Contemporary dental practice in the UK: demographic details and practising arrangements in 2008.

Objectives: To determine, by postal questionnaire, the demographic profile and practising details of general dental practitioners in the UK in 2008.

Methods: A piloted 89 question postal questionnaire was distributed in 2007/2008 to 1,000 dentists, with effective addresses in the UK, whose names and addresses were obtained by random selection from the General Dental Council (GDC) register.

Results: Six hundred and ninety-one questionnaires were returned, of which 662 were useable - an acceptable 66% useable response rate.

Dental practitioners and ill health retirement: causes, outcomes and re-employment.

Aim: The aim of this project was, by means of a questionnaire to ill health retirees, to determine the factors which have contributed to the premature retirement of general dental practitioners (GDPs) due to ill health.

Methods: A questionnaire was designed to determine the effects of illness and ill health retirement (IHR) on the lives of those dentists who were affected. This was distributed to 207 dentists who were known to have retired because of ill health but were not suffering from serious, debilitating or life-threatening illnesses.

Oral exposure of PBDE-47 in fish: toxicokinetics and reproductive effects in Japanese Medaka (Oryzias latipes) and fathead minnows (Pimephales promelas).

The toxicokinetics of 2,2,4,4-tetrabromodiphenyl ether (PBDE-47) was studied in the Japanese Medaka (Oryzias latipes) after a single oral exposure followed by termination at specific time points. The effects of repeated oral exposure to PBDE-47 on reproductive performance was assessed using a pair breeding experimental design with fathead minnows (Pimephales promelas) given daily PBDE-47 exposures for 25 days, during which fecundity was measured as an indicator of reproductive performance. Medaka and fathead minnows were orally exposed to PBDE-47 by bioencapsulation in brine shrimp, Artemia sp.

Role of changes in renal hemodynamics and P-450 metabolites of arachidonic acid in the reversal of one-kidney, one clip hypertension.

Objective: To examine the role of changes in renal hemodynamics and P-450 metabolites of arachidonic acid in the reversal of one-kidney, one clip (1-K,1C) hypertension in rats.

Design: The stimulus for the release of an antihypertensive lipid from the kidney is not known. This study examined whether cortical or papillary blood flow is altered after removal of the clip from the renal artery of 1-K,1C hypertensive rats, and the effects of blockade of the renal metabolism of arachidonic acid by P-450 with 17-octadecynoic acid (17-ODYA) on the fall in blood pressure.

Purification of class I medullipins from the venous effluent of isolated normal kidneys perfused under high pressure with saline.

Medullipin I (Med I) is a vasodepressor prohormone which is continuously elaborated into the renal venous effluent (RVE) of isolated rat kidneys perfused under high pressure. We have improved the yield of Med I by substituting saline for the albumin perfusate previously reported; and considerably improved refinement by directly fractionating the crude lipid extract of the RVE with high pressure liquid chromatography. The results show that Med I, as defined by previous physiologic and pharmacologic criteria, is not a single molecule.

Secretion of medullipin I by the kidney involves the cytochrome P-450 enzyme system.

Objective: To determine whether secretion of medullipin I by the kidney is dependent on the cytochrome P-450 enzyme system in Sprague-Dawley and spontaneously hypertensive rats (SHR).

Methods: Isolated kidneys from Sprague-Dawley rats were perfused with 5% human albumin gassed with 95% O2 and 5% CO2 at 185 mmHg. The resultant renal venous effluent was tested in the SHR for medullipin I-type vasodepressor activity.

Renal vasodepressor mechanisms: the medullipin system.

Renal vasodepressor hormone: Medullipin I is the renomedullary vasodepressor hormone secreted by the renomedullary interstitial cells of the renal papilla. It is conveyed to the liver where it is converted to its active form, medullipin II. Medullipin II is a vasodilator that suppresses sympathetic tone and causes diuresis and natriuresis.

Lipomedullipinoma: a source of hypermedullipinemia.

Previously we reported a case of persistent hypotension associated with hypermedullipinemia (Blood Pressure 1992; 1:138-148). The hypermedullipinemia appeared to result from the autonomous secretion of medullipin I (Med I) by renomedullary interstitial cells (RIC's) in the patient's remaining endstage kidney. The patient subsequently died.

Persistent hypotension associated with hypermedullipinemia: a new syndrome.

A new syndrome is described in a patient with advanced renal insufficiency. This consists of severe and persistent hypotension causing weakness but associated with a clear mental status. Also present is evidence for decreased vascular reactivity.

Secretion of medullipin I by the kidney requires oxygen.

Objective: To test the hypothesis that the secretion of medullipin I by the kidney involves an oxidative step.

Design: Medullipin I is secreted by kidney renomedullary interstitial cells and is converted to medullipin II by the liver. Medullipin I can be derived from the kidney in the renal venous effluent by perfusing normal rat kidneys with 95% O2- 5% CO2 at an elevated pressure (180 mmHg).

Biologic differences between vasodilator prostaglandins and medullipin I.

Vasodepressor prostaglandins (PGs), PGE2, PGI2, and medullipin I (Med I) are synthesized in the kidney. These vasodilator substances are thought to be involved in the antihypertensive function of the kidney. At issue is whether there are biologic differences between the vasodilator PGs and Med I.

Medullipin system. Generation of medullipin II by isolated kidney-liver perfusion.

Perfusion of isolated normal rat kidneys with blood at elevated blood pressure (180-200 mm Hg) followed by perfusion of the renal perfusate through an isolated normal rat liver under venous pressure yielded in the plasma of the hepatic effluent a vasodepressor lipid having the chromatographic and biological characteristics of medullipin II. These findings support the view that medullipin II is the final product of the renohepatic axis of blood pressure control.

The medullipin system of blood pressure control.

The medullipin system of BP control has its cellular component in the renomedullary interstitial cells (RICs) of the renal papilla. The RICs secrete medullipin I which is conveyed to the liver to be activated into Med II. This activation appears to involve the cytochrome P-450 dependent enzyme system of the liver.

Antihypertensive action of medullipin I given by mouth.

Perfusion of normal rat kidneys with 5% human albumin in a balanced salt solution bubbled with oxygen yielded medullipin I (Med I) in the renal venous effluent. The presence of Med I in the renal venous effluent has been established by thin-layer chromatography, by the type of vasodepressor effect when injected intravenously as a bolus into the hypertensive rat, by inhibition of the vasodepressor effect of the renal venous effluent by Tween 20 and SKF 525A (proadifen, inhibitor of cytochrome P-450), and by removal of the liver from the circulation (a procedure that inhibits extracted Med I). Med I so derived lowered blood pressure of spontaneously hypertensive rats when injected into the stomach by an indwelling tube or when given by mouth.

Secretion of medullipin I by isolated kidneys perfused under elevated pressure.

1. Medullipin I (Med I) is a hormone extracted from renal papillae and its renomedullary interstitial cells (RIC). Med I is stimulated by elevation of the renal artery perfusion pressure.

Renal function in rats with angiotensin II-salt-induced hypertension: effect of thromboxane synthesis inhibition and receptor blockade.

This study was designed to assess the contribution of thromboxane (Tx) A2 to the pathogenesis of renal dysfunction in rats with angiotensin II (Ang II)-salt hypertension. Hypertension was induced in rats drinking 0.15 mol/l NaCl by infusion of Ang II (125 ng/min, intraperitoneally) for 12 days.

Histopathology of severe renal vascular damage in blacks.

During the 1970s renal biopsies were obtained after blood pressure had been controlled in 41 black patients in Memphis who had severe hypertension plus excretory renal failure. An additional 13 binephrectomy specimens were also studied. This material yielded significant information on the state of the renal arteries--arterioles under these circumstances.

Renal and circulatory effects of medullipin I, as studied in the in-vivo cross-circulated isolated kidney and intact Wistar-Kyoto (WKY) rat.

The renal medulla harbours powerful humoral antihypertensive mechanisms, as earlier explored in unclipping experiments on renal hypertensive rats or in normotensive isolated kidneys cross-circulated at increased perfusion pressures from 'donor rats', in which renal function also seemed to be affected. Injection of the renomedullary factor medullipin I (Med I; formerly ANRL) mimics these haemodynamic responses, and Med I seems to be one of the most important mediators of the depressor effects. The present study was performed to analyse further the haemodynamic and, particularly, the renal effects of Med I, using anaesthetized intact WKY rats and constant-pressure perfused (90 mmHg) isolated WKY kidneys, cross-circulated by these intact 'donor' rats.

Biologic contrasts between medullipin I and vasoactive glyceryl compounds.

Medullipin I causes a delayed onset depressor response when injected intravenously into rats. The glyceryl compounds selachyl alcohol (SA) and monoolein (MO) cause similar vasodepression. The neutral lipid 1-O-hexadecyl-2-acetyl-sn-glycerol (HAG) was suggested by Blank et al to be medullipin I (Med I, formerly ANRL).

The renal antihypertensive endocrine function: its relation to cytochrome P-450.

Unclipping the Goldblatt hypertensive rat lowers the blood pressure by cells in the renal papilla, the renomedullary interstitial cells (RIC), secreting a hormone that is part of a vasodilator system. A vasodilator, termed medullipin I, can be extracted from the renal papilla. Medullipin I and the renal venous effluent following unclipping have identical biologic properties.

Glycosaminoglycans of the rat renomedullary interstitium: ultrastructural and biochemical observations.

The rat renal papillary interstitum which contains abundant proteoglycans is a unique area important in renal function. These proteoglycans were studied ultrastructurally by ruthenium red fixation and staining and phosphate-buffered fixation before and after enzyme digestion. A tissue culture of rat renomedullary interstitial cells, the predominant cell of the renal papillary interstitum, was studied for its ability to synthesize proteoglycans and the proteoglycans were then analyzed.