Light changes the atmospheric reactivity of soot

Soot particles produced by incomplete combustion processes are one of the major components of urban air pollution. Chemistry at their surfaces lead to the heterogeneous conversion of several key trace gases; for example NO₂ interacts with soot and is converted into HONO, which rapidly photodissociates to form OH in the troposphere. In the dark, soot surfaces are rapidly deactivated under atmospheric conditions, leading to the current understanding that soot chemistry affects tropospheric chemical composition only in a minor way. We demonstrate here that the conversion of NO₂ to HONO on soot particles is drastically enhanced in the presence of artificial solar radiation, and leads to persistent reactivity over long periods. Soot photochemistry may therefore be a key player in urban air pollution.     

Morphology and intercellular communication in glial cells of intramural ganglia from the guinea-pig urinary bladder.

Neurons in most peripheral ganglia are surrounded by satellite glial cells (SCs), but these cells have so far received little attention. We used immunohistochemistry and intracellular injections of tracers to characterize SCs in the intramural ganglia of the guinea-pig urinary bladder, which are part of the parasympathetic system. Intracellular injections of horseradish peroxidase (HRP) revealed two morphological types: cells that surrounded neurons and are SCs proper, and bipolar cells with processes that projected into the nerve fiber bundles connecting the ganglia. SCs were immunopositive for glutamine synthetase (GS) and S100beta and immunonegative for glial fibrillary acidic protein (GFAP). Injections of Lucifer yellow (LY) or biocytin (molecules known to cross gap junctions) into single SCs showed that these cells have a very low degree of intercellular coupling. A mean of 0.31 and 0.71 cells were coupled to the injected cells, using LY and biocytin, respectively. It appears that SCs in the bladder ganglia are distinct from central and enteric glial cells in the small degree of their coupling and in the absence of GFAP immunostaining.     

Broken appointment behavior in a dental school environment

The present study was designed to determine the prevalence of broken appointments of female and male patients scheduled for third, fourth, and fifth year dental students. Data was obtained from computers used for patient scheduling at two campuses of the dental college. The proportion of broken appointments at these facilities was computed using the X2 -test to determine a difference between males and females. Results showed that male patients (14.9%) had a higher proportion of broken appointments than female patients (12.4%). Such differences among gender was statistically significant (p=4.218). The highest percentage of broken appointments was during December of 2001. Thirty four percent of these broken appointments were in the Restorative Clinic at the Darraiyah Campus (DUC) serving primarily male patients and 24% in the Removable Partial Denture Clinic at the Malaz Campus (MUC) serving only female patients. It was concluded the percentage of broken appointment s is considered to be unacceptable because of the negative impact on student learning and, ultimately, their academic progress.     

Interstitial cells of Cajal--their role in pacing and signal transmission in the digestive system

Interstitial cells of Cajal (ICC) are located in most parts of the digestive system. Although they were discovered over 100 years ago, their function began to be unravelled only recently. Morphological observations have led to a number of hypotheses on the possible physiological roles of ICC: (1) these cells may be the source of slow electrical waves recorded in gastrointestinal (GI) muscles; (2) they participate in the conduction of electrical currents, and (3) mediate neural signals between enteric nerves and muscles. These hypotheses were supported by experiments in which the ICC-containing layer was removed surgically, or when ICC were ablated chemically, and as a consequence the slow waves were absent. Electrophysiological experiments on isolated cells confirmed that ICC can generate rhythmic electrical activity and can also respond to messenger molecules known to be released from enteric nerves. In mice mutants deficient in ICC, or in mice treated with antibody against the protein c-Kit, slow wave activity was impaired. These results support the role of ICC as pacemaker cells. Physiological studies have shown that ICC in certain GI regions are important for signal transmission between nerves and smooth muscle. There is evidence that pathological changes in ICC may be associated with GI motility disorders. The full interpretation of the role of ICC in disease conditions will require much further study on the physiology and pharmacology of these cells.     

Glial cell plasticity in sensory ganglia induced by nerve damage

Numerous studies have been done on the effect of nerve injury on neurons of sensory ganglia but little is known about the contribution of satellite glial cells (SCs) in these ganglia to post-injury events. We investigated cell-to-cell coupling and ultrastructure of SCs in mouse dorsal root ganglia after nerve injury (axotomy). Under control conditions SCs were mutually coupled, but mainly to other SCs around a given neuron. After axotomy SCs became extensively coupled to SCs that enveloped other neurons, apparently by gap junctions. Serial section electron microscopy showed that after axotomy SC sheaths enveloping neighboring neurons formed connections with each other. Such connections were absent in control ganglia. The number of gap junctions between SCs increased 6.5-fold after axotomy. We propose that axotomy induces growth of perineuronal SC sheaths, leading to contacts between SCs enveloping adjacent neurons and to formation of new gap junctions between SCs. These changes may be an important mode of glial plasticity and can contribute to neuropathic pain.     

Rapid effects of MPTP in the mouse colon

Mechanical responses of the mouse colon to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were measured in vitro. MPTP caused muscle relaxation with an onset time of about 10 s. This relaxation was inhibited by propranolol. Pretreatment of the animals with reserpine significantly reduced the MPTP-induced relaxation. These observations indicate that MPTP liberates a catecholamine (presumably noradrenaline) from nerve terminals in the colon wall. The mechanism underlying this effect is not yet clear but it appears that oxidation to 1-methyl-4-phenyl-pyridinium is not required.     

Decreased density of ganglia and neurons in the myenteric plexus of familial dysautonomia patients

Background: Familial dysautonomia (FD) is a hereditary disease of the autonomic and sensory nervous system. A prominent manifestation of FD is gastrointestinal dyscoordination, which contributes to the morbidity and mortality in FD. Aim: As the myenteric plexus is an essential factor in gastrointestinal motility control, we compared its morphology in appendices of FD patients and controls. Methods: Appendices from FD patients (N=19) were obtained during surgery of fundoplication and gastrostomy; normal appendices (N=17) were obtained from patients suspected to suffer from acute appendicitis, in whom, however, the appendix was found to be normal. Specimens were stained histochemically for NADPH diaphorase (NADPH-d) and in a blinded manner examined under a light microscope for seven morphologic parameters: ganglionic density, neuronal density, ganglionic area, number of stained neurons per ganglion, nerve bundle width, ratio between nervous tissue area and total area, and neuronal area. Results: Ganglionic density was 10.13 per mm² in controls versus 5.01 per mm² in FD (p<0.05). Neuronal density was 70.12 per mm² in controls, compared with 22.09 per mm² in FD (p<0.01). The other parameters were not different between the two groups. Conclusion: Densities of myenteric ganglia and neurons of FD patients were significantly lower than in controls. This deficiency may contribute to the pathogenesis of FD gastroenteropathy.     

Monosodium glutamate daily oral supplementation: study of its effects on male reproductive system on rat model

Monosodium glutamate (MSG) is widely used in food preparation industry and has been consumed regularly. Previous studies had reported on effects of MSG when given at extremely high dosages, the results are not applicable to human equivalent intake. Therefore, the present study aimed to evaluate the effect of MSG on sperm quality and changes in reproductive organs of adult male rats when taken at average human daily intake (ADI). Twenty-four adult male rats were randomly assigned into three groups; NC (Normal control), MSG60 and MSG120 where MSG was given orally at 60 mg/kg and 120 mg/kg to each respective group. All treatments were conducted for 28 consecutive days. MSG at estimated ADI of 120 mg/kg body weight resulted in a significant drop in sperm quality (p < 0.05) when compared to both control and MSG60 groups. A significant decrease in the weight of reproductive organs was also apparent (p < 0.05). Moreover, oxidative status evaluation showed that treatment of MSG induces oxidative stress in the testis, more severely at a dose of 120 mg/kg body weight. These findings are supported by alterations in the observed histology of reproductive organs. This study shows that an intake dose of 120 mg/kg body weight MSG could cause significant damage to the reproductive system.

Abbreviations: MSG: Monosodium glutamate; ADI: average daily intake; PUFA: polyunsaturated fatty acid; FSH: follicle stimulating hormone; LH: luteinizing hormone; TCA: tricarbocylic acid; PF: prostatic fluid     

Thermally-stable high energy storage performances and large electrocaloric effect over a broad temperature span in lead-free BCZT ceramic

Ba_0.85Ca_0.15Zr_0.10Ti_0.90O₃ (BCZT) relaxor ferroelectric ceramics exhibit enhanced energy storage and electrocaloric performances due to their excellent dielectric and ferroelectric properties. In this study, the temperature-dependence of the structural and dielectric properties, as well as the field and temperature-dependence of the energy storage and the electrocaloric properties in BCZT ceramics elaborated at low-temperature hydrothermal processing are investigated. X-ray diffraction and Raman spectroscopy results confirmed the ferroelectric–paraelectric phase transition in the BCZT ceramic. At room temperature and 1 kHz, the dielectric constant and dielectric loss reached 5000 and 0.029, respectively. The BCZT ceramic showed a large recovered energy density (W_rec) of 414.1 mJ cm⁻³ at 380 K, with an energy efficiency of 78.6%, and high thermal-stability of W_rec of 3.9% in the temperature range of 340–400 K. The electrocaloric effect in BCZT was explored via an indirect approach following the Maxwell relation at 60 kV cm⁻¹. The significant electrocaloric temperature change of 1.479 K at 367 K, a broad temperature span of 87 K, an enhanced refrigerant capacity of 140.33 J kg⁻¹, and a high coefficient of performance of 6.12 obtained at 60 kV cm⁻¹ make BCZT ceramics potentially useful coolant materials in the development of future eco-friendly solid-state refrigeration technology.

Thermally-stable recovered energy density and significant electrocaloric temperature change over a broad temperature span in BCZT ceramic elaborated by low-temperature hydrothermal processing.