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Biomedical subjects

R Case

Publications and source records attributed to R Case.

At least 19 recordsLinked to original sources
PubMed2003

Protection against recurrent ocular herpes simplex virus type 1 disease after therapeutic vaccination of latently infected mice.

The potential of therapeutic vaccination of animals latently infected with herpes simplex virus type 1 (HSV-1) to enhance protective immunity to the virus and thereby reduce the incidence and severity of recurrent ocular disease was assessed in a mouse model. Mice latently infected with HSV-1 were vaccinated intranasally with a mixture of HSV-1 glycoproteins and recombinant Escherichia coli heat-labile enterotoxin B subunit (rEtxB) as an adjuvant. The systemic immune response induced was characterized by high levels of virus-specific immunoglobulin G1 (IgG1) in serum and very low levels of IgG2a. Mucosal immunity was demonstrated by high levels of IgA in eye and vaginal secretions. Proliferating T cells from lymph nodes of vaccinated animals produced higher levels of interleukin-10 (IL-10) than were produced by such cells from mock-vaccinated animals. This profile suggests that vaccination of latently infected mice modulates the Th1-dominated proinflammatory response usually induced upon infection. After reactivation of latent virus by UV irradiation, vaccinated mice showed reduced viral shedding in tears as well as a reduction in the incidence of recurrent herpetic corneal epithelial disease and stromal disease compared with mock-vaccinated mice. Moreover, vaccinated mice developing recurrent ocular disease showed less severe signs and a quicker recovery rate. Spread of virus to other areas close to the eye, such as the eyelid, was also significantly reduced. Encephalitis occurred in a small percentage (11%) of mock-vaccinated mice, but vaccinated animals were completely protected from such disease. The possible immune mechanisms involved in protection against recurrent ocular herpetic disease in therapeutically vaccinated animals are discussed.

Animals↗
PubMed2001

Sequence-dependent interactions of two forms of UvrC with DNA helix-stabilizing CC-1065-N3-adenine adducts.

The uvrA, uvrB, and uvrC genes of Escherichia coli control the initial steps of nucleotide excision repair. The uvrC gene product is involved in at least one of the dual incisions produced by the UvrABC complex. Using single-stranded (ss) DNA affinity chromatography, we have separated two forms of UvrC from both wild-type E. coli cells and overproducing cells. UvrCI elutes at 0.4 M KCl, and UvrCII elutes at 0.6 M KCl. In general, both forms, in the presence of UvrA and UvrB, actively incise UV-irradiated and CC-1065-modified DNA in the same fashion; i.e., they incise six to eight nucleotides 5' to and three to five nucleotides 3' to a photoproduct or a CC-1065-N3-adenine adduct. They produce different incisions, however, at a CC-1065-N3-adenine adduct in the sequence 5'-GATTACG- present in the MspI-BstNI 117 bp fragment of M13mp1. UvrABCI incises at both the 5' and 3' sides of the adduct (UvrABCI cut), while UvrABCII incises only at the 5' side (UvrABCII cut). Mixing UvrCI and UvrCII results in both UvrABCI and UvrABCII cuts, and the levels of these two types of cutting are proportional to the amount of UvrCI and UvrCII. DNase I footprints of the MspI-BstNI 117 bp DNA fragment containing a site-directed CC-1065-adenine adduct at the 5'-GATTACG- site show that UvrCII, but not UvrCI, binds to the adduct site. Furthermore, the pattern of DNase I footprints induced by UvrCII binding differs from the pattern of the footprints induced by UvrA, UvrAB, and UvrABCI binding. Interestingly, while the presence of unirradiated DNA enhances the efficiency of UvrABCII in incising UV-irradiated DNA, it does not enhance UvrABCII incision of the CC-1065-N3-adenine adduct formed at 5'-GATTACG-. These results show that two different forms of UvrC differ in DNA binding properties as well as incision modes at some kinds of DNA damage.

Adenine↗
PubMed2001

Using point-of-care CD34 enumeration to optimize PBSC collection conditions.

BACKGROUND: A PBSC graft containing 4-5 x 10(6) CD34(+) cells/kg is considered optimal in terms of durable engraftment. Tracking CD34 kinetics via point-of-care testing during PBSC mobilization could determine which (and when) patients will yield an optimal product. We evaluated whether microvolume fluorimetry (MVF) would be useful in optimizing PBSC mobilization/harvest and if it will shorten our standard 6 h collection. METHODS: Absolute CD34 values were obtained using the IMAGN 2000 and STELLer CD34 assay (50 microL sample volume). Peripheral blood (PB) CD34 values from 30 patients undergoing PBSC mobilization were used to generate a PB CD34-based algorithm that would predict collection day/duration of apheresis. The algorithm was then used prospectively to collect PBSC products on 50 hematologic malignancy (HM) patients. RESULTS: Using the algorithm, patients were assigned to either a 6 (11-20 CD34/microL), 4 (21-49 CD34/microL) or 2 (> or = 50 CD34/microL) h collection. Patients with a CD34 value < or = 10/microL were re-tested. All patients (n = 43) predicted to mobilize reached the optimal CD34 (4-5 x 10(6)/kg) value with 1.0 apheresis procedure; seven patients had < or = 10/microL (nonmobilizers). The majority (75%) had apheresis charges decreased by 33-66%; 47% only required a 2 h procedure and 28% required 4 h. All patients demonstrated rapid trilineage engraftment. DISCUSSION: Absolute PB CD34 measurement using MVF offers a rapid and reliable approach to obtaining optimal PBSC products with minimal technical expertise. Although not a replacement for conventional flow cytometry, it meets the requirements for a point-of-care procedure.

Algorithms↗
PubMed2000

Searching for kinesin's mechanical amplifier.

Kinesin, a microtubule-based motor, and myosin, an actin-based motor, share a similar core structure, indicating that they arose from a common ancestor. However, kinesin lacks the long lever-arm domain that is believed to drive the myosin power stroke. Here, we present evidence that a much smaller region of ca. 10-40 amino acids serves as a mechanical element for kinesin motor proteins. These 'neck regions' are class conserved and have distinct structures in plus-end and minus-end-directed kinesin motors. Mutagenesis studies also indicate that the neck regions are involved in coupling ATP hydrolysis and energy into directional motion along the microtubule. We suggest that the kinesin necks drive motion by undergoing a conformational change in which they detach and re-dock onto the catalytic core during the ATPase cycle. Thus, kinesin and myosin have evolved unique mechanical elements that amplify small, nucleotide-dependent conformational changes that occur in their similar catalytic cores.

Animals↗
PubMed1996

Modeling the dynamic interplay between general and specific change in children's conceptual understanding.

In introducing this chapter, I pointed out that traditional theories of learning and of cognitive development were in conflict with regard to the effects of specific learning. Developmental theorists saw general structures as influencing specific learning but not being affected by it, whereas learning theorists took the opposite view - that general structures (if they existed) were affected only by specific experiences. In the formulation of neo-Piagetian theory, both general and specific effects were acknowledged; however, general effects were assigned to mental capacity and specific ones to the child's schematic repertoire. Thus, the possibility of reciprocal influence did not emerge (or at least was not explored). In the present chapter, I have proposed the existence of such a reciprocal influence and explored its consequences. At a general level, the two consequences that follow are (1) that the overall pace of development is accelerated and (2) that the profile of development is evened out because benefits obtained from high-frequency learning experiences are passed on, via the mediation of the central conceptual structure, to low-frequency ones. These two effects were then advanced as one possible explanation for the difference in the data obtained between different cultures and different social classes. In the former case, the explanation utilized the notion that the benefits of high-frequency learning could be passed on to low-frequency situations via the mediation of general structures; in the latter case, the explanation drew on the notion that experiential loops can accelerate or decelerate development by magnifying experiential differences that are relatively small but that prevail across most of the tasks that a child encounters. The last half of the present chapter was devoted to specifying the dynamics of this sort of interaction in mathematical terms. The data that were obtained in Chapters III and V were extremely regular and showed an even pattern of development across different tasks; hence, they could conceivably be modeled with single curves or even straight lines. The mathematical model chosen to fit these findings was much more complex, however. Each growth curve was generated by an expression that contained a dynamic tension between two opposing categories of effect: those whose tendency is to make different developmental pathways disperse (different growth rates and the effect of compounding) and those whose tendency is to hold development to a single course (the constraints imposed by a growing carrying capacity and the "binding together" or "squeezing" effect generated by the reciprocal feedback loop). The disadvantage of this sort of modeling is clearly its complexity. An equally clear advantage, however, is that it allows one to provide a unified explanation for a set of data that might otherwise seem quite disparate and to express relations in quantitative rather than merely qualitative terms. This, in turn, permits one to check the entire set of proposed relations for their consistency, and to explore the dynamic pattern of their interaction, by conducting "intellectual experiments" and checking them against common sense and/or existing data sets. In the present chapter, this approach has been used for the effects of social class and of culture. In principle, however, it could potentially be used equally to explore the effects of other variables, such as those that underlie intellectual retardation and/or "giftedness". At least for the moment, then, the mathematical modeling approach looks promising.

Child↗
PubMed1996

Cross-cultural investigations.

In Piaget's system, the development of children's cognitive structures is seen as progressing through a universal sequence from sensorimotor, to concrete, to formal logical thought. The data that have been obtained on his measures are problematic in their support for this view, however, because they indicate that adults in traditional societies often fail his formal tasks. Piaget's (1972) interpretation of such findings was that they indicated a problem with his measures, not his theory - if appropriate measures were available, he believed that formal logical operations would be found in all cultures and social groups. Our own interpretation differs. While we acknowledge that adults in all cultures are capable of thinking in a fashion that is more sophisticated, subtle, and complex than that of young children, we see the highest forms of thought as being dependent on the mastery of systems that are cultural creations and not universal human attainments - and we see Piaget's system of formal operations as being just one example of the sort of system that can be created by a culture and passed on from one generation to the next. In a previous investigation, Fiati (1992) studied children who were growing up in isolated, agricultural villages in the Volta region of West Africa. In these communities, life was still a traditional one, and children's experiences with time, money, and mathematical computation were considerably different from those of children who were attending schools in the nearby towns. Under these conditions, Fiati found that village children's skill in using numbers or in thinking about quantitative variables did not develop to a very high level as compared to that of their peers in the towns or as compared to their own thinking about social issues. In the terms used in the present Monograph, it appeared as though children's central conceptual structures for number - in contrast to their central conceptual structures for narrative - did not advance much past the unidimensional level. Are unidimensional structures, at least, universal? Very probably the answer to this question is yes. Although systems for counting, for example, vary widely, no culture has yet been found in which counting does not play some role or where young children fail to pass Piaget's conservation of number test (Saxe, 1988). It seems highly likely, therefore, that a mental counting line of some sort is a universal construction. The situation in the domain of narrative is quite similar. Although folktales vary widely from one culture to the next, no culture has been reported in which folktales play no role whatever or where the story line of existing folktales does not have some form of intentional component (Propp, 1922/1968). The mental story line may thus be a universal construction as well. Finally, no culture has been reported in which some form of decorative art is not present or in which no technology exists for launching a projectile along a desired trajectory. If these activities require a mental reference line of some sort, then this would be a candidate for universal conceptual attainment as well. In the present series of studies, our investigations were confined to societies that are modern, highly literate, and schooled. Thus, our interest was in demonstrating a universal progression well beyond the unidimensional level, in the sorts of structure that are crucial to life in a modern industrial culture. In fact, this was what we found in each of our studies. On our tests of central conceptual structures, children progressed through the same stages and at the same rate. By contrast, on our tests of more specific understanding, especially on those dealing with issues on which different cultures place different emphasis, we found large and significant cross-national differences. From this we conclude that, if a culture values a particular task or set of tasks and invests a great deal of effort in teaching them, it is likely that the

Adult↗
PubMed1994

Nonhydrolyzable phosphotyrosyl mimetics for the preparation of phosphatase-resistant SH2 domain inhibitors.

Src homology 2 (SH2) domains participate in protein tyrosine kinase (PTK)-mediated cellular signal transduction through their ability to bind with high affinity to phosphotyrosyl (pTyr)-bearing protein sequences. Although peptides containing pTyr competitively inhibit the binding between phosphoproteins and cognate SH2 proteins in a sequence-specific manner, such peptides are rapidly dephosphorylated by cellular phosphatases. We now describe our efforts to develop SH2 inhibitory peptides containing phosphatase-resistant pTyr surrogates. The parent compound, (phosphonomethyl)phenylalanine (Pmp), is a phosphonate-based mimetic of pTyr in which the phosphate ester oxygen (> COPO3H2) has been replaced by a methylene unit (> CCX2PO3H2, X2 = H2). Pmp analogues bearing fluorine (X2 = H, F or X2 = F2) or hydroxyl (X2 = H, OH) substituents on the phosphonate alpha-methylene carbon have been prepared and incorporated into peptides for use as SH2 domain inhibitors. In an assay using the C-terminal SH2 domain of phosphatidylinositol (PI) 3-kinase, peptides having a GXVPML sequence [where X = pTyr, Pmp, hydroxy-Pmp (HPmp), monofluoro-Pmp (FPmp), and difluoro-Pmp (F2Pmp)] exhibited binding potency in the order HPmp < Pmp < FPmp < F2Pmp = pTyr. Distinct peptide sequences which bind selectively with Src and Grb2 SH2 domains were also prepared with pTyr and F2Pmp. The F2Pmp peptides bound with high (0.2- to 5-fold) relative affinity, compared to analogous pTyr peptides. We conclude that peptides containing F2Pmp bind to SH2 domains with high affinity and specificity and, being resistant to cellular phosphatases, should provide a generally useful tool for disrupting SH2 domain-mediated signaling pathways in intact cells.

Amino Acid Sequence↗
PubMed1992

A simple method of concentrating monoclonal antibodies from culture supernatant by ultrafiltration.

How to obtain concentrated monoclonal antibodies from culture supernatant is of great importance to many scientists today. In this report, a simple, single-step technique is described to concentrate monoclonal antibodies directly from hybridoma-culture supernatant. The contaminants can be removed from the supernatant by using an ultrafiltration unit which allows macromolecules of less than 100,000 MW to pass through leaving behind monoclonal antibodies which is purified and concentrated more than 25-fold.

Antibodies, Monoclonal↗
PubMed1992

The role of the frontal lobes in the regulation of cognitive development.

Between the ages of 1.5 and 5 years, and again between the ages of 5 and 10 years, a sequence of changes takes place in children's behavior which indicates a fundamental reorganization of their attentional, executive, and self-reflexive processes. In the present article, these changes are summarized, and evidence is adduced to support the claims (1) that these changes are frontally mediated and (2) that the underlying mechanism that generates them is similar to the one that generates the changes in EEG coherence during the same time period. The psychological model that has been hypothesized to explain the cycles of cognitive development (Case, 1992) is then compared to the physiological model that has been proposed to explain cycles of EEG development (Thatcher, 1992). It is shown that the two models are complementary, both in the underlying developmental sequence that they postulate and in the recursive dynamic they propose for producing movement through this sequence. A number of implications and predictions are derived, which follow from the proposition that the two sets of changes are different manifestations of a common underlying process.

Attention↗
PubMed1989

Recognition and repair of 2-aminofluorene- and 2-(acetylamino)fluorene-DNA adducts by UVRABC nuclease.

Recognition of damage induced by N-hydroxy-2-aminofluorene (N-OH-AF) and N-acetoxy-2-(acetylamino)fluorene (NAAAF) in both phi X174 RFI supercoiled DNA and a linear DNA fragment by purified UVRA, UVRB, and UVRC proteins was investigated. We have previously demonstrated that N-OH-AF and NAAAF treatments produce N-(deoxyguanosin-8-yl)-2-aminofluorene (dG-C8-AF) and N-(deoxyguanosin-8-yl)-2-(acetylamino)fluorene (dG-C8-AAF), respectively, in DNA. Using a piperidine cleavage method and DNA sequence analysis, we have found that all guanine residues can be modified by N-OH-AF and NAAAF. These two kinds of adducts have different impacts on the DNA helix structure; while dG-C8-AF maintains the anti configuration, dG-C8-AAF is in the syn form. phi X174 RF DNA-Escherichia coli transfection results indicate that while the uvrA, uvrB, and uvrC gene products are needed to repair dG-C8-AAF, the uvrC, but not the uvrA or uvrB gene products, is needed for repair of dG-C8-AF. However, we have found that in vitro the UVRA, UVRB, and UVRC proteins must work in concert to nick both dG-C8-AF and dG-C8-AAF. In general, the reactions of UVRABC nuclease toward dG-C8-AF are similar to those toward dG-C8-AAF; it incises seven to eight nucleotides from the 5' side and three to four nucleotides from the 3' side of the DNA adduct. Evidence is presented to suggest that hydrolysis on the 3' and 5' sides of the damaged base by UVRABC nuclease is not simultaneous and that at least occasionally hydrolysis occurs only on the 3' side or on the 5' side of the damage site. The possible mechanisms of UVRABC nuclease incision for AF-DNA are discussed.

2-Acetylaminofluorene↗