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Biomedical subjects

A Rom

Publications and source records attributed to A Rom.

7 recordsLinked to original sources
PubMed1992

Calcium channel blockers inhibit retinal degeneration in the retinal-degeneration-B mutant of Drosophila.

Light accelerates degeneration of photoreceptor cells of the retinal degeneration B (rdgB) mutant of Drosophila. During early stages of degeneration, light stimuli evoke spikes from photoreceptors of the mutant fly; no spikes can be recorded from photoreceptors of the wild-type fly. Production of spike potentials from mutant photoreceptors was blocked by diltiazem, verapamil hydrochloride, and cadmium. Little, if any, effect of the (-)-cis isomer or (+)-cis isomer of diltiazem on the light response was seen. Further, the (+)-cis isomer was approximately 50 times more effective than the (-)-cis isomer in blocking the Ca2+ spikes, indicating that diltiazem action on the rdgB eye is mediated by means of blocking voltage-sensitive Ca2+ channels, rather than by blocking the light-sensitive channels. Application of the Ca(2+)-channel blockers (+)-cis-diltiazem and verapamil hydrochloride to the eyes of rdgB flies over a 7-day period largely inhibited light-dependent degeneration of the photoreceptor cells. Pulse labeling with [32P]phosphate showed much greater incorporation into eye proteins of [32P]phosphate in rdgB flies than in wild-type flies. Retarding the light-induced photoreceptor degeneration in the mutant by Ca(2+)-channel blockers, thus, suggests that toxic increase in intracellular Ca2+ by means of voltage-gated Ca2+ channels, possibly secondary to excessive phosphorylation, leads to photoreceptor degeneration in the rdgB mutant.

Action Potentials↗
PubMed1992

Calcium is necessary for light excitation in barnacle photoreceptors.

Illumination of barnacle (Balanus amphitrite) photoreceptors is known to increase the membrane permeability to sodium and Ca2+ ions resulting in a depolarizing receptor potential. In this report, we show that lanthanum (La3+), a known inhibitor of Ca-binding proteins, reversibly eliminates the receptor potential of barnacle photoreceptors when applied to the extracellular space. Similar reversible elimination of the light response was obtained by removing extracellular Ca2+ by application of the calcium chelating agent EGTA. Iontophoretic injection of Ca2+, but not K+ into the cells protected both the transient and the steady-state phases of the receptor potential from elimination by EGTA while only the transient phase was protected in the presence of La3+. The EGTA experiments suggest that internal Ca2+ is necessary for light excitation of barnacle photoreceptors while the La3+ experiments suggest that La(3+)-sensitive inward current is necessary to maintain excitation during prolonged light.

Animals↗
PubMed1985

Verb usage by educable mentally retarded children.

The purpose of this study was to investigate the semantic and morphological nature of verb usage by educable mentally retarded (EMR) children. Three groups of children were studied in structured and non-structured situations in which the verb system was the core interest. There were 15 mentally retarded younger children (8.6-9.6 years), 19 mentally retarded older children (10.0-12.6 years) and a control group of 17 normal children (5.0-6.0 years). Results showed that EMR children use fewer conjugations than normal children of similar or lower mental age, and thus they can express fewer verb-case relations. In particularly EMR children show limited use of process-verb relations. It was further found that EMR children are restricted in the morphological processing of verbs in past and future tenses.

Child↗
PubMed1983

The use of nonverbal pragmatic behaviors by language-impaired and normal-speaking children.

The use of six nonverbal pragmatic behaviors was investigated for three groups of subjects. The experimental group (LI) consisted of 20 language-impaired children who were in stages III and IV of linguistic development. One control group (NSY) consisted of 20 normal-speaking children equated with the experimental group on the basis of mean length of utterance. Another control group (NSO) consisted of 20 normal-speaking children equated with the experimental group by chronologic age. The NSY were younger, whereas the NSO were of the same age as the LI. Two individuals observed each child and a peer playing with toys and recorded the presence of the six behaviors for each subject. The LI and the NSY and the NSO did not differ significantly for five behaviors. Play was the only behavior that distinguished the groups. The clinical implications of the results are discussed.

Child, Preschool↗
PubMed1981

A comparison of verbal communicative skills of language impaired and normal speaking children.

This investigation compared the speech act usage of language impaired and normal speaking children. Twenty language impaired subjects (LI) in stages III and IV constituted the experimental group. One control group consisted of 20 normal speaking younger children (NSY) equated with the language impaired subjects by MLU. The other control group consisted of 20 older normal speaking children (NSO) equated with the experimental group by chronological age. Two observers independently identified ten speech acts used by the subjects during free play sessions with a peer. The results indicated that the same speech acts were used in similar proportions by all three groups. The NSO used more utterances than the LI and NSY subjects. The NSO used describing and acknowledging speech acts more than the LI or NSY. Answering was used more frequently by the LI than the NSO. Requesting an action was used more frequently by the NSY than the NSO. The results suggest that language impaired subjects are able to use a variety of speech acts but that they appear to be delayed in their pragmatic development. Clinical implications of the data are presented.

Age Factors↗