Prevention of overweight and obesity in a Norwegian public health care context: a mixed-methods study.

BACKGROUND: Greater understanding about the prevention and treatment of overweight and obesity in preschool children within public health care is needed. This study assessed the impact of The First Steps module in routine primary health care including mapping of height/weight and diet followed by parental counselling of healthy habits on overweight and obesity in children aged 2 to 7 years. Further, we explored the experiences of public health nurses (PHNs) with the module. METHODS: Body weight and height obtained in 2014 and 2016 were extracted retrospectively for 676 children from the health records of children at 2, 4, or 6 years of age in five child health centers in Southern Norway. Sex- and age-adjusted body mass index (BMI) z-scores and weight status classifications were calculated according to the International Obesity Task Force reference values. Impact was assessed as change in mean BMI z-scores for children with under-, normal-, and overweight, respectively, and as proportion of children with overweight and obesity. In focus groups, PHNs described their experiences with the practical application of the module. Focus group transcripts were analyzed using Braun and Clarke's thematic analysis. RESULTS: Mean BMI z-scores decreased from 2014 to 2016 in overweight children (- 0.26) and increased in children with under- (0.63) and normal weight (0.06), whereas the proportion of children with overweight and obesity was stable. PHNs believed that the module provides them with new tools that are useful for addressing the intricacies of childhood obesity. They described counseling sessions with families as "moving upstream in a river" and that overweight and obesity may be one of many complex challenges for these families. CONCLUSIONS: Mean BMI z-score decreased in children with overweight during the 2 years after initiation of The First Steps module. PHNs considered the module as useful for addressing children's overweight and obesity, which was perceived as one of several complex challenges for most of these families. Specialist and evidence-based support is needed to address overweight and obesity in children in primary care. Further research should focus on integrating the issues relating to overweight and obesity within other family problems.

On the formation and role of reactive oxygen species in light-driven LPMO oxidation of phosphoric acid swollen cellulose.

Light-driven activation of lytic polysaccharide monooxygenases (LPMOs) has been attributed to the transfer of high redox potential electrons from excited photopigments to the enzyme. However, due to the formation of reactive oxygen species (ROS) in such a system, not only electrons from the pigments but also ROS could be part of the enzyme mechanism. This work investigates the role of ROS in the oxidation of phosphoric acid swollen cellulose (PASC) by a light-driven LPMO system. Our results clearly show that the addition of superoxide dismutase or catalase to remove ROS did not attenuate the capacity of the light-driven LPMO system to oxidize PASC, as measured by formation of oxidized oligosaccharides. We conclude that ROS are not part of the light-driven LPMO activation; hence, transfer of high redox potential electrons from the excited photopigment to the LPMO remains the most likely mechanism under the conditions tested in this study.

Acute and sub-lethal effects in juvenile Atlantic salmon exposed to low µg/L concentrations of Ag nanoparticles.

Silver nanoparticles (Ag-NP) are components in numerous commercial products and are discharged into the environment in quantities that are largely unknown. In the present study, juvenile Atlantic salmon were exposed to 1, 20, and 100 µg/L (48 h, static renewal) of a commercially available Ag-NP colloidal suspension in natural (soft) lake water. A solution of AgNO(3) containing 20 µg/L Ag(I) ions was also included to discriminate the effect of NPs from that of ionic silver. Furthermore, the commercial Ag-NP suspension was compared to an in-house synthesised colloidal NP suspension prepared from AgNO(3) and NaBH(4) in citrate buffer. The size distribution of Ag in all exposure solutions was characterised by 0.22 µm filtration and 10 kDa hollow fibre cross-flow ultrafiltration in combination with ICP-MS. All exposures were characterised by a relatively high proportion of Ag-NP in the colloidal size fraction 3-220 nm. For assessment of biological effects, acute toxicity, gill histopathology, blood plasma parameters (Na, Cl, glucose, haemoglobin), and gene expression of a selection of gill biomarkers were measured. Results showed that the gills accumulated Ag in all exposure groups apart from the fish exposed to 1 µg/L Ag-NP. Accumulated Ag caused concentration-dependent response increases in general stress markers such as plasma glucose and gill gene expression of heat shock protein 70. Furthermore, induction of the metallothionein A gene indicated that Ag had been internalized in the gills, whereas a concentration-dependant inhibition of Na/K ATPase expression indicated impaired osmoregulation at as low as 20 µg/L concentrations of Ag-NP. The commercial Ag-NP suspension caused acute gill lamellae necrosis at high concentrations (100 µg/L), potentially giving rise to the substantial (73%) fish mortality at this concentration. The two different Ag-NP preparations gave comparable results for several endpoints measured, but differed in MT-A induction and mortality, thus emphasising the variation in effects that may arise from different Ag-NP preparations.

Quantitative assessment of macrophages in the muscularis externa of mouse intestines.

Quantification of intestinal cells is challenging for several reasons: The cell densities vary throughout the intestines and may be age dependent. Some cell types are ramified and/or can change shape and size. Additionally, immunolabeling is needed for the correct identification of cell type. Immunolabeling is dependent on both up- and down-regulation of the antigen being labeled as well as on the primary and secondary antibodies, the fixation, and the enhancement procedures. Here, we provide a detailed description of immunolabeling of CD169(+) cells and major histocompatibility class II antigen (MHCII(+) ) cells and the subsequent quantification of these cells using design-based stereology in the intestinal muscularis externa. We used young (5-weeks-old) and adult (10-weeks-old) mice. Cell densities were higher in jejunum-ileum, when compared with colon. In jejunum/ileum, the cell densities increased in oral-anal direction in adults, whereas the densities were highest in the midpart in young animals. In colon, the cell densities decreased in oral-anal direction in both groups of animals. Except for the density of MHCII(+) cells in colon, the cell densities were highest in young animals. Densities of CD169(+) and MHCII(+) cells did not differ, except in the colon of young animals where the CD169(+) density was almost twice as high as the MHCII(+) density. CD169 and MHCII antigens seem to be expressed simultaneously by the same cell in jejunum/ileum. We conclude that cell densities depend on both the age of the mouse and on the location in the intestines.

Tenacibaculum sp. associated with winter ulcers in sea-reared Atlantic salmon Salmo salar.

Coldwater-associated ulcers, i.e. winter ulcers, in seawater-reared Atlantic salmon Salmo salar L. have been reported in Norway since the late 1980s, and Moritella viscosa has been established as an important factor in the pathogenesis of this condition. As routine histopathological examination of winter ulcer cases in our laboratory revealed frequent presence in ulcers of long, slender rods clearly different from M. viscosa, a closer study focusing on these bacteria was conducted. Field cases of winter ulcers during 2 sampling periods, 1996 and 2004-2005, were investigated and long, slender rods were observed by histopathological examination in 70 and 62.5% of the ulcers examined, respectively, whereas cultivation on marine agar resulted in the isolation of yellow-pigmented colonies with long rods from 3 and 13% of the ulcers only. The isolates could be separated into 2 groups, both identified as belonging to the genus Tenacibaculum based on phenotypic characterization and 16S rRNA sequencing. Bath challenge for 7 h confirmed the ability of Group 1 bacterium to produce skin and cornea ulcers. In fish already suffering from M. viscosa-induced ulcers, co-infection with the Group 1 bacterium was established within 1 h. Ulcers from field cases of winter ulcers and from the transmission experiments tested positive by immunohistochemistry with polyclonal antiserum against the Group 1 bacterium but not the Group 2 bacterium. Our results strongly indicate the importance of the Group 1 bacterium in the pathogenesis of winter ulcers in Norway. The bacterium is difficult to isolate and is therefore likely to be underdiagnosed based on cultivation only.

Bacterial adherence in otitis media: determination of N-acetylgalactosamine (GalNAc) residues in the submucosal glands and surface epithelium of the normal and diseased Eustachian tube.

BACKGROUND: Acute otitis media (AOM) is the most common childhood infection caused by bacteria. The pathogenesis of AOM implicates initial adherence of a pathogen to the nasopharyngeal epithelium, which is followed by bacterial colonization of the middle ear cavity through the Eustachian tube. N-acetylgalactosamine (GalNAc) is an important constituent of mucins and GalNAc containing sugar residues seem to be essential for initial adherence of respiratory bacteria to the surface of epithelial cells. OBJECTIVE: To explore the localization of GalNAc residues, we incubated Eustachian tube sections from Streptococcus pneumoniae infected and normal control rats with seven biotinylated, GalNAc recognizing lectins: Bauhinia purpurea lectin (BPA), Psophocarpus tetragonolobus lectin (PTA), Helix aspersa lectin (HAA), Helix pomatia lectin (HPA), Phaseolus lunatus lectin (PLA), Sophora japonica lectin (SJA) and Vicia Villosa isolectin B4 (VVA-B4). RESULTS: The mucin producing epithelium and submucosal glands of the normal Eustachian tube contained GalNAc residues, as evidenced by binding of several of the lectins. Lectin binding specificity and intensity changed following acute middle ear infection. BPA was the only lectin that exclusively stained the surface epithelium and the serous acini of the submucosal glands in the infected animals, whereas no binding was detected in the normal controls. HPA, HAA, PTA and VVA-B4 binding to surface epithelial cells increased after infection, indicating an active secretion of GalNAc containing glycans. Quantitative analysis of submucosal gland staining intensity showed significantly more GalNAc residues in the normal Eustachian tube, compared to infected animals. CONCLUSION: We conclude that the mucous producing elements of the normal rat Eustachian tube contain GalNAc residues essential for respiratory pathogen adherence. In addition, the GalNAc residue specificity and reacting intensity change in relation to acute infection, which may be important in relation to subsequent development of secretory otitis media or formation of a bacterial biofilm in the middle ear. The results show that GalNAc residues increased in both the submucosal serous glands and in the surface epithelium of the Eustachian tube after middle ear infection with S. pneumoniae.

Biofilms and type III secretion are not mutually exclusive in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that causes acute and chronic infections in immunocompromised individuals. It is also a model organism for bacterial biofilm formation. Acute infections are often associated with planktonic or free-floating cells, high virulence and fast growth. Conversely, chronic infections are often associated with the biofilm mode of growth, low virulence and slow growth that resembles that of planktonic cells in stationary phase. Biofilm formation and type III secretion have been shown to be reciprocally regulated, and it has been suggested that factors related to acute infection may be incompatible with biofilm formation. In a previous proteomic study of the interrelationships between planktonic cells, colonies and continuously grown biofilms, we showed that biofilms under the growth conditions applied are more similar to planktonic cells in exponential phase than to those in stationary phase. In the current study, we investigated how these conditions influence the production of virulence factors using a transcriptomic approach. Our results show that biofilms express the type III secretion system, whereas planktonic cells do not. This was confirmed by the detection of PcrV in the cellular and secreted fractions of biofilms, but not in those of planktonic cells. We also detected the type III effector proteins ExoS and ExoT in the biofilm effluent, but not in the supernatants of planktonic cells. Biofilm formation and type III secretion are therefore not mutually exclusive in P. aeruginosa, and biofilms could play a more active role in virulence than previously thought.

Igf1r+/CD34+ immature ICC are putative adult progenitor cells, identified ultrastructurally as fibroblast-like ICC in Ws/Ws rat colon.

The colon of Ws/Ws mutant rats shows impairment of pacemaker activity and altered inhibitory neurotransmission. The present study set out to find structural correlates to these findings to resolve mechanisms. In the colon of Ws/Ws rats, interstitial cells of Cajal associated with Auerbach's plexus (ICC-AP) were significantly decreased and ICC located at the submuscular plexus and intramuscular ICC were rarely observed based on immunohistochemistry and electron microscopy. Ultrastructural investigations revealed that there was no overall loss of all types of interstitial cells combined. Where loss of ICC was observed, a marked increase in fibroblast-like ICC (FL-ICC) was found at the level of AP. Immunoelectron microscopy proved FL-ICC to be c-Kit(-) but gap junction coupled to each other and to c-Kit(+) ICC; they were associated with enteric nerves and occupied space normally occupied by ICC in the wild-type rat colon, suggesting them to be immature ICC. In addition, a marked increase in immunoreactivity for insulin-like growth factor 1 receptor (Igf1r) occurred, co-localized with CD34 but not with c-Kit. A significantly higher number of Igf1r(+)/CD34(+) cells were found in Ws/Ws compared to wild-type rat colons. These CD34(+)/Igf1r(+) cells in the Ws/Ws colon occupied the same space as FL-ICC. Hence we propose that a subset of immature ICC (FL-ICC) consists of adult progenitor cells. Immunohistochemistry revealed a reduction of neurons positive for neuronal nitric oxide synthase. The functional capabilities of the immature ICC and the regenerative capabilities of the adult progenitor cells need further study. The morphological features described here show that the loss of pacemaker activity is not associated with failure to develop a network of interstitial cells around AP but a failure to develop this network into fully functional pacemaker cells. The reduction in nitrergic innervation associated with the Ws mutation may be the result of a reduction in nitrergic neurons.

The macrophage system in the intestinal muscularis externa during inflammation: an immunohistochemical and quantitative study of osteopetrotic mice.

Intestinal inflammation results in disturbed intestinal motility in humans as well as in animal models. This altered function of smooth muscle cells and/or the enteric nervous system may be caused by activation of macrophages in muscularis externa and a thereby following release of cytokines and chemokines that causes influx of mononuclear cells and neutrophilic granulocytes. We subjected osteopetrotic (op/op) mice that lack certain macrophage subtypes, e.g. macrophages in the muscularis externa and +/+ mice to LPS to induce inflammatory cell influx. The densities of F4/80+, MHCII+, and myeloperoxidase+ cells were quantified using stereological sampling. In +/+ mice we found that MHCII+ cells outnumber F4/80+ cells and that LPS injection increased the density of MHCII+ cells temporarily but not that of F4/80+ cells. This indicates that an upregulation of MHCII antigen takes place and that two or more macrophage subtypes with comparable morphologies exist. Osteopetrotic mice lacked MHCII+, CD169+, and F4/80+ cells after either treatment, which indicate that these cells are CSF-1-dependent. LPS induced VCAM-1 activation of the vessels, modest influx of granulocytes, as well as an iNOS-activation in a cell type different from macrophages in both +/+ and op/op mice.

Pacemaker activity and inhibitory neurotransmission in the colon of Ws/Ws mutant rats.

The aim of this study was to characterize the pacemaker activity and inhibitory neurotransmission in the colon of Ws/Ws mutant rats, which harbor a mutation in the c-kit gene that affects development of interstitial cells of Cajal (ICC). In Ws/Ws rats, the density of KIT-positive cells was markedly reduced. Wild-type, but not Ws/Ws, rats showed low- and high-frequency cyclic depolarization that were associated with highly regular myogenic motor patterns at the same frequencies. In Ws/Ws rats, irregular patterns of action potentials triggered irregular muscle contractions occurring within a bandwidth of 10-20 cycles/min. Spontaneous activity of nitrergic nerves caused sustained inhibition of muscle activity in both wild-type (+/+) and Ws/Ws rats. Electrical field stimulation of enteric nerves, after blockade of cholinergic and adrenergic activity, elicited inhibition of mechanical activity and biphasic inhibitory junction potentials both in wild-type and Ws/Ws rats. Apamin-sensitive, likely purinergic, inhibitory innervation was not affected by loss of ICC. Variable presence of nitrergic innervation likely reflects the presence of direct nitrergic innervation to smooth muscle cells as well as indirect innervation via ICC. In summary, loss of ICC markedly affects pacemaker and motor activities of the rat colon. Inhibitory innervation is largely maintained but nitrergic innervation is reduced possibly related to the loss of ICC-mediated relaxation.

Interrelationships between colonies, biofilms, and planktonic cells of Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a gram-negative bacterium and an opportunistic human pathogen that causes chronic infections in immunocompromised individuals. These infections are hard to treat, partly due to the high intrinsic resistance of the bacterium to clinically used antibiotics and partly due to the formation of antibiotic-tolerant biofilms. The three most common ways of growing bacteria in vitro are as planktonic cultures, colonies on agar plates, and biofilms in continuous-flow systems. Biofilms are known to express genes different from those of planktonic cells, and biofilm cells are generally believed to closely resemble planktonic cells in stationary phase. However, few, if any, studies have examined global gene expression in colonies. We used a proteomic approach to investigate the interrelationships between planktonic cells, colonies, and biofilms under comparable conditions. Our results show that protein profiles in colonies resemble those of planktonic cells. Furthermore, contrary to what has been reported previously, the protein profiles of biofilms were found to more closely resemble those of exponentially growing planktonic cells than those of planktonic cells in the stationary phase. These findings raise some intriguing questions about the true nature of biofilms.

Motility patterns and distribution of interstitial cells of Cajal and nitrergic neurons in the proximal, mid- and distal-colon of the rat.

The aim of this work was to study the patterns of spontaneous motility in the circular and longitudinal muscle strips and to characterize the distribution of c-kit positive interstitial cells of Cajal (ICCs) and nitrergic neurons (nNOS) in the proximal, mid- and distal-colon of Sprague-Dawley rats. We described two types of spontaneous contractions: high frequency (HF) and low frequency (LF) contractions, which were recorded in the presence of tetrodotoxin, suggesting a non-neurogenic origin. Regional differences were found in the motility patterns depending on the muscle layer and on the part of the colon studied. Muscle strips without submuscular plexus (SMP) showed only LF contractions. The density of ICCs was of the same magnitude along the extent of the colon: about 90-120 cells mm(-2) at Auerbach's plexus (AP) and 50-60 cells mm(-2) at the SMP. nNOS positive cells were found at the level of the AP and the major density was found in the mid-colon. Electrical field stimulation abolished LF but did not affect HF contractions. Our results indicate that HF contractions are due to the ICC network found associated with the submuscular plexus (ICC-SMP). The origin of LF contractions is still unknown.

Key parameters in sludge dewatering: testing for the shear sensitivity and EPS content.

The fraction of extractable extracellular polymeric substances (EPS) and the shear sensitivity (k(ss)) are key parameters with respect to sludge dewatering, affecting the dry matter content of dewatered sludge and the dewatering rate and conditioner demand, respectively. Methods are described for determination of the two key parameters by use of the same laboratory test reactor. The implications of such characterisation with respect to dewatering are discussed based on examples of application to sludge processing and novel process development for sludge minimisation.

Identification and characterization of Carnobacteria isolated from fish intestine.

Eleven bacterial strains were isolated from the gastrointestinal tract of four fish species, Atlantic salmon (Salmo salar L.), Arctic charr (Salvelinus alpinus L.), Atlantic cod (Gadus morhua L.) and wolffish (Anarhichas lupus L.). All the strains were Gram-positive rods, non-sporing, catalase and oxidase-negative, able to grow at pH 9.0 but not on acetate containing media (pH < or = 5.4), and were fermentative. They had a high content of oleic acid (18:1 n-9) in cellular lipid, and were found to belong to the genus Carnobacterium by phenotypic criteria. The eleven carnobacteria strains were further identified on the basis of 16S rDNA sequence analysis and AFLP(TM) fingerprinting.

Expression of connexin 37, 40, and 43 mRNA and protein in renal preglomerular arterioles.

Gap junctions allow direct intercellular coupling between many cells including those in the vascular wall. Studies of connexin expression in cells of the microcirculatory system are very few in number. However, cell-to-cell communication between cells of the arteriolar wall may be particularly important in microcirculatory control. We investigated the expression of connexins 43, 40, and 37 (Cx43, Cx40, Cx37) mRNA and proteins in primary cultures of smooth muscle cells (SMC) from rat renal preglomerular arterioles and in the aortic cell line A7r5. Furthermore protein expression in preglomerular arterioles in frozen sections was evaluated. SMC were isolated from kidneys using an iron oxide sieve method and explant technique. Total RNA from these cultures was tested by RT-PCR analysis for the expression of the three connexins mRNA. Using immunofluorescence we examined whether the expression pattern of connexin protein in the cell culture and frozen sections corresponded to the mRNA expression. The data show that A7r5 and preglomerular SMC express mRNA for Cx37 in addition to Cx43 and Cx40. In A7r5 cells the mRNA for Cx43, Cx40, and Cx37 are translated to protein, whereas cultured preglomerular SMC and the media of afferent arterioles in frozen sections only showed Cx40 immunoreactivity.

Evidence supporting presence of two pacemakers in rat colon.

Intracellular microelectrodes and organ bath techniques were used to study spontaneous cyclic electrical and mechanical activity in the rat colon. Electron microscopy and immunohistochemical studies showed two major populations of interstitial cells of Cajal (ICC): one associated with Auerbach's plexus (ICC-AP) and one with the submuscular plexus (ICC-SMP). The ICC-SMP network partly adhered to the submucosa when removed and was generally strongly damaged after separation of musculature and submucosa. Similarly, longitudinal muscle removal severely damaged AP. Two electrical and mechanical activity patterns were recorded: pattern A, low-frequency (0.5--1.5 cycles/min), high-amplitude oscillations; and pattern B, high-frequency (13--15 cycles/min), low-amplitude oscillations. Pattern A was recorded in preparations with intact AP but absent in those without intact AP. Pattern B was recorded in preparations with intact SMP but was absent in those lacking SMP. With full-thickness strips, the superimposed patterns A and B were recorded in circular muscle. When longitudinal muscle mechanical activity was recorded, only pattern A was present. We conclude that two pacemakers regulate rat colonic cyclic activity: the ICC-SMP network (responsible for cyclic slow waves and small-amplitude contractions) and the ICC-AP network (which may drive the cyclic depolarizations responsible for high-amplitude contractions). This is the first report showing consistent slow wave activity in the rodent colon.

Lactic acid bacteria associated with the digestive tract of Atlantic salmon (Salmo salar L.).

The present study reports the effect of excessive handling stress and starvation on the lactic acid bacteria associated with the digestive tract of Atlantic salmon (Salmo salar L.). A relatively low population level (approximately 2 x 103 bacteria per gram wet tissue) of viable adherent heterotrophic bacteria was associated with the digestive tract (foregut, midgut and hindgut). Of the 752 bacterial isolates isolated from diet, water and the digestive tract, 201 isolates belonged to the carnobacteria. Of these isolates, one from the diet, one from the rearing water and 80 from the gastrointestinal tract, were further identified on the basis of 16S rDNA sequence analysis. All these isolates were identified as being Carnobacterium piscicola-like. Daily repeated stress and starvation of the fish over 11 d had no influence on the total culturable bacterial numbers or population level of C. piscicola associated with the digestive tract. C. piscicola-like isolates colonizing the various intestinal regions (foregut, midgut and hindgut) were also screened for their ability to produce growth inhibitory compounds active against the fish pathogen Aeromonas salmonicida. Of the 199 C. piscicola isolates tested, 139 inhibited growth of the pathogen.

Characterization of human RNA splice signals by iterative functional selection of splice sites.

An iterative in vitro splicing strategy was employed to select for optimal 3' splicing signals from a pool of pre-mRNAs containing randomized regions. Selection of functional branchpoint sequences in HeLa cell nuclear extract yielded a sequence motif that evolved from UAA after one round of splicing toward a UACUAAC consensus after seven rounds. A significant part of the selected sequences contained a conserved AAUAAAG motif that proved to be functional both as a polyadenylation signal and a branch site in a competitive manner. Characterization of the branchpoint in these clones to either the upstream or downstream adenosines of the AAUAAAG sequence revealed that the branching process proceeded efficiently but quite promiscuously. Surprisingly, the conserved guanosine, adjacent to the common AAUAAA polyadenylation motif, was found to be required only for polyadenylation. In an independent experiment, sequences surrounding an optimal branchpoint sequence were selected from two randomized 20-nt regions. The clones selected after six rounds of splicing revealed an extended polypyrimidine tract with a high frequency of UCCU motifs and a highly conserved YAG sequence in the extreme 3' end of the randomized insert. Mutating the 3' terminal guanosine of the intron strongly affects complex A formation, implying that the invariant AG is recognized early in spliceosome assembly.

Op/op mice defective in production of functional colony-stimulating factor-1 lack macrophages in muscularis externa of the small intestine.

The osteopetrotic (op/op) mutant mouse possesses an inactivating mutation in the colony-stimulating factor-1 (CSF-1) gene, which results in the absence of certain macrophages and in osteopetrosis, following a lack of osteoclasts. Studies of the op/op mouse indicate that CSF-1-dependent tissue macrophages may belong to a trophic and/or scavenger subpopulation, which through their effect on other cell types can significantly affect tissue functions, and that cells which are CSF-1 independent have antigen presentation and immunological functions. We have previously identified a cell system of regularly distributed macrophages in the muscularis externa of the small intestine and wanted to extend these studies to the op/op mouse. The present investigations with light- and electron-microscopic methods using fluorescent dextran, methylene blue and immunohistochemistry (F4/80, anti-kit receptor, anti-CD3, anti-CD45R/B220) show that macrophages are absent from the muscle layers, with only an occasional macrophage present in the subserosa. In the lamina propria and submucosa, macrophage numbers are reduced. In all other respects the muscularis externa appears normal, including normal organization and number of interstitial cells of Cajal. Control and op/op mice both lack cells expressing CD3 (T lymphocytes), CD45R/B220 (B lymphocytes) and mast cells in the muscularis externa. This leaves the muscularis externa macrophages as the most likely source of local cytokine production under such conditions as postoperative ileus and intussusception in infants, where the muscularis externa appears to be one target of cytokines. We conclude that the lack of macrophages, combined with the preservation of otherwise normal structure, will make the op/op mouse a valuable model by which to assess the functions and relative importance of the muscularis externa macrophages in relation to intestinal motility under normal and pathological conditions.