Retinoic acid receptors interact physically and functionally with the T:G mismatch-specific thymine-DNA glycosylase

The pleiotropic effects of retinoids are mediated by nuclear receptors that are activated by 9-cis- or all-trans-retinoic acid to function as ligand-dependent transcription factors. In a yeast one-hybrid screen for proteins capable of interacting with native retinoic acid receptor (RAR), we have isolated the T:G mismatch-specific thymine-DNA glycosylase (TDG), which initiates the repair of T:G mismatches caused by spontaneous deamination of methylated cytosines. Here, we report that TDG can interact with RAR and the retinoid X receptor (RXR) in a ligand-independent manner, both in yeast and in vitro. Mapping of the binding sites revealed interaction with a region of the ligand binding domain harboring alpha-helix 1 in both RAR and RXR. In transient transfection experiments, TDG potentiated transactivation by RXR from a direct repeat element spaced by one nucleotide (DR1) and by RXR/RAR heterodimers from a direct repeat element spaced by five nucleotides (DR5). In vitro, TDG enhanced RXR and RXR/RAR binding to their response elements. These data indicate that TDG is not only a repair enzyme, but could also function in the control of transcription.

The epidemic of human papillomavirus and oropharyngeal cancer in a Canadian population

BACKGROUND

Sexually transmitted infection with the human papillomavirus (hpv) is responsible for a significant burden of human cancers involving the cervix, anogenital tract, and oropharynx. Studies in the United States and Europe have demonstrated an alarming increase in the frequency of hpv-positive oropharyngeal cancer, but the same direct evidence does not exist in Canada.

METHODS

Using the London Health Sciences Centre pathology database, we identified tonsillar cancers diagnosed between 1993 and 2011. Real-time polymerase chain reaction was then used on pre-treatment primary-site biopsy samples to test for dna from the high-risk hpv types 16 and 18. The study cohort was divided into three time periods: 1993-1999, 2000-2005, and 2006-2011.

RESULTS

Of 160 tumour samples identified, 91 (57%) were positive for hpv 16. The total number of tonsillar cancers significantly increased from 1993-1999 to 2006-2011 (32 vs. 68), and the proportion of cases that were hpv-positive substantially increased (25% vs. 62%, p < 0.002). Those changes were associated with a marked improvement in 5-year overall survival (39% in 1993-1999 vs. 84% in 2006-2011, p < 0.001). When all factors were included in a multivariable model, only hpv status predicted treatment outcome.

INTERPRETATION

The present study is the first to provide direct evidence that hpv-related oropharyngeal cancer is increasing in incidence in a Canadian population. Given the long lag time between hpv infection and clinically apparent malignancy, oropharyngeal cancer will be a significant clinical problem for the foreseeable future despite vaccination efforts.

Involvement of nitric oxide in survival of random pattern skin flap

A free radical gas, nitric oxide, has many useful functions when produced under physiological conditions by neurons and endothelial cells. However, excess nitric oxide has been reported to exert cytotoxic effects by direct toxicity or by reaction with superoxide. The effect of nitric oxide on the microcirculation in the periphery of a flap remains unclear, and its effect on flap survival is also unknown because nitric oxide has a dual action. Thus, we attempted to clarify the effect of nitric oxide on survival of rat random pattern skin flaps by the use of an endothelial constitutive nitric oxide synthase inhibitor (i.p. administration of 50 mg/kg N(G)-nitro-L-arginine) and the substrate of nitric oxide synthase (i.p. administration of 1 g/kg L-arginine). Three kinds of experiments were done using a total number of 120 animals: (1) time course measurement of blood flow in the flap periphery was performed using a laser Doppler flowmeter (30 rats), (2) the length of the surviving area of flaps was measured 1 week after raising the flap (60 rats), and (3) Western blot analysis was used to determine the time course of changes in the amount of endothelial constitutive nitric oxide synthase and the formation of 3-nitro-L-tyrosine, which is a marker of peroxynitrite-mediated (i.e., nitric oxide-dependent) tissue damage (30 rats). Inhibition of endothelial constitutive nitric oxide synthase by N(G)-nitro-L-arginine significantly decreased the length of the surviving area of skin flap (p < 0.01 compared with the control), which was associated with a decrease in the blood flow of the proximal portion of the flap. On the other hand, exogenous L-arginine increased the survival length of skin flap significantly (p < 0.01 compared with the control), which was associated with an increase in blood flow of the distal portion of the flap even though there was nitric oxide-mediated oxidative tissue damage. These results suggest that nitric oxide produced by endothelial constitutive nitric oxide synthase plays a role in maintaining circulation in the skin flap periphery and that L-arginine administration contributes to reduction of ischemic necrosis in the skin flap.

Cellular artificial skin substitute produced by short period simultaneous culture of fibroblasts and keratinocytes

We developed a novel artificial skin substitute consisting of two collagen sponge layers with different pore sizes and cross-link densities. Fibroblasts suspended in 0.5 ml Dulbecco-modified Eagle's medium (DMEM) + 10% fetal bovine serum (FBS) were seeded on the lower dermal sponge layer, then epidermal collagen sponge and 0.1 ml suspension of keratinocytes in KGM were layered in this order. After a few hours, the medium was changed to DMEM + 5% FBS. These processes were carried out in one day, and the composite layers were then cultured by the air-liquid interface culture method. Three to five days after seeding, keratinocytes had grown to about ten layers, and fibroblasts had grown three-dimensionally into the lower dermal sponge layer. This novel cellular artificial skin substitute was grafted onto nude mice and took in 4 weeks. This skin substitute has the advantage of a shorter culturing period than previously cultured skins, and may be clinically useful for grafting that is urgently required in patients with severe generalised burns.

Responses of periodontal ligament stem cells on various titanium surfaces

OBJECTIVE

Periodontal ligament has been reported to have adult stem cells (PDLSCs) which are responsible to regenerate the alveolar bone tissue after tooth is removed from its socket. Also PDLSCs may be the stem cells responsible for the osseointegration of titanium implants after installing the implant immediately in the fresh extracted socket. Here we tested cellular responses of PDLSCs on the various titanium surfaces to verify this notion.

MATERIALS AND METHODS

Titanium disc were prepared for the different surface textures; smooth machined, blasted with 75 and 125 μm Al(2) O(3) particles, and anodized. PDLSCs were cultured on these titanium discs and tested their proliferation and gene expressions of osteocalcin, osteopontin, type I collagen, and GAPDH.

RESULTS

  Proliferation of PDLSCs was higher on the rough surface blasted with 75 μm Al(2) O(3) particles. Osteocalcin expression was increased on the Al(2) O(3) particle treated-surface regardless of its particle size. Type I collagen expression was generally decreased with time in 6 days culture.

CONCLUSIONS

In this experiment, it was shown that cultured PDLSCs proliferate in higher rate on the rough surface especially at the 75 μm Al(2) O(3) particle treated surface than other surfaces. Also, osteocalcin was highly expressed on the rough surfaces treated with 75 μm and 125 μm Al(2) O(3) particles.

Versatility of modified planimetric Z-plasties in the treatment of scar with contracture

The planimetric Z-plasty proposed by Roggendorf provides elongation by excision of a pair of triangular pieces of tissue. The application of planimetric Z-plasties has been modified by making the vertical angle flexible, and making them continuous in the same or in opposite directions. Continuous planimetric Z-plasties in the same direction elongate an oblique contracture in the longitudinal direction. Continuous planimetric Z-plasties in an alternative direction elongate a disproportioned scar contracture in the longitudinal direction. Both techniques partially reduce unsightly scarring. Furthermore, they can be used in combination with V-Y-plasties. These modifications permit rational planing of the treatment of complicated scars with contracture.

Reconstruction of orbicularis oris and levator labii superioris muscles in secondary repair of unilateral cleft lip

We devised a new method to repair the depression of the nasal floor and inferolateral displacement of the alar base and to reconstruct the philtrum in the secondary repair of unilateral cleft lip. Depression of the nasal floor and inferolateral displacement of the alar base were corrected by advancing a lump of the levator labii superioris, the levator labii superioris alaeque nasi, and the upper part of the superficial orbicularis oris muscles to the anterior nasal spine. When the depression of the nasal floor was too severe to repair using these muscles only, a cranially-based de-epithelialised flap of the scar region on the upper lip was inserted under the nasal floor. The lower, greater part of the superficial orbicularis oris muscle was dissected to the nasolabial fold, brought towards the midline, and laid on the surface of the same muscle on the medial side to be sutured. When the depression of the nasal floor was not severe, the lower, greater part of the superficial orbicularis oris muscle was passed through a tunnel pierced beneath the de-epithelialised scar tissue and sutured to the corresponding components on the medial side to reinforce the philtral ridge. In both cases, if the deep orbicularis oris muscle in the vermilion had been interrupted, it was reconstructed by end-to-end anastomosis. Operative results were evaluated in 76 patients using photographs taken preoperatively and postoperatively. Elevation of the nasal floor and correction of the alar base were achieved in most patients, while reconstruction of the philtrum was achieved in cases in which the skin tension at the suture line was weak.

Formation of 4-hydroxy-2-nonenal-modified proteins and 3-nitro-L-tyrosine in rat island skin flaps during and after ischemia

4-Hydroxy-2-nonenal (HNE)-modified proteins and 3-nitro-L-tyrosine were evaluated as a specific marker of reactive oxygen species (ROS)- and nitric oxide (NO)-mediated peroxynitrite-induced tissue injuries in ischemic and reperfused skin flap by Western blot analysis. Specimens were taken from island skin flaps of rats during the following three conditions: ischemia only, 5 hours of ischemia and reperfusion, and 10 hours of ischemia and reperfusion. HNE-modified proteins and 3-nitro-L-tyrosine increased with ischemic time (3, 6, and 10 hours postischemia). In the reperfused skin flap after both 5 and 10 hours of ischemia, HNE-modified proteins and 3-nitro-L-tyrosine were increased 3 hours postreperfusion, and they reached a maximum 6 hours after reperfusion. HNE-modified proteins and 3-nitro-L-tyrosine 1 hour postreperfusion were higher with 10 hours ischemia-reperfusion than with 5 hours ischemia-reperfusion. These results indicate (1) that ROS- and NO-induced peroxynitrite-mediated cytotoxicity in ischemic flaps is dependent on the ischemic period and (2) that ROS- and NO-induced peroxynitrite-mediated cytotoxicity occurs during an early stage of reperfusion if the ischemic period is long.

Nipradilol, a new beta-blocker with vasodilatory properties, in experimental portal hypertension: a comparative haemodynamic study with propranolol

The haemodynamic effects of nipradilol, a new non-selective beta-adrenoreceptor blocker with vasodilating actions like nitroglycerin, were examined in rats with portal hypertension due to portal vein stenosis. Portal hypertensive rats were divided into five groups receiving infusion of placebo, 3 mg of propranolol, 300, 600 and 1200 micrograms of nipradilol. At its highest dose, nipradilol achieved a reduction of 34.4 +/- 4.4% in heart rate which was similar to that in the propranolol group (36.5 +/- 2.4%). Also for other systemic haemodynamic parameters, the nipradilol 1200 micrograms group exhibited changes not significantly different from those in the propranolol group; mean arterial pressure (-13 vs -14%), cardiac index (-37 vs -31%) and systemic vascular resistance (+29 vs +32%). In contrast to the similar changes in the systemic circulation, a 1200 micrograms dose of nipradilol lowered portal pressure significantly more than propranolol (-4.3 +/- 0.6 vs -2.9 +/- 0.2 mmHg, P < 0.05). Nipradilol then reduced portal blood flow by 22% (P < 0.05) without a significant change in portocollateral resistance. On the other hand, propranolol not only caused a reduction in portal blood flow of 30% (P < 0.01), but also an increase in portocollateral resistance of 21% (P < 0.05). The results suggest that nipradilol may ensure a more effective control of portal hypertension than propranolol, presumably via its venodilatory action on portocollateral vessels.