Structure, function, and pharmacology of NMDA receptor channels

NMDA receptors have received much attention over the last few decades, due to their role in many types of neural plasticity on the one hand, and their involvement in excitotoxicity on the other hand. There is great interest in developing clinically relevant NMDA receptor antagonists that would block excitotoxic NMDA receptor activation, without interfering with NMDA receptor function needed for normal synaptic transmission and plasticity. This review summarizes current understanding of the structure of NMDA receptors and the mechanisms of NMDA receptor activation and modulation, with special attention given to data describing the properties of various types of NMDA receptor inhibition. Our recent analyses point to certain neurosteroids as NMDA receptor inhibitors with desirable properties. Specifically, these compounds show use-dependent but voltage-independent block, that is predicted to preferentially target excessive tonic NMDA receptor activation. Importantly, neurosteroids are also characterized by use-independent unblock, compatible with minimal disruption of normal synaptic transmission. Thus, neurosteroids are a promising class of NMDA receptor modulators that may lead to the development of neuroprotective drugs with optimal therapeutic profiles.

Photoperiod regulates genes encoding melanocortin 3 and serotonin receptors and secretogranins in the dorsomedial posterior arcuate of the Siberian hamster

The mechanism(s) involved in the regulation of the seasonal-appropriate body weight of the Siberian hamster are currently unknown. We have identified photoperiodically regulated genes including VGF in a sub-region of the arcuate nucleus termed the dorsomedial posterior arcuate (dmpARC). Gene expression changes in this nucleus so far account for a significant number of those reported as photoperiodically regulated and are therefore likely to contribute to seasonal physiological responses of the hamsters. The present study aimed to identify additional genes expressed in the dmpARC regulated by photoperiod that could be involved in regulating the activity of this nucleus with respect to seasonal physiology of the Siberian hamster. Using laser capture microdissection coupled with a microarray analysis and a candidate gene approach, we have identified several photoperiodically regulated genes in the dmpARC that are known to have roles in secretory and intracellular signalling pathways. These include secretogranin (sg) III and SgVI (secretory pathway), melanocortin 3 receptor (MC3-R) and serotonin (5-HT) receptors 2A and 7 (signalling pathway), all of which increase in expression under a short photoperiod. The spatial relationship between receptor signalling and potential secretory pathways was investigated by dual in situ hybridisation, which revealed that 5-HT2A and 5-HT7 receptors are expressed in neurones expressing VGF mRNA and that a sub-population (approximately 40%) of these neurones express MC3-R. These gene expression changes in dmpARC neurones may reflect the functional requirement of these neurones for seasonal physiological responses of the hamster.

Hypothalamic energy balance gene responses in the Sprague-Dawley rat to supplementation of high-energy diet with liquid ensure and subsequent transfer to chow

Energy dense, high fat, high sugar, foods and beverages in our diet are a major contributor to the escalating global obesity problem. Here, we examine the physiological and neuroendocrine effects of feeding rats a solid high-energy (HE) diet with or without a liquid supplement (Ensure) and the consequence of subsequently transferring animals back to chow (C). Outbred Sprague-Dawley rats were fed C until 49-56 days of age, and then transferred a HE diet for 3 weeks before allocation to one of two weight-matched groups. Over the next 10 weeks, one group remained on HE diet, whereas the other had access to the liquid diet, chocolate Ensure (EN), in addition to HE diet (HE + EN). Half the rats from each group were then killed, and the remainder were returned to C for 3 weeks. Supplementation of the HE diet with EN accelerated weight gain and increased daily energy intake, adipose tissue mass, and circulating leptin levels. Transferring animals back to C caused a decrease in bodyweight in the HE + EN group, whereas HE animals were weight stable. Both groups also exhibited voluntary hypophagia, although the magnitude and duration of this response was greater in HE + EN animals. The only effect of Ensure on the hypothalamic genes studied was on tyrosine kinase B expression in the ventromedial hypothalamic nucleus (VMH), which was increased in rats given the supplement. Withdrawal of the obesogenic diets decreased gene expression for cocaine-and-amphetamine regulated transcript (CART) and dynorphin (DYN) in the arcuate nucleus (ARC), and DYN and brain-derived neurotrophic factor (BDNF) in the VMH, whereas neuropeptide Y (NPY) gene expression in the ARC was increased. These changes were independent of previous dietary history. EN supplementation generates distinct physiological responses, yet has a minimal effect on hypothalamic neuropeptide or receptor gene expression, possibly due to the development of leptin resistance. Withdrawal of obesogenic diets induces changes in the gene expression consistent with NPY, CART and BDNF attempting to oppose weight gain on either HE or HE + EN.

Late complications of incisional hernias following prosthetic mesh repair

BACKGROUND

Incisional hernias still continue to be a serious problem for surgeons. In this study, we aimed to investigate the effects of polypropylene mesh and mersilene mesh, which are frequently employed in incisional hernias, as well as the effects of their application techniques on late complications.

METHODS

Two-hundred-sixty-four open abdominal hernia repairs were performed between 1986--2000, using prosthetic materials: polypropylene mesh and mersilene mesh were used in hernia repair. Mesh was placed as onlay, underlay and sandwich techniques. Follow-up data were obtained from medical records.

RESULTS

Comparisons were made with respect to surgical techniques and to late complications such as recurrence, enterocutaneous fistula, intestinal obstruction, and infections. Enterocutaneous fistulas developed in two patients. Recurrence occurred in 6.4 per cent. Chronic infection and wound sinus formation occurred in 5 per cent. The causes of recurrence included smoking, cellulitis, chronic infection/sinus tract, upper abdominal localization, and obstruction. Fistula formation occurred in patients with no peritoneal prevention, which was statistically significant (p=0.012). Chronic infection/sinus tract was high in patients for whom mersilene mesh was used, and enterocutaneous fistula occurred in 2 patients.

CONCLUSION

To prevent late complications, it is necessary to avoid the contact of mesh with bowel.

[Perforated peptic ulcers]

Two hundred forty-eight patients were operated for perforated peptic ulcer between 1983 and 1998. Of the patients 112 (45.1%) had chronic, 34 (13.7%) had acute ulcer history and 102 (41.2%) had no ulcer history. Of the patients 228 (92.0%) had duodenal, 9 (3.6%) had juxtapyloric, 6 (2.4%) had marginal, and 5 (2.0%) had antral ulcer. Forty two patients (16.9%) admitted within 12 hours and 206 patients (83.1%) between 12 hours and six days after perforation. Simple closure and omental patch was performed in 32 patients (12.9%) who had severe concomitant illness and 126 (50.8%) intraabdominal sepsis, truncal vagotomy + pyloroplasty in 32 (12.9%), simple closure + omental patch + truncal vagotomy + gastroenterostomy in 34 (13.7%), simple closure + omental patch + parietal cell vagotomy in 21 (8.5%), truncal vagotomy + antrectomy in 3 (1.2%). Patients who didn't have definitive procedure received H2 receptor blockers or proton pomp inhibitors. One hundred ninety-three patients (77.8%) underwent endoscopic control. Two of 53 patients with definitive procedure (3.8%) and 34 of 140 patients (24.3%) with simple closure had recurrence. Two patients in simple closure group underwent parietal cell vagotomy, the others received medical treatment. The recurrence rate was significantly higher in simple closure group (p < 0.01).

Effect of nitric oxide synthase inhibitor on experimentally induced burn wounds

BACKGROUND

Nitric oxide (NO) may have an important role in the healing of burn wounds. This study investigated the effect of NO on experimentally induced burn wounds by preventing NO synthesis.

METHODS

A total of 40 mice weighing 25 to 30 g were used in this study. The shaved skin on the back of the mice was immersed in 100 degrees C water for 10 seconds to achieve a partial-thickness scald burn. The mice were divided into two groups of 20. In group I (control group), 17.5 mg/kg of serum physiologic (placebo) was injected intraperitoneally two times a day for 15 days. In group II (study group), 17.5 mg/kg of aminoguanidine (NO synthase inhibitor) was injected intraperitoneally two times a day for 15 days. On day 15 of the burn, the animals were killed and the burn areas were investigated histologically. Histologic changes such as epithelial proliferation, abscess, collagen, and granulation tissue were evaluated.

RESULTS

Epithelial proliferation, formation of collagen, and granulation tissue with rich capillaries observed in the control group were statically significantly higher than those observed in the study group (z = -2.022, p < 0.05; z = -2.02, p < 0.05; and z = -2.022, p < 0.05; respectively).

CONCLUSION

We concluded that healing of the burn wound is delayed by preventing NO synthesis.