Immune senescence: significance of the stromal microenvironment

The immune system undergoes age-associated changes known as immunosenescence, resulting in increased susceptibility to infections, cancers and autoimmunity in the aged. The basis of our understanding of immunosenescence has been derived primarily from studies examining intrinsic defects within many of the cells of the immune system. While these studies have provided insight into the mechanisms of immunosenescence, a picture is now emerging that the stromal microenvironment within lymphoid organs also contributes significantly to the age-associated decline of immune function. These extrinsic defects appear to impact the functional activity of immune cells and may offer a potential target to recover immune activity. Indeed, rejuvenation studies which have targeted the stromal niche have restored immune function in aged successfully, highlighting the impact of the microenvironment towards the aetiology of immunosenescence.

Effect of diet on serum 25-hydroxyvitamin D concentration in the short-beaked echidna (Tachyglossus aculeatus)

BACKGROUND

Elevated concentrations of 25-hydroxyvitamin D (25(OH)-D) were diagnosed in captive short-beaked echidnas (Tachyglossus aculeatus) from three different zoological facilities within Australia.

RESULTS

The mean serum 25(OH)-D concentration in the wild echidnas was 24.7 nmol/L and was significantly higher in captive echidnas from all three facilities: Facility 1, mean 335.5 nmol/L (P < 0.001); Facility 2, mean 187.2 nmol/L (P = 0.003); Facility 3, mean 194 nmol/L (P = 0.005). Animals did not appear to have clinical manifestations of vitamin D toxicosis. The increased serum 25(OH)-D concentration was attributed to excessive dietary intake and a reduction in the amount of vitamin D(3) in the diet of echidnas from Facility 1 resulted in a marked decrease in the serum 25(OH)-D concentrations (mean 33 nmol/L). The reduction in serum 25(OH)-D concentration was statistically significant (P = 0.002) and the resulting concentrations were similar to those of wild echidnas (P = 0.212).

CONCLUSION

It is not known what effect an elevated serum 25(OH)-D concentration has on echidnas.

Using graded motor imagery for complex regional pain syndrome in clinical practice: failure to improve pain

BACKGROUND

There is good evidence from studies conducted in a single-centre research setting for the efficacy of graded motor imagery (GMI) treatment, a complex physiotherapy intervention, to reduce pain in long-standing complex regional pain syndrome (CRPS). However, whether GMI is effective in clinical practice is not established.

AIM

To establish whether GMI is effective in clinical practice.

METHODS

We undertook a prospective audit of GMI treatment at two UK centres with a special interest in the management of patients with CRPS. All patients received GMI, in conjunction with a range of other 'best practice' physical and psychological interventions.

RESULTS

The patients' average pain intensities did not improve with treatment [centre 1: n = 20, pre-post numeric rating scale (NRS) difference 0.6 [confidence interval (CI) -0.3 to 1.5]; centre 2: n = 12, pre-post NRS difference 0.2 (CI: -0.9 to 1.2)]. Patients at centre 1 reported significant functional improvement. Improved performance on left/right judgement replicated in both centres seen in the clinical trials.

CONCLUSIONS

The failure of our real-world implementation of GMI suggests that better understanding of both the GMI methodology and its interaction with other treatment methods is required to ensure that GMI research results can be translated into clinical practice. Our results highlight challenges with the translation of complex interventions for chronic pain conditions into clinical practice.

The challenges of meeting nutritional requirements in children and adults with epidermolysis bullosa: proceedings of a multidisciplinary team study day

This is a report of a study day held in London on 3 March 2010 to discuss measures with which to meet the nutritional requirements of patients with epidermolysis bullosa (EB). Members of national and international multidisciplinary teams (MDTs) caring for patients with EB attended this event. The study day focused on four challenging aspects of management intimately associated with nutritional status in EB, necessitating close cooperation between MDT members: iron-deficiency anaemia, gastrostomy placement and feeding, muscle mass and mobility, and dental health. The study day provided a unique forum for dietitians, doctors, nurses, physiotherapists, psychologists, psychotherapists, dentists, dental hygienists and occupational therapists to share knowledge and debate problems common to all who strive to promote best practice in this rare and complex group of conditions.

Gastrointestinal complications of epidermolysis bullosa in children

BACKGROUND

Epidermolysis bullosa (EB) is a group of inherited disorders characterized by skin and mucous membrane fragility. Gastrointestinal (GI) complications have been described in many types of EB and are responsible for significant morbidity.

OBJECTIVES

To delineate the nature and frequency of GI complications in a large cohort of paediatric patients with EB and to postulate why some complications occur more commonly in some specific subtypes.

METHODS

The case notes of 223 children with EB seen at a national referral centre were examined retrospectively for the presence of GI symptoms, investigations and interventions.

RESULTS

GI complications were present in 130/223 (58%) of all patients. In EB simplex, constipation and gastro-oesophageal reflux (GOR) were frequently observed. In junctional EB, failure to thrive and protein-losing enteropathy (PLE) were the prominent GI manifestations. Constipation was common in patients with dystrophic EB (DEB) requiring laxatives and in some cases fibre supplementation. GOR affected three-quarters of those with recessive DEB, two-thirds also having significant oesophageal strictures. Over half of patients with recessive DEB required gastrostomy insertion. Diarrhoea affected a small but significant proportion of children with recessive DEB with macroscopic and/or microscopic changes of colitis in the majority.

CONCLUSION

GI problems in EB are very common with subtype specificity for some of these complications. The occurrence of diarrhoea, PLE and colitis in the context of EB has not been highlighted previously, and may arise secondarily to antigenic exposure in the gut lumen as a result of mucosal fragility.

Functional magnetic resonance imaging studies of opioid receptor-mediated modulation of noxious-evoked BOLD contrast in rats

RATIONALE

Functional magnetic resonance imaging (fMRI) in rats can non-invasively identify brain regions activated by physiological stimuli and the effects of pharmacological intervention on these responses.

OBJECTIVES

This study was conducted to investigate the effects of systemic administration of the mu-opioid receptor agonist morphine on whole brain functional signal intensity in anaesthetised rats; to investigate whether pre-treatment with the opioid receptor antagonist naloxone blocks the effects of morphine; to determine whether pre-treatment with morphine attenuates noxious-evoked changes in whole brain functional signal intensity.

METHODS

Continuous whole brain fMRI scanning was used to study brain signal intensity prior to, and following, systemic administration of morphine (5 mg/kg, n=7), systemic administration of naloxone (1 mg/kg) and morphine (n=8). Effects of pre-treatment with saline (n=5) or morphine (5 mg/kg, n=5) on formalin (5%, intraplantar)-evoked changes in signal intensity were determined. Data were processed using SMP99 with fixed-effects analysis (p<0.05).

RESULTS

Morphine produced significant positive bilateral increases in signal intensity in the cingulate cortex, amygdala, thalamus, hypothalamus and PAG (p<0.05), and these effects were blocked by naloxone. Intraplantar injection of formalin produced a significant positive increase in signal intensity in the cingulate cortex, somatosensory cortex, amygdala, thalamus, hypothalamus and PAG (p<0.05). Morphine attenuated formalin-evoked increases in signal intensity in the PAG, amygdala, hypothalamus and cingulate cortex.

CONCLUSION

Our data demonstrate that morphine modulates noxious-evoked changes in signal intensity in discrete brain regions. fMRI studies in rats are able to identify specific brain regions involved in the pharmacological modification of physiologically evoked changes in regional brain activation.

Reciprocal regulation of polarized cytokine production by effector B and T cells

Although B cells produce cytokines it is not known whether B cells can differentiate into effector subsets that secrete polarized arrays of cytokines. We have identified two populations of "effector" B cells (Be1 and Be2) that produce distinct patterns of cytokines depending on the cytokine environment in which the cells were stimulated during their primary encounter with antigen and T cells. These effector B cell subsets subsequently regulate the differentiation of naïve CD4+ T cells to TH1 and TH2 cells through production of polarizing cytokines such as interleukin 4 and interferon gamma. In addition, Be1 and Be2 cells could be identified in animals that were infected with pathogens that preferentially induce a Type 1 and Type 2 immune response. Together these results suggest that, in addition to their well defined role in antibody production, B cells may regulate immune responses to infectious pathogens through their production of cytokines.

Interferon gamma eliminates responding CD4 T cells during mycobacterial infection by inducing apoptosis of activated CD4 T cells

In Mycobacterium bovis Bacille Calmette-Guérin (BCG)-infected wild-type mice, there was a large expansion of an activated (CD44(hi)) splenic CD4 T cell population followed by a rapid contraction of this population to normal numbers. Contraction of the activated CD4 T cell population in wild-type mice was associated with increased apoptosis of activated CD4 T cells. In BCG-infected interferon (IFN)-gamma knockout (KO) mice, the activated CD4 T cell population did not undergo apoptosis. These mice accumulated large numbers of CD4(+)CD44(hi) T cells that were responsive to mycobacterial antigens. Addition of IFN-gamma to cultured splenocytes from BCG-infected IFN-gamma KO mice induced apoptosis of activated CD4 T cells. IFN-gamma-mediated apoptosis was abolished by depleting adherent cells or Mac-1(+) spleen cells or by inhibiting nitric oxide synthase. Thus, IFN-gamma is essential to a regulatory mechanism that eliminates activated CD4 T cells and maintains CD4 T cell homeostasis during an immune response.

The defects in effector generation associated with aging can be reversed by addition of IL-2 but not other related gamma(c)-receptor binding cytokines

Aged naive CD4 T cells produce low levels of IL-2, leading to inefficient generation of effectors. The cells expand poorly, giving rise to few effectors with less activated phenotypes and reduced ability to produce cytokines. The aged cells also respond less vigorously in vivo. Addition of exogenous IL-2 or other gamma(c) receptor-signaling cytokines, restores expansion. However, only effectors generated in the presence of IL-2, are able to produce IL-2 in normal amounts and to become polarized to secrete Th2 cytokines. The defect in IL-2 production may be the only critical deficiency of aged naive CD4 T cells. Importantly, memory CD4 T cells generated from the IL-2 "restored" effectors are also deficient in IL-2 production, suggesting that a heritable change occurs during aging which effects production of IL-2 by resting naive and memory CD4 T cells, but not by optimally generated effectors.

Interleukin 2, but not other common gamma chain-binding cytokines, can reverse the defect in generation of CD4 effector T cells from naive T cells of aged mice

Development of effectors from naive CD4 cells occurs in two stages. The early stage involves activation and limited proliferation in response to T cell receptor (TCR) stimulation by antigen and costimulatory antigen presenting cells, whereas the later stage involves proliferation and differentiation in response to growth factors. Using a TCR-transgenic (Tg(+)) model, we have examined the effect of aging on effector generation and studied the ability of gamma(c) signaling cytokines to reverse this effect. Our results indicate that responding naive CD4 cells from aged mice, compared with cells from young mice, make less interleukin (IL)-2, expand poorly between days 3 to 5, and give rise to fewer effectors with a less activated phenotype and reduced ability to produce cytokines. When exogenous IL-2 or other gamma(c) signaling cytokines are added during effector generation, the Tg(+) cells from both young and aged mice proliferate vigorously. However, IL-4, IL-7, and IL-15 all fail to restore efficient effector production. Only effectors from aged mice generated in the presence of IL-2 are able to produce IL-2 in amounts equivalent to those produced by effectors generated from young mice, suggesting that the effect of aging on IL-2 production is reversible only in the presence of exogenous IL-2.

GnRH action on luteal steroidogenesis during pregnancy

The results of our study presented here establishes that gonadotropin-releasing hormone (GnRH) acts directly on the corpus luteum, leading to suppressed production and release of progesterone and thus disrupting pregnancy. A GnRH-agonist (GnRH-Ag) treatment suppressed the luteal and serum progesterone levels. This suppression is neither mediated by a fall in ovarian testosterone production nor its conversion to estradiol. Although the treatment suppressed the nuclear estradiol-receptor content and binding sites for LH in the corpus luteum, it had no effect on the luteal binding sites for GnRH and prolactin within 24 h. GnRH-Ag augmented the plasma levels of luteinizing hormone, decreased the magnitude of nocturnal surges of prolactin, and had no effect on luteal cyclic adenosine 5'-monotriphosphate levels. Yet, the treatment had no effect on the luteal content of free cholesterol. We have also demonstrated, for the first time, the presence of steroidogenic acute regulatory protein and peripheral benzodiazepine receptor in the rat corpus luteum, and the suppression of these proteins by GnRH-Ag leads to reduced steroidogenesis by the corpus luteum. Concomitantly, P450 side-chain cleavage enzyme, its activity, and its mRNA content and 3beta-hydroxy-steroid dehydrogenase content in the corpus luteum decreased. The treatment suppressed the plasma levels of pregnenolone and 20alpha-dihydroprogesterone. These data suggest that the suppression of luteal steroidogenesis by GnRH-Ag may be due to its inhibitory effect on the cholesterol transport and/or on the enzymes involved in the steroidogenic pathway. Furthermore, based on other observations made in our laboratory, we propose a hypothesis that an endogenous GnRH is present in the corpus luteum/ovary during pregnancy in the rat and that this GnRH may play a physiological role in the regulation, maintenance, and/or termination of pregnancy.

Substratum of pleiotrophin (HB-GAM) stimulates rat CG-4 line oligodendrocytes to adopt a bipolar morphology and disperse: primary O-2A progenitor glial cells disperse similarly on pleiotrophin

Pleiotrophin (HB-GAM), an extracellular matrix-associated protein with a high content of basic amino acid residues, is expressed in the central nervous system during late pre- and early post-natal development and promotes neurite outgrowth in vitro. Here, we show that, on a substratum of pleiotrophin formed from a 5 or 10 microg/ml solution, undifferentiated rat CG-4 line oligodendrocytes adopt a bipolar morphology and disperse over the substratum, as we have previously shown with poly-L-lysine (Rumsby et al. Neurosci. Res. Commun. 23:101-109, 1998). On pleiotrophin substrata formed from coating solutions of 1 microg/ml and below, CG-4 line cells form aggregates and do not disperse, as is also the case with poly-L-lysine. The same dispersing effect is observed with rat primary 0-2A progenitor glial cells on pleiotrophin substrata from solutions of 5 and 10 microg/ml: 0-2A cells aggregate together on pleiotrophin substrata formed from lower concentrations and do not disperse. A pleiotrophin substratum enhances proliferation of CG-4 line oligodendrocytes and primary 0-2A progenitor glial cells. The results show that pleiotrophin provides a substratum that can influence progenitor oligodendrocyte morphology, aid cell dispersion, and perhaps also enhance progenitor oligodendrocyte cell growth.

From naive to effector--alterations with aging

We have used a T-cell receptor transgenic mouse model to study the role of antigen in the changes that occur as T cells age. We find that the characteristic shift in the CD4 population to a predominance of memory phenotype T cells which accompanies aging in non-transgenic mice does not occur, suggesting that this shift is a result of antigenic stimulation. Thus at least one component of aging must be antigen dependent. When responses of naive CD4 T cells from aged and young mice are directly compared in vitro, the former are relatively deficient in their ability to produce IL-2 and IL-3, they express altered levels of P-glycoprotein and they proliferate less well in the absence of exogenous cytokines. When the ability of both naive populations to generate effectors is compared, the number of effectors generated from aged naive cells is much reduced and the effectors generated express lower levels of IL-2R alpha and produce reduced levels of cytokines. Importantly, addition of IL-2 restores proliferation of aged naive T cells, restores efficient effector generation and results in effectors seemingly indistinguishable from those derived from young CD4 cells. Similar phenotypic and functional changes seen with aging are also found in T-cell populations from IL-2 and IL-2R alpha knockout mice. Thus the loss of optimal IL-2 production may participate in the aging process and may represent the main antigen-independent defect in the CD4 T-cell population.

The incidence of delirium in psychiatric inpatient units

OBJECTIVES

To estimate prospectively the incidence of delirium in psychiatric inpatients and to identify risk factors for delirium in this population.

METHOD

The subjects were nondelirious patients newly admitted to the Calgary General Hospital. The Delirium Symptom Interview (DSI), the Confusion Assessment Method (CAM), and the Mini-Mental State Examination (MMSE) were used to identify incident cases of delirium. In order to evaluate the potential impact of selection bias, we conducted a supplementary analysis using record linkage to an electronic administrative data base with coverage of the target population.

RESULTS

Of 420 admissions to the hospital, 401 subjects provided informed consent and were not delirious at the time of admission. There were 9 incident cases of delirium. The cumulative incidence rate was, therefore, 2.14 per 100 admissions. The record linkage analysis did not uncover evidence of selection bias. Delirium was associated with a significantly increased length of stay in hospital.

CONCLUSIONS

Delirium is an uncommon incident event in the psychiatric inpatient population. The incidence rate reported here may be useful as a benchmark for the identification of excessive rates in other inpatient settings. Since delirium is sometimes related to modifiable therapeutic factors, an excessive rate should prompt a search for its causes.

Constipation in epidermolysis bullosa: successful treatment with a liquid fiber-containing formula

In epidermolysis bullosa (EB), chronic constipation, painful defecation, and fecal impaction frequently contribute to malnutrition and growth failure. Standard treatments for constipation, such as increased intake of conventional dietary fiber and fluids and/or the use of laxatives and stool softeners, are largely unsuccessful. We evaluated by questionnaire the use of a fiber-containing liquid formula (Enrich) in 20 chronically constipated children with dystrophic EB. All derived substantial improvement in constipation when taking 250 to 750 ml Enrich per day. We recommend that such a fiber-containing food be prescribed for chronic constipation in EB. In cases of fecal impaction, this should be preceded by bowel cleansing.

Age-related changes in CD4 T cells of T cell receptor transgenic mice

Much of the decrease in immunoresponsiveness seen in elderly populations is associated with changes in T cells responses. The observed functional changes include decreased responsiveness to T cell receptor stimulation and altered profiles of cytokine secretion. At the same time there is a decrease in the proportion of T cells that express a naive phenotype (CD44lo, CD45RBhi, CD62Lhi) and an increase in those that express a memory phenotype (CD44hi, CD45RBlo, CD62Llo). These changes are thought to result in the increased susceptibility to infection and decreased efficacy of vaccination that are observed in the elderly population. In this paper, we compare our published findings of the changes in antigen-specific T cell responsiveness using aged T cell receptor transgenic (TCR Tg) mice to what is known using conventional murine models. The specific antigen recognized by this transgenic T cell receptor apparently does not appear in the environment and the T cells expressing the Tg retain a naive phenotype. Similar to the findings in aged humans and rodents, the TCR Tg+ and TG- CD4 T cells from aged transgenic mice display decreased capacities for proliferation and cytokine secretion. Although the proportion of CD4 T cells that possess a memory phenotype increased in aged TCR Tg mice, they are Tg-. These findings support the presence of age-related deficiencies which do not depend on response to antigen. The implications of these findings are discussed.

Antigen-independent changes in naive CD4 T cells with aging

In the elderly, a dramatic shift within the CD4+ T cell population occurs, with an increased proportion having a memory phenotype with markedly decreased responsiveness. To determine what aspects of the aged phenotype are dependent upon repeated contact with antigen in the environment, we examined CD4+ cells isolated from TCR Tg mice. There is good evidence that no cross-reacting antigens for the Tg TCR recognizing pigeon cytochrome c are found in the environment of the animal, so that alterations in the Tg CD4+ cells with aging are likely to be due to antigen-independent processes. We found that in aged animals, TCR transgene(pos) CD4+ cells, although decreased in number and antigen responsiveness, maintain a naive phenotype rather than acquiring a prototypical aged memory phenotype. In contrast, the population of transgene(1o-neg) CD4+ cells increase in proportion and express the aged phenotype. Consistent with their naive status, transgene(pos) cells of aged individuals remain CD44lo CD45RBhi, secrete IL-2 and not IL-4 or IFN-gamma upon antigenic stimulation, and require co-stimulation to proliferate to anti-CD3 stimulation. These findings suggest that the aging-associated shift to CD4 cells expressing the memory phenotype is dependent on antigenic stimulation. However, the decrease in antigen responsiveness of naive transgenepos cells, as revealed by a lower secretion of IL-2 and IL-3 and a lower proliferative capacity, suggests that additional intrinsic changes occur with aging that do not depend on encounter with antigen.

Transglutaminase forms midkine homodimers in cerebellar neurons and modulates the neurite-outgrowth response

Midkine is a prominent acyl donor substrate for the protein cross-linking enzyme transglutaminase type 2 in rat brain neurons. Transglutaminase type 2 and midkine immunoreactivity are regionally colocalized in developing cerebellar cortex. Monomeric midkine is present in the embryonic dorsal rhombic lip which gives rise to the cerebellar cortex. A high-molecular weight (29-30 kDa) midkine appears during postnatal cerebellar development. The presence of the high-molecular weight midkine in cultured cerebellar cortical interneurons is dependent upon culture conditions. Transglutaminase catalyzes the calcium-dependent cross-linking of midkine predominantly into 29-30 kDa dimers. Dimer-formation of midkine in vitro and in cultured neurons is reduced in the presence of a transglutaminase inactivator. Neurons plated onto previously cross-linked midkine exhibit larger growth cones and enhanced neurite outgrowth compared to those plated onto monomeric midkine alone.

Gastrostomy and growth in dystrophic epidermolysis bullosa

Chronic malnutrition and growth failure are features of severe dystrophic epidermolysis bullosa (DEB). Conventional dietetic intervention is of limited benefit. Oesophageal dilatation or reconstruction to alleviate stricture is associated with substantial risks. Surgical placement of a feeding gastrostomy is a comparatively straightforward procedure, provided that specialized anaesthetic and surgical techniques are employed. Gastrostomy insertion was undertaken in 18 children with severe DEB and the effects of this intervention were retrospectively evaluated. The majority received button devices (inserted primarily) and gastrostomy feeding supplemented oral intake. One year postoperatively, the average increase in weight standard deviation scores (SDS) of 13 patients was 0.9 SDS (95% confidence interval 0.44, 1.35) and in height 0.42 SDS (95% confidence interval 0.05, 0.79). One patient developed an incisional hernia and four patients experienced minor leakage around the gastrostomy entry site. Two patients never accepted their gastrostomies, which were therefore removed. Two further patients died for reasons unrelated to the procedure. Our observations suggest that gastrostomy feeding can play a valuable role in severe DEB and is associated with minimal morbidity. Such intervention is best undertaken before growth failure is established, and prior to puberty.

Transforming growth factor beta (TGF beta) is produced by and influences the proliferative response of Xenopus laevis lymphocytes

Both TGF beta 2 and 5 have been described in the South African clawed frog Xenopus laevis and have been cloned from the tadpole-derived fibroblast cell line, XTC. Because TGF beta has such a profound inhibitory effect on the mammalian immune system, this study was performed to determine whether TGF beta: (a) has any in vitro effects on the growth of Xenopus lymphoblasts, and (b) is produced by mitogen-activated Xenopus lymphocytes. Following stimulation with mitogen or alloantigen, T lymphocytes from Xenopus secrete a T-cell growth factor (TCGF) that is functionally homologous to mammalian interleukin-2 (IL-2). Both recombinant human TGF beta 1 and Xenopus TGF beta 5 inhibit TCGF-induced proliferation of Xenopus splenic blasts and this inhibition can be reversed with anti-pan TGF beta antiserum. The Xenopus mitogen-induced saturated ammonium sulfate precipitated TCGF-containing supernatant (SAS TCGF SN) also contains latent TGF beta as assayed on mink lung fibroblasts and Xenopus splenic blasts, and experiments utilizing anti-TGF beta antiserum showed that only TGF beta 5 is present in this supernatant.

Further characterization of an interleukin-2-like cytokine produced by Xenopus laevis T lymphocytes

A T-cell growth factor (TCGF) is produced by antigen- or mitogen-stimulated T lymphocytes from the South African clawed frog Xenopus laevis. This study further defines the physical and biological properties of this cytokine and demonstrates that TCGF is biochemically similar to mammalian interleukin-2 (IL-2). Biologically active TCGF eluted from SDS-PAGE displays a M(r) of 16 kD and lectin-affinity chromatography indicates that the three-dimensional configuration of carbohydrates on TCGF and human IL-2 is similar. Secretion of TCGF is detectable 1 day after stimulation of splenocytes with the T-cell mitogen phytohemagglutinin (PHA) and peaks following 2 to 3 days of stimulation. Finally, despite the biological and physical similarities between Xenopus TCGF and mammalian IL-2, anti-human IL-2 monoclonal antibodies do not recognize Xenopus TCGF.

Nutrition in dystrophic epidermolysis bullosa

In dystrophic epidermolysis bullosa (EB), a combination of diminished food intake and increased nutritional requirements commonly leads to malnourishment. Adequate nutrition in these patients could provide many benefits, including improved growth, accelerated healing, decreased susceptibility to infection, and enhanced well-being. We assessed nutrition status of children with dystrophic EB, and evaluated the benefits of nutritional advice in those who were considered malnourished. The majority of patients had inadequate intakes of a wide spectrum of nutrients, including those who appeared to be relatively mildly affected. We were unable to secure persisting substantial improvements in dietary intake despite thorough counseling. Adequate nutrition in patients with dystrophic EB depends on active nutritional support starting from birth. The need for more invasive techniques of nourishment, such as nasogastric and gastrostomy feeding, may have to be considered earlier than is currently the case.

Beta-endorphin C-terminal peptide evokes arachidonic acid release from cortical neurones

The release of free [3H]arachidonic acid and its metabolites (AAM) from mouse embryo cortical neurones cultured in serum-free medium stimulated by beta-endorphin C-terminal dipeptide (glycl-L-glutamine, Gly-Gln) was investigated. Gly-Gln but not the related dipeptide, glycyl-glutamic acid, caused a 2-fold elevation of AAM release which was blocked in the absence of extracellular calcium, in the presence of 5 mM magnesium and by the phospholipase A2 (PLA2) inhibitor, mepacrine. Other proopiomelanocortin (POMC) peptides did not elicit AAM release. The response to Gly-Gln was unaffected by D-amino-2-phospho-5-valeric acid (AP5) and 7-chlorokynurenic acid (7-ClKY), antagonists respectively at the ligand and allosteric glycine binding sites of the NMDA glutamate receptor subtype. However, it was inhibited in a dose-dependent manner by antagonists at the phencyclidine (PCP) and sigma sites. The results suggest that Gly-Gln causes AAM release by activating PLA2 through the mediation of a PCP/sigma-like receptor.

A monoclonal antibody against the human IL-2 receptor binds to paraformaldehyde-fixed but not viable frog (Xenopus) splenocytes

Others have reported that a monoclonal anti-human IL-2 receptor antibody (anti-CD25) specifically binds a membrane receptor on Xenopus laevis PHA-induced and paraformaldehyde-fixed splenic blasts. In this paper, we present evidence suggesting that this binding is an artifact of membrane damage. Specifically, significant binding of anti-CD25 could only be achieved if the lymphoblasts were acid-washed and/or paraformaldehyde-fixed prior to being incubated with the fluoresceinated antibody. For example, in a representative experiment 95% of paraformaldehyde-fixed blasts, about 19% of acid-washed but not fixed blasts, but fewer than 2% of viable (untreated) blasts were positive for the CD25 epitope. Paraformaldehyde is known to alter membrane permeability. The DNA dye propidium iodide (PI) was used to demonstrate that the acid washing procedure also causes membranes to become permeable. Flow cytometric analyses of acid-washed PHA-induced splenic blasts doubly stained with the anti-CD25 antibody and PI showed that only 1.5% of the cells that were positive for CD25 did not stain with PI. Additionally, the anti-CD25 antibody, which immunoprecipitated a molecule from human lymphoblasts of between 50 and 60 kDa, did not immunoprecipitate any surface molecules from 125I-labeled Xenopus splenic blasts. Since binding of anti-CD25 to Xenopus splenic blasts appears to occur only after membrane damage, the antibody may be recognizing a cross-reactive internal epitope that is not involved in ligand binding on the cell surface.

NMDA receptors activate the arachidonic acid cascade system in striatal neurons

Receptors for excitatory amino-acid transmitters on nerve cells fall into two main categories associated with non-selective cationic channels, the NMDA (N-methyl-D-aspartate) and non-NMDA (kainate and quisqualate) receptors. Special properties of NMDA receptors such as their voltage-dependent blockade by Mg2+ (refs 3, 4) and their permeability to Na+, K+ as well as to Ca2+ (refs 5, 6), have led to the suggestion that these receptors are important in plasticity during development and learning. They have been implicated in long-term potentiation (LTP), a model for the study of the cellular mechanisms of learning. We report here that glutamate and NMDA, acting at typical NMDA receptors, stimulate the release of arachidonic acid (as well as 11- and 12-hydroxyeicosatetraenoic acids from striatal neurons probably by stimulation of a Ca2+-dependent phospholipase A2. Kainate and quisqualate, as well as K+-induced depolarization were ineffective. Our results provide direct evidence in favour of the hypothesis, that arachidonic acid derivatives, produced by activation of the postsynaptic cell, could be messengers that cross the synaptic cleft to modify the presynaptic functions known to be altered during LTP. In addition, we suggest that NMDA receptors are the postsynaptic receptors which trigger the synthesis of these putative transynaptic messengers.

The role of the conjugated carbonyl of cytochalasin A in contractility inhibitions

A study of the mechanism of action of cytochalasin A (CA) in relation to its structural features and to its selective inhibition of certain contractile processes has been initiated. Quantitative structure-function analyses with several CA-related cytochalasins - including synthetic 21,22-dihydro-CA (DHCA), the 22-beta mercaptoethanol CA-adduct, (CA-2ME), and the 22-dithiothreitol CA-adduct (CA-DTT) - have been carried out in a temperature sensitive gel-sol extract from Ehrlich ascites tumor cells. Each drug congener was purified to homogeneity by HPLC prior to biological testing. The undiminished inhibitory indices of DHCA and CA-2ME (ID50 congruent to 3.7 x 10(-7) M) overrules the prior circumstantial evidence accumulated for the obligatory electrophilic interaction of this drug, at its alpha-beta-unsaturated ketone region, with presumptive receptor nucleophiles.

The growth and differentiation of transitional epithelium in vitro

The development of rat transitional epithelial cells grown on conventional non-permeable surfaces was compared with development on permeable collagen supports. On glass or plastic surfaces, cells grew as expanding nomolayer sheets. Once confluent, growth continued with a bilayer being formed in most areas and apical cells being continuously sloughed off. Although most cells were interconnected by desmosomes, and junctional complexes were formed, no other indications of differentiation were observed. After 2-3 wk of growth, division stopped and cel death ensued. In contrast, single-cell suspensions plated on collagen-coated nylon disks reassociated into multicellular islands and commenced growth. Mitoses were confined to the basal cells in contact with the permeable substrate. The islands developed into epithelial trilayers, tapering to monolayers along spreading edges. Once the islands were confluent, stratification was completed and appeared similar to that observed in vivo. Germinal cells formed a basal lamina, and the upper layer was composed of large, flattened cells with an unusually thick asymmetrical plasma membrane on the apical surface. Electron microscopic and radioactive tracers demonstrated "leaky" zonulae occludentes with a restricted permeability to small molecules. The movement of urea was retarded in comparison to water. Unlike the slow turnover of adult epithelium in vivo, maturation and sloughing of apical cells were measurable. Transfer of cells could be effected and growth maintained for up to 4 mo. These results may indicate the necessity of a nutrient-permeable growth surface for the polarized differentiation of adult transitional epithelium.