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Biomedical subjects

R M Pittilo

Publications and source records attributed to R M Pittilo.

At least 19 recordsLinked to original sources
PubMed1991

Ultrastructural studies of the effects of the ionophore lasalocid on Eimeria tenella in chickens.

The ultrastructural development of Eimeria tenella was studied in experimentally infected chicks fed 90 ppm lasalocid, an ionophorous anticoccidial antibiotic. Drug treatment was timed to target-specific endogenous stages. At 6 h after infection, many sporozoites within the epithelium showed degradation as a result of drug action. Only a few intact sporozoites were seen. The drug caused outer-membrane blistering, large surface swellings and enlarged mitochondria in both first- and second-generation merozoites. No effect on the gamonts was discerned.

Animals↗
PubMed1991

Granulomatous vasculitis in Crohn's disease.

This study investigated a possible vascular origin for granulomas in Crohn's disease. Twenty-four consecutive resected specimens of small and large intestinal Crohn's disease were preserved by arterial perfusion-fixation with 10% formol saline, at mean arterial pressure (100 mm Hg). Fifteen specimens contained granulomas on routine examination of H&E-stained sections. These 15 specimens were examined in detail using a range of immunohistochemical staining techniques to identify vascular structures and granulomas. A total of 485 granulomas were found, 85% of which were identified as being directly involved in vascular injury. The majority (77%) of granulomas were deep to the mucosa; they were found most frequently in the submucosa (42%). The techniques used in this study enhanced the recognition of granulomatous vasculitis. The results suggest that the majority of granulomas in Crohn's disease form within walls of blood vessels. Vascular localization of granulomatous inflammation suggests that the intestinal microvasculature contains an early element in the pathogenesis of Crohn's disease.

Crohn Disease↗
PubMed1990

Effect of lasalocid on the development of Eimeria tenella in chicken embryos.

Sporozoites of Eimeria tenella were treated with lasalocid in vitro and their viability tested by inoculating them into the allantoic cavity of 11-day-old chicken embryos. Concentrations of 0.1, 1.0 and 10.0 micrograms ml-1 reduced sporozoite viability, as judged by oocyst production. Injections into the embryos of 5, 50 or 500 micrograms of lasalocid 92-93 h after infection also reduced oocyst production, indicating activity against the later stages of the life cycle.

Animals↗
PubMed1990

Nicotine and cigarette smoking: effects on the ultrastructure of aortic endothelium.

The aortic endothelium from rats has been examined by scanning (SEM) and transmission electron microscopy (TEM) following nicotine administration or cigarette smoking. Nicotine was administered to rats by subcutaneous injections at concentrations of 1, 5, 10 and 20 mg/kg or by continuous subcutaneous pumps delivering a solution of 0.54 g/ml of nicotine at the rate of 1 microliter/h for 7 days. Animals were exposed to fresh smoke from eight cigarettes, each yielding 19 mg tar and 1.5 mg nicotine. Twenty minutes after subcutaneous injections, no endothelial abnormalities were evident by SEM, apart from at the high dose where minimal endothelial damage was seen. Limited endothelial damage was discerned following nicotine infusion and this consisted of microvillus formation, platelet adhesion and some cell separation. TEM revealed no endothelial changes in any of the animals. Cigarette smoking, however, resulted in considerable endothelial morphological changes consisting of the formation of blebs, microvillus-like projections, increased numbers of plasmalemmal vesicles and an increase in the numbers of Weibel-Palade bodies. The results suggest that components of cigarette smoke other than nicotine are responsible for the endothelial cell changes associated with smoking.

Animals↗
PubMed1989

Pathogenesis of Crohn's disease: multifocal gastrointestinal infarction.

In a prospective study, specimens of resected small and large intestine from fifteen patients with Crohn's disease were prepared by heparin-saline vascular perfusion, followed by either resin casting of the mesenteric vascular supply and tissue maceration or glutaraldehyde perfusion-fixation, resin casting, and tissue clearance. The specimens were examined by macrophotography, histopathology, and either scanning or transmission electronmicroscopy. A pathogenetic sequence of events in Crohn's disease was seen--vascular injury, focal arteritis, fibrin deposition, arterial occlusion mainly at the level of the muscularis propria, followed by tissue infarction or neovascularisation. These features were confined to segments of intestine affected by Crohn's disease and did not occur in normal bowel. The findings suggest that Crohn's disease is mediated by multifocal gastrointestinal infarction. This pathogenetic process is compatible with many of the clinical features of Crohn's disease, and its recognition has important implications for the identification of the primary cause of the illness and advances in clinical management.

Cecum↗
PubMed1989

Repopulation of guinea-pig skin by melanocytes during wound healing: a morphometric study.

Epidermal keratinocytes and melanocytes have a close functional interrelationship. In order to study this relationship we used computer-assisted three-dimensional morphometry (CAM) to investigate the shape and size changes of the cutaneous melanocyte in healing guinea-pig skin. The combination of CAM with osmium iodide staining and resin embedding of tissue gave excellent results and allowed qualitative and quantitative morphometric assessment of melanocytes in vertical epidermal sections. The changes in melanocytes and keratinocytes during healing of a standard 1 cm full thickness wound in the guinea-pig were studied. After an initial decrease, more melanocytes per mm2 of epidermis were seen (from 36 days). These were smaller in volume with shorter, less branched dendrites compared to controls. An unexpected finding was a late phase of melanocyte proliferation, at the end of our study period (99 days). Clearly, the complex changes in the melanocyte-keratinocyte relationship during wound healing continue throughout and beyond the period of our study.

Animals↗
PubMed1988

Effects of autologous mesothelial cell seeding on prostacyclin production within Dacron arterial prostheses.

Canine abdominal aortas have been replaced with Dacron arterial prostheses to assess the effects of mesothelial cell seeding on graft prostacyclin and thromboxane A2 release. At both 2 weeks and 6 weeks after surgery, three seeded and two unseeded control grafts were examined for prostacyclin release. In addition, thromboxane release was assessed in one seeded and one unseeded graft. Sections of aorta and graft were removed and incubated in PBS containing either 10 microM calcium ionophore A23187 or 20 microM arachidonic acid. The incubation mixture was sub-sampled at 5 min intervals over a 20 min period to assess the progressive release of prostacyclin and thromboxane A2 using a radioimmunoassay for 6-keto-prostaglandin F1 alpha and thromboxane B2 respectively. In seeded grafts, 6-keto-prostaglandin F1 alpha release averaged 15 per cent compared with aorta at 2 weeks and 45 per cent compared with aorta at 6 weeks. By contrast, release from unseeded grafts was undetectable at 2 weeks; however, by 6 weeks there was some release amounting to 15 per cent compared with aorta. There was a statistically significant increase in the release of 6-keto-prostaglandin F1 alpha from mesothelial cell seeded grafts at 6 weeks compared with unseeded grafts (P less than 0.01). Thromboxane release from the graft sections was variable and unrelated to whether the grafts had been seeded or not. These preliminary results, showing that grafts seeded with autologous peritoneal mesothelial cells release more prostacyclin than unseeded grafts, further highlight the role of the mesothelial cell as an alternative to the endothelial cell for improving the patency of arterial Dacron prostheses in the early postoperative days.

Animals↗
PubMed1988

Ultrastructural observations of microgametogenesis in Eimeria bakuensis (Syn. E. ovina) of sheep.

The ultrastructure of microgametogenesis of Eimeria bakuensis was studied in the intestinal epithelium of an experimentally infected sheep. During development the nuclei became situated peripherally in the microgamont. Nuclear chromatin condensed into peripheral, dense portions that became the nuclei of the microgametes. The young microgamont was surrounded by a very narrow parasitophorous vacuole which widened during development and contained a few intravacuolar folds. Fissures and invaginations developed in the microgamont at the time the flagella began to grow. Polysaccharide granules were not present in the early and intermediate microgamonts but increased in number during the later stages and remained in the residual cytoplasm of the mature stage.

Animals↗
PubMed1988

The effect of nicotine on human endothelial cell release of prostaglandins and ultrastructure.

The acute and sub-acute effects of nicotine at concentrations between 10(-9)M and 10(-2)M on human umbilical vein endothelial cell release of prostacyclin and prostaglandin E2 and the sub-acute effect on the endothelial cell ultrastructure have been examined. The acute effect of nicotine on prostaglandin release has been assessed by measuring release of prostacyclin and prostaglandin E2 following stimulation of confluent monolayers of endothelial cells with A23187 in the presence of nicotine. The sub-acute effect has been assessed by measuring A23187 stimulated release of prostacyclin and prostaglandin E2 from endothelial cells grown to confluence in the presence of nicotine. The cell monolayers were also examined for morphological and ultrastructural changes using light and electron microscopy. Nicotine treated and untreated cells released minimal amounts of prostaglandin E2. Concentrations of nicotine between 10(-9)M and 10(-4)M did not inhibit release of prostacyclin or induce morphological changes. Acute exposure to 10(-3)M nicotine resulted in a statistically significant inhibition of prostacyclin release, however, sub-acute exposure did not inhibit prostaglandin release or effect the cell morphology. Acute and sub-acute exposure to 10(-2)M nicotine resulted in a statistically significant inhibition of prostacyclin release. This was accompanied by the appearance of large translucent cytoplasmic inclusions which did not appear to be lipid rich as indicated by the negative uptake of oil-red-O and osmium tetroxide. This study shows that concentrations of nicotine comparable to the plasma levels of smokers (10(-9)-10(-6)M) do not induce morphological changes or effect the release of endothelial prostaglandins.

Calcimycin↗
PubMed1987

Ultrastructural studies of the effects of amprolium and dinitolmide on Eimeria acervulina macrogametes.

Medication of chicks with 125 ppm amprolium or dinitolmide adversely affected oocyst sporulation of Eimeria acervulina (Weybridge strain). Dinitolmide delayed oocyst production and no oocyst wall formation was seen up to 168 h post infection. Both drugs caused large numbers of abnormally small wall-forming bodies to be produced in the macrogametes. In amprolium-fed chicks, abnormal oocyst wall formation was seen. It was concluded that the main drug action was against wall forming bodies of type 2.

Amprolium↗