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Biomedical subjects

A Levitt

Publications and source records attributed to A Levitt.

29 records · Page 2Linked to original sources
PubMed1992

The effect of light on oxygen-induced vasoproliferative retinopathy in newborn kittens.

The effect of bright fluorescent light (115 fc) on oxygen-induced retinopathy in newborn kittens was compared with that of complete darkness and cyclic illumination of 12 hr of bright light (115 fc) and 12 hr of complete darkness. No significant difference was found in the extent of preretinal vasoproliferation and retinal ultrastructural findings among the three groups of kittens reared in different levels of illumination and a control group raised in a standard laboratory illumination level of 40 fc. These results confirmed that light is not a required factor for the development of oxygen-induced retinopathy in kittens.

Animals↗
PubMed1991

Syllable-internal structure and the sonority hierarchy: differential evidence from lexical decision, naming, and reading.

Treiman (1983) and others have argued that spoken syllables are best characterized not as linear strings of phonemes, but as hierarchically organized units consisting of an onset (initial consonant or consonant cluster) and a rime (the vowel and any following consonants) and that the rime is further divided into a peak or nucleus (the vowel) and a coda (the final consonants). It has also been argued that the sonority (or vowel-likeness) of the consonant closest to the peak, which is a function of its phonetic class, may have an effect on the strength of boundaries determined by the hierarchical division of the syllable (e.g., Treiman, 1984). We examined the evidence for syllable-internal structure and for sonority in two experiments that employed visually presented stimuli and lexical decision, naming, and reading tasks. Our results provide support for the breakdown of the rime into a peak and a coda and for an effect of the sonority of the postvocalic consonant on that break. This pattern occurred only in our lexical decision tasks, so the effect is assumed to be postlexical. We did not find an effect of the onset-rime boundary, perhaps because of an unanticipated effect of word frequency. Our results are discussed in terms of phonological coding in short-term memory.

Adult↗
PubMed1989

The Tc2 transposon in Caenorhabditis elegans.

A second family of transposons, named Tc2 elements, has been identified in the nematode Caenorhabditis elegans. Tc2 elements are polymorphic in sequence and are present in different numbers in different strains. Like the transposon Tc1, Tc2 is active in the germ line of some C. elegans strains. A high rate of transposition has been observed in the progeny of certain interstrain crosses, where transposition events are frequent enough to be detected in blot hybridization experiments, without the use of a genetic screen. Our data suggest that transposition of Tc1 and Tc2 may be regulated by the same genomic factors.

Animals↗
PubMed1989

Health maintenance issues of the elderly. Immunization.

The elderly are frequently underimmunized against vaccine-preventable infectious diseases. Comprehensive immunization of patients for vaccine-preventable diseases represent a major challenge for physicians treating the elderly. The healthy elderly should be specifically targeted since they are most likely to mount an appropriate immune response to the vaccine. Programs to identify inadequately immunized patients should be widely implemented.

Aged↗
PubMed1988

Context effects in two-month-old infants' perception of labiodental/interdental fricative contrasts.

We investigated 2-month-old infants' perception of a subset of highly confusable English fricatives. In Experiment 1, infants discriminated modified natural tokens of the voiceless fricative pair [fa]/[oa] but only when the syllables included their frication noises. They also discriminated the voiced pair [va]/[oa] both with and without fricative noises. These results parallel those found with adults by Carden, Levitt, Jusczyk, and Walley (1981). In Experiment 2 [f] and [o] noises were appended to [a], and the same [f] noise was appended to the previously indiscriminable fricationless versions of [fa] and [oa]. Infants discriminated both pairs of stimuli, indicating that (a) the frication is a sufficient cue for [fa]/[oa] discrimination and that (b) it provides a context for discriminating the [f] and [o] formant transitions. We conclude that infants' perception of labiodental/interdental fricative contrasts show evidence of context effects similar to those observed with adults.

Humans↗
PubMed1987

Normal lung perfusion scan with extensive thromboembolic disease.

A 50-year-old woman with unexplained pulmonary hypertension had normal findings on six-view lung perfusion scan prior to open lung biopsy. The biopsy demonstrated old organized thrombi. The patient expired and autopsy disclosed extensive thromboembolic disease, both old and new. A six-view lung scan may not distinguish primary pulmonary hypertension from thromboembolic hypertension when diffuse symmetrical thrombi are present. Under such conditions, when invasive diagnostic procedures have an unacceptable morbidity, empiric anticoagulation should be considered.

Female↗
PubMed1985

Regulation of Tcl transposable elements in Caenorhabditis elegans.

C. elegans strains contain variable numbers of a 1.6-kb transposable genetic element. Activity of this element, which is denoted Tcl, shows regulation at at least two levels. At one level, excision of Tcl elements occurs in somatic cells at a frequency several orders of magnitude higher than in germ cells. Evidence is presented suggesting that this results from regulation at the level of trans-acting functions that are required for excision or that repress excision. At the second level, germ line transposition of Tcl occurs at greater frequency in some strains than in others. The hypothesis is proposed that this is because Tcl is one component of a two-element system, the second element of which differs between strains. Evidence for a second putative transposable element family in C. elegans is presented. This family has properties that suggest a relationship to Tcl. This possibility is currently under investigation.

Animals↗
PubMed1985

Two integrated partial repeats of simian virus 40 together code for a super-T antigen.

We determined that the coding sequence for a 100-kilodalton super-T antigen found in Simian virus 40 mouse transformants spanned two separate partial repeats of the viral genome. The downstream repeat contained a complete Simian virus 40 large-T-antigen gene, whereas the upstream repeat was a truncated copy of the same gene. When the repeats were separated by subcloning, the capacity to code for the super-T antigen was lost. A small insertion or deletion in the origin-control region which preceded the second repeat could also destroy the ability to code for the 100-kilodalton protein. Our data suggest that differential splicing between parts of two gene copies was responsible for the additional molecular weight of this super-T antigen.

Animals↗
PubMed1983

Battered women presenting in general practice.

The problems of battered women have recently been highlighted. They consult doctors, who can be an important source of help. We examined their initial presenting complaint to general practitioners. Questionnaires were sent to 27 London refuges for battered women and to 100 randomly selected general practitioners. Seventy-two women and 49 doctors replied. The results indicated that these women are more likely to present with psychological symptoms. Many cases are not detected because the battering is concealed. The attitude of doctors may prevent these patients discussing their real problems. Further studies are needed.

Adult↗