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Biomedical subjects

R Gillett

Publications and source records attributed to R Gillett.

At least 19 recordsLinked to original sources
PubMed1996

Testing hypotheses about working memory capacity.

When an individual is engaged in sampling from a finite population, an assessment of their working memory for previously sampled objects is often desired. An extension of the classical occupancy distribution provides a framework for testing hypotheses about working memory capacity, based on a general model of working memory in which the individual retains a record of m previous inspections (and hence does not make the mistake of resampling these objects) and samples with replacement objects outside the current memory set. The buffer size m provides a common metric for assessing the effect of variables on performance in search tasks involving different numbers of items, or locations.

Animals↗
PubMed1994

Choice autonomy and memory for spatial locations in six-year-old children.

Six-year-old children were presented with 12 identically labelled locations in a room and required to search non-redundantly for the six that contained rewards. On each day they could commit Across-Trial Memory (ATM) errors by visiting non-rewarded locations, or Within-Trial Memory (WTM) errors by revisiting locations previously visited that day. Groups were trained for nine days, either walking or pushed in a wheelchair, and with or without freedom of choice. They were then tested, walking with freedom of choice. Performance of the task improved significantly across training days in groups allowed free choice, whether walking or transported, and was superior at test to that of non-choosing groups. Throughout training and testing, the ATM component of performance was superior in groups allowed free choice. WTM was more accurate than would be expected by chance in all subjects at all stages of the experiment, but did not differ between groups. The problem of comparing WTM scores in groups differing in ATM accuracy was discussed. It was concluded that the primary benefit of free choice in spatial memory tasks is that it promotes accurate environmental segmentation, and that WTM is little affected by training or environmental familiarity.

Child↗
PubMed1993

Prescriptions for medical research. I--Management within the Medical Research Council.

In their submission to the government in advance of the white paper on science policy in the United Kingdom the Medical Research Council commends the MRC's own approach to managing directly funded research. But a series of semi-structured interviews with the directors of some of the MRC's units suggests a gap between the MRC's model of managed research and the reality. Although such units are theoretically managed from MRC head office (and units are charged an overhead for this), in practice each unit runs its own affairs. Between major reviews average contact time with the head office contact person is seven hours a year. The first paper argues that a purchaser-provider split would recognise the benefits of decentralisation and allow units to bid for research funds from several sources, the successful ones guaranteeing their survival through a rolling series of research programmes. The second paper criticises the MRC's cumbersome peer review system. Reliance on outside experts atrophies the scientific skills of head office staff and builds delays into decision making. A purchaser-provider model would allow the head office scientific staff to act like commercial research and development managers, commissioning research, and using the outcome, rather than peer review, as a criterion for continued funding.

Academies and Institutes↗
PubMed1986

The nature of the inflammatory infiltrates in childhood gingivitis, juvenile periodontitis and adult periodontitis: immunocytochemical studies using a monoclonal antibody to HLADr.

Routinely fixed and processed gingival biopsies from childhood gingivitis, juvenile periodontitis and chronic adult periodontitis patients have been stained immunocytochemically with a monoclonal anti HLADr antibody to aid in the identification and quantification of cell types in the inflammatory infiltrates. Using immunoperoxidase staining and morphological criteria, 9 cell types were quantified in 30 patients. Lesions in the 3 groups were found to differ widely both in size and composition. In the small childhood gingivitis lesions, most cells were small lymphocytes, over half of which were HLADr positive, whereas in juvenile periodontitis biopsies, well over half the infiltrate was plasma cells. The chronic adult periodontitis samples showed greater variability in composition between these 2 extremes, perhaps reflecting differences in disease activity. These results suggest that, when disease is quiescent, the volume of inflamed gingival connective tissue is small and is dominated by B-small lymphocytes, whilst on activation, the lesion increases in size and much of the B-lymphocyte population is transformed to plasma cells. This view corroborates the results of other workers with regard to juvenile periodontitis, but suggests a different interpretation of the quiescent lesion of childhood gingivitis from that current in the literature.

Adult↗
PubMed1982

Bacterial invasion of the periodontium in a case of juvenile periodontitis.

A case of juvenile periodontitis is described where biopsy material taken from a lower right incisor during periodontal surgery revealed plaque-derived bacteria present within the periodontal connective tissue. The gingival connective tissue contained an inflammatory infiltrate which exhibited a profound loss of collagen and was dominated by plasma cells, many of which had a bizarre cytoplasmic morphology, The invading bacteria were morphologically heterogeneous but mainly gram-negative. Some were found in a patchy distribution in the apical margins of the inflammatory infiltrate and more numerous groups of organisms were in the collagenous connective tissue apical to the infiltrated area. Polymorphonuclear neutrophils (PMN) were seen in association with the bacteria and some PMN showed phagocytosis of bacteria without significant degranulation. This is the first description of bacterial penetration of the periodontium in juvenile periodontitis; it is not known how frequently this occurs but it is an interesting finding in a condition where there is known impairment of one branch of the host's defence mechanisms, namely pMN phagocytosis and degranulation.

Adult↗
PubMed1982

An ultrastructural and enzyme cytochemical study of the response of the neutrophil series to a local inflammatory stimulus in the rat.

Changes in neutrophil precursor populations in the bone marrow and their alkaline phosphatase reactivity following an inflammatory stimulus were studied in the rat using an osmiophilic method. Seven groups each of 3 Sprague-Dawley rats received subcutaneous injections of turpentine, and femoral marrow was examined at intervals up to 72 hr. Depletion of mature neutrophils resulted in an increased first in the myeloblast-promyelocyte compartment and at 48-72 hr in the myelocyte-metamyelocyte population. By 72 hr replenishment of the mature neutrophil marrow population had begun. Within 6 hr marked acceleration of cytoplasmic maturation was evident, together with accelerated synthetic activity, manifested by marked dilatation of the rough endoplasmic reticulum and an enlarged Golgi. Together with these changes there was an increase in the number of alkaline phosphatase reactive cells, which was evident first in the myeloblast-promyelocyte population at 2 hr. An absolute increase in the amount of enzyme reaction product associated with individual cells was also seen.

Alkaline Phosphatase↗
PubMed1981

Benign thyroid inclusions within cervical lymph nodes: an alarming incidental finding.

Small clusters of microscopically normal thyroid follicles within cervical lymph nodes are very occasionally encountered during histological examination. We support the view that provided the thyroid gland is not palpable and a technetium thyroid scan is normal, these should be regarded as benign thyroid inclusions and do not represent small metastatic lesions from thyroid carcinoma. We report an example of these inclusions in a cervical lymph node which was removed incidentally during the excision of a branchial cyst in a 25-year-old woman. The inclusion was too small to be noticed macroscopically and consisted of a small aggregation of histologically normal thyroid follicles situated in the subcapsular region of the lymph node.

Adult↗
PubMed1980

Scanning electron microscopic observations of the surface of the initial lesion in experimental streptococcal endocarditis in the rabbit.

The surfaces of vegetations in the first 24 h after initiation of experimental streptococcal endocarditis in rabbits were examined systematically using the scanning electron microscope (SEM). Most of the observed fields were occupied by amorphous material but with the SEM very small features of interest could be identified. Erythrocytes were more frequent before 6 h and leukocytes were rarely seen. Bacteria were significantly more frequent at 10/15 min and at 20 h. It is suggested that bacteria lodge on the vegetation surface following inoculation and that after a lag phase colonies are formed within the vegetation which reach the surface again at about 20 h.

Animals↗
PubMed1979

Light microscope and electron microscope alkaline phosphatase cytochemistry of rat bone marrow leukocytes.

An enzyme cytochemical method yielding an osmiophilic reaction product, visible at both the light and electron microscope levels, has been applied to the study of alkaline phosphatase in rat bone marrow cells. The enzyme is present in both eosinophils and, in much smaller amounts, in neutrophils. In both cases it is present on the plasma membrane, and in eosinophils intracellular aggregations of reaction product are also seen. The specific granules in both cell types fail to react and the enzyme is first detectable at the promyelocyte stage. Thus the enzyme is demonstrable before specific granule formation begins in the neutrophil, indicating that they are not a significant site of alkaline phosphatase activity in the rat.

Alkaline Phosphatase↗
PubMed1978

Differential leucocyte counts: a comparison of results using light and electron microscopy.

A method is described for handling leucocytes from an inflammatory peritoneal exudate prior to electron microscopy, which allows differential counts from ultra-thin sections to be made. The results of counts from ultrathin sections, viewed on the electron microscope, are compared with samples from the same cell populations prepared on a cytocentrifuge and counted by light microscopy. The results from several cell populations of widely different compositions show clearly that with suitable care taken over preparation and orientation, ultrathin sections can yield comparable differential counts to those obtained by standard light microscope procedures. Possible sources of error are discussed and the advantages of ultrastructural counting assessed. The method has a wide application wherever accurate differential counts are required from cell suspensions processed for electron microscopy.

Ascitic Fluid↗
PubMed1978

Ultrastructural localization of alkaline phosphatase in rat eosinophil leucocytes.

The ultrastructural localization of alkaline phosphatase in eosinophil leucocytes, obtained from experimentally-induced peritoneal exudates in rats, has been studied using an osmiophilic technique with 2-naphthylthiolphosphoryl dichloride as substrate, fast Blue BBN as diazonium salt and postosmication with 1% aqueous osmium tetroxide. With this method identical incubation procedures could be used for both light and electron microscope examination. Eosinophils were the only cells which contained alkaline phosphatase. The enzyme was predominantly associated with the outer surface of the plasma membrane, being present in much lower concentrations in cytoplasmic cisternae. Eosinophil granules only rarely showed reaction product. The plasma membrane location of alkaline phosphatase in eosinophil leucocytes is identical to that recently demonstrated in the human neutrophil.

Alkaline Phosphatase↗