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Biomedical subjects

D Jones

Publications and source records attributed to D Jones.

At least 487 records · Page 27Linked to original sources
PubMed1992

Pathological changes in the brain of a patient with familial Alzheimer's disease having a missense mutation at codon 717 in the amyloid precursor protein gene.

The brain of a 61-year-old patient with familial Alzheimer's disease, showing a missense (valine----glycine) mutation at codon 717 of the amyloid precursor gene, has been examined at postmortem. Sections of brain showed pathological features entirely typical of Alzheimer's disease with no unusual characteristics. It seems therefore that this particular mutation is indeed pathogenic and that the altered amyloid precursor protein resulting from expression of this mutation is processed in a way that triggers or promotes the pathological cascade of Alzheimer's disease.

Adult↗
PubMed1992

Retrovirus insertion into herpesvirus in vitro and in vivo.

Retroviruses and herpesviruses are naturally occurring pathogens of humans and animals. Coinfection of the same host with both these viruses is common. We report here that a retrovirus can integrate directly into a herpesvirus genome. Specifically, we demonstrate insertion of a nonacute retrovirus, reticuloendotheliosis virus (REV), into a herpesvirus, Marek disease virus (MDV). Both viruses are capable of inducing T lymphomas in chickens and often coexist in the same animal. REV DNA integration into MDV occurred in a recently attenuated strain of MDV and in a short-term coinfection experiment in vitro. We also provide suggestive evidence that REV has inserted into pathogenic strains of MDV in the past. Sequences homologous to the REV long terminal repeat are found in oncogenic MDV but not in nononcogenic strains. These results raise the possibility that retroviral information may be transmitted by herpesvirus and that herpesvirus expression can be modulated by retroviral elements. In addition, retrovirus may provide a useful tool to characterize herpesviral function by insertional mutagenesis.

Animals↗
PubMed1992

Hemolymph concentrations of host ecdysteroids are strongly suppressed in precocious prepupae of Trichoplusia ni parasitized and pseudoparasitized by Chelonus near curvimaculatus.

Regulation of ecdysteroid production in lepidopteran prepupae was studied using a parasitic wasp (C. near curvimaculatus) which specifically suppresses host prepupal ecdysteroid production after the induction of precocious host metamorphosis. At the developmental stage at which the hemolymph of the unparasitized metamorphosing host has its maximum titer of prepupal ecdysteroids, the hemolymph of 4th instar "truly parasitized" hosts (hosts with a surviving endoparasite) had a strongly reduced ecdysteroid titer. However, during the photophase about 12 h later, just prior to emergence of the parasite larva, an ecdysteroid peak was observed in the host hemolymph. Fourth instar pseudoparasitized prepupal hosts (in which the endoparasite was not present or died early in development) exhibited a sustained suppression in the hemolymph ecdysteroid titer. Small 5th instar pseudoparasitized hosts, which normally would molt to a 6th instar prior to metamorphosis, but which precociously attained the prepupal stage, also had a strongly reduced ecdysteroid titer. The late increase observed in truly parasitized hosts could be completely prevented by surgical removal of the parasite 24 h earlier, resulting in a titer similar to that in pseudoparasitized hosts. HPLC analysis of ecdysteroids in normal, truly parasitized, and 4th or 5th instar pseudoparasitized prepupae showed that both ecdysone and 20-OH ecdysone* were suppressed in truly and pseudoparasitized prepupae, with ecdysteroid levels being lowest in pseudoparasitized hosts. These data, and those of Brown and Reed-Larsen (Biol Contr 1, 136 [1992]), showing endoparasite secretion of ecdysteroids just prior to its emergence from the host, strongly indicate that: (1) the prepupal peak in truly parasitized hosts originates from the endoparasite, and (2) the low level of ecdysteroids in pseudoparasitized hosts results from the host's intrinsic inability to express a normal level of prepupal ecdysteroid titer. While precocious 4th or 5th instar prepupae of similar size had similarly suppressed ecdysteroid titers, smaller 4th instar prepupae had a lower ecdysteroid titer than larger, precocious 5th instar prepupae. Rare 5th instar pseudoparasitized prepupae that were of nearly normal size showed a prepupal ecdysteroid titer distinctly greater than those of the usual smaller, precocious 5th instar prepupae. The data suggest that the competence of the host to express a normal hemolymph titer of prepupal ecdysteroids is more closely correlated with the size of the prepupae than with the instar attained.

Animals↗
PubMed1992

Characterization of gap junctions between osteoblast-like cells in culture.

The structure of gap junctions in osteoblast-like cells (OBs) and the connexins (cx) that build up these structures were characterized by ultrastructural, immunocytochemical, and molecular techniques. Ultrastructural studies revealed numerous gap junctions which were mostly located on processes of neighboring cells. Immunofluorescence labeling using two different antibodies (specific to mouse live cx26 and cx32 and to a peptide-specific rat heart gap junction protein cx43) gave evidence that in OBs, gap junctions consist mainly of cx43. The presence of cx43 in cultured OB was also confirmed by Western blot analysis. Dye-coupling with Lucifer yellow led to a staining of up to 30 neighboring cells. Parallel intracellular recordings showed that membrane potential amplitude changes (4-5 mV) are typically related to those in the coupled cells. Thus, there is morphological and functional evidence for intercellular communication between OB in culture. OBs in culture express the same connexins as observed in vivo and may serve as a model to investigate electrophysiological events in response to different stimulation signals.

Animals↗
PubMed1992

A note on Streptomyces No. 6, a chitosanase-producing actinomycete.

This communication reports the deposit of Streptomyces No. 6 in the National Collection of Industrial Bacteria, Aberdeen, AB2 1RY, Scotland, UK (Accession number 13037) and gives some references on its use in lysing cell walls of fungi in the Mucorales leading to protoplast formation. Its use in biotechnological fields is also referred to.

Glycoside Hydrolases↗
PubMed1992

Deposition of amyloid beta protein in non-Alzheimer dementias: evidence for a neuronal origin of parenchymal deposits of beta protein in neurodegenerative disease.

In two elderly patients with frontal lobe dementia and in two others with progressive aphasia an inverse relationship between the severity of beta protein deposition and the principal pathology of these disorders was noted. Deposition of beta protein occurred only in areas of cortex where functional (viable) neurones were still present and was absent where neuronal decimation had taken place. Such findings suggest that the presence of functional neurones is necessary for beta protein deposition to occur and, therefore, that neurones may be the source of the amyloid protein that is deposited within brain parenchyma not only in these disorders but also in other conditions, particularly Alzheimer's disease.

Aged↗
PubMed1992

Comparison of nedocromil sodium at two dosage frequencies with placebo in the management of chronic asthma.

Nedocromil sodium (4 mg b.d. or q.i.d.) was added to the therapy of 76 chronic asthmatic patients in a four-centre, double-blind cross-over, placebo-controlled trial. Patients had troublesome symptoms uncontrolled by high doses of inhaled corticosteroids (mean 1450 micrograms). In 54 patients who completed the study, nedocromil sodium was significantly more efficacious than placebo (P < 0.01) in relieving morning chest-tightness and cough, in reducing total diary card score and nocturnal bronchodilator usage, and in increasing morning and evening peak flow. Asthma severity at clinic visits decreased significantly (P = 0.001) following treatment with nedocromil sodium, which was globally rated more effective than placebo (P < 0.01). Treatment differences favored q.i.d. over b.d. dosage but without statistical significance. There were no serious adverse effects. Although the pulmonary function changes were small, these findings suggest that the addition of nedocromil sodium may benefit asthmatic patients who are inadequately controlled by high doses of inhaled corticosteroids.

Adolescent↗
PubMed1992

Privileged access by irrelevant speech to short-term memory: the role of changing state.

Memory for visually presented items is impaired by speech that is played as an irrelevant background. The paper presents the view that changing state of the auditory material is an important prerequisite for this disruption. Four experiments studied the effects of sounds varying in complexity in an attempt to establish which features of changing state in the auditory signal lead to diminished recall. Simple unvarying or repetitive speech sounds were not sufficient to induce the irrelevant speech effect (Experiment 1): in addition, simple analogues of speech, possessing regular or irregular envelopes and using a range of carriers, failed to imitate the action of speech (Experiment 2). Variability of between-utterance phonology in the irrelevant stream (Experiment 3) emerged as a crucial factor. Moreover, predictability of the syllable sequence did not reduce the degree of disruption (Experiment 4) suggesting that supra-syllabic characteristics of the speech are of little importance. The results broadly support the idea that disruption of short-term memory only occurs when the speech stream changes in state. It is argued that disruption occurs in memory when cues to serial order based on phonological representations of heard material interfere with the phonological codes of visual origin. It is suggested that cues to changing state of the speech input contaminate those associated with items of visual origin, which are already in a phonological store.

Adolescent↗
PubMed1992

Temporal and spatial expression patterns of the small heat shock (hsp16) genes in transgenic Caenorhabditis elegans.

The expression of the hsp16 gene family in Caenorhabditis elegans has been examined by introducing hsp16-lacZ fusions into the nematode by transformation. Transcription of the hsp16-lacZ transgenes was totally heat-shock dependent and resulted in the rapid synthesis of detectable levels of beta-galactosidase. Although the two hsp16 gene pairs of C. elegans are highly similar within both their coding and noncoding sequences, quantitative and qualitative differences in the spatial pattern of expression between gene pairs were observed. The hsp16-48 promoter was shown to direct greater expression of beta-galactosidase in muscle and hypodermis, whereas the hsp16-41 promoter was more efficient in intestine and pharyngeal tissue. Transgenes that eliminated one promoter from a gene pair were expressed at reduced levels, particularly in postembryonic stages, suggesting that the heat shock elements in the intergenic region of an hsp16 gene pair may act cooperatively to achieve high levels of expression of both genes. Although the hsp16 gene pairs are never constitutively expressed, their heat inducibility is developmentally restricted; they are not heat inducible during gametogenesis or early embryogenesis. The hsp16 genes represent the first fully inducible system in C. elegans to be characterized in detail at the molecular level, and the promoters of these genes should find wide applicability in studies of tissue- and developmentally regulated genes in this experimental organism.

Animals↗
PubMed1992

Evidence for p55-p75 heterodimers in the absence of IL-2 from Scatchard plot analysis.

The high affinity receptor for IL-2 is composed of at least two chains, a p55 chain that binds IL-2 with low affinity and a p75 chain that binds with intermediate affinity. Two molecular mechanisms have been proposed for the formation of the high affinity receptor-ligand complex: The affinity conversion model proposes that the high affinity receptor is formed via stepwise binding in which IL-2 first binds to the p55 chain and the resulting complex then associates with the p75 chain to form a high affinity ternary complex. In the performed heterodimer model the p55 and p75 chains form a non-covalently linked high affinity heterodimer in the absence of IL-2. We show that these two models can be distinguished on the basis of equilibrium binding experiments using cell lines expressing different numbers of p55 chains. To make this distinction we develop a general model for the interaction of IL-2 with its various receptors. We than analyze the case in which heterodimers exist in the absence of IL-2 and the case in which no preformed heterodimers exist. For both cases we predict the shape of equilibrium Scatchard plots. We then show that published IL-2 binding studies are consistent with a model in which a large concentration of preformed heterodimers is present on the cell surface and inconsistent with a model in which preformed heterodimers are absent from the cell surface. The models that we develop should have general applicability to the entire class of receptor systems in which low and intermediate affinity chains interact to constitute a high affinity receptor.

Cell Membrane↗
PubMed1992

Delayed hemorrhagic pericardial effusion: case reports of a complication from severe blunt chest trauma.

The rare occurrence of delayed hemorrhagic pericardial effusion requiring treatment is reported following significant blunt chest trauma (AIS greater than or equal to 3) in three patients from 12 to 15 days after injury. Cardiomegaly was suspected on serial chest roentgenograms, and the pericardial effusion was confirmed by echocardiography. Two of three patients required systemic anticoagulation early after their admission to the hospital. It is currently unknown whether the number of delayed hemorrhagic pericardial effusions is increasing with the use of certain anticoagulation treatment regimens.

Adult↗
PubMed1992

Irrelevant speech and serial recall: implications for theories of attention and working memory.

Irrelevant speech markedly impairs serial recall of visually presented lists, even though the person is asked to ignore the speech. In this, the first major review of the phenomenon, we conclude that (i) the effect occurs in memory rather than at encoding; (ii) within memory, the disruption occurs as a result of a confluence of information at the phonological rather than at the articulatory stage of coding; (iii) speech does not have privileged access to memory, since its disruptive effects may be attenuated by habituation; and (iv) disruption occurs as a result of the changing state of the auditory channel, not as had previously been thought the phonological similarity of visual and auditory streams, and is particularly sensitive to pitch changes in both speech and non-speech stimuli. These conclusions are discussed in the light of two complementary theoretical constructs: a cascading filter system responsible for the access of speech to memory and a system of coding within memory sensitive to changing state of the stream responsible for disruption of serial order. Recommendations are made also for empirical work to refine these constructs.

Attention↗
PubMed1992

Histology of skeletal muscle in adults with GH deficiency: comparison with normal muscle and response to GH treatment.

The histology of needle biopsy specimens of skeletal muscle from the vastus lateralis was quantitatively assessed in a group of adults with growth hormone (GH) deficiency, most of whom had hypopituitarism treated with conventional pituitary hormone replacement. The mean age of the 21 patients (16 males and 5 females) was 39 +/- 2 (SEM). Comparisons were made with age- and sex-matched controls following six months double-blind, placebo-controlled treatment with recombinant human GH (rhGH) in the GH-deficient patients. Before treatment, needle muscle biopsies from patients with GH deficiency showed mean type I and II fibre areas of 5,153 +/- 273 and 4,828 +/- 312 microns 2 respectively, which did not differ from the controls (4,482 +/- 306 and 4,699 +/- 310 microns 2). Percentages of type I fibres were similar in the two groups (47.2 +/- 2.5% in GH deficiency and 45.3 +/- 2.2% in controls). No difference in the variability of type I or II fibre areas was demonstrated between the groups. Correlations between the relative contribution to total fibre area by type I fibres (mean fibre area x percent) and maximal oxygen uptake (p = 0.006), and between type II fibres and quadriceps force (p = 0.035) were noted in GH-deficient adults before treatment. Following rhGH treatment, no change was noted in mean fibre areas, variability of fibre areas, or percentage of either fibre type.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗