Showing papers by "University of Maryland, Baltimore County published in 1991"
TL;DR: The results suggest that maternal self-efficacy mediates relations between maternal competence and other psychossocial variables and may play a crucial role in determining parenting behavior and infant psychosocial risk.
Abstract: This study tests the idea that mothers' self-efficacy beliefs mediate the effects on parenting behavior of variables such as depression, perceptions of infant temperamental difficulty, and social-marital supports. Subjects were 48 clinically depressed and 38 nondepressed mothers observed in interaction with their 3-13-month-old infants (M = 7.35 months). As predicted, maternal self-efficacy beliefs related significantly to maternal behavioral competence independent of the effects of other variables. When the effects of self-efficacy were controlled, parenting competence no longer related significantly to social-marital supports or maternal depression. In addition, maternal self-efficacy correlated significantly with perceptions of infant difficulty after controlling for family demographic variables. These results suggest that maternal self-efficacy mediates relations between maternal competence and other psychosocial variables and may play a crucial role in determining parenting behavior and infant psychosocial risk.
1,111 citations
TL;DR: Modification of DNA bases in mammalian chromatin upon treatment with hydrogen peroxide in the presence of ferric and cupric ions was studied, indicating a possible site-specific formation of hydroxyl radical when metal ions are bound to chromatin.
236 citations
TL;DR: A review of the relevant research on the Milgram paradigm reveals that the evidence on situational determinants of obedience is less clear than is generally recognized; contrary to the commonly held view, personality measures can predict obedience; another kind of dispositional variable, enduring beliefs, is also implicated in the obedience process and approaches suggested by interactionist perspectives can provide some integration of the literature as mentioned in this paper.
Abstract: Among the far-reaching implications that have been drawn from Milgram's obedience research is that situations powerfully override personal dispositions as determinants of social behavior. A focused review of the relevant research on the Milgram paradigm reveals that the evidence on situational determinants of obedience is less clear than is generally recognized; contrary to the commonly held view, personality measures can predict obedience; another kind of dispositional variable, enduring beliefs, is also implicated in the obedience process and approaches suggested by interactionist perspectives can provide some integration of the literature. The article concludes with a discussion of the broader inferences about obedience and social behavior called for by this review and the enduring significance of Milgram's obedience research
229 citations
01 Jan 1991
TL;DR: Finite state, finite action, stochastic games over an infinite time horizon, algorithms for the computation of minimax optimal stationary strategies in the zerosum case, and of Nash equilibria in stationary Strategies in the nonzerosum case are surveyed.
Abstract: We consider finite state, finite action, stochastic games over an infinite time horizon. We survey algorithms for the computation of minimax optimal stationary strategies in the zerosum case, and of Nash equilibria in stationary strategies in the nonzerosum case. We also survey those theoretical results that pave the way towards future development of algorithms.
173 citations
TL;DR: In this article, the validity of maternally derived Attachment Q-Set security scores as indexes of attachment security was examined in a study of preschool-age children with attachment Q-set scores.
Abstract: Construct validity of maternally derived Attachment Q-Set security scores as indexes of attachment security was examined in this study of preschool-age children
163 citations
TL;DR: Structural evidence is presented that stomatopod crustaceans have the receptors necessary for colour and polarization vision, and that all retinular cells in rows one to four of the mid-band, and the distal most retInular cells over most of the retina, are not sensitive to polarized light.
Abstract: Stomatopod crustaceans possess compound eyes divided into three distinct regions: two peripheral retinae - the dorsal and ventral hemispheres - and the mid-band. Throughout the eye, in particular in the midband, there are many structural adaptations that potentially enable different portions of the eye to perform different visual tasks. A high degree of optical overlap between these eye regions allows the parallel sampling of various parameters of light from one direction in space. In consecutive papers, we present structural evidence that stomatopods have the receptors necessary for colour and polarization vision. The first paper describes the retinal structures that suggest the existence of polarization sensitivity in stomatopods. mid-band rows five and six, together with the hemispheres, are probably involved in this visual process. By using two strategies, rhabdomal modification and varying the orientation of similar ommatidial units in the three eye regions, stomatopods have the capacity to analyse polarized light in a very detailed manner. All the species included in this study live in shallow, tropical waters where polarized light signals are abundant. It therefore seems likely that their eyes have evolved to take advantage of such environmental cues. Structural evidence also suggests that all retinular cells in rows one to four of the mid-band, and the distal most retinular cells (R8) over most of the retina, are not sensitive to polarized light. These mid-band rows are instead adapted for colour detection. This function of the stomatopod retina and structural features concerned with colour sensitivity are described in paper II (Phil. Trans. R. Soc. Lond. B 334, 57-84 (1991)).
143 citations
TL;DR: The purification, amino acid sequence, and two-dimensional 1H NMR results are reported for the rubredoxin (Rd) from the hyperthermophilic archaebacterium Pyrococcus furiosus, an organism that grows optimally at 100 degrees C.
Abstract: The purification, amino acid sequence, and two-dimensional 1H NMR results are reported for the rubredoxin (Rd) from the hyperthermophilic archaebacterium Pyrococcus furiosus, an organism that grows optimally at 100 degrees C. The molecular mass (5397 Da), iron content (1.2 +/- 0.2 g-atom of Fe/mol), UV-vis spectrophotometric properties, and amino acid sequence (60% sequence identity with Clostridium pasteurianum Rd) are found to be typical of this class of redox protein. However, P. furiosus Rd is remarkably thermostable, being unaffected after incubation for 24 h at 95 degrees C. One- and two-dimensional 1H nuclear magnetic resonance spectra of the oxidized [Fe(III)Rd] and reduced [Fe(II)Rd] forms of P. furiosus Rd exhibited substantial paramagnetic line broadening, and this precluded detailed 3D structural studies. The apoprotein was not readily amenable to NMR studies due to apparent protein oxidation involving the free cysteine sulfhydryls. However, high-quality NMR spectra were obtained for the Zn-substituted protein, Zn(Rd), enabling detailed NMR signal assignment for all backbone amide and alpha and most side-chain protons. Secondary structural elements were determined from qualitative analysis of 2D Overhauser effect spectra. Residues A1-K6, Y10-E14, and F48-E51 form a three-strand antiparallel beta-sheet, which comprises ca. 30% of the primary sequence. Residues C5-Y10 and C38-A43 form types I and II amide-sulfur tight turns common to iron-sulfur proteins. These structural elements are similar to those observed by X-ray crystallography for native Rd from the mesophile C. pasteurianum. However, the beta-sheet domain in P. furiosus Rd is larger than that in C. pasteurianum Rd and appears to begin at the N-terminal residue. From analysis of the secondary structure, potentially stabilizing electrostatic interactions involving the charged groups of residues Ala(1), Glu(14), and Glu(52) are proposed. These interactions, which are not present in rubredoxins from mesophilic organisms, may prevent the beta-sheet from "unzipping" at elevated temperatures.
141 citations
TL;DR: Results indicate involvement of hydroxyl radicals in the mechanism of nuclear DNA damage in mammalian cells caused by H2O2.
122 citations
TL;DR: These adaptations include brightly coloured intrarhabdomal filters, apparent lateral filters and a photoreceptor tiering system unique to the crustacea which allow the spectrum of light available to stomatopods to be sampled over a broad spectral range by receptors with narrowly tuned sensitivities.
Abstract: The stomatopod eye is divided into three distinct regions, two peripheral \`hemispheres' and a dividing mid-band Each of these areas has a separate function and it is the six rows of ommatidia in the mid-band which are the main subject of study here Rows one to four of the mid-band are probably not sensitive to polarized light (paper I (Phil Trans R Soc Lond B 334, 33-56 (1991))) and instead possess many structural features which suggest that they are concerned with colour analysis and perhaps colour vision This, the second of two consecutive papers, examines these adaptations in detail They include brightly coloured intrarhabdomal filters, apparent lateral filters and a photoreceptor tiering system unique to the crustacea Cronin & Marshall (J comp Physiol 166, 261-275 (1989b)) have shown that mid-band rows one to four contains at least eight distinct visual pigments These, in combination with the structures described here, allow the spectrum of light available to stomatopods to be sampled over a broad spectral range by receptors with narrowly tuned sensitivities It is the photostable screening and filtering pigments, rather than the visual pigments, which are examined in detail in this paper These have been divided into two categories: (i) the \`standard' retinal pigments: those that are often found in other crustacean eyes; (ii) the `unusual' retinal pigments: some of these are unique to stomatopod eyes and may be involved in colour vision
106 citations
TL;DR: In this paper, Price presents the Primitive Art in Civilized Places (PICA), a collection of 19th-century paintings of primitive art in civilised places, including:
Abstract: Primitive Art in Civilized Places. Sally Price. Chicago:University of Chicago Press, 1989.145 pp. 14 pi.
101 citations
Posted Content•
TL;DR: In this article, the authors examined circumstances under which this empirical pattern could be observed and examined the implications for brand-name price levels, and for the brand name price response to entry, of health sector trends that may have the effect of expanding the size of the cross-price-sensitive segment of the market.
Abstract: Empirical studies suggest that entry of generic competitors results in minimal decreases or even increases in brand-name drug prices as well as sharp declines in brand-name advertising This paper examines circumstances under which this empirical pattern could be observed The analysis focuses on models where the demand for brand-name pharmaceuticals is divided into two segments, only one of which is cross-price-sensitive Brand-name firms are assumed to set price and advertising in a Stackelberg context; they allow for responses by generic producers but the latter take decisions by brand-name f inns as given Brand-name price and advertising responses to entry are shown to depend upon the properties of the reduced-form brand-name demand function Conditions for positive price responses and negative advertising responses are derived We also examine the implications for brand-name price levels, and for the brand-name price response to entry, of health sector trends (such as increasing HMO enrollments) that may have the effect of expanding the size of the cross-price-sensitive segment of the market The paper concludes with a review of recent empirical research and suggestions for future work on the effects of generic entry
TL;DR: Two-dimensional NMR spectroscopic and computational methods were employed for the structure determination of an 18-residue peptide with the amino acid sequence of the C-terminal retroviral-type zinc finger domain from the nucleocapsid protein (NCP) of HIV-1.
Abstract: Two-dimensional NMR spectroscopic and computational methods were employed for the structure determination of an 18-residue peptide with the amino acid sequence of the C-terminal retriviral-type (r.t.) zinc finger domain from the nucleocapsid protein (NCP) of HIV-1 (Zn(HIV1-F2)). Unlike results obtained for the first retroviral-type zinc finger peptide, Zn (HIV1-F1) broad signals indicative of confomational lability were observed in the {sup 1}H NMR spectrum of An(HIV1-F2) at 25 C. The NMR signals narrowed upon cooling to {minus}2 C, enabling complete {sup 1}H NMR signal assignment via standard two-dimensional (2D) NMR methods. Distance restraints obtained from qualitative analysis of 2D nuclear Overhauser effect (NOESY) data were sued to generate 30 distance geometry (DG) structures with penalties in the range 0.02-0.03 {angstrom}{sup 2}. All structures were qualitatively consistent with the experimental NOESY spectrum based on comparisons with 2D NOESY back-calculated spectra. These results indicate that the r.t. zinc finger sequences observed in retroviral NCPs, simple plant virus coat proteins, and in a human single-stranded nucleic acid binding protein share a common structural motif.
TL;DR: In Escherichia coli K-12, expression of zwf, the gene for glucose 6-phosphate dehydrogenase, is coordinated with the cellular growth rate and induced by superoxide-generating agents, and its DNA sequence resembles the discriminator sequence of stable RNA genes, which has been implicated in stringent control and growth-rate-dependent regulation.
Abstract: In Escherichia coli K-12, expression of zwf, the gene for glucose 6-phosphate dehydrogenase, is coordinated with the cellular growth rate and induced by superoxide-generating agents. To initiate the study of the molecular mechanisms regulating its expression, the gene was cloned and its DNA sequence was determined. The 5' ends of zwf mRNA isolated from cells growing in glucose and acetate minimal media were mapped. The map was complex in that transcripts mapped to -45, -52, and -62, with respect to the beginning of the coding sequence. Three analytical methods were used to search the DNA sequence for putative promoters. Only one sequence for a promoter recognized by the sigma 70 form of RNA polymerase was found by all three search routines that could be aligned with a mapped transcript, indicating that the other transcripts arise by processing of the mRNA. A computer-assisted search did not reveal a thermodynamically stable long-range mRNA secondary structure that is capable of sequestering the translation initiation region, which suggests that growth-rate-dependent regulation of glucose 6-phosphate dehydrogenase level may not be carried out by a mechanism similar to the one for the gene (gnd) for 6-phosphogluconate dehydrogenase. The DNA segment between the -10 hexamer and the start point of transcription resembles the discriminator sequence of stable RNA genes, which has been implicated in stringent control and growth-rate-dependent regulation.
TL;DR: A three layered back-propagation neural network was trained to recognize E. coli promoters of the 17 base spacing class and can be used to define and search for any DNA regulatory sequence for which there are sufficient exemplars.
Abstract: A three layered back-propagation neural network was trained to recognize E. coli promoters of the 17 base spacing class. To this end, the network was presented with 39 promoter sequences and derivatives of those sequences as positive inputs; 60% A + T random sequences and sequences containing 2 promoter-down point mutations were used as negative inputs. The entire promoter sequence of 58 bases, approximately -50 to +8, was entered as input. The network was asked to associate an output of 1.0 with promoter sequence input and 0.0 with non-promoter input. Generally, after 100,000 input cycles, the network was virtually perfect in classifying the training set. A trained network was about 80% effective in recognizing 'new' promoters which were not in the training set, with a false positive rate below 0.1%. Network searches on pBR322 and on the lambda genome were also performed. Overall the results were somewhat better than the best rule-based procedures. The trained network can be analyzed both for its choice of base and relative weighting, positive and negative, at each position of the sequence. This method, which requires only appropriate input/output training pairs, can be used to define and search for any DNA regulatory sequence for which there are sufficient exemplars.
TL;DR: The source of the catalytic power of KSI is discussed via comparison of the free energy profile for the KSI-catalyzed isomerization with those for the acetate-catalystzed isomersization and the aqueous reaction at pH 7.5.
Abstract: Knowledge of the partitioning of the putative dienol intermediate (2) by steroid isomerase (KSI) (Hawkinson et al. 1991), in conjunction with various steady-state kinetic parameters, allows elucidation of the detailed free energy profile for the KSI-catalyzed conversion of 5-androstene-3,17-dione (1) to 4-androstene-3,17-dione (3). This free energy profile shows four kinetically significant energy barriers (substrate binding, the two chemical steps, and dissociation of product) that must be traversed upon conversion of 1 to 3. Thus, no single step of the catalytic cycle is cleanly rate-limiting. The source of the catalytic power of KSI is discussed via comparison of the free energy profile for the KSI-catalyzed isomerization with those for the acetate-catalyzed isomerization and the aqueous reaction at pH 7. Similarities between the energetics of the KSI-catalyzed and triosephosphate isomerase catalyzed reactions are also noted.
Journal Article•
TL;DR: Tandem mass spectrometry with high energy collisional activation is shown to provide reliable analysis of the isotope-labeling patterns in the conjugated products, leading to the conclusion that the aziridinium ion is opened in the Conjugation of phosphoramide mustard in both the enzyme-catalyzed and the chemical reactions.
Abstract: The conjugations of cyclophosphamide and of phosphoramide mustard with glutathione are shown to be catalyzed by hepatic cytosolic glutathione-S-transferases. Cyclophosphamide conjugation is also catalyzed by microsomal glutathione-S-transferases, both in intact microsomes and after solubilization and immobilization. Deuterium isotope labels are used to test whether chloride is directly displaced by glutathione in the enzyme-catalyzed conjugations, or whether conjugation takes place via symmetrical cyclic aziridinium ions. Tandem mass spectrometry with high energy collisional activation is shown to provide reliable analysis of the isotope-labeling patterns in the conjugated products. This experiment leads to the conclusion that the aziridinium ion is opened in the conjugation of phosphoramide mustard in both the enzyme-catalyzed and the chemical reactions. Cyclophosphamide, on the other hand, is shown to be conjugated through direct displacement of chloride.
01 Jan 1991
TL;DR: N-terminal sequencing showed that UGA at codon 7 was decoded as tryptophan in wild-type cells, at an efficiency of about 6%.
Abstract: Replacement of cat-86 codon 7 or 144 with the UGA codon permitted the gene to confer chloramphenicol resistance in wild-type Bacillus subtilis. UAA replacements of the same codons resulted in a chloramphenicol-sensitive phenotype in wild-type B. subtilis and a chloramphenicol-resistant phenotype in suppressor-positive strains. N-terminal sequencing showed that UGA at codon 7 was decoded as tryptophan in wild-type cells, at an efficiency of about 6%.
TL;DR: For zero sum limiting average games, this formulation reduces to a linear objective, nonlinear constraints program, which finds the “best” stationary strategies, even whenε-optimal stationary strategies do not exist, for arbitrarily smallε.
Abstract: Stationary equilibria in discounted and limiting average finite state/action space stochastic games are shown to be equivalent to global optima of certain nonlinear programs. For zero sum limiting average games, this formulation reduces to a linear objective, nonlinear constraints program, which finds the “best” stationary strategies, even whene-optimal stationary strategies do not exist, for arbitrarily smalle.
TL;DR: To assess optimal saccharification performance, α-cellulose and dilute acid pretreated aspen (DAA) wood meal were subjected to various loadings of commercial cellulase and β-D-glucosidase preparations.
Abstract: To assess optimal saccharification performance, α-cellulose and dilute acid pretreated aspen (DAA) wood meal were subjected to various loadings of commercial cellulase and β-D-glucosidase preparations. Fifteen international filter paper units (IFPU)/g cellulose content and 30 IFPU/g cellulose content were required to digest 95% of the available cellulose in α-cellulose and pretreated aspen, respectively. The optimal supplementation ratios, based on Genencor GC 123 cellulase and β-D-glucosidase from Novo SP 188 for the α-cellulose and DAA digestions range from 0.25 to 0.5 and 0.12 to 0.25, respectively.
TL;DR: Loewen et al. as discussed by the authors used a Bacillus subtilis library of Tn917∷lacZ insertions for mutants that were unable to grow in the presence of normally sublethal concentrations of hydrogen peroxide.
TL;DR: NMR studies of the zinc adduct with the NCP isolated directly from HIV‐1 particles provide solid evidence that zinc finger domains are formed that are conformationally similar (if not identical) to the peptide structures.
Abstract: Nuclear magnetic resonance (NMR) methods have been used to address issues regarding the relevance and feasibility of zinc binding to "zinc finger-like" sequences of the type C-X2-C-X4-H-X4-C [referred to as CCHC or retroviral-type (RT) zinc finger sequences]. One-dimensional (1D) NMR experiments with an 18-residue synthetic peptide containing the amino acid sequence of an HIV-1 RT-zinc finger domain (HIV1-F1) indicate that the sequences are capable of binding zinc tightly and stoichiometrically. 1H-113Cd spin echo difference NMR data confirm that the Cys and His amino acids are coordinated to metal in the 113Cd adduct. The 3D structure of the zinc adduct [Zn(HIV1-F1)] was determined to high atomic resolution by a new NMR-based approach that utilizes 2D-NOESY back-calculations as a measure of the consistency between the structures and the experimental data. Several interesting structural features were observed, including (1) the presence of extensive internal hydrogen bonding, and (2) the similarity of the folding of the first six residues to the folding observed by X-ray crystallography for related residues in the iron domain of rubredoxin. Structural constraints associated with conservatively substituted glycines provide further rationale for the physiological relevance of the zinc adduct. Similar NMR and structural results have been obtained for the second HIV-1 RT-zinc finger peptide, Zn(HIV1-F2). NMR studies of the zinc adduct with the NCP isolated directly from HIV-1 particles provide solid evidence that zinc finger domains are formed that are conformationally similar (if not identical) to the peptide structures.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: Under physiological conditions, the intact enzyme displays greater binding free energy for single-stranded polynucleotides than the 8-kDa fragment, suggesting that the latter may carry a truncated binding site, and the role of beta-polymerase in DNA repair is evaluated.
TL;DR: In this paper, the ligand specificity of a gamma delta T-cell receptor (TCR) derived from a mouse Tcell hybridoma (KN6) was studied, and it was shown that the TL-specific ligand recognized by KN6 is controlled by an MHC-linked gene that most probably maps in the TL region.
Abstract: We have studied the ligand specificity of a gamma delta T-cell receptor (TCR) derived from a mouse T-cell hybridoma (KN6). KN6 cells reacted with syngeneic (C57BL/6) cells from various origins (splenocytes, thymocytes, peritoneal exudate cells, etc.) and cells from many different mouse strains. KN6 reactivity against cells from a panel of congenic and recombinant mouse strains demonstrated that the ligand recognized by KN6 is controlled by an MHC-linked gene that most probably maps in the TL region. We cloned this gene and formally proved that it does map in the TL region. This gene turned out to be a novel class I gene (designated T22b) belonging to a hitherto unidentified cluster of TL region genes in strain C57BL/6. This gene was expressed in many different tissues and cell types. We also examined the tissue expression of several other TL genes. One of these, the structural gene (T3b) encoding the thymus leukemia (TL) antigen from C57BL/6 mice, was specifically expressed in the epithelium of the small intestine. Since the intestinal epithelium of the mouse is known to be the homing site for a subset of gamma delta T cells (i-IEL) bearing diverse TCR with V7 rearranged gamma chains, we propose that the T3b gene product is part of the ligand recognized by some of the i-IEL. Our data support the idea that gamma delta T cells might be specific for non-classical class I or class I-like molecules and suggest that gamma delta TCR and non-classical MHC co-evolved for the recognition of a conserved set of endogenous or foreign peptides.
TL;DR: It is demonstrated that expression of certain allogeneic MHC‐class‐I genes can lead to tumor‐specific immunity, and that such transfectants can protect against challenges of wild‐type tumor cells.
Abstract: Mouse Sal sarcoma cells are lethal in the autologous A/J (KkDd) host. In order to improve the immune response to the Sal tumor, Sal cells have been transfected with syngeneic MHC-class-II or allogeneic MHC-class-I genes. MHC-class-II transfectants are uniformly rejected by the autologous host and immunization with them protects against subsequent Sal challenge. The improved immunity is probably the result of enhanced generation of tumor-specific Th cells. We hypothesize that class-II+ tumor cells trigger an improved Th-cell response because they directly present Sal tumor antigens in the context of class-II molecules to Th cells, by-passing professional APC. Studies by others have demonstrated that antigen presentation requires an intracellular signal transmitted by the cytoplasmic domain of the APC class-II molecule. Sal cells expressing class-ll antigens with truncated cytoplasmic domains are as malignant as wild-type Sal cells. These experiments therefore support the role of tumor-cell class-II molecules as antigen presentation elements, and demonstrate the requirement for intact class-II molecules for tumor protection. Sal cells have also been transfected with allogeneic MHC-class-I genes. Although Kb-transfected cells are not rejected by A/J mice, Db-transfected Sal cells and Kb- plus Db-transfected cells are rejected. The Db transfectants effectively immunize A/J mice against subsequent Sal challenge. These experiments demonstrate that expression of certain allogeneic MHC-class-I genes can lead to tumor-specific immunity, and that such transfectants can protect against challenges of wild-type tumor cells. Transfection of tumor cells with syngeneic MHC-class-II or allogeneic MHC-class-I genes may therefore be a potential strategy for improving tumor-specific immunity in the autologous host.
TL;DR: Time as a variable in behavior analysis is discussed in this paper, where the authors discuss the properties of individual stimuli and responses and the processes of discrimination and differentiation that occur over extended periods of time.
Abstract: Publisher Summary This chapter discusses time as a variable in behavior analysis. Behavior takes place in time and has temporal dimensions. As an independent variable, time is an essential property of the environments within which behavior occurs. As a dependent variable, it includes not only response durations but also the distribution of responses in time. Each stimulus dimension has intrinsic properties, and those of the temporal dimension differ in important ways from those of other stimulus dimensions such as wavelength, intensity, and spatial extent. The molecular properties of behavior involve the properties of individual stimuli and responses. The processes of discrimination and differentiation are molar as they are aspects of populations of stimuli and responses observed over extended periods of time. If the search for behavior mediating timing were successful, the outcome might be regarded as relevant to the organism's temporal receptor.
Journal Article•
TL;DR: It is hypothesized that the transfectants induce protective immunity by functioning as APC for tumor peptides, and stimulating tumor-specific Th cells, and stimulated intracellular signaling via the cytoplasmic domain.
Abstract: Transfection of syngeneic MHC class II genes into the lethal mouse SaI tumor abrogates the malignancy of the tumor in the autologous host, and protects the host against subsequent challenges with the wild type class II- tumor. We have hypothesized that the transfectants induce protective immunity by functioning as APC for tumor peptides, and stimulating tumor-specific Th cells. Recent in vitro studies suggest that Ag presentation by class II-restricted APC requires the cytoplasmic domain of the class II molecule, and may involve intracellular signaling via the cytoplasmic domain. To determine if the class II cytoplasmic domain is required for enhanced tumor-specific immunity, SaI mouse sarcoma cells were transfected with syngeneic Aak and Abk genes with truncated cytoplasmic domains. These transfectants are as malignant as wild type class II- SaI cells in autologous A/J mice. Stimulation of tumor-specific immunity by class II+ tumor cells is therefore dependent on the class II cytoplasmic region, and may involve intracellular signaling events.
TL;DR: Comparison (FASTA algorithm) of the primary structure of the oyster MTs with those of other species indicated a higher similarity with vertebrate MTs than withThose of other invertebrates.
TL;DR: Given a convex function : IR+ !
TL;DR: It is found that four-sector tandem mass spectrometry with high-energy collisional activation provides qualitative analysis of viral phosphatidyl lipids in considerable detail, as well as semiquantitative information.
Abstract: A number of phosphatidylcholines have been isolated from an HIV-1/MN preparation by reversed-phase high-performance liquid chromatography (HPLC) and analyzed by fast atom bombardment mass spectrometry (FABMS), FABMS/MS, and FABMS/MS/MS in both positive- and negative-ion modes. Negative-ion FABMS/MS with high-energy collisions was used to identify the length of the acyl groups and the degree of saturation, as well as their position on the glyceride group. FABMS/MS in the positive-ion mode was used to identify the polar head group. Negative-ion FABMS/MS/MS was used to locate positions of double bonds in acyl groups. We find that four-sector tandem mass spectrometry with high-energy collisional activation provides qualitative analysis of viral phosphatidyl lipids in considerable detail, as well as semiquantitative information. Approximate quantitation of the phosphatidylcholine content of the HIV-1/MN preparation by measuring relative peak heights of molecular ions in FABMS reveals an array of phosphatidylcholines consistent with that found in human erythrocytes, indicating the likely source of lipids in the viral membrane to be the host cell membrane.