The relationship between quality of life and disability across the lifespan for people with spinal cord injury.

STUDY DESIGN: Prospective cross-sectional survey. OBJECTIVES: To compare quality of life (QOL) for people with spinal cord injury (SCI) and their able-bodied peers and to investigate the relationship between QOL and disability (impairments, activity limitations and participation restrictions) across the lifespan, for people with SCI. SETTING: A community outreach service for people with SCI in Queensland, Australia. METHODS: A random sample of 270 individuals who sustained SCI during the past 60 years was surveyed using a guided telephone interview format. The sample was drawn from the archival records of a statewide rehabilitation service. QOL was measured using the World Health Organization Quality of Life Assessment Instrument-Bref, impairment was measured according to the American Spinal Injury Association classification and the Secondary Condition Surveillance Instrument, activity limitations using the motor subscale of the Functional Independence Measure and participation restrictions using the Community Integration Measure. Lifespan was considered in terms of age and time since injury. Correlation and regression analyses were employed to determine the relationship between QOL and components of disability across the lifespan. RESULTS: QOL was significantly poorer for people with SCI compared to the Australian norm. It was found to be associated with secondary impairments, activity limitations and participation restrictions but not with neurological level, age or time since injury. The single most important predictor of QOL was secondary impairments whereas the second most important predictor was participation. CONCLUSION: To optimize QOL across the lifespan, rehabilitation services must maintain their focus on functional attainment and minimizing secondary conditions, although at the same time enabling participation.

Immuno-characterisation of neuroendocrine cells of the rat thymus gland in vitro and in vivo.

Primary cell cultures and organ fragments of rat thymus were characterised by use of a panel of antibodies raised against the neural adhesion molecule L1, tyrosine hydroxylase, protein gene product 9.5, nerve growth factor, calcitonin gene-related peptide, glial fibrillary acidic protein, vimentin, pan-cytokeratin, a ganglioside of neural crest and neuroendocrine cells (A2B5), and thymulin (4 beta). Immunoreactivity for neural markers only was identified in a single morphology (nerve-like) of cell in culture and throughout the adult thymus as fine, tortuous staining. Immunoreactivity for endocrine markers only was identified in polygonal epithelial-like cells in culture, throughout viable tissue in fragment culture and in the subcapsular cortex of the adult thymus. Immunoreactivity for both endocrine and neural markers was identified in three distinct morphologies in cell culture: elongate, spherical, and stellate. Similar results were observed in the mitotic periphery of the cultured fragments and in the medulla and cortico-medullary junction of the adult thymus. Cells with immunoreactivity to A2B5 were present in primary and fragment cultures and occurred throughout the adult thymus. The apparent diversity of cell immunoreactivity in primary and fragment thymic cultures suggests that numerous neural and endocrine factors may be required for the development and/or regeneration of the thymic microenvironment.

The thymus in the mouse changes its activity during pregnancy: a study of the microenvironment.

The mouse thymus changes dramatically during pregnancy. It shrinks in size, and the cortex is extensively reduced from midpregnancy onwards. Despite this, there is surprisingly little evidence for any increase in apoptosis, and considerable evidence that mitosis of thymocytes continues throughout pregnancy. In spite of overall involution the thymic medulla actually expands in midpregnancy due to a combination of mitosis of epithelial cells and an accumulation of lymphocytes. The extent and nature of these changes are examined in this study at the ultrastructural level. The epithelial cells of the subcapsular cortex (type 1 cells) become wrinkled and exhibit powers of phagocytosis, whilst the other cortical epithelial cells are relatively unchanged, although the formation of epithelial/thymocyte rosettes and thymic nurse cells is more clearly seen in midpregnancy than usual. Other changes associated with pregnancy involve the medullary epithelial cells that undergo an increased level of mitosis. Their greater numbers surround accumulations of lymphocytes to form the characteristic medullary epithelial rings. Cell movement through blood vessel walls was clearly observed in midpregnancy, but not at other times. Interdigitating cells in the medulla become more conspicuous as pregnancy proceeds and the cells become phagocytic. The endoplasmic reticulum in plasma cells becomes expanded, indicating increased secretory activity. These results highlight the active nature of the thymus in pregnancy in spite of its involution. This picture contradicts the conventional notion that an involuted thymus is inactive.

The brain and thymus have much in common: a functional analysis of their microenvironments.

Research into the neural and immune systems has begun to converge. Since the first reports that interleukins play important roles in both systems and that lymphocytes secrete neuronal factors, scientists have been surprised by the ever-increasing list of interactions. Here, Rolf Mentlein and Marion Kendall examine the major supporting cells of the brain and thymus - astrocytes and thymic epithelial cells - the similar neuroectodermal origin of which could explain such fundamental analogies.

Immunohistochemical and ultrastructural evidence for myelopoiesis in the scid/scid mouse thymus.

The ultrastructure of scid mouse thymus (a small encapsulated epithelial mass within the precardial fat pad) is described. The epithelium did not form cortex or medulla and hence remained relatively undifferentiated. Small unmyelinated nerves innervated the capsule, the major blood vessels and were distributed between the epithelial cells. Fenestrated blood vessels were common. Thymocytes were not identified but numerous granulocytes, mast cells and some fibroblasts, macrophages and interdigitating cells were present. All stages of granulopoiesis were observed in scid thymus. A very small number of immunoreactive ER-MP58 cells indicated bone marrow derived myeloid precursor cells, and low numbers of ER-MP12+ and ER-MP20+ mononuclear cells indicated stages of myeloid cells committed to the granulocyte/macrophage lineage. Cells containing proliferating nuclear cell antigen (cells in G1, S and G2-M stage) were present throughout the thymic mass. BALB/c thymuses contained cortical foci of p53+ cells whereas in scid mice, p53 positive cells were scattered singly throughout the thymus. This study indicates that the presence of moderately extensive myelopoiesis within the scid mouse thymus has potential for the study of extramedullary haematopoiesis, and also that it is important to bear this function in mind when using the scid mouse as an immunological model for thymus reconstitution and for creating 'organoid' cultures.

Dietary minerals in the gastrointestinal tract: hydroxypolymerisation of aluminium is regulated by luminal mucins.

The regulation of mineral absorption in the gastrointestinal tract is poorly understood. Recent work has identified an intracellular metal-ion transporter but considerable evidence suggests that both soluble and mucosally associated luminal metal-binding ligands regulate initial uptake. Molecules ranging from low molecular weight organic acids to large glycoproteins have been suggested but a definite role for any such species has remained elusive. Here, a series of analytical techniques, allowing for this wide variation in potential binding ligands, was applied to the study of intestinal contents and tissue of rats following different feeding protocols. Aluminium, that has a low endogenous background and maintains a high concentration in the gastrointestinal tract, was investigated as a suitable dietary metal with hydrolytic behaviour similar, for example, to copper, iron and zinc. High resolution nuclear magnetic resonance spectroscopy identified a number of endogenous low molecular weight weak ligands that are secreted into the intestinal lumen. These may slow the rate of hydroxy-polymerisation of hydrolytic metals, allowing their effective donation to less mobile, higher molecular weight binding ligands. Histochemical staining suggested that such species may be soluble mucins as these were consistently associated with luminal aluminium. Significantly, this interaction prevented hydroxy/phosphate precipitation of aluminium, even at supraphysiological levels of the element. This was confirmed with X-ray micro-analysis investigations of ex vivo luminal contents. Nevertheless, from phase distribution experiments, the majority (60-95%) of luminal aluminium was associated with the intestinal solid phase and further histochemistry confirmed this to be gelatinous mucus, chiefly as the mucosally adherent layer. All results suggest a major role for mucus in regulating the gastrointestinal absorption of aluminium. It is proposed that, initially, soluble luminal mucus prevents the hydroxy-precipitation of hydrolytic metals at intestinal pH, allowing their effective donation to the mucus layer. Based on the differing reported metal-mucus interactions, elements that bind well to mucus (Al3+, Fe3+), with kinetically slow rates of ligand exchange (Al3+ < Fe3+) will be less well absorbed than poorly bound elements with kinetically faster rates of ligand exchange (Cu2+, Zn2+ etc.). This mechanism would readily explain many of the reported observations on mineral availability, including the marked variation in absorption of different elements, the differential effects of dietary ligands on mineral uptake and the competition for absorption between different metals.

Expression of parathyroid hormone-related protein and the parathyroid hormone/parathyroid hormone-related protein receptor in rat thymic epithelial cells.

Thymic epithelial cells are an important source of cytokines and other regulatory peptides which guide thymocyte proliferation and maturation. Parathyroid hormone-related protein (PTHrP), a cytokine-like peptide, has been reported to affect the proliferation of lymphocytes in vitro. The studies presented here were undertaken to test the hypotheses that PTHrP is produced locally within the thymus where it could influence thymocyte maturation and, more specifically, that thymic epithelial cells (TEC) could be the intrathymic source of PTHrP expression. To this end, immunohistochemical studies were performed to localise PTHrP and the PTH/PTHrP receptor within the adult rat thymus. Antibodies directed against 2 different PTHrP epitopes, PTHrP(1-34) and PTHrP(34-53), demonstrated prominent specific PTHrP immunoreactivity in both subcapsular and medullary TEC. In addition, faint but specific staining for PTHrP was seen in the cortex, interdigitating between cortical lymphocytes while sparing epithelial-free subcapsular areas, thus suggesting that cortical TEC could also be a source of PTHrP immunoreactivity. In contrast, PTH/PTHrP receptor immunoreactivity was only seen in medullary and occasional septal TEC; no evidence of cortical or lymphocytic PTH/PTHrP receptor immunoreactivity was detected. Immunohistochemical studies of cultured cytokeratin-positive rat TEC confirmed the results of these in situ studies as cultured TEC were immunoreactive both for PTHrP and the PTH/PTHrP receptor. Thus these results demonstrate that PTHrP is produced by the epithelial cells of the mature rat thymus. This suggests that PTHrP, a peptide with known cytokine, growth factor and neuroendocrine actions, could exert important intrathymic effects mediated by direct interactions with TEC, or indirect effects on PTH/PTHrP receptor-negative thymocytes.

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.

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.

Immunoreactivity of neural crest-derived cells in thymic tissue developing under the rat kidney capsule.

In order to study the functional development of a thymus in an experimental model, small pieces of adult rat thymic tissue were cultured for 9 days and implanted under the kidney capsule of littermates. The tissues were examined with a panel of antibodies raised against thymic and neural factors and neural crest cells at intervals from 5 to 13 days. At 5 days post-implantation, there were groups of L1+ cells within the implants that reacted with antibodies raised against neural and neural crest cell markers. L1+ cells were highly mitotic, rounded cells measuring 8.7 +/- 0.6 micrometer in diameter. Double immunostaining with different combinations of antibodies showed that 94% of the L1+ cells were also TH+, and many were HNK-1/NCAM+, PGP 9.5+, NGF+, chromogranin A+, VIP+, S100+, CGRP+, GAD+, and A2B5+. A few were also pan-cytokeratin+. These results indicate that these cells are derived from neural crest derived cells and belong to the neuroepithelial line of development. The L1+ cells were most numerous before nerves appeared (about Day 9) and reduced in number and extent as the thymus differentiated. The neural crest cells occasionally had long cytoplasmic extensions, but it was not possible to decide if they formed the nerves that appeared in the implants. Adult thymuses also contained a population of L1+ and HNK-1/NCAM+ cells, mainly in the subcapsular cortex, the septa, and the medulla. These cells could be a source of neural crest cells able to repopulate the implant. The adult thymus may always contain a reservoir of cells potentially capable of producing neuropeptides and transmitter factors required for thymic growth and regeneration.

Neuropeptides exert direct effects on rat thymic epithelial cells in culture.

To determine if major thymic neuropeptides and neurotransmitters can directly influence the functional activity of cultured rat thymic epithelium, neuropeptides and neurotransmitters were applied, and intercellular communication, proliferation, and thymulin secretion assessed. After injections of a mixture of lucifer yellow dextran (too large to pass gap junctions) and cascade blue (which does) into single cells, some neuropeptides decrease dye coupling: 0.1 mM GABA (P < 0.0001), 100 nM NPY (P < 0.0001), 100 nM VIP (P < 0.001), 100 nM CGRP (P < 0.001), 100 nM SP (P < 0.01), and 0.1 mM histamine (P < 0.01), whereas 0.1 mM 5-HT, 1 mM acetylcholine, and 1 microM isoproterenol (beta-adrenergic agonist) had no effect. Proliferation (incorporation of tritiated thymidine) was increased by CGRP (P = 0.004) and histamine (P < 0.02), but decreased by isoproterenol (P = 0.002), 5-HT (P = 0.003), and acetylcholine (P < 0.05). The percentage of multinucleate cells was decreased after isoproterenol (2.5%), and increased after 5-HT (21.3%), GABA (15%), and histamine (15.1%). Compared to controls, thymulin in the supernatant was decreased after challenge with acetylcholine (52%), isoproterenol (71%), 5-HT (73%), and histamine (84%). This study demonstrates direct effects of neuropeptides and neurotransmitters on functional aspects of cultured thymic epithelial cells.

Thymic microenvironment at the light microscopic level.

The thymus is a primary lymphoid organ that serves the immune system by providing an optimal microenvironment for developing T cells to rearrange the genes encoding the T-cell receptor and to undergo positive and negative selection in shaping the peripheral T-cell repertoire. The microenvironment of the organ is peculiar among lymphoid organs, as the supporting stroma consists of reticular epithelial cells. Bone marrow-derived interdigitating cells and macrophages are the main accessory cell populations. The epithelium, interdigitating cells, and macrophages each contribute to the T-cell selection process. During the last decade knowledge has been gathered that these cell populations show a considerable heterogeneity, as documented for subcellular features and immunologic phenotype. This heterogeneity may reflect various stages in differentiation, but may otherwise be linked to the functional activity of the cells. The authors survey the major cell populations, i.e., epithelial cells and lymphocytes. Macrophages and interdigitating cells are briefly discussed. Emphasis is given to functional aspects of histologic/ cytologic features.

Immuno-electron microscopy of the thymic epithelial microenvironment.

Normal T cell development depends upon interactions between progenitor cells and the thymic microenvironment. Monoclonal antibodies (Mabs) have been used to define subtypes of thymic epithelium by light microscopy (clusters of thymic epithelial staining [CTES]). We have now used a range of these Mabs together with gold-coupled reagents in immuno-electron microscopy to study the fine cellular distribution of the molecules to which the antibodies bind. Anti-cytokeratin antibodies were used to identify all thymic epithelial cells, while the distribution of MHC class II molecules was revealed with Mabs to shared nonpolymorphic determinants. MR6, a CTES III Mab, shows strong surface labelling of cortical epithelial cells and thymic nurse cells and very weak surface staining of thymocytes, medullary macrophages, and interdigitating cells. Mab 8.18 (CTES V) also labels a cell surface molecule; this is present on Hassall's corpuscles and associated medullary epithelial cells. The molecules detected by Mabs MR6 and 8.18 are therefore located in a position where they are available to interact with external cellular and soluble signals within the thymus. In contrast, Mabs MR10 and MR19 (CTES II) recognise intracellular molecules within subcapsular, perivascular, and medullary epithelium. A similar distribution was seen with Mab 4beta, directed against the thymic hormone thymulin, although, in addition to the expected intracellular epithelial staining, large lymphoblasts in the subcapsular zone showed surface positivity, indicating the presence of thymulin bound to surface receptors on these early lymphoid cells. As expected, MHC class II molecules were expressed on some medullary and essentially all cortical epithelial cells. However, although most subcapsular epithelium was class II-negative, some cells did express these MHC molecules on their apical surface and on the surface of their cytoplasmic extensions into the cortex. Interestingly, some cortical epithelial cells surrounding capillaries were positive for both MR6 (CTES III) and for MR10, MR19, and 4beta (CTES II). Double-labelling experiments, using MR6 and MR19 simultaneously, revealed a double-positive perivascular epithelial cell population in the thymic cortex. The possibility that these cells represent a thymic epithelial progenitor population is discussed.

Modulation of dye-coupling and proliferation in cultured rat thymic epithelium by factors involved in thymulin secretion.

Cultures of rat thymic epithelium were used to measure the effect of thymulin secretagogues on dye-coupling and proliferation. Dye-coupling was assessed after the injection of lucifer yellow dextran which cannot permeate the connexin pore of gap junctions and the smaller, permeant cascade blue. In addition to gap junctional communication, larger intercellular bridges were demonstrated by the transfer of lucifer yellow dextran between cells. The extent of intercellular communication was found to be influenced by both cell density and the number of passages. In control cultures, intercellular communication was reduced in cell groups of low (< 20 cells/group) or high cell densities (> 100 cells/group) compared with groups of 20-60 cells. The highest coupling indices were found in subcultures 20-30. Taking these factors into account, significant decreases in coupling index were observed after pretreatment of test cultures with factors known to influence the secretion of thymulin (5 U/ml interleukin 1 (alpha and beta), 1 microM progesterone, 1 microM oestrogen, 1 microM testosterone, 1 ng/ml adrenocorticotropic hormone, 100 nM rat growth hormone) but 7.5 ng/ml thymulin had no effect on dye-coupling. The nonspecific gap junction uncoupler, octanol, abolished dye-coupling. Cellular proliferation, as measured by the uptake of tritiated thymidine, showed that the same factors that reduced coupling also increased proliferation. None of these factors affected the number of multinucleate cells present, except interleukin-1beta which caused a significant reduction in the average number of nuclei per cell. Thus rat thymic epithelium in vitro provides a model for the study of the direct action of factors on cells of the thymic microenvironment.

Studies on rat and human thymus to demonstrate immunoreactivity of calcitonin gene-related peptide, tyrosine hydroxylase and neuropeptide Y.

The peptidergic and noradrenergic innervation of rat and human thymus was investigated by immunohistochemistry at the light and electron microscopical level (avidin-biotin-complex, sucrose-phosphate-glyoxylic-acid, and immunogold techniques). The distribution of noradrenergic neural profiles, and positive immunoreactivity for calcitonin gene-related peptide (CGRP), tyrosine hydroxylase (TH) and neuropeptide Y (NPY) is described in female rats during ageing, and in human children. In the neonatal rat thymus, the arteries and septa are well supplied by fine varicose nerves. In older animals (2 wk-1 y) the number of septa and blood vessels increase and consequently also the innervation. No nerves were found in the cortex. Apart from the innervation of the septal areas, immunoreactivity for CGRP and TH was present in thymic cells. Except for the young rats (neonatal-14 d), all rats showed CGRP positivity in subcapsular/perivascular epithelial cells (type 1 cells). All rat thymuses also contained a few TH positive cells in the medulla, which could only be confirmed as epithelial cells (type 6 cells) in children. Type 1 cells in the human thymus were not CGRP positive, but as in the rat, there were similar TH positive cells in the medulla. It was concluded that in addition to nerves containing CGRP, noradrenaline or dopamine, epithelial cells also contain these transmitters. They could therefore act on different cells (compared with neural targets) in a paracrine manner.

Characterisation of inorganic microparticles in pigment cells of human gut associated lymphoid tissue.

Macrophages at the base of human gut associated lymphoid tissue (GALT), become loaded early in life with dark granular pigment that is rich in aluminium, silicon, and titanium. The molecular characteristics, intracellular distribution, and source of this pigment is described. Laser scanning and electron microscopy showed that pigmented macrophages were often closely related to collagen fibres and plasma cells in GALT of both small and large intestine and contained numerous phagolysosomes, previously described as granules, that are rich in electron dense submicron sized particles. Morphological assessment, x ray microanalysis, and image electron energy loss spectroscopy showed three distinct types of microparticle: type I - spheres of titanium dioxide, 100-200 nm diameter, characterised as the synthetic food-additive polymorph anatase; type II - aluminosilicates, < 100-400 nm in length, generally of flaky appearance, often with adsorbed surface iron, and mostly characteristic of the natural clay mineral kaolinite; and type III - mixed environmental silicates without aluminium, 100-700 nm in length and of variable morphology. Thus, this cellular pigment that is partly derived from food additives and partly from the environment is composed of inert inorganic microparticles and loaded into phagolysosomes of macrophages within the GALT of all human subjects. These observations suggest that the pathogenicity of this pigment should be further investigated since, in susceptible individuals, the same intracellular distribution of these three types of submicron particle causes chronic latent granulomatous inflammation.

Assessment of toxic metal exposure following the Camelford water pollution incident: evidence of acute mobilization of lead into drinking water.

Following the incident of acidic pollution of water by aluminium sulfate centred around Camelford in July 1988, we have carried out a retrospective analysis of the mobilization of toxic metals to residents of the area. An advanced nuclear technique was used to measure trace levels of elements within hair, thus, avoiding surface contamination. In contrast to controls, lead, but no other toxic metals, was consistently found within sections of hair that dated to mid-1988 from four residents; they must, therefore, have consumed this metal around the time of the incident. The source of this lead was probably local water pipe residue, and this was found on analysis to have a matrix specific to such soft-water areas that, prior to the incident, had slowly accumulated certain toxic metals such as cadmium and uranium and particularly lead. Lead is mobilized from such residues by acidic water and could, therefore, have heavily contaminated mains water after the incident. However, analyses of residents' plasma and whole blood, and of urine following a lead-chelation test, showed no evidence of either long-term increased body burdens of toxic metals or depletion of essential elements. In addition, we found no evidence of continued poor water quality in the area. In conclusion, during a short period following the pollution, some residents who consumed mains water would have been acutely exposed to lead and other toxic metals. Prediction of the scale of metal exposure to individuals was not possible owing to heterogeneity of the water distribution network, but long-term effects to residents from lead are not anticipated.(ABSTRACT TRUNCATED AT 250 WORDS)

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.