Ultrasound of the Spleen

Ultrasound (US) is a very useful means of noninvasively examining the spleen. Imaging is generally achieved via an intercostal approach using gray scale US supplemented by color flow to assess vasculature. Normal spleen appears uniform with vessels radiating and converging at the hilum. US readily identifies accessory spleens, a common congenital variation. Splenomegaly can be identified by US, however, it is not useful in differentiating the many causes of an enlarged spleen. Focal splenic masses are identified as cystic or solid by US, and features such as calcification, wall thickening, internal debris, and gas may be demonstrated in cystic type masses. Granulomatous calcification may be seen with US and cavernous hemangiomata typically have a characteristic US appearance. US can demonstrate typical features of splenic infarction. Splenic injury can be detected with US, however, whether US is the most appropriate first line investigation for suspected splenic injury is yet to be determined. It is a very useful follow-up modality for monitoring splenic injuries detected by either US or computed tomography which are treated conservatively.     

Effect of gastrin-releasing peptide on rat hippocampal extracellular GABA levels and seizures in the audiogenic seizure-prone DBA/2 mouse

Gastrin-releasing peptide (GRP), a selective agonist for the BB(2) subtype of bombesin receptor, is reported to depolarise GABAergic interneurons in the stratum oriens layer of the hippocampus. Such an action might lead to increased extracellular levels of GABA in the hippocampus, and result in an anti-convulsant effect with this peptide. We have tested this hypothesis by determining the effect of GRP on extracellular levels of GABA in the ventral hippocampus of the freely moving rat using in vivo microdialysis, and by intracerebroventricular (i.c.v.) administration of GRP to audiogenic seizure-prone DBA/2 mice prior to exposure to the noise of an electric bell. Following local perfusion in the ventral hippocampus by reverse dialysis GRP (10 microM) significantly raised levels of GABA in the recovered dialysates by approximately 40%. In the seizure studies, GRP (30-300 ng) increased the latency to tonic seizure, the number of mice convulsing and reduced the incidence of lethality. In both dialysis and seizure studies, the effects of GRP were blocked by the selective BB(2) receptor antagonist, [D-Phe(6), Leu-NHEt(13)]bombesin (6-13). These experiments provide further functional evidence that activation of the BB(2) receptor may modulate neurotransmission in the hippocampus, and that this action may confer anti-convulsant properties on agonists acting at the BB(2) receptor in the brain.     

Regulation of glucocorticoid receptor mRNA and heat shock protein 70 mRNA in the developing sheep brain

Fetal hypothalamo-pituitary-adrenal (HPA) activity increases dramatically at term in sheep, however, little is known about the regulation of glucocorticoid feedback in the developing brain. Heat shock protein 70 (hsp70) is closely associated with glucocorticoid actions within the cell. We hypothesized that there is a decrease in glucocorticoid negative feedback in the brain, near term, resulting from changes in the expression of glucocorticoid receptors (GR) and hsp70. Brains were removed at various stages of development. GR mRNA levels in the paraventricular nucleus (PVN) and cortex, and hsp70 mRNA in the PVN were determined by in situ hybridization. In the hippocampus, GR mRNA levels were measured by Northern analysis. In the PVN, GR mRNA was present by d60. GR mRNA levels reached a peak at d100-110, but then decreased significantly with progression of gestation, and were lowest at term. Hippocampal GR mRNA levels were highest on day 130 of gestation, decreasing to low levels at term. In the cerebral cortex, GR mRNA levels were expressed at high levels in all layers of the cortex by day 110 of gestation with levels decreasing to term. Hsp70 mRNA was present in both parvocellular and magnocellular regions of the PVN, and there was no significant change in late gestation. In conclusion, (1) The high levels of GR mRNA present in the PVN, hippocampus and cerebral cortex during fetal life are likely important in development of these structures at a time when circulating glucocorticoids are low. (2) Changes in GR mRNA levels in the PVN are not associated with alterations in the expression of hsp70. (3) The decrease in GR mRNA in the hippocampus and PVN in late gestation, at a time when fetal plasma cortisol is increasing, likely facilitates maintained hypothalamic drive to the pituitary corticotroph.     

The development of the emetic reflex in the house musk shrew, Suncus murinus

The emetic (retching and vomiting) reflex is an important component of the body's defence system against accidentally ingested toxins and emesis is also a common symptom of disease and a side-effect of a number of pharmacological therapies. The development of the reflex has been the subject of few systematic studies. The aim of this study was to characterise the development of the emetic reflex in Suncus murinus (the house musk shrew) using emetic stimuli acting via three different afferent pathways: motion via the vestibular system, pyrogallol via abdominal vagal afferents and resiniferatoxin (a capsaicin analog) via the brainstem. The emetic reflex was not present to any stimulus prior to postnatal day 10 but the onset of the response to motion lagged behind that to the other stimuli in not being present until postnatal day 15. Body weight was not a determinant of the presence of the reflex. It is proposed that the delayed presence of the emetic reflex in Suncus makes it an ideal species in which to investigate factors regulating its development.     

The effects of cyclophosphamide on neurotransmission in the urinary bladder of Suncus murinus, the house musk shrew

This study has shown that cyclophosphamide treatment of the insectivore Suncus murinus, causes a down regulation in both muscarinic and P2X receptors, together with a reduced responsiveness to exogenous histamine (0.3 mM) in the urinary bladder. Electrical field stimulation (70 V, 0.3 ms, 0.5-16 Hz, 10 s every 5 min) of bladders from both control and cyclophosphamide-treated animals showed identical responses. Since post-junctional alterations have been revealed by the reduced responsiveness to exogenous carbachol (0.1 microM-3 mM) and beta,gamma-methylene ATP (0.3-300 microM), it would appear that in the bladders of cyclophosphamide-treated animals there is also a pre-junctional effect, increased transmitter release compensating for the down regulation of the receptors. As the pattern of neurotransmission of the bladder of suncus more closely resembles that of human detrusor than other commonly studied laboratory animals, this insectivore appears to be a useful animal model for the study of bladder neurotransmission in pathophysiological conditions.