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Biomedical subjects

N Buckley

Publications and source records attributed to N Buckley.

At least 37 records · Page 2Linked to original sources
PubMed1994

p53 Protein accumulates in Cushings adenomas and invasive non-functional adenomas.

The p53 protein, a negative regulator of cell growth, plays an important role in the pathogenesis of many human tumours following gene mutation and/or deletion. We screened a large number of sporadic pituitary tumours for p53 protein accumulation suggestive of gene mutation. Samples were divided into benign adenomas (n = 95) and invasive tumours with local or distant invasion (n = 26). All main tumour classes were represented. Putative p53 mutations were detected by immunohistochemistry on paraffin-embedded sections using polyclonal CM-1 and monoclonal DO-7 and PAb1801 antibodies. Results were compared to normal post-mortem pituitary tissue controls (n = 17). p53 protein accumulation was detected in invasive tumours (16%), but only in corticotrophinomas (2/4) and non-functional tumours (4/15). In non-invasive adenomas, protein accumulation was observed only in ACTH-secreting tumours where 50% were positive (16/32). No protein accumulation was identified in any control tissue. These results indicate that p53 protein accumulation may play a role in the development of Cushings adenomas and in the progression of non-functional tumours to the invasive state.

Adenoma↗
PubMed1993

Slow-release verapamil poisoning. Use of polyethylene glycol whole-bowel lavage and high-dose calcium.

OBJECTIVE: To present three cases of slow-release verapamil poisoning that demonstrate the prolonged absorption of the drug and the role of polyethylene glycol and high-dose calcium in management. CLINICAL FEATURES: Three patients with slow-release verapamil poisoning are presented. An 18-year-old woman took 2.3 g and developed hypotension and bradyarrhythmias 18 hours after ingestion, despite gastric lavage and administration of charcoal at three hours. A 23-year-old woman took 4.8 g and presented two hours later clinically unaffected. A 44-year-old woman presented 24 hours after taking 15-20 g. She had a systolic blood pressure of 50 mmHg, no measurable diastolic blood pressure and bradyarrhythmias. INTERVENTION AND OUTCOME: Case 1 responded to administration of 30 g of calcium and fluids intravenously. Case 2 was given polyethylene glycol on admission which resulted in passage of a tablet bezoar and no toxicity. Polyethylene glycol was ineffective in Case 3. She responded initially to high doses of calcium and other treatments, but subsequently died of hypotension and cardiac conduction block 39 hours after the overdose. CONCLUSION: The severity of poisoning with slow-release verapamil warrants aggressive pre-emptive treatment. Polyethylene glycol should be used routinely irrespective of the clinical state. High doses of calcium may be required to treat conduction block and hypotension.

Adolescent↗
PubMed1993

Agonist activation of transfected human M1 muscarinic acetylcholine receptors in CHO cells results in down-regulation of both the receptor and the alpha subunit of the G-protein Gq.

CHO cells stably transfected with cDNA encoding the human M1 muscarinic acetylcholine (HM1) receptor were treated with the cholinergic agonist carbachol at various concentrations for differing times. Levels of the HM1 receptor and of a range of G-proteins were subsequently measured. Carbachol treatment of the transfected cells caused a substantial down-regulation of cellular levels of the alpha subunit of Gq (Gq alpha), but did not significantly alter cellular levels of the alpha subunits of Gs or Gi2. A small decrease in levels of G-protein beta-subunit was also produced. Parallel assessment of agonist-induced down-regulation of the HM1 receptor demonstrated that it was lost in concert with the G-protein. Similar concentrations of carbachol (5 microM) were required to produce half-maximal stimulation of inositol phosphate generation and loss of each of the HM1 receptor and Gq alpha, and half-maximal losses of both receptor and Gq alpha were produced by 3 h of treatment with 1 mM-carbachol. By contrast, treatment of the non-transfected parental CHO cells, which do not express detectable levels of the receptor, with carbachol had no effect on cellular Gq alpha levels. Concurrent treatment of the HM1-expressing CHO cells with carbachol and cycloheximide indicated that suppression of protein synthesis de novo did not mimic the effect of carbachol, and hence even complete inhibition of transcription of the Gq alpha gene and/or translation of pre-existing Gq alpha mRNA could not account for the agonist-induced effect. We have previously noted that cellular levels of both Gs alpha [McKenzie and Milligan (1990) J. Biol. Chem. 265, 17084-17093] and the alpha subunits of the pertussis-toxin-sensitive G-proteins Gi1, Gi2 and Gi3 [Green, Johnson and Milligan (1990) J. Biol. Chem. 265, 5206-5210] can be regulated in certain cell systems by agonist activation of receptors expected to interact with these G-proteins. These results demonstrate that the same is true of Gq alpha and suggest that agonist-induced co-ordinate loss of receptors and associated G-proteins may be a more common feature than has been appreciated to date.

Animals↗
PubMed1989

Circadian rhythms for calcium, inorganic phosphorus, and parathyroid hormone in primary hyperparathyroidism: functional and practical considerations.

We obtained serial serum and urine samples from 14 patients with primary hyperparathyroidism both before and 3 to 9 months after excision of their parathyroid adenomas to (1) determine whether the circadian rhythms for calcium, phosphorus, and parathyroid hormone (PTH) previously described in normal human beings are disturbed in this disorder; (2) gauge the effect of surgical treatment on the patterns observed before intervention; and (3) ascertain whether time(s) of blood sampling can be defined for optimal biochemical detection of the disease. Significant rhythms for serum phosphorus, ionized calcium, PTH, urine phosphorus, and urine calcium were observed in many but not all patients before and after surgery. Nonetheless, collective analysis revealed the following: (1) diurnal patterns for serum ionized calcium, phosphorus, urine calcium, and urine phosphorus in patients with primary hyperparathyroidism both before and after surgery, whereas a rhythm for serum PTH was uniquely observed after surgical treatment; and (2) no significant correlation between preoperative serum ionized calcium and PTH but restoration of the expected reciprocal relationship between these variables after surgery. Although variability in individual expression of the rhythm for PTH precludes precise definition of a sampling "window" when hormone levels are likely to be highest, collection of data at points throughout the day helped establish the diagnosis of primary hyperparathyroidism in several patients with borderline serum biochemistries.

Adenoma↗
PubMed1989

Primary hyperparathyroidism: a new experimental animal model.

Although potentially useful in the understanding of hypercalcemic states, a satisfactory animal model of primary hyperparathyroidism has not been developed. Models that use transplants of supernumerary parathyroid (PT) glands or chronic parathyroid hormone (PTH) infusion are not ideal for many reasons. We report a new animal model in which athymic nude mice were used as recipients of human PT tissue heterografts. Three groups received 14, six, or one piece of PT adenoma tissue, and one group received six pieces of normal PT tissue. The significantly higher PTH levels in mice that received adenoma heterografts versus those with similar amounts of normal tissue suggest that adenomatous tissue is functionally distinct. A dose-response relationship between induction of hypercalcemia and the number of pieces implanted was in evidence, although only a small percentage of the mice with high PTH levels developed hypercalcemia. This differential response could be the result of any of several factors: (1) loss of ability to secrete bioactive PTH, (2) differing secretion rates among donor adenomas, (3) variability in host responsiveness to human PTH, and (4) requirement of additional factor(s) to generate consistently the hypercalcemia characteristic of human primary hyperparathyroidism.

Animals↗
PubMed1987

Metastatic tumors in the hand from adenocarcinoma of the colon.

Osseous metastases to the hand are rare. The primary site is usually in the lung, breast, or kidney. Two cases of metastatic tumor in the hand from adenocarcinoma of the colon are reported herein. These patients presented two and four years after initial resections of colonic carcinomas. General aspects of diagnosis, etiology, and management are discussed.

Adenocarcinoma↗
PubMed1986

A monoclonal antibody against meningococcus group B polysaccharides distinguishes embryonic from adult N-CAM.

The neural cell adhesion molecules (N-CAM) occur chiefly in two molecular forms that are selectively expressed at various stages of development. Highly sialylated forms prevalent in embryonic and neonatal brain are gradually replaced by less sialylated forms as development proceeds. Here we describe a monoclonal antibody raised against the capsular polysaccharides of meningococcus group B (Men B) which specifically distinguishes embryonic N-CAM from adult N-CAM. This antibody recognizes alpha 2-8-linked N-acetylneuraminic acid units (NeuAc alpha 2-8). Immunoblot together with immunoprecipitation experiments with cell lines or tissue extracts showed that N-CAM are the major glycoproteins bearing such polysialosyl units. Moreover we could not detect any sialoglycolipid reactive with this antibody in mouse brain or in the neural cell lines examined. By indirect immunofluorescence staining this anti-Men B antibody decorated cells such as AtT20 (D16/16), which expressed the embryonic forms of N-CAM, but not cells that expressed the adult forms. In primary cultures this antibody allowed us to follow the embryonic-to-adult conversion in individual cells. In addition, the existence of cross-reactive polysialosyl structures on Men B and N-CAM in embryonic brain cells for caution in efforts to develop immunotherapy against neonatal meningitis.

Animals↗
PubMed1985

Comparative study of the effects of hyperthermia and BCNU on BCNU-sensitive and BCNU-resistant 9L rat brain tumor cells.

1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU)-sensitive and BCNU-resistant 9L rat brain tumor cells were treated with BCNU at graded temperatures between 37 and 44 degrees C. The cytotoxic effects of hyperthermia alone on both cell lines were the same. Treating both cell lines with BCNU at temperatures above 37 degrees C caused a progressive increase in cell kill. All survival curves for drug-sensitive cells had shoulders followed by a region of exponential cell kill; dose enhancement ratios calculated at the 10% survival level ranged from 1.7 to 3.0. Survival curves for drug-resistant cells were exponential without a shoulder; dose enhancement ratios ranged from 3.3 to 8.4. For each cell line, a similar amount of the increased cell kill could be explained on the basis of the increases concentration of reactive species produced by hydrolysis of BCNU at elevated temperatures. The amount of cell kill that cannot be explained on this basis, however, suggests that factors other than an increase in the concentration of reactive species at higher temperatures are involved in the enhanced cell killing. Possible mechanisms include a heat-induced change in the structure of DNA chromatin and the effect of isocyanate deactivation of repair enzymes, both of which could lead to an increase in the number of crosslinks formed and therefore to an increase in cytotoxicity.

Animals↗
PubMed1984

Effect of cell-cell interactions on drug sensitivity and growth of drug-sensitive and -resistant tumor cells in spheroids.

Multicellular spheroids were grown from mixtures of rat brain tumor cells sensitive (9L) and resistant (R3) to 1,3-bis(2-chloroethyl)-1-nitrosourea. Percentages of each cell subpopulation in these spheroids were estimated with the sister chromatid exchange assay and were found to be approximately the same as those used to initiate spheroids. Spheroids grown from 9L cells alone had a higher growth rate than spheroids grown from R3 cells alone. However, the growth rate of mixed-cell spheroids was essentially the same as that of pure 9L spheroids and was independent of the percentages of R3 cells in mixed-cell spheroids. The sensitivity of 9L cells in mixed-cell spheroids treated with 1,3-bis(2-chloroethyl)-1-nitrosourea, estimated by changes in the number of sister chromatid exchanges per metaphase induced by treatment, decreased as the percentage of R3 cells increased. These effects are probably the result of an interaction between the two cell subpopulations held in three-dimensional contact, a situation similar to that in tumors in situ. The results suggest why one cell subpopulation of tumors does not become dominant during growth and indicate that interactions between cell subpopulations can influence the sensitivity of one subpopulation to 1,3-bis(2-chloroethyl)-1-nitrosourea.

Animals↗
PubMed1984

Autoradiographic localisation of muscarinic receptors in guinea-pig intestine: distribution of high and low affinity agonist binding sites.

Muscarinic receptors mediate a variety of intestinal functions including smooth muscle contraction, ganglionic transmission and water and electrolyte secretion. In this study, we have used [3H]quinuclidinyl benzilate ([3H]QNB) in an in vitro autoradiographic method to map the distribution of muscarinic receptors in guinea-pig ileum, colon and caecum. In addition, the relative distribution of low and high affinity agonist binding sites was assessed by the addition of the muscarinic agonist, carbachol, to selectively inhibit the binding of [3H]QNB to the high affinity sites. Although quantitative differences existed, the overall distribution of muscarinic receptors was similar in the 3 regions of intestine examined. Autoradiograph grains were found distributed over the myenteric and sub-mucous plexuses, the longitudinal and circular muscle layers and in the case of the colon, the muscularis mucosa. The inclusion of carbachol demonstrated that a greater proportion of high affinity sites were associated with the musculature than with the enteric plexuses. These findings are discussed in relation to the role of muscarinic mechanisms in intestinal motility and secretion.

Animals↗