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Biomedical subjects

M D Kendall

Publications and source records attributed to M D Kendall.

85 records · Page 5Linked to original sources
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↗
PubMedDate not supplied

Improved transport incubator temperature control with insulating thermal cover.

INTRODUCTION: Cold stress, secondary to heat loss, can compromise infants in transport incubators during interfacility transfer. With current incubator designs, considerable radiant heat loss occurs. The use of additional external thermal insulation to reduce heat loss has been recommended for infant transports in cold environments. METHOD: A laboratory experiment was done to compare the rate of heat loss from a transport incubator with and without a commercially available, thermal insulating cover in place. The environment was a commercial freezer simulating subzero environmental temperatures. Measurements included air temperatures. inside the incubator and freezer, patterns of heater action and duration of battery power output. The significance of the different rates of cooling was compared using Pearson's r. Suboptimal battery performance was excluded by repeating one arm of the study with an external battery in place of the internal unit. RESULTS: The rate of heat loss from the incubator was: 1) significantly slower when the covered and uncovered incubators were compared (r2 = 0.52), and 2) essentially identical for the uncovered incubator with either the internal or the external battery (r2 = 0.96). CONCLUSION: In the laboratory setting, external thermal insulation slows transport incubator radiant heat loss. Clinically, this effect likely would benefit infants at risk of cold stress during interfacility transports.

British Columbia↗
PubMedDate not supplied

Cadmium and mercury nephrotoxicity.

Despite increasing attempts to control environmental pollution, changes in the distribution and bioavailability of toxic metals like mercury and cadmium are still occurring. Apart from natural processes, other contributory factors include the gradual spread of industrialization, the use of sewage sludge as a fertilizer and the acidification of Northern Hemisphere groundwater. Animals (including man and domestic varieties) can accumulate harmful concentrations of toxic metals. We therefore looked for damage to the kidneys in seabirds contaminated with mercury and cadmium and made comparisons with kidneys from three other groups of animals: seabirds from an uncontaminated colony, metal-dosed birds and metal-dosed mice. We report here that, comparing all these groups of animals, individuals with comparatively high levels of metals had nephrotoxic lesions of a similar type and severity. Moreover, the metal concentrations at which damage began and at which biochemical changes could be detected were below those presently considered as relatively safe for humans by the World Health Organization.

Animals↗
PubMedDate not supplied

Use of cultured thymic tissues for the regeneration of the thymus.

An account of research conducted on the transplantation of thymic cells and tissues in order to restore the functional activity of the thymus is reviewed, and discussed in the context of current concepts. Although most rodent work has been conducted on the transplantation of cultured fragments under the kidney capsule, human transplantation studies and models have used other sites or other species such as the severe combined immunodeficient mouse as hosts. The factors affecting the growth of thymic cells in culture is considered in detail since the methodology can strongly influence the cells favoured under culture conditions. An extension of this work to characterize both thymic fragments implanted under the kidney capsule of rats and cultured thymic cells has recently led to the appreciation that the adult thymus must contain a small number of neural crest-like cells. These cells have a high level of proliferation in the implanted fragments, expand in culture, and belong to a family of cytokeratin-positive cells exhibiting immunoreactivity for a wide range of neuropeptides and transmitters. Thus primary cultures of thymus can contain a wide range of glia-like cells. This can be explained by the fact that the thymus, in addition to having a mesenchymal neural crest component, is probably derived from cardiac neural crest. Closely associated neural crest also has glia-like properties (the supporting cells of the enteric nervous system). These finding can account for the large number of reports of epithelial cells of the adult thymus being immunoreactive to antibodies raised to neuroendocrine and neurotransmitters. Neuroimmune interactions in the thymus are more fundamental than previous work had suggested.

Animals↗
PubMedDate not supplied

Rapid progesterone actions on thymulin-secreting epithelial cells cultured from rat thymus.

Many soluble factors of neural, endocrine, paracrine and autocrine origin are present in the thymus and modulate its function. Long-term effects of sex steroids have been documented for thymocytes and cells of the thymic microenvironment. In this report we examine rapid actions of progesterone upon aspects of epithelial cell physiology. Progesterone (0.1-10 microM) was applied to cultured thymulin-secreting thymic epithelial cells (TS-TEC) and changes in transmembrane potential, transmembrane current, intracellular calcium levels and thymulin secretion were assessed. Rapid changes in electrophysiology and intracellular calcium provide evidence for a membrane-bound progesterone receptor in these cells, in addition to classical cytoplasmic receptors. Application of progesterone to TS-TEC caused electrophysiological changes in 56% of cells (n = 40), activating an inward current (-24 +/- 9 pA at 1 microM, n = 7, p < 0.02) and dose-dependent depolarization (7.1 +/- 1.8 mV at 1 microM, n = 19, p < 0.01). Intracellular calcium levels, monitored by the ratiometric fluorescent calcium indicator fura-2, increased within seconds of progesterone (1 microM) application. Progesterone (1 microM) increased thymulin levels in supernatant, as measured by ELISA, above the levels in the preapplication period (142 +/- 16% of the preapplication period, n = 3, p < 0.02). This effect was reduced in the presence of cobalt chloride which blocks voltage-dependent calcium channels. In addition, TS-TEC in culture were immunoreactive to antibody AG7. This antibody was raised to a membrane-bound antigen involved in calcium influx subsequent to progesterone binding in sperm. Thus we suggest that progesterone acts upon many aspects of TS-TEC physiology through both cytoplasmic and membrane-bound receptors.

Animals↗
PubMedDate not supplied

The release of luteinizing hormone from pituitaries perifused with thymic extracts.

Medium obtained by the perifusion of fragments of adult male CSE rat thymuses stimulates the release of luteinizing hormone (LH) from the anterior pituitary gland in vitro. The release of the stimulatory factor/s from the thymus appears to be stimulated by the depolarizing concentration of K+ and to be Ca++-dependent. Perifusates from heart, liver and spleen did not elicit the response suggesting that the effect is specific to the thymus gland. Neither LH nor its releasing hormone, LHRH, were detectable in the thymus perifusates by RIA. Levels of facteur thymique serique (FTS), as measured by bioassay are highest in K+ stimulated fractions that exhibit the greatest LH releasing activity. In separate experiments in vitro FTS, but not two other thymic peptides, thymopoietin and thymosin alpha 1, caused a dose-related release of LH from pituitary tissue. That ability of thymic perifusates to cause the release of LH was age-related because tissue from neonatal and ageing males failed to release compounds with any significant effect on the pituitary release of LH. However, when the thymus was enlarged in ageing rats as a result of orchidectomy 1 month before sacrifice LH release was similar to that observed in young male adults.

Aging↗