Effect of Postnatal Exposure to N Nitrosodiethylamine on the Myenteric Plexus of Rat.

Background: Humans are continuously exposed to the different types of nitrosamines found in the diet, drinking water, tobacco smoking, and work place. These are the potential source of exposure in the present population. Nitrosamines are found mainly in cured meat products, smoked preserved foods, beer, whiskey, pickled and salty preserved food materials. Nitrosamines have cytotoxic, carcinogenic and mutagenic properties. Nitrosamines exert toxic or mutagenic effects by promoting DNA damage, oxidative stress and reactive oxygen species formation that causes increased lipid peroxidation, adduct formation, and pro-inflammatory cytokine activation. Increased chronic exposure of low doses of nitrosamines is unavoidable in current environmental conditions. The nitrosamine explored in this study is N-Nitrosodiethylamine (NDEA), representing environmentally significant nitrosamine. Materials and Methods: The present study was conducted on pups of wistar rats, (Rattus norvergicus). Six pregnant wistar rats having same pregnancy time were taken. After delivery sixteen pups were chosen randomly. The control and the experimental groups had eight pups each. Sterile water and NDEA were given as 0.2mg/kg intraperitonea daily to the control and the experimental groups of rat pups respectively, from postnatal day 1 to postnatal day 20. All the rat pups were sacrificed on postnatal day 21 to obtain the tissues of the gastrointestinal tract. Results: A significant reduction of morphometric parameters such as the area, the perimeter and the ferret diameter of the perikaryon of the myenteric neurons of the experimental group found .The number of the myenteric neurons per unit area of muscularis externa was also significantly reduced in the NDEA treated wistar rat pups. Conclusions: Chronic low-level exposure of N-Nitrosodiethylamine (NDEA) caused significant effect on the histoarchitecture of myenteric plexus of wistar rats.

Molecular & phenotypic characterization of Staphylococcus epidermidis in implant related infections.

Background & objectives: The discrimination between the Staphylococcus epidermidis colonizing the deep seated indwelling devices and those which are mere commensals has always been a challenge for the clinical microbiologist. This study was aimed to characterize the S. epidermidis isolates obtained from device related infection for their phenotypic and molecular markers of virulence and to see whether these markers can be used to differentiate the pathogenic S. epidermidis from the commensals. Methods: Fifty five S. epidermidis isolates from various device related infections such as endophthalmitis following intra-ocular lens (IOL) implantation, intravascular (IV) catheter related sepsis and orthopaedic implant infections, were studied for slime production, biotyping, antibiotic sensitivity; and mec A and ica positivity by the recommended procedures. Results: Twenty three (41.8%) isolates were multi-drug resistant, 26 (65.2%) were slime producers, 30 (54.5%) were adherent, 23 (41.8%) possessed the intercellular adhesin (ica) gene, and 28 (50.9%) harboured the mec A gene. Biotypes I and III were the commonest, most members of which were multi- drug resistant. Twenty two (73.3%) of the 30 adherent bacteria were slime producers as opposed to only 4 (16%) of the 25 non-adherent bacteria (P<0.001). A vast majority i.e. 21 (91.3%) of the 23 ica positive organisms were adherent to artificial surfaces in contrast to only 9 (28.1%) of the 32 non-ica positive organisms (P<0.001). Twenty (86.9%) of the 23 ica positive bacteria were slime producers, as opposed to only 6 (18.7%) of the 32 ica negative bacteria (P<0.001). Of the 23 multi-drug resistant isolates, 19 (82.6%) carried the mec A gene. Interpretation & conclusions: The present findings showed that ica AB and mec A were the two important virulence markers of S. epidermidis in implant infections and slime was responsible for the sessile mode of attachment on the devices.

Ultrastructural analysis of slime positive & slime negative Staphylococcus epidermidis isolates in infectious keratitis.

BACKGROUND & OBJECTIVE: Slime is a major determinant of Staphylococcus epidermidis adherence.The established methods of laboratory detection of slime production by this organism i.e., Christensen's tube method and congo red agar plate method, can both yield inconclusive and/or intermediate results. We, therefore tried to find out electronmicroscopically the localization of slime in relation to the bacterial cell wall and look for the effect, if any of the slime location on the staphylococcal adherence as well as on the quantum of slime production. METHODS: A total of 132 coagulase negative staphylococci from cases of infectious keratitis were identified as S. epidermidis following the recommended protocol. Slime was detected both by Christensen's tube method and congo red agar plate method. Antibiotic sensitivity testing was performed by standardized disc diffusion method. Adherence of the organisms to artificial surfaces was determined by a quantitative method and transmission electron microscopy was carried out by the conventional techniques. RESULTS: Of the total 132 isolates, 57 (43.2%) were slime positive and 75 (56.8%) were slime negative.Twenty seven (47.4%) of the 57 slime producing organisms were multi drug resistant as compared to only 12 (16%) of 75 nonslime-producing organisms (P<0.001). A majority i.e., 45 (78.9%) of 57 adherent organisms were slime producers as against 12 (16%) of 75 nonadherent organisms. Electron microscopic study revealed a thick viscid layer of slime anchoring to the bacterial cell wall, especially in adherent organisms and those yielding positive slime test. Some of the organisms showed loose nonadherent slime and those were mostly nonadherent to artificial surfaces. INTERPRETATION & CONCLUSION: Slime and multi drug resistance were the important virulence factors of S. epidermidis in bacterial keratitis. It was the adherent slime (i.e., slime in intimate association with the bacterial cell wall as shown by electron microscopy) only, which was responsible for resistance to multiple antibiotics and for the adhesion phenomenon observed in the quantitative slime test.

Age-related decrease in rod bipolar cell density of the human retina: an immunohistochemical study.

During normal ageing, the rods (and other neurones) undergo a significant decrease in density in the human retina from the fourth decade of life onward.Since the rods synapse with the rod bipolar cells in the outer plexiform layer, a decline in rod density (mainly due to death)may ultimately cause an associated decline of the neurones which,like the rod bipolar cells,are connected to them.The rod bipolar cells are selectively stained with antibodies to protein kinase C-alpha.This study examined if rod bipolar cell density changes with ageing of the retina, utilizing donor human eyes (age: 6-91 years).The retinas were fixed and their temporal parts from the macula to the mid-periphery sectioned and processed for protein kinase C-alpha immunohistochemistry.The density of the immunopositive rod bipolar cells was estimated in the mid-peripheral retina (eccentricity: 3-5 mm)along the horizontal temporal axis.The results show that while there is little change in the density of the rod bipolar cells from 6 to 35 years (2.2%), the decline during the period from 35 to 62 years is about 21% and between seventh and tenth decades,it is approximately 27%.

Visual outcome and electron microscopic features of indocyanine green-assisted internal limiting membrane peeling from macular hole of various aetiologies.

PURPOSE: To describe the visual outcome of internal limiting membrane (ILM) peeling for macular hole of various aetiologies and ultrastructural features of the ILM. MATERIALS AND METHODS: The study was conducted on 40 eyes of 38 patients. Thirty eyes with full thickness macular hole were treated with vitrectomy and removal of ILM. Ten eyes with retinal detachment served as negative controls and these patients underwent vitrectomy and ILM removal. The surgical specimens were examined by transmission electron microscopy. RESULTS: The anatomical success rate of the first operation was 90% in idiopathic and myopic groups, whereas it was 100% in traumatic macular hole group. Visual improvement of (3) two lines was noted in 80% of the cases. Electron microscopy revealed the presence of ILM in all surgical specimens. Proliferation of astrocytes and synthesis of new collagen along the inner surface of ILM was noted in the surgical specimens. CONCLUSION: Our findings suggest that the ILM removal helps in closure of the macular hole and retinal reattachment. Vitrectomy with ILM peeling is a reasonable surgical approach to treat macular holes of idiopathic, myopic and traumatic aetiology.

Differential expression of syntaxin-1 and synaptophysin in the developing and adult human retina.

Synaptophysin and syntaxin-1 are membrane proteins that associate with synaptic vesicles and presynaptic active zones at nerve endings, respectively. The former is known to be a good marker of synaptogenesis; this aspect, however, is not clear with syntaxin-1. In this study, the expression of both proteins was examined in the developing human retina and compared with their distribution in postnatal to adult retinas, by immunohistochemistry. In the inner plexiform layer, both were expressed simultaneously at 11-12 weeks of gestation, when synaptogenesis reportedly begins in the central retina. In the outer plexiform layer, however, the immunoreactivities were prominent by 16 weeks of gestation. Their expression in both plexiform layers followed a centre-to-periphery gradient. The immunoreactivities for both proteins were found in the immature photoreceptor, amacrine and ganglion cells; however, synaptophysin was differentially localized in bipolar cells and their axons, and syntaxin was present in some horizontal cells. In postnatal-to-adult retinas, synaptophysin immunoreactivity was prominent in photo-receptor terminals lying in the outer plexiform layer; on the contrary, syntaxin-1 was present in a thin immunoreactive band in this layer. In the inner plexiform layer, however, both were homogeneously distributed. Our study suggests that (i) syntaxin-1 appears in parallel with synapse formation; (ii) synaptogenesis in the human retina might follow a centre-to-periphery gradient; (iii) syntaxin-1 is likely to be absent from ribbon synapses of the outer plexiform layer, but may occur at presynaptic terminals of photoreceptor and horizontal cells, as is apparent from its localization in these cells, which is hitherto unreported for any vertebrate retina.

Localization of glutamate in the human retina during early prenatal development.

In this study we have localized glutamate (GLU) in fetal (14-25 weeks gestation, Wg) human retinas by immunohistochemistry. At 14 Wg, GLU-immunoreactivity (IR) was localized only in the central part of retina, showing a prominently labelled nerve fiber layer. A few ganglion cells and displaced amacrine cells were very weakly labelled. At 17 Wg, GLU was localized conspicuously in many ganglion cells, displaced amacrine cells, some amacrine cells and the prospective photoreceptor cell bodies in the neuroepithelial layer. With progressive development at 20 and 25 Wg, the IR for GLU was found additionally in the Muller cell end feet, some bipolar cells as well as in the horizontal cells that were aligned in a row along the outer border of the inner nuclear layer of the central retina. The photoreceptor cell bodies in the outer nuclear layer were also prominently immunopositive for GLU. The developmental distribution of GLU in the human retina tends to indicate that it plays an important role in the differentiation and maturation of retinal neurons.