia and appear to serve a nutritive role in spermatogenesis. Because of the secretory, absorptive, or nutritive function of the metallothionein-localizing cells in the organs studied, we suggest that metallothionein may be involved in metal storage or transport in addition to its commonly proposed detoxification role.
Coprecipitation of heat shock proteins with a cell surface glycoprotein.
Authors: Hughes E N , August J T
Published: May 2006

Monoclonal antibodies recognizing a mouse cell surface glycoprotein of Mr 90,000 were found to coprecipitate the Mr 70,000 and 72,000 heat shock-induced proteins of NIH/3T3 cells. These two smaller proteins were among the most abundant components of heat-treated NIH/3T3 cells. The Mr 70,000 component was not detected in normal cells whereas there was a low rate of incorporation of [35S]methionine into the Mr 72,000 polypeptide in the absence of heat shock. Tryptic peptide mapping and two-dimensional gel electrophoresis indicated that the coprecipitated and heat shock-induced polypeptides were identical and that the Mr 70,000 and 72,000 components contained homologous peptides. Also, the heat shock proteins had extensive structural homology with a cytoskeleton-associated protein of HeLa cells. The results suggest that the Mr 90,000 cell surface glycoprotein and the Mr 70,000 and 72,000 heat shock-inducible proteins mediate an association between the plasma membrane and the cell cytoskeleton.
In vivo horizontal oncogenesis by a human tumor in nude mice.
Authors: Goldenberg D M , Pavia R A
Published: May 2006

A human mucinous cystadenocarcinoma of the ovary was propagated in nude mice. After cryopreservation of the 3rd-passage xenograft for 4 years, subsequent in vivo transplants showed the emergence of two distinct populations, one resembling the original human adenocarcinoma and the other resembling a spindle-cell sarcoma. These two tumor cell populations were confirmed to be human and murine, respectively, by cytogenetic study, and the epithelial tumor cells were further shown to be of human origin by immunoperoxidase staining of blood group A antigen. Separation of the two tumor cell populations in vitro permitted the independent propagation of the human and murine tumor cells in vitro and in vivo. The murine sarcoma was also capable of growth in ordinary BALB/c mice. These results indicate that human cancer cells can induce malignancy in adjacent, putatively normal, cells of nude mice in vivo.
Effect of species pool size on species occurrence frequencies: Musical chairs on islands
Authors: Diamond Jared
Published: May 2006

If species interactions affect species distributions, then species occurrence frequencies (ν

i

), defined as the fraction of an archipelago's islands that species
i
inhabits, should vary with species pool size. A “natural experiment” approximating this test is provided by the Bismarck, Solomon, and New Hebrides archipelagoes, whose bird species pools decrease in that order, the species of each archipelago being mostly a subset of those of the next richer archipelago. The average ν for an archipelago's species decreases with archipelago pool size. In the archipelago with the largest pool, most species are on few islands and few species are on most islands, whereas the reverse is true in the archipelago with the smallest pool. For species shared between two or more archipelagoes, ν

i

decreases with pool size or number of species in the same guild. These interarchipelagal differences in ν

i

or average ν reflect differences in level of interspecific competition, which reduces νs in species-rich archipelagoes in two ways: usually, by reducing a species' incidence on small islands and restricting the species to larger islands; less often (for so-called supertramps), by restricting a species to small islands.
Crosslink precursors for the dipteran puparium
Authors: Sugumaran Manickam , Lipke Herbert
Published: May 2006

During sclerotization of puparial proteins, tyrosine, lysine, and histidine were converted to highly basic aromatic metabolites. Peptides generated from the sclerotized cuticle with
N
-bromosuccinimide included the basic derivatives among the hydrolysis products. The absorbance maxima of the aromatic metabolites were 25 nm lower than those of the conventional tyrosyl peptides, with phenolic character poorly expressed or absent. Post-translational modification of the structural proteins preceded visual expression of tanning because aromatic conjugates also were present prior to pupariation. These results are consistent with a crosslinking mechanism favoring covalent bonding between protein chains.
Higher order DNA structure in macronuclear chromatin of the hypotrichous ciliate Oxytricha nova.
Authors: Lipps H J , Gruissem W , Prescott D M
Published: May 2006

On lysis of macronuclei from the ciliated protozoan Oxytricha at 0.5-2 M NaCl, the DNA, which is normally found as discrete molecules ranging from 0.5 to 20 kilobases, appears in high molecular weight aggregates. Various treatments of the macronuclear lysate (i.e., nucleases, proteases, variation of salt, pH, and temperature) indicate that preservation of the aggregate structure depends on both nucleic acid-nucleic acid and nucleic acid-protein interactions. Purification of the DNA-protein complex after lysing the nuclei in 2 M NaCl shows that one major nuclear protein copurifies with the DNA. As shown by DNA-protein binding experiments, this protein has a high affinity for DNA; however, no evidence for sequence specificity of the protein binding was obtained. Chromatin reconstitution experiments suggest that the protein in itself is not sufficient for DNA aggregation in nuclei, but other factors, possibly the native chromatin structure, are required. Electron microscopy of the purified DNA-protein complex showed structures similar to those observed previously with in vitro-aggregated purified macronuclear DNA (14). A model is presented in which the terminal inverted repeat sequences found on all macronuclear DNA molecules interact with each other forming multistranded DNA complexes. The formation of these structures may be accelerated and stabilized by a protein in vivo.
Preparation of a spectral probe derivative of the hemocyanin biopolymer: effects of allosteric interactions on the coupled binuclear copper active site.
Authors: Hwang Y T , Solomon E I
Published: May 2006

A series of derivatives for both the arthropod and mollusc hemocyanin biopolymers has been prepared; the derivatives contain a small fraction of electron paramagnetic resonance-detectable half-met [Cu(II) CU(I)] sites dispersed among the non-detectable oxy binuclear copper active sites. Upon deoxygenation, large changes in the electron paramagnetic resonance signal of these half-met spectral probe derivatives are observed, which are further adjusted by the heterotropic effectors Ca2+ and H+. The active site structural changes indicated that these spectral changes as the hemocyanins go from a relaxed to a tensed quaternary structure are then discussed.
Reconstitution of a variant macrophage cell line defective in oxygen metabolism with a H2O2-generating system.
Authors: Tanaka Y , Kiyotaki C , Tanowitz H , Bloom B R
Published: May 2006

A variant clone, C3C, derived from the cloned macrophage cell line J774.16 lacks the capacity to produce O2- or H2O2 after appropriate stimulation. When the parental and variant cell lines were infected with epimastigotes of Trypanosoma cruzi, the parasites were killed or their growth was inhibited by the parental line, but they grew readily in the variant clone C3C. It was possible to reconstitute the variant cell line with an enzyme system targeted to the lysosomal compartment capable of generating a single oxygen metabolite, H2O2. This was accomplished by allowing the cells to phagocytize zymosan particles covalently coupled with glucose oxidase (GO-Zy particles). Approximately one-third of the H2O2 theoretically expected to be produced by the ingested GO-Zy particles could be detected outside the cells by the cytochrome c peroxidase assay; this fraction may represent the efficiency of extracellular assays for H2O2 production. When T. cruzi-infected clone C3C cells were reconstituted with GO-Zy particles, upon addition of glucose, intracellular killing of the parasites occurred. It was possible to estimate the level of H2O2 production required to kill a single parasite (8.7 x 10(-7) nmol/min) by GO-Zy particles in suspension and to formulate a first approximation of the killing potency of the reconstituted cells--i.e., number of parasites expected to be killed--that correlated well with the observed growth of the parasites intracellularly.
Isolation and characterization of rat skeletal muscle and cytoplasmic actin genes.
Authors: Nudel U , Katcoff D , Zakut R , Shani M , Carmon Y , Finer M , Czosnek H , Ginsburg I , Yaffe D
Published: May 2006

Southern blots of rat genomic DNA indicate the existence of at least 12 EcoRI DNA fragments containing actin gene sequences. By using specific probes and stringent conditions of hybridization, it was found that only one of these fragments contains sequences of the skeletal muscle alpha-actin gene. Recombinant bacteriophages originating from eight different actin genes were isolated from rat genomic DNA libraries. One of them, Act 15, contains the skeletal muscle actin gene. Another clone, Act I, contains a gene coding for a cytoplasmic actin, identified tentatively as the beta-actin gene. Both genes have a large intron very close to the 5' end of their transcribed region, followed by several small introns. DNA sequence analysis and comparison with the available data on actin genes in other organisms indicated an interesting relationship between the positions of introns and the evolutionary relatedness. Several intron sites are conserved from at least the echinoderms to the vertebrates; others appear to be present in some actin genes and not in others.
Entrainment and resonance in glycolysis
Authors: Termonia Yves , Ross John
Published: May 2006

We have proposed a comprehensive model for the glycolytic reaction mechanism and have shown the possibility of self-tuning to resonance, with consequent increase in efficiency of energy transduction by separating the model into two subsystems: one for the phosphofructokinase (PFKase; ATP:D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) reaction and the other for the pyruvate kinase (PKase; ATP:pyruvate 2-
O
-phosphotransferase, EC 2.7.1.40) reaction. The purpose of this article is to present an alternative theoretical approach—one more directly applicable to experimental situations—for the detection of these effects without the need for any decomposition. The approach consists in studying the response of such systems to externally applied periodic perturbations inside the fundamental entrainment band by computation. We show, in agreement with previous results obtained for simpler reaction schemes, that large increases and decreases in dissipation may occur in a narrow range of the period of entrainment of the entire mechanism. If the period of the autonomous glycolytic oscillation past marginal stability approaches a value,
T
0
lim
, that is close to the period of relaxation oscillation of the PKase subsystem,
T
PKase
, then tuning of the primary oscillophor, the PFKase system, has been effected by the PKase system; in such cases we predict, for larger values of the amplitude of perturbation, two peaks in the response spectrum: one near the period of the autonomous oscillation and the other at the period of the PKase system. For small amplitudes of perturbation, there is only one resonance peak near the period of the autonomous oscillation. If
T
0
lim
is not close to
T
PKase
, then there is only one resonance peak for small and large amplitudes of external perturbations. Our computer results lead to a classification of the chemical species in the reaction mechanism into two categories. The first category has the following two properties. (
i
) When fundamental entrainment occurs, the amplitude of the response in all species in the reaction mechanism is largest when the oscillation in the perturbation of a chemical species is in phase with the oscillation of that variable in the mechanism. (
ii
) If the amplitude of the external periodic perturbation is monitored in time so as to keep that variable in the mechanism always constant, then there is no oscillatory response in the whole reaction pathway. The variables having these two properties have been found to be essential for the generation of self-sustained oscillations in our model. For the second category neither of these two properties holds.
Phase transitions in phosphatidylcholine multibilayers
Authors: Westerman Philip W. , Vaz Maria João , Strenk Lawrence M. , Doane J. William
Published: May 2006

The
2
H NMR spectrum of a multilamellar dispersion of 1-myristoyl-2-[14,14,14-
2
H
3
]myristoyl-
sn
-glycero-3-phosphocholine with 1 mol% cholesterol in excess water has been recorded at temperatures between -15°C and 36°C. Motionally averaged quadrupole coupling constants 〈ν
Q
〉 and motionally induced asymmetry parameters η are obtained by spectral analysis. Values of these quantities indicate that, at temperatures below -4°C, any rotational motion of the molecules about their molecular long axis is slow on the NMR time scale. At temperatures immediately above the pretransition these same parameters show that a fast-rotational motion is occurring about the molecular long axis. This rotational motion is hindered in that the molecules flip about a twofold symmetry axis. Between -4°C and the pretransition, spectra appear as the superposition of two powder patterns, one corresponding to the pattern observed below -4°C and the other to the pattern above the pretransition. The relative contribution of the latter increases with temperature until the pretransition is reached. These data have been interpreted in two ways: either the sample between -4°C and the pretransition contains two populations of rapidly and slowly rotating molecules, or there is only a single population of molecules undergoing a 180° flipping motion on the time scale of the NMR measurement. The latter interpretation is more consistent with other experimental findings. At the temperature of the main transition the hydrocarbon chains melt. In the absence of cholesterol, spectra are more complex in that the line shape is reproduced by the superposition of three spectral powder patterns between -4°C and the pretransition and by the superposition of two spectral patterns above the pretransition. It is postulated that these two patterns observed above the pretransition are in direct correspondence to the two ripple structures observed by freeze-fracture electron microscopy in the absence of cholesterol.