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↗

PubMed1991

Expiratory flow rate curves for monitoring upper and lower airway obstruction during anesthesia.

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Airway Obstruction↗

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↗

PubMed1988

Recognition of the DNA helix stabilizing anthramycin-N2 guanine adduct by UVRABC nuclease.

The binding of the anti-tumor antibiotic anthramycin to a defined linear DNA fragment was investigated using both exonuclease III and lambda exonuclease. We show that most of the guanine residues are reactive toward anthramycin; however, several guanine residues showed preferential reactivity for the drug. Using purified UVRA, UVRB and UVRC proteins we present evidence that these three proteins in concert are able to recognize and produce specific strand cleavage flanking anthramycin-DNA adducts. The cleavage of anthramycin adducts by UVRABC nuclease is specific and results in strand breaks at five or six bases 5' and three or four bases 3'-flanking an adduct. At some guanine residues single incisions were observed only on one side of the adduct. The 5' strand breaks observed often occurred as doublet bands on sequencing gels, indicating plasticity in the site of 5' cleavage whereas the 3' cleavage did not show this effect. When DNA fragments modified with elevated levels of anthramycin were used as substrates the activity of the UVRABC nuclease toward the anthramycin adducts decreased. Possible mechanisms for the recognition and specific cleavage of the helix-stabilizing anthramycin DNA adduct and other helix destabilizing lesions by the UVRABC nuclease are discussed.

Anthramycin↗

PubMed1982

Breast cancer skin test antigens of increased sensitivity prepared from vesicular stomatitis virus-infected tumor cells.

Crude membrane (CM) extracts were prepared from five cultured breast tumor lines (MDA-MB-157, MDA-MB-231, ZR75-1, HS0578T, and MCF-7) which had been infected with vesicular stomatitis virus (VSV) to augment their antigenicity. In skin test trials, CM extracts of uninfected MCF-7 cells elicited positive response in 0 of 13 (0%) tests in breast cancer patients, while VSV-MCF-7 elicited positive responses in 11 of the same 13 patients (84.6%). CM extracts of VSV-ZR75-1 and VSV-MCF-7 elicited greater delayed hypersensitivity responses (mm induration at 48 hr) in breast cancer patients than in patients with lung carcinoma or melanoma. Although the sensitivity of VSV-ZR75-1 was too low (ten of 28, or 35.7% of tests positive) to be useful as a skin test antigen, VSV-MCF-7 elicited positive responses in 30 of 38 (78.9%) tests in breast cancer patients, as compared to two of 15 (13.3%) and two of 13 (15.4%) of tests in patients with lung carcinoma and melanoma, respectively. The "virus-augmented" CM extract of cultured MCF-7 cells exhibited markedly greater sensitivity as compared to control MCF-7 extracts (P less than .005), with a high degree of specificity for breast cancer patients as compared to patients with the other neoplasms (P less than .00001). The results of skin testing with VSV-MCF-7 CM extracts demonstrated antigenic cross-reactivity with a large number of breast cancer patients, a finding of great importance for any potential immunotherapy and/or immunodiagnosis.

Adult↗

PubMed1982

Collaborative evaluation of rolling ball viscometer for measuring somatic cells in abnormal milk.

The Ruakura rolling ball viscometer was evaluated in 3 laboratories along with currently approved instrumental methods for measuring somatic cells in milk and the Wisconsin mastitis test. Replacement of the Teepol reagent with Wisconsin mastitis test reagent in the rolling ball viscometer was also evaluated. Both repeatability and reproducibility were satisfactory for all methods evaluated. The instrumental methods each gave higher readings than the other 3 methods. Use of Wisconsin mastitis test reagent in the rolling ball viscometer improved both repeatability and reproducibility. Additional work on standardization is suggested to match rolling ball viscometer readings with those of the instrumental methods.

Animals↗

PubMed1981

Elastic applicator.

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Orthodontic Appliances↗

PubMed1978

Melanoma skin test antigens of improved sensitivity prepared from vesicular stomatitis virus-infected tumor cells.

Crude membrane (CM) extracts from three different cultured human melanoma lines that were "virus-augmented" (infected with vesicular stomatitis virus (VSV) and subsequently inactivated by ultraviolet light) produced positive skin tests in 17 of 20 (85%), 11 of 20 (55%), and 13 of 18 (72%) tests, respectively, performed in 20 melanoma patients. Identical CM extracts from the same melanoma lines that had not been infected with VSV gave positive skin tests in 2 of 20 (10%), 4 of 20 (20%), and 2 of 18 (11%) tests, respectively, performed in the 20 melanoma patients, and no positive tests in the control patients. The 3 virus-augmented extracts were positive in only 2 of 18 (11%), 0 of 18 (0%), and 1 of 17 (6%) control subjects, respectively. The controls consisted of six normal volunteers and 12 patients with cancers other than melanoma. The "virus-augmented" CM extracts thus exhibited markedly greater sensitivity without significant loss of specificity as compared to nonvirus augmented extracts when used as tumor-specific melaonma skin test antigens.

Adult↗

PubMed1977

Movement of labelled decamethonium in muscle fibres of the rat.

1. Tritium-labelled decamethonium accumulated in diaphragm muscles of the rat in vitro with a peak at the end-plate region and the distributions were fitted by Gaussian curves. 2. Prolonged wash in physiological saline (10 hr) produced some loss in radioactivity but no detectable spread of the labelled compound along the fibres, which indicated that the decamethonium was not in a mobile form. 3. Rats injected with labelled decamethonium showed radioactivity in the diaphragm muscles after 21 days. 4. A slow spread of the labelled compound along the fibres was detected, and from the widening of the Gaussian curves the apparent diffusion coefficient was 1.2 X 10(-8) cm2sec-1, which is less than 1/500 of that in free solution.

Animals↗