Search PubMed⌕ Search

Biomedical subjects

G B Williams

Publications and source records attributed to G B Williams.

At least 37 records · Page 2Linked to original sources
PubMed1987

Distal duodenal carcinoma and intussusception.

Adenocarcinoma of the duodenum is an uncommon malignancy that usually presents itself with either obstructive symptoms or jaundice, depending on its location. The diagnosis should be suspected in any patient with a high small bowel obstruction, weight loss, or chronic abdominal pain. Endoscopy and barium contrast x-ray films are the preferred initial studies; enteroclysis may provide additional information. Surgical resection offers the only hope for long-term survival, which should approach 50% with resectable tumors.

Adenocarcinoma, Mucinous↗
PubMed1987

Albumin adsorption and retention on C18-alkyl-derivatized polyurethane vascular grafts.

The short-term albumin affinity and thrombo-resistance of a polyether polyurethane vascular graft have been improved. The method is based on the C18 alkylation of the polymer. Thrombus formation by a planimetric technique and albumin retention on wire-reinforced polyurethane tubes, both C18 alkylated and untreated, were measured in short-term (4-h) exposure at femoral arterial sites in the dog. 125I-Albumin was preabsorbed on tubes and then exposed to blood for successive 2-h periods. Albumin uptake on alkylated tubes prior to blood exposure and retention following 2 h of blood exposure were significantly greater than on controls. Following a fast desorption phase in blood, the remaining albumin was more slowly desorbed from alkylated than from control tubes. Reincubation with albumin and blood reexposure produced a similar tendency, suggesting blood conditioning does not reduce the albumin affinity-enhancing property of C18 alkylation in the short term. Blood-preconditioning experiments suggested endogenous albumin has a high affinity for the C18-alkylated surface. Scanning electron microscopic examination showed thrombus and platelet densities were higher on control than on alkylated surfaces. These results suggest in vivo albumin affinity is increased for C18-alkylated polyurethane, which may be linked to decreased thrombus formation on these surfaces.

Adsorption↗
PubMed1986

Management of intra-abdominal aneurysms associated with periarteritis nodosa.

Periarteritis nodosa is a disease of small and medium-sized arteries, frequently associated with multiple visceral artery aneurysms. Infrequently, these aneurysms rupture, usually with fatal results. A case of spontaneous rupture of a middle colic artery aneurysm in a patient with periarteritis nodosa is reported, and similar cases in the literature are reviewed. Treatment of a ruptured visceral artery aneurysm requires ligation or resection of the aneurysm without delay. Residual aneurysms are treated with cyclophosphamide and/or prednisone in an attempt to induce regression of the aneurysms. An arteriogram performed after 3 to 4 months of medical therapy determines the need for further surgical intervention.

Aneurysm↗
PubMed1986

NH3 and propionate modulate the morphological response of aggregation-competent Dictyostelium discoideum to cAMP.

Two metabolites, NH3 and propionic acid, are known to act as morphogens during the development of Dictyostelium discoideum, specifically altering the course of morphogenesis and cytodifferentiation. They have also been shown to modulate the cAMP relay in this organism: NH3 by restricting intracellular accumulation, and propionate by inhibiting extracellular release. In the present study, we utilized the light-scattering properties of aggregation-competent cells in agitated suspension to demonstrate that the morphological responses of such cells to exogenous cAMP are also modulated by NH3 and propionate in a manner that has interesting implications for the overall control of morphogenetic movements in D. discoideum. Our experiments were conducted using a newly designed continuous-flow apparatus that represents a significant improvement in the technique. The apparatus is described in detail.

Ammonium Chloride↗
PubMed1985

Albumin coatings resistant to shear-induced desorption.

Using an immunoferritin-transmission electron microscopic technique, we studied the effects of C18 alkylation and fluid shear on the distribution of albumin absorbed to a segmented polyether polyurethane. Samples were exposed to 25 mg/dl albumin solution at 0, 100 or 1500 s-1 wall shear rate for 1 min. Others underwent static incubation with albumin solution for 20 mins, followed by exposure to phosphate buffered saline at 0, 100 or 1500 s-1 for 1 min. Significant increases in uniformity and density of the albumin adsorbate were observed for all C18 alkylated surfaces, at all wall shear rates. C18 alkylation also significantly decreased the rate of shear-induced desorption of albumin. Results suggest that C18 treatment may promote the rapid development and retention of an endogenous albumin layer for blood contacting materials.

Adsorption↗
PubMed1984

Modulation of the cAMP relay in Dictyostelium discoideum by ammonia and other metabolites: possible morphogenetic consequences.

Using a perfusion technique (P.N. Devreotes, P.L. Derstine, and T.L. Steck, 1979, J. Cell Biol. 80, 291-299), it has been shown that cAMP secretion by aggregation-competent cells in response to an exogenous cAMP signal is significantly reduced by exposure to NH4Cl or any of a set of carboxylic acids that includes propionate, succinate, pyruvate, and acetate. The effects of NH4Cl and any of the carboxylic acids are additive and the combinations restrict cAMP secretion to barely detectable or insignificant levels. The inhibitions are rapidly expressed, and are reversible. The activity of NH4Cl is marked at pH 7.2 and undetectable at pH 6.2. Hence, NH3 is presumably the active molecular species. Propionate activity is significantly greater at pH 6.2 than 7.2, indicating that the un-ionized acid is the active species. The data presented herein indicate that these effects are exerted via two separate and independent routes. During exposure of cAMP-stimulated cells to NH4Cl, the decrease in intracellular cAMP accumulation was even greater than the decrease in extracellular accumulation. Hence, NH3 appears to act as a cAMP accumulation inhibitor (CAI). In contrast, exposure to carboxylic acid concentrations that drastically reduce extracellular cAMP accumulation can actually enhance or, at worst, only slightly reduce intracellular accumulation. Hence, the carboxylic acids appear to act as cAMP release inhibitors (CRI). Stationary phase cells incubated on solid substratum in the presence of NH4Cl plus succinate (or propionate) for 18 hr failed to exhibit even the earliest signs of aggregation. If then harvested and redeposited in the absence of the metabolites, they proceeded through the morphogenetic sequence with approximately normal kinetics, suggesting that no significant morphogenetic competence had been achieved during their previous tenure. The morphogenetic implications of cAMP relay modulation are discussed.

Adenosine Triphosphate↗
PubMed1984

Reversible inhibition of aggregation-related cohesivity in Dictyostelium discoideum by diffusible metabolites.

Evidence presented elsewhere (G.B. Williams, E.M. Elder, and M. Sussman 1984, Dev. Biol. 105, 377-388) indicates that NH3 and certain carboxylic acids including propionate, succinate, and acetate modulate the cAMP relay in Dictyostelium discoideum. The former appears to act as a cAMP accumulation inhibitor, the latter as cAMP release inhibitors. The cohesive properties of aggregation competent cells have been assayed quantitatively in the presence of these modulators. The following results were obtained: (1) At pH 7.5, EDTA-resistant cohesivity was greatly inhibited by NH4C within the concentration range tested (30-3.8 mM). Even at the higher concentrations the effect was not immediate but required ca. 10 min for full expression. At the lower concentrations, the inhibitory level was only slightly reduced but the time for full expression progressively increased. At pH 6.5, the level of inhibition was marginal, indicating that NH3 is the active molecular species. By themselves, neither ambient pH nor ionic strength appeared to affect cohesive performance within the ranges employed. The inhibition was immediately and completely reversed upon removal of NH4Cl or a shift of ambient pH from 7.5 to 6.5. The presence of cycloheximide did not affect the recovery of cohesivity after NH4Cl removal. (2) The presence of 15 mM succinate, propionate, or acetate also reduced cell cohesivity. The timing and extent of the inhibition were identical at pH 7.5 and 6.5. The inhibition was expressed immediately and was reversible. Each of the acids acted synergistically with NH4Cl. The relative potencies of these metabolites acting singly or in combination as inhibitors of cohesivity corresponded roughly to their potencies as modulators of the cAMP relay (Williams et al., 1984). (3) The sensitivity to the metabolites was stage specific, being maximal during and shortly after aggregation and disappearing abruptly at 11-12 hr. This corresponds to the time at which this cohesive system, responsible for the end-to-end cell associations evident during aggregation (H. Beug, G. Gerisch, S. Kempff, V. Riedel, and G. Cremer, 1970, Exp. Cell. Res. 63, 147-158) is supplanted by a newly arisen, serologically and genetically distinct system which thereafter maintains the integrity of the aggregate (C. Steinemann and R.W. Parish, 1980, Nature (London) 286, 721-724; D.K. Wilcox and M. Sussman, 1981, Dev. Biol. 82, 102-112, and Proc. Natl. Acad. Sci. USA 78, 358-362; C.L. Saxe III and M. Sussman, 1982, Cell 29, 755-759). The activities of the metabolites, detailed above, are discussed in relation to their previously demonstrated activities as morphogens.

Ammonia↗
PubMed1983

The multidisciplinary team approach to exenteration of the pelvis.

The experience of a newly formed, multidisciplinary, pelvic exenteration team is presented which consists of a gynecologic oncologist, a general surgeon and a urologist. The first 20 exenterations performed by this team are reviewed. Nine patients had no postoperative problems, and of the 11 patients who did have complications, all but two, which resulted in death, were corrected without resultant debilitation. Fourteen of the 18 patients who survived the operation are tumor-free for as long as three years postoperatively. Operative proficiency as well as operative mortality and morbidity have certainly improved quite significantly as the team has gained experience.

Adult↗
PubMed1982

The role of parathyroidectomy in the management of hyperparathyroidism in patients on maintenance haemodialysis and after renal transplantation.

Between March 1964 and March 1980, 36 (34 dialysis, 2 transplant) of 327 patients accepted for the maintenance dialysis/transplantation programme at Charing Cross Hospital were submitted to parathyroidectomy. There were four main indications: persistent hypercalcaemia, progressive phalangeal erosions, aseptic necrosis of the femoral head and height loss with abnormal bone biopsy despite normal hand radiographs. At parathyroidectomy, 4 glands were removed in 1 patient, 3 1/2 glands in 24, 3 glands in 7, 2 glands in 3 and a single large gland in 1 patient. The operation was followed by improvement in 28 patients, no change in 5, and progression of hyperparathyroidism in 3.2 of the 28 patients who improved later relapsed and were treated with 1,25-(OH)2 vitamin D3. 4 patients were submitted to a further parathyroidectomy and improved considerably. We would conclude that, although parathyroidectomy is an effective and safe procedure, it is to be hoped that careful monitoring of bone state and early administration of 1,25-(OH)2 vitamin D3 may reduce the need for parathyroidectomy.

Adult↗
PubMed1981

Carcinoma of the bladder treated by interstitial irradiation.

A retrospective study is presented of 180 patients with clinically infiltrating transitional cell carcinoma of the bladder treated by interstitial irradiation. The cases were re-classified by clinical tumour extent and histopathological grace according to the UICC (1978) classification. The actuarial survival rates and complications are presented and treatment policy reviewed.

Aged↗
PubMed1980

The role of anterograde pyelography in the transplant kidney.

Ureteral obstruction or sloughing must be considered as a cause of non-function or poor function of the transplanted kidney. Established investigative techniques may not exclude a ureteral lesion conclusively or define its exact site if present. The role of anterograde pyelography in this situation is discussed. It is concluded that anterograde pyelography is a simple, safe and valuable investigation of the outflow tract of the transplanted kidney.

Humans↗