PubMed Health⌕ Search

Biomedical subjects

J S Chappell

Publications and source records attributed to J S Chappell.

At least 19 recordsLinked to original sources
PubMed1991

A mechanism for acute aluminium toxicity in fish.

Aluminium is acutely toxic to fish in acid waters. The gill is the principal target organ and death is due to a combination of ionoregulatory, osmoregulatory and respiratory dysfunction. The toxic mechanism has hitherto received little direct consideration and is unknown. In this paper the mechanism of acute aluminium toxicity is approached from a chemical perspective. Symptomatic evidence of toxicity is taken from the literature and combined with our own research to elucidate a biochemically sound model to describe a possible mechanism of acute aluminium toxicity in fish. The proposed model delineates the chemical conditions immediately adjacent to the gill surface and emphasizes their importance in aluminium's toxic mode of action. The mechanism is shown to be bipartite. Aluminium binding to functional groups both apically located at the gill surface and intracellularly located within lamellar epithelial cells disrupts the barrier properties of the gill epithelium. The concomitant iono- and osmoregulatory dysfunction results in accelerated cell necrosis, sloughing and death of the fish. The mechanism of epithelial cell death is proposed as a general mechanism of aluminium-induced accelerated cell death.

Acid Rain↗
PubMed1991

Electrolyte effects on bilayer tubule formation by a diacetylenic phospholipid.

A general effect by dissolved electrolytes to destabilize the curvature of bilayer tubules prepared from the diacetylenic phospholipid, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine is not found. This observation discounts the role of an electrostatic interaction between polarization charges on the edges of a ferroelectric bilayer as a means by which the cylindrical curvature may be stabilized in these structures (de Gennes, P. G. 1987. C. R. Acad. Sci. Paris. 304:259-263). The solution-mediated ionic interactions of electrolytes with this phospholipid appear not to influence significantly the relative stability of the crystalline state of the tubule, but at high levels of a few salts, may affect the nucleation and growth of the crystalline bilayer. Curvature of the bilayer in these tubular structures apparently derives from an interaction that is not very sensitive to the presence of electrolytes. Cylindrical curvature may alternatively arise from a bending force within the bilayer that is intrinsic to the anisotropic packing of the lipid molecules (Helfrich, W., and J. Prost. 1988. Phys. Rev. A38:3065-3068; Chappell, J. S., and P. Yager. 1991. Chem. Phys. Lipids. In press), and may therefore be largely determined by the packing interactions within the hydrophobic region of the tubular bilayer.

Calorimetry↗
PubMed1988

The chemistry of aluminum and silicon in relation to Alzheimer's disease.

Aluminosilicates have been identified at the core of senile plaques in Alzheimer's disease, and aluminum has been found within neurons bearing neurofibrillary tangles. Here we show that aluminum species interact with silicic acid, Si(OH)4--a normal component of plasma--to form aluminosilicate species solubilized by citrate. A switch in the binding of aluminum from silicate to phosphate at pH less than 6.6 calls attention to the strong binding of cationic aluminum species to proximate phosphate groups, as in the inositol phosphates, and to the potential effect on the activity of the phosphoinositide-derived intracellular messenger system. The chemistry may throw light on the debated relationship between aluminum and Alzheimer's disease.

Aluminum↗
PubMed1984

Splenic preservation.

The current principle of splenic preservation in both adults and children is now well accepted, and the reason for this is outlined. The surgical anatomy is briefly discussed and a method of handling the patient with splenic trauma is described. Splenic preservation is vital as regards protection of the child against infection, both in cases involving trauma and for other conditions previously treated by splenectomy.

Humans↗
PubMed1982

The radiological investigation of hepatocellular carcinoma in children.

Malignant liver tumours are not unusual in infancy and childhood. Hepatocellular carcinoma is however much less common than hepatoblastoma. Four children with hepatocellular carcinoma, 2 Black and 2 White, have been seen at Baragwanath Hospital and the Johannesburg Hospital in the past 8 years. Three children were under 4 years of age, with no known predisposing cause; 1 child was 11 years old and had a history of tyrosinosis. The radiological investigation of liver tumours is discussed.

Carcinoma, Hepatocellular↗
PubMed1979

Upper gastro-intestinal endoscopy in chidren.

Fibre-optic endoscopy of the upper gastro-intestinal tract has been successfully performed in 55 patients (60 examinations) with one complication related to general anaesthesia. Fifty-six of these examinations were performed under general anaesthesia in children ranging from 1 to 14 years. Four examinations were done without an anaesthetic. The instruments used were the Olympus GIF-K (forward oblique gastroscope) in the older children and the GIF-P2 (end-viewing paediatric gastroscope) in the younger patients. Indications for examination included gastro-intestinal bleeding, confirmation or exclusion of peptic ulceration as suspected on barium studies, persistent and recurrent vomiting, chronic abdominal pain, and the evaluation of gastro-oesophageal reflux. The need for careful selection of patients is emphasized since general anaesthesia is considered essential in the majority of chidren.

Adolescent↗
PubMed1978

The surgical management of chalasia of the oesophagus.

The Hill operation was used to correct chalasia of the oesophagus in 4 children under 1 year of age. Results in all 4 were good, 2 having been followed up for 2 years after surgery and the other 2 for 9 and 12 months respectively. There was no mortality or morbidity associated with surgery or endoscopy and biopsy. Oesophagitis is an important criterior for deciding which patient should be treated surgically in the under-1-year age group. Clinical assessment, radiological evaluation and finally endoscopy and biopsy are important in establishing the presence of persistent oesophagitis. Because of the difficulty of performing manometry in these patients, it has only been performed in those under 4 weeks of age.

Endoscopy↗
PubMed1977

Management of meconium ileus by resection and end-to-end anastomosis.

Six patients with meconium ileus, in whom bowel resection and end-to-end anastomosis were performed, are presented. Meconium ileus may be simple or complicated. The simple form may be treated by Gastrografin enema. Surgery is indicated if conservative treatment fails and for patients with a complicated obstruction. Provided the bowel is disobstructed and carefully resected, end-to-end anastomosis is preferable. Confirmation of the diagnosis by careful histological examination of the resected bowel is urged.

Cystic Fibrosis↗