The negative feedback action of progesterone on luteinizing hormone release is not associated with changes in GnRH mRNA expression in the Ewe.

Progesterone is the ovarian hormone that times events in the ovine reproductive cycle. When elevated, this ovarian hormone acts centrally to inhibit both the tonic and surge modes of gonadotrophin releasing hormone (GnRH) release. Two studies were performed to address the underlying neural mechanisms. The first tested the hypothesis that the rapid rise in GnRH release, that results from an acute fall in progesterone concentrations (such as occurs following luteolysis), is temporally associated with a rapid rise in the cellular content of GnRH mRNA. Three groups of ovariectomised (OVX) ewes were treated with exogenous progesterone for 10 days, while one remained steroid free (OVX, n=7). To determine the effects of acute progesterone (P) withdrawal, ewes were killed on day 10 while implants were still in place (OVX+P, n=6) or 4 (OVX-P4, n=7) or 12 h (OVX-P12, n=7) after progesterone removal. Coronal sections through the rostral portion of the medial preoptic area (rPOA) were processed for cellular in-situ hybridization for GnRH mRNA. An increase in progesterone concentrations markedly suppressed luteinizing hormone (LH) release, while removal of the implants caused progesterone concentrations to fall (P<0.01) within 1 h and LH pulse frequency to increase (P<0.05) within 4 h. Despite these progesterone-induced changes in LH/GnRH release there were no differences in the cellular content of GnRH mRNA among the four groups. In the second study, three groups of ovariectomised ewes were used to determined whether the inhibitory actions of early (EL; n=8) and mid-luteal (ML; n=8) phase concentrations of progesterone on LH release are accompanied by a decrease in GnRH mRNA expression. P inhibited the secretion of LH in a dose dependant manner; pulses of LH were virtually absent in the ML group. Despite this marked inhibitory steroid action, there was no significant difference in the cellular content of GnRH mRNA among the OVX, OVX (EL) and OVX (ML) groups. Thus, both the negative feedback actions of physiological concentrations of progesterone on GnRH release and the rapid escape from progesterone-inhibition are independent of changes in the cellular content of GnRH mRNA. These data suggest that the mechanism by which progesterone controls the timing of events in the ovine oestrous cycle is primarily by altering the secretion of GnRH rather than GnRH biosynthesis.

Treatment of a branchial sinus tract by sclerotherapy.

A 16-year-old female presented with a sinus on the skin just medial to the right clavicle, which had discharged clear fluid on a daily basis for a number of years. A sinogram was performed and showed a long sinus tract extending from the region of the right clavicle to the lateral pharyngeal wall. Surgical treatment would have required an extensive procedure and seemed inappropriate in view of the relatively mild symptoms the patient was experiencing. Instead sclerotherapy was used to induce healing of the lesion. This was performed using 3% sodium tetradecyl sulphate foam delivered via a catheter along the entire length of the tract. There were no immediate complications from this procedure and on review at 1 and 6 weeks post-procedure the patient reported a significant improvement in the fluid discharge. At 1 year post-procedure this improvement had been sustained. The patient did report an occasional discharge from the sinus tract orifice at the base of her neck, but she did not feel that this was a significant problem and declined any further treatment.

Simulators in catheter-based interventional radiology: training or computer games?

Training in interventional radiology (IR) relies on a traditional apprenticeship; to protect patients, expert supervision is mandatory until knowledge, attitudes and practical skills have been certified as satisfactory. However, the current quality of IR training is threatened by reduced time for trainees to learn, as well as a loss of basic diagnostic, training cases to non-invasive imaging. At the same time, IR techniques are becoming a focus of interest to a range of other clinical specialities. To address this training shortfall there is a need to develop novel training alternatives such as simulator models. Few simulator models in any medical field have been successfully validated to show improved clinical skills in treating patients. To date no endovascular simulator has met this standard. A good simulator must be based around key performance measures (metrics) derived from careful analysis of the procedure to be replicated. Metrics can be determined by trained psychologists from a direct analysis of the content of the job or task to be tested. The identification of these critical measures of performance is a complex process which must be tailored to a training curriculum to be effective. Simulators based on flawed metrics will invariably lead to unsatisfactory assessment. It follows that simulator development must involve the statutory licensing authorities. Equally it is essential that we do not assume that training on a particular simulator will correlate with the ability to perform the task in the real world. This "transfer of training" must be rigorously proven by validation studies.