Search PubMed⌕ Search

Biomedical subjects

J Egan

Publications and source records attributed to J Egan.

At least 91 records · Page 5Linked to original sources
PubMed1984

Non-organic failure to thrive: a developmental perspective.

Like other segments of the child's development, eating behavior follows a sequential pattern. To understand the infant's or child's feeding problems which can lead to failure to thrive or dwarfism we propose that a child's progression be studied through three stages of development: homeostasis, attachment and separation-individuation. Specific feeding problems can arise at each of these stages of development and consequently impede the child's weight gain. During the period of homeostasis the infant learns to regulate himself, to suck, to swallow and to time the onset and termination of feedings by giving signals of hunger and fullness. If he is unable to master these, he cannot be fed effectively. Failure to master these basic feeding skills interferes with the next developmental task of attachment and also impedes development of motor skills, language and affective engagement. During the period of attachment, the infant establishes distinct interactional patterns with his caretakers. Lack of engagement between mother and infant leads to lack of pleasure and lack of appetite or even to severe dysfunctional feeding patterns like vomiting and rumination. Feeding problems in the third developmental stage of separation and individuation can arise because of maladaption in the attachment phase or because of new difficulties which center around issues of autonomy vs. dependency. At this stage, the infant learns means-end differentiation and begins to understand that his actions elicit certain consequences. If the infant's struggle between autonomy and dependency gets caught in the feeding situation, the infant's emotional needs can dictate his eating behavior. The infant refuses to eat either to have his emotional hunger for mother's attention met or to assert his autonomy and to express his anger toward her. In order for the infant to learn to differentiate between his physiological feelings of hunger and his emotional need states, the caregiver needs to give contingent responses by offering food when the infant is hungry and comfort when the infant is distressed. Feeding problems which can create, co-exist with, or result from a growth problem must be considered within a developmental context. As the infant progresses through the developmental stages of homeostasis, attachment, and separation, he masters phase-appropriate feeding skills which help him to progress from reflex sucking to autonomous feeding. Early identification of maladaptive feeding behavior will assist the pediatrician in making timely interventions.

Child↗
PubMed1983

Experimental transmission of duck hepatitis B virus.

Susceptibility to experimental infection with duck hepatitis B virus (DHBV) was explored, with the objective of defining procedures that were both rapid and reproducible. For the purpose of these experiments, a small flock of DHBV-free breeders was established as a source of susceptible eggs and ducklings, since ca. 10% of the ducks (all ages) from commercial flocks were DHBV infected. Intravenous inoculation of DHBV into 15-day duck embryos from the DHBV-free flock produced a persistent infection, with a high-titer viremia, in at least 80% of the injected animals. The tissue tropism of DHBV in these experimentally infected animals was similar to that associated with natural, congenital infections from viremic ducks to their progeny. Virus antigen was found not only in hepatocytes and bile duct epithelium of liver, but also in cells associated with exocrine and endocrine pancreas, and in proximal convoluted tubular epithelium of kidney. Infection of embryonic liver was rapid, as evidenced by active synthesis of DHBV-DNA by reverse-transcription of RNA by 24 hr postinjection. During this latter analysis, formation of supercoiled viral DNA appeared to precede the reverse-transcription phase of viral DNA synthesis, suggesting that this species may be important in initiation of infection.

Animals↗
PubMed1983

Dissociation of the site of origin from the site of cryo-termination of ventricular tachycardia.

We performed conventional electrogram mapping and cryomapping in dogs with one-week-old experimentally-induced myocardial infarctions and programmed stimulation-induced sustained ventricular tachycardias to assess whether there is a correlation between the "site of origin" and site of cryo-termination of ventricular tachycardia (VT). Electrogram maps showed that 4 of 8 induced sustained VTs were due to macro- and 4 of 8 to microre-entry. Local cooling of the site of origin terminated 4 of 4 microre-entrant VTs, but only 1 of 4 macrore-entrant VTs. In the other 3 macrore-entrant VTs, the sites of cryo-termination were 2, 2.5, and 4 cm distant from the sites of origin. In contrast, cooling of the mid-to-late diastolic portions of the re-entry loops terminated all 8 VTs. These data demonstrate a dissociation of the site of origin from the site of cryo-termination of macrore-entrant VT.

Animals↗
PubMed1981

The tyrT locus: termination and processing of a complex transcript.

The tyrT locus of E. coli contains a 208 bp spacer region that separates two copies of sequence encoding tRNATyr1. The spacer includes a 120 bp sequence that is homologous to a sequence that is repeated three times in the distal portion of the tyrT locus. The tyrT locus possesses a graded set of transcription termination sites that are spaced at 180 base intervals, corresponding to the distal repeated gene structure. The major termination site occurs within the second repeat unit, 225 bases beyond the mature tRNA sequences. In the presence of a temperature-sensitive rho protein there is increased read-through at this site to a termination site located 180 bases downstream in the third repeat and to several termination sites even further downstream. The primary native transcript, in the region distal to the second tRNA, carries the information for a low molecular weight, extremely basic protein. Although analogous coding sequences are present in the spacer and other repeat units, because of single base substitutions these sequences are pseudogenes. The parallel between the tyrT and TyrU gene clusters is discussed in relation to dual function transcripts that specify both tRNA and protein.

Bacterial Proteins↗
PubMed1979

The effect of amitriptyline and mianserine (Org. GB94) on food motivated behaviour of rats trained in a runway: possible correlation with biogenic amine concentration in the limbic system.

Rats on a 23 h food deprivation schedule were trained to run down a straight runway for a food reward. Neither amitriptyline nor mianserine had an effect on the running time for the food reward during the period of continuous reinforcement. However both antidepressants delayed the extinction of this response. It seems unlikely that this effect on extinction was due to an altered motivation for the food reward as amitriptyline significantly decreased the food intake of the experimental animals while mianserine increased the food intake throughout the period of the experiment. The observation that both these antidepressants reduce the speed of extinction of rewarded behaviour may be explicable in terms of observed changes in the concentration of biogenic amines in the limbic system.

Amitriptyline↗
PubMed1978

Structural analysis of the tRNA1Tyr gene of Escherichia coli. A 178 base pair sequence that is repeated 3.14 times.

The distal region of the tRNA1Tyr gene has been sequenced and found to have an unusual structure. It consists of a 178 base pair sequence that is repeated 3.14 times. The first repeat unit commences 19 base pairs before the end of the sequences encoding the mature tRNA, and these 19 base pairs are repeated faithfully at the beginning of each repeat unit. In the last fractional unit the repeated sequence extends only six base pairs beyond this 19 base pair sequence. Sequence information extends for 62 base pairs beyond the 3.14 repeating units, and no resemblance to the repeating sequence, or any other region of the tRNA1Tyr gene, is found. There are only 14 sites at which one of the repeats differs from the others; 11 of these are transitions, and the rest are transversions. The evolutionary implications of the differences are discussed. One of the differences, which occurs in the second repeat unit, corresponds to the location of the in vitro p-dependent transcription termination site. This is discussed along with other implications of the repeated structure.

Base Sequence↗
PubMed1978

A rho-dependent termination site in the gene coding for tyrosine tRNA su3 of Escherichia coli.

A set of partially overlapping DNA restriction fragments that support promoter-dependent transcription of the tRNATyr1 gene of Escherichia coli has been used to study site-specific termination in vitro. Transcription termination occurs at a specific site 224-226 nucleotides beyond the end of the structural gene and is completely dependent on rho-factor. Certain features of this site suggest differences from other termination sites previously studied. A role for specific sequence recognition is suggested.

Base Sequence↗
PubMed1976

Identification of gasoline contamination of ground-water by gas chromatography.

Individual components that make up different grades of gasoline - or gasolines of the same grade produced by different manufacturers - are resolved and identified by gas chromatography using packed columns and a flame ionization detector. Contaminants at levels as low as 0.5 mu1/1 may be identified by the method if samples of gasoline from the source of contamination can be obtained for comparison. The uniqueness of this method is that it can be applied for routine analysis without the use of sophisticated complements for the gas chromatograph.

Chromatography, Gas↗
PubMed1974

The sites of transcription and translation for Euglena chloroplastic aminoacyl-tRNA synthetases.

We find that cycloheximide completely blocks the light-induced apearance of Euglena chloroplastic aminoacyl-tRNA synthetases in dark-grown cells of Euglena gracilis var. bacillaris. Streptomycin, on the other hand, has no effect on the light-induction of these organellar enzymes. These observations, together with the finding that an aplastidic mutant (strain W(3)BUL, which has neither significant plastid structure nor detectable chloroplast DNA) contains low levels of the chloroplastic synthetases, indicate that the chloroplastic synthetases are transcriptional products of nuclear genes and are translated on cytoplasmic ribosomes prior to compartmentalization within the chloroplasts.

Amino Acyl-tRNA Synthetases↗