Biomedical subjects

M Rispoli

Publications and source records attributed to M Rispoli.

At least 19 recordsLinked to original sources

PubMed1994

Pronoun case overextensions and paradigm building.

Pronoun case errors, or overextensions, like *me want it are characteristic of English child language. This paper explores a hypothesis that the morphological structure of a pronoun influences the pattern of these errors. The Language Acquisition Device (LAD) attempts to analyse English pronoun case forms into stems and affixes, but cannot because of their irregularity. Nevertheless the LAD extracts a phonetic core for each pronoun (e.g./m-/ for the 1st sg.,/h-/ for the 3rd masc. sg.). The phonetic core blocks the overextension of suppletive nominative forms like I and she. This hypothesis predicts strong differences in the frequency and types of errors between pronouns with suppletive nominatives and those without. Evidence for this hypothesis was found in a transcript database of twelve children, with data collected in one hour samples every month from 1;0 to 3;0. 20,908 pronouns were examined, 1347 of which were errors. Statistical analyses of these data provide support for this hypothesis.

Child Language↗

PubMed1992

Discourse and the acquisition of eat.

English has several classes of transitive verbs which can optionally appear without an undergoer. Despite their similar syntactic subcategorization, there are at least three different semantic subclasses that allow undergoer omission. Information sources based on surface structure, for example, syntactic bootstrapping, cannot inform the child of the semantic representation of these verbs. The focus of this paper is the acquisition of a single English verb, eat. The transcripts of 40 children, who were audiotaped monthly from 1;0 to 3;0, showed that eat was the first member of this verb class to be acquired. Some 1276 eat sentences were analysed for the presence of overt undergoer arguments across levels of cumulative verb lexicon (CVL) size, and two discourse conditions: (1) UNDERGOER ACCESSIBLE and (2) OPEN (to undergoer omission). Results indicate that undergoer omission became associated with discourse conditions when CVL size rose above 75 types, at MLU approximately 2.4 and age approximately 2;3. This suggests that two-year-old children are sensitive to a relationship between undergoer omission and discourse context.

Female↗

PubMed1991

Histones and DNA methylation in mammalian chromatin. Differential inhibition by histone H1.

Histones (from calf thymus or from human placenta), if renatured in the presence of EDTA, caused a severe inhibition of in vitro methylation of double-stranded DNA (from Micrococcus luteus) by human placenta DNA methyltransferase. The absence of EDTA during the histone renaturation procedure abolished--at least in the 'physiological' range of the histones/DNA ratio--the inhibition. The H1 component was responsible for this inhibition, no effect being exerted by the other histones. H1 preparations were more effective if renatured in the presence of EDTA--90% inhibition being reached at a 0.3:1 (w/w) H1/DNA ratio. It seems likely that the requirement for the presence of EDTA during the renaturation process is correlated to its ability to induce a fairly stable ordered conformation of the histones, although this effect could also be shown with the 'inactive' H2a, H2b and H3 components, and was instead less evident with histone H1. The restriction to histone H1 of the ability to inhibit enzymic DNA methylation may account for the lower methylation levels present in the internucleosomal DNA of mammalian chromatin.

Animals↗

PubMed1991

The mosaic acquisition of grammatical relations.

The view that grammatical relations have substantial essence, designated as 'subject' or 'object' has difficulty in accounting for the variety of naturally acquirable grammatical relations. The acquisition of grammatical relations is examined from a theoretical framework, ROLE AND REFERENCE GRAMMAR, in which grammatical relations are decomposed into two separate types of structure: logical (semantic) structure and information (pragmatic) structure. The acquisition of grammatical relations from four languages is compared: (1) the definite accusative suffix and pragmatically motivated word order of Turkish; (2) Kaluli verb agreement, case and focus marking postpositions, and pragmatically motivated word order; (3) Hungarian definite and indefinite verb conjunction; and (4) Italian participial agreement and anaphoric, accusative case pronouns. Two conditions on structures are found to cause difficulty: the neutralization of a semantic or pragmatic distinction by interfering structures (e.g. Kaluli and Italian), and global case marking which forces the child to discover relevant semantic characteristics of both the actor and the undergoer (e.g. Hungarian and Kaluli). Structures that encode semantic or pragmatic distinctions independently are more easily acquired (e.g. Turkish). Piecing together discrete structures in a mosaic fashion, the child can acquire the great variety of grammatical relations that exist in human languages.

Child Language↗

PubMed1990

Lexical assignability and perspective switch: the acquisition of verb subcategorization for aspectual inflections.

This paper explores how children learn the range of aspect inflections to which a verb is amenable. The data considered are from observations of three Japanese boys aged between 1:10 and 2:1. Analyses focus on the children's mastery of Aktionsart specific intersentential patterns. For example, in one pattern, a caregiver asks nani shiteiru? 'What is someone or something doing'. The conventional answer is with the continuative -te iru form of a verb that expresses an activity. Three conclusions are drawn. First, lexical assignment had begun before aspectual inflections were used to signal temporal perspective switch. Secondly, lexical assignment began with anchorpoints tying certain lexical contrasts to the Aktionsart of minimal sentences. Thirdly, overgeneralizations of aspect inflections are due to the difficulty of acquiring devices that signal temporal perspective switch.

Child, Preschool↗

PubMed1989

Acquisition of complementation.

This study concerns the acquisition of complex sentences with perception and epistemic verbs that take a second verb in their complements. The acquisition of complementation began between two and three years of age in this longitudinal study of four children's spontaneous speech. The results of the study showed that (1) complement types and complementizer connectives and (2) the discourse contexts in which complementation occurred were specific to individual matrix verbs. The most frequent verbs acquired were the perception verbs see and look and the epistemic verbs think and know. Developments in both discourse and syntax indicated that these verbs expressed attitudes of certainty/uncertainty toward the content expressed in their complements. The results are discussed in terms of both linguistic and psychological factors in the acquisition of complex sentences with complementation.

Child, Preschool↗

PubMed1989

[Evaluation of heart rate changes in the aged. An ambulatory electrocardiography study. Arrhythmias in the aged].

The Holter examinations of 111 subjects aged more than 65 who then underwent dynamic ecg were investigated in order to assess the clinical significance of cardiac arrhythmias in geriatric age. Group A was formed of 53 patients with no clinical signs of cardiovascular diseases. Thirty-two patients with clinical evidence of ischaemic cardiopathy made up Group B and 26 with arterial hypertension formed Group C. The Holter examinations were evaluated in accordance with current guidelines, considering the basic rhythm, heart rate, pulse formation and conduction disturbances and supraventricular and ventricular hyperkinetic arrhythmias. Sinus base rhythm was present in most cases whereas atrial fibrillation was noted in a similar percentage in the three groups, whether or not cardiovascular disease was present. Supraventricular and ventricular hyperkinetic arrhythmias were extremely common in the elderly and made no discrimination between patients with ischaemic cardiopathy or hypertension and the clinically healthy; for example, ventricular tachycardia was observed in 10.6% of Group A subjects, in 7.1% of Group B and 8.6% of Group C. To conclude, the clinical significance of heart rhythm changes in the elderly remains obscure because in most subjects they are not related to the presence of cardiovascular disease.

Age Factors↗

PubMed1988

Localization, in human placenta, of the tightly bound form of DNA methylase in the higher order of chromatin organization.

In human placenta, the DNA of all subfractions of the third level of chromatin organization exhibits similar values of the methylcytosine-to-cytosine ratio. The tightly bound form of DNA methyltransferase is mostly recovered in the 'stripped loop' fraction, although, on the basis of the DNA content, the 'stripped loops' and the 'stripped matrix' appear to possess a similar amount of the enzyme. DNA methyltransferase activity is instead totally absent from the 'digested matrix', i.e., from the fraction remaining after digestion of the 'stripped matrix' with DNAase I. Upon addition of exogenous DNA methyltransferase, however, the DNA of this fraction, which is only 1% (in weight) of the total chromatin DNA and which has a length of approx. 9 kbp, can readily undergo methylation.

5-Methylcytosine↗

PubMed1988

Do tightly-bound chromatin proteins play a role in DNA methylation?

When chromatin matrix, "stripped" from its loosely-bound components by extraction with 3 M NaCl, is extensively digested with DNAase I, a fraction is obtained, which carries no endogenous DNA methyltransferase activity but which is a good substrate for externally added enzyme. Under the same conditions, protein-free DNA isolated from this fraction can instead hardly be methylated, this different behaviour pointing to a role of DNA-tightly-bound proteins in favoring or promoting the catalytic action of the enzyme. A similar stimulation of enzymatic methylation could also be shown when, in the presence of this same fraction, single stranded Micrococcus luteus DNA was incubated with placental methyltransferase, using S-adenosylmethionine as a methyl donor. This finding can be correlated to the existence, in chromatin loops, of small regions which resist digestion by DNAase I also after high-salt removal of their loosely-bound components (presumably because of the presence of tightly-bound proteins) and whose DNA is characterized by high methylation levels and, at the same time, by high relative content of thymine.

Binding Sites↗

PubMed1987

Inactivation of de novo DNA methyltransferase activity by high concentrations of double-stranded DNA.

The activity of eukaryotic DNA methyltransferase diminishes with time when the enzyme is incubated with high concentrations (200-300 micrograms/ml) of unmethylated double-stranded Micrococcus luteus DNA. Under similar conditions, single-stranded DNA induces only a limited decrease of enzyme activity. The inactivation process is apparently due to a slowly progressive interaction of the enzyme with double-stranded DNA that is independent of the presence of S-adenosyl-L-methionine. The inhibited enzyme cannot be reactivated either by high salt dissociation of the DNA-enzyme complex or by extensive digestion of the DNA. Among synthetic polydeoxyribonucleotides both poly(dG-dC).poly(dG-dC) and poly(dA-dT).poly(dA-dT), but not poly(dI-dC).poly(dI-dC), cause inactivation of DNA methyltransferase. This inactivation process may be of interest in regulating the 'de novo' activity of the enzyme.

DNA↗

PubMed1986

Substrate preferences of human placental DNA methyltransferase investigated with synthetic polydeoxynucleotides.

A DNA methyltransferase partly purified from human placenta has been tested on a variety of synthetic polydeoxynucleotides. The results showed that: the enzyme is most active as a 'maintenance' or 'hemi-' methylase but also has some de novo methylating activity; the presence or absence of A or T in the substrate strand has little influence on maintenance or de novo activity, while polymers containing C but not G in the same strand are poor de novo substrates and bind poorly to the enzyme; single-stranded polymers are about as good substrates as double-stranded ones, and the effects of nucleotide composition (particularly G and mC content) on enzyme activity with single strands are similar to those with double-stranded polymers; strands in which all the cytosines are methylated bind the enzyme well. A mechanism is suggested involving two different sites on the enzyme that recognize CG and mCG, and which rationalizes the activity of eukaryotic DNA methyltransferases towards single-stranded DNA.

DNA↗

PubMed1985

Effects of histamine H1-receptor stimulation on coronary hemodynamics in man.

Exogenous histamine in man induces significant cardiovascular effects mediated by activation of H1 and H2-receptors present on human heart and on coronary arteries. We studied the effects of selective H1-receptor stimulation on human coronary hemodynamics in 10 patients undergoing cardiac catheterization. All patients were pretreated with cimetidine before the histamine infusion (0.5 micrograms/kg/min i.v. for 5 min). Six of these patients had normal coronary arteries and four had single vessel coronary artery disease (CAD) and vasospastic angina. During the study heart rate was held constant (100 beats/min) by coronary sinus pacing. We measured mean aortic pressure (MAP), coronary sinus blood flow (CSBF), coronary vascular resistance (CVR) and myocardial oxygen consumption (MVO2) at rest, during histamine infusion, and 10 min after the end of the infusion. During infusion, MAP decreased from 103 +/- 5 to 85 +/- 6 mmHg (p less than 0.02) and CVR from 1.00 +/- 0.16 to 0.81 +/- 0.14 mmHg/ml/min (p less than 0.05); CSBF and MVO2 did not significantly change. All parameters returned to baseline at the end of the infusion. The response was similar in patients with normal coronary arteries and in 3 patients with CAD. Only one patient with CAD developed angina with ST segment elevation in D3, reduction in CSBF and an increase in CVR. These results indicate that H1-receptor stimulation in man induces significant coronary dilatation and that histamine infusion after cimetidine pretreatment is unlikely to provoke coronary spasm in patients with vasospastic angina.

Adult↗

PubMed1985