Biomedical subjects

M D Kendall

Publications and source records attributed to M D Kendall.

10 recordsLinked to original sources

PubMed1992

The thymus: new views of an old gland.

The existence of the thymus was recognised by ancient scientists and doctors, although its vital role in the development and maintenance of the competent T cell repertoire has been fully appreciated only comparatively recently. Current research is now moving on to explore the role of the thymus in interactions between the brain, the nervous system and the immune response. This is an exciting new field which should lead to advances in the management, treatment and prognosis of disease in man and animals.

Receptors, Antigen, T-Cell↗

PubMed1992

Thymulin and its role in immunomodulation.

Even though thymulin was isolated, sequenced and characterised some 20 years ago and later identified as a thymic hormone involved in immunomodulation, much more work is still required to further understanding of the mechanisms of action(s) of this peptide. Since the observation, by a semiquantitative bioassay, of diminished levels of thymulin in immunodeficiency and autoimmune disease, new data obtained by radioimmunoassay have not only confirmed previous observations but also demonstrated that thymulin plays a role in the interaction between the immune system and the neuro-endocrine system. In this paper we give an up to date account of recent developments in research into the role of thymulin in immunomodulation.

Amino Acid Sequence↗

PubMed1979

Ultrastructural studies on erythropoiesis in the avian thymus. I. Description of cell types.

Thymus lobes from three species of birds, Quelea quelea, Passer domesticus and Sturnus vulgaris, have been examined ultrastructurally. The component cell types are compared with their counterparts in mammalian thymus glands, and found to be similar. Greater differences between small, intermediate and enlarged lobes of one species than exist between species. Developing erythroid cells are present in most enlarging and some enlarged glands. They appear to be developing at the expense of lymphoid cells in some birds. The origin of these cells is discussed. Cells that are possible candidates for the production of some thymic hormones are also described.

Animals↗

PubMed1979

Ultrastructural studies on erythropoiesis in the avian thymus. II. A stereological analysis of the lymphoid and erythroid cells.

The cortex of enlarging thymic lobes from adult haemorrhaged Quelea quelea were found to be similar to those of wild birds where the thymic enlargement was occurring naturally. A detailed stereological analysis of cells broadly designated as lymphoid, and the construction of models to account for the results, indicates that the enlarging thymic lobe contains both large and small blast cells, a heterogenous group of medium lymphocytes, erythroid cells, and two types of very small lymphocytes. The distinction between early erythroid cells and some lymphocytes, despite this detailed analysis is very difficult, but it is possible in enlarging thymic lobes that up to 42% of the lymphoid cells may have erythroid characteristics.

Animals↗

PubMed1978

The effect of haemorrhage on the cell populations of the thymus and bone marrow in wild starlings (Sturnus vulgaris).

Following the withdrawal of blood from the brachial vein of adult wild starlings (Sturnus vulgaris) changes in the cell populations within the bone marrow and thymus were observed over an eight day period. The packed cell volume, haemoglobin content and reticulocyte count of the peripheral blood was determined before and after haemorrhage. The maximum effect of the haemorrhage was observed in the bone marrow after four days when the population of small lymphocytes, and basophilic erythroid precursors were reduced to less than 1%. At the same time the percentage of another line of erythroid cells increased to 68%. This second erythroid lineage was the major erythroid line in the thymus, and again maximum representation occurred at 4 days post haemorrhage. After this the thymus became predominantly lymphoid and started to increase in size. The two erythroid lines are described and their status with regard to avian thrombocytes is also discussed. The peripheral blood had not attained the pre-haemorrhagic values for reticulocyte counts by eight days although the packed cell volumes and haemoglobin contents were similar.

Animals↗

PubMed1977

Effects of anti-inflammatory drugs on serum chemistry.

1. Biochemical abnormalities are frequently observed when the sera of rheumatoid patients are analyzed. 2. The serum cholesterol, bilirubin, glucose and proteins are significantly related to the activity of the disease. 3. The possible effects of drug therapy are discussed and described. It seems that the way in which drugs modify a patient's serum chemistry may be used to assess the efficacy with which they control the inflammatory process.

Anti-Inflammatory Agents↗

PubMed1975

Morphological changes in the thymus of young and adult red-billed queleas Quelea quelea (aves).

In a wild population of red-billed queleas Quelea quelea L. (Ploceidae: weaver-birds) sampled throughout the year in East Africa, the thymus was found to enlarge in young birds shortly after hatching, remain enlarged during the juvenile stage, and regress towards the end of the postjuvenile moult. In adults, recrudescence occurred in many individuals during the prenuptial and postnuptial moults, and also in most if not all individuals, of both sexes, for a brief period during a breeding session. Thymus enlargement in both young and adults has been found to be accompanied by marked erythropoietic activity within the gland, and it is suggested that this activity is related to an increased demand for erythrocytes which may occur during moult and breeding.

Age Factors↗

PubMed1975

Histological changes associated with enlargement and regression of the thymus glands of the red-billed quelea Quelea quelea L. (Ploceidae: weaver-birds).

Thymic lobes form over 200 red-billed queleas, Quelea quelea L., were examined histologically. Samples were taken from embryos about to hatch, juveniles and adults. The lobes varied in size from very small to very enlarged (1- greater than 5 mm long). The constituent cell types are described in detail and the occurrence of these cells in different sized lobes is discussed. A cycle of events is proposed which accounts for the observations presented here. It is suggested that the large numbers of erythroid cells found in the cortex of some individuals were developing in situ. The significance of erythropoiesis within the thymus is discussed.

Age Factors↗

PubMed1975

EMMA-4 analysis of iron in cells of the thymic cortex of a weaver-bird (Quelea quelea).

Combined morphological and analytical studies with the EMMA-4 analytical electron microscope have enabled very early erythroid cells to be identified within the cortex of enlarging thymic lobes of Quelea quelea. These early erythroid cells have pale cytoplasm (sometimes with ferritin-like crystals present), slightly pachychromatic nuclei and have fewer cell organelles (mitochondria) than lymphocytes. Counts for iron were approximately 70% lower than counts from mature erythrocytes found free in the cortex. Iron was also recorded from some epithelial reticular cells and pyknotic nuclei; no iron was recorded from small lymphocytes (thymocytes) in the cortex. The presence of very early erythroid cells is a further indication that erythropoiesis occurs in situ in the avian thymus.

Animals↗

PubMed1975

Sizes and numbers of nuclei in the cortex of thymus glands of red-billed weavers Quelea quelea.

The cortex of the thymus glands of embryos, chicks, juveniles, fledglings and adults from several colonies of Quelea quelea were studied using an image analyser (Quantimet 720) to determine cell populations and nuclear sizes. Just prior to hatching the lobes showed a high level of mitosis and consisted of predominantly small lymphocytes. The larger glands of chicks and juveniles had higher cell populations; pyknotic cells and erythrocytes occurred free in the cortex. The lobes of adults were more variable but in general mitosis occurred in enlarging glands of adults from colonies with eggs; most lobes contained pyknotic cells but not in such high numbers as in lobes from chicks and fledglings. Erythrocytes were common, occurring in large numbers in the cortex in some birds. The factors affecting the interpretation of these data are discussed in detail.

Age Factors↗