SIRT1 contributes to telomere maintenance and augments global homologous recombination

SIRT1 is a positive regulator of telomere length and attenuates age-associated telomere shortening.

Yeast Sir2 deacetylase is a component of the silent information regulator (SIR) complex encompassing Sir2/Sir3/Sir4. Sir2 is recruited to telomeres through Rap1, and this complex spreads into subtelomeric DNA via histone deacetylation. However, potential functions at telomeres for SIRT1, the mammalian orthologue of yeast Sir2, are less clear. We studied both loss of function (SIRT1 deficient) and gain of function (SIRT1^super) mouse models. Our results indicate that SIRT1 is a positive regulator of telomere length in vivo and attenuates telomere shortening associated with aging, an effect dependent on telomerase activity. Using chromatin immunoprecipitation assays, we find that SIRT1 interacts with telomeric repeats in vivo. In addition, SIRT1 overexpression increases homologous recombination throughout the entire genome, including telomeres, centromeres, and chromosome arms. These findings link SIRT1 to telomere biology and global DNA repair and provide new mechanistic explanations for the known functions of SIRT1 in protection from DNA damage and some age-associated pathologies.

[Reproduction and growth of the fish Lutjanus guttatus (Pisces: Lutjanidae) in the Gulf of Nicoya, Costa Rica]

Reproduction and growth of the fish Lutjanus guttatus (Pisces: Lutjanidae) in the Gulf of Nicoya, Costa Rica. The fish Lutjanus guttatus is important in the fisheries of Golfo de Nicoya, Costa Rica where they are captured with varied gear mainly by the artisanal fleet. We measured specimens from the commercial catch of 2002-2006. Gonadal state was determined macroscopically and age with otoliths The total length-total weight relationship was y = 0.0236x(2.8153) and total length-eviscerated weight y = 0.0216x(2.8129). Simplified relationships were y = 0.0173x3 and y = 0.0162x3. There is year-round reproduction with peaks in March (dry season) and September (rainy season). Male-female sexual ratio was 1:1. The age-length key for the gulf shows availability until the 6 years of age. The von Bertalanffy growth curve is L(t) = 65,9 (1-e(-0.13(t+2,66))).

Comparison of the performance of the Gea extracorporeal knot with the Roeder extracorporeal knot and the classical knot

BACKGROUND

Laparoscopy is useful to treat surgical diseases, yet tying sutures in the cavity is a challenge. A knot to secure tissue approximation, which would be hand-made, secure, simple, easy, quick, reliable, and extracorporeal without extra mechanical devices, was developed and named the Gea knot.

METHODS

A comparative study of the Gea knot, the Roeder knot, and the classical surgical knot, as the gold standard, using polypropylene, silk, catgut, polyglycolic acid, and Polyglactin 910, all of them of 1-0 caliber, was performed in pigs. Measurements were time to perform, slippage, and breaking point which was measured with a manual digital tensiometer.

RESULTS

The Gea knot was significantly faster statistically to perform than the Roeder knot and more resistant against rupture and slippage. The slippage rate was significantly lower statistically in the Gea knot than in the Roeder knot when Polyglactin 910 and polypropylene were used.

CONCLUSION

The Gea knot is a good alternative for laparoscopic procedures.

Ventilatory and cardiovascular responses to hypoxia and exercise in Andean natives living at sea level

This study was designed to determine in subjects born at high altitude who move to sea level (HA-SL: born at 3500 m or above; n = 25) whether their cardiorespiratory responses to hypoxia and exercise are similar to those of sea level natives (SL,n = 25). The average age (39 +/- 7.3 yr), weight (72 +/- 7.3 kg), and height (1.71 +/- 0.01 m) did not differ between the SL and HA-SL subjects. All subjects were studied at rest or during exercise (60 W on cycle ergometer) while breathing room air (F(IO2) = 0.21 and P(B) = 760) or hypoxia (F(IO2) = 0.115 and PB = 760) in the following order: (1) normoxia at rest (NX-Rs), (2) hypoxia at rest (HX-Rs, 11.5% O(2)), hypoxia at exercise (HX-Ex), and normoxia at exercise (NX-Ex). Each period lasted 5 min. In absolute values, HA-SL showed significantly higher ventilation (V(E), L/min) during exercise in both normoxia and hypoxia and higher oxygen saturation (Sa(O2), %) during hypoxia both at rest and in exercise. They also had lower end-tidal CO(2) values (P(ETCO2), torr) at rest in both normoxia and hypoxia, but a higher P(ETCO2) in hypoxic exercise. Heart rate (HR, beats/min) was lower at rest in both normoxia and hypoxia, but higher in exercise. With acute hypoxia, Sa(O2) decreased less in the HA-SL than in the SL at rest (HA-SL, 9.2 +/- 0.8; SL, 12.0 +/- 0.82) and during exercise (HA-SL, 18.3 +/- 1.1; SL, 21.2 +/- 1.2). In conclusion, this study shows that HA-SL natives have increased ventilation and heart rate during exercise once their lifelong hypoxia is relieved.

Arthroscopic extirpation of an osteoid osteoma of the acetabulum

We present the case of a 16-year-old boy with an 18-month history of pain in the left groin for 18 months. In addition to the simple radiographic examination, magnetic resonance imaging, bone scan, and computed tomography were necessary to finally diagnose an acetabulum osteoid osteoma (AOO). Excision of the lesion was performed arthroscopically and pathologic testing confirmed the diagnosis. The patient's symptoms disappeared immediately after the surgery, and had not reappeared as of the 6-month postoperative evaluation. We conclude that arthroscopic excision of an AOO is possible and avoids the aggressive open approach as well as operative hip dislocation.

Inter and intra-species-related differences in the regulation of the cardiac autonomic system

The heart rate response to isoproterenol (HR-Iso), density and affinity (kd) of beta-adrenergic (beta-AR) and muscarinic (M2) receptors were compared among three rodents with different generation-life histories of confinement and of high altitude exposure. The European guinea pig (Cavia porcellus) (EGp), a laboratory animal that arrived in Europe after the Spanish Conquest of South America and the Peruvian guinea pig (C. porcellus) (PGp), a semi-wild animal that came from the altiplano to sea level at least 25 generations ago, were used for intra-species comparison. Wistar rats (WR) were used for inter-species comparison as representative of a typical sea level laboratory animal. The HR-Iso was lower in EGp than in the PGp. The PGp showed the highest beta-AR density (P < 0.0005) and the highest beta-AR kd values (P < 0.0005) when compared to both EGp and WR groups (beta-AR Bmax (fmol mg-1 prot), WR, 19 +/- 4; Egp, 34 +/- 10; PGp, 74 +/- 15. beta-AR kd (pM), WR, 24 +/- 10; Egp, 17 +/- 7; PGp, 39 +/- 14). In contrast, PGp showed lower M2 receptor density values than the EGp (P < 0.0005). The WR had the highest M2 receptor densities (M2 Bmax (fmol mg-1 prot), WR, 188 +/- 15; Egp, 147 +/- 9; PGp, 118 +/- 6 and M2 kd (pM), WR, 65 +/- 12; Egp, 67 +/- 6; PGp, 92 +/- 2). The inter and intra-species differences found may be related to their respective history of confinement rather than to their history of exposure to high altitude.

Similar hypoxic ventilatory responses in sea-level natives and high-altitude Andean natives living at sea level

High-altitude (HA) natives have blunted ventilatory sensitivities to hypoxia, and it is uncertain whether this blunting is reversible on migration to sea level (SL). To study this, the ventilatory sensitivities to hypoxia of HA natives residing near SL were compared with those of SL natives. Two studies were performed. In study A, 24 HA subjects who had lived above 3,000 m for an average of 14 yr and had been resident at SL for an average of 23 yr were compared with 23 SL controls. In study B, 25 HA subjects who had lived above 3,500 m for at least 20 yr and had been resident at SL for no more than 5 yr were compared with 25 SL controls. Hypoxic sensitivities were assessed by breathing seven progressively more hypoxic gas mixtures that contained progressively more CO2 in an attempt to maintain isocapnia throughout. The ventilatory sensitivities to hypoxia (l . min-1 . %-1 . m-2) did not differ significantly (by analysis of variance) between HA and SL natives in either study A (-0.51 +/- 0.25, mean +/- SD) or study B (-0.34 +/- 0. 15), but the ventilatory sensitivities did differ significantly between the two studies for reasons which are not entirely clear. We conclude that HA natives residing at SL, even if previously at HA for >20 yr, do not maintain the severely blunted hypoxic responses that have been reported in such individuals.

Changes in whole blood oxygen affinity and eggshell permeability in high altitude chickens translocated to sea level

High altitude (HA; n = 5) chickens (Gallus gallus) with a high oxygen hemoglobin (Hb) affinity were transported from their birthplace (Puno, Perú 4,000 m) down sea level (Lima, Perú). The in vivo whole blood oxygen affinity (P50) and the eggshell permeability (P) were studied after several months living at sea level and in the first (F1) and second (F2) generations born at sea level. Our approach was to analyze changes in Hb affinity and eggshell permeability, considered as indicators of HA adaptation in birds. Our results show an increase of the P50 values (a decrease in Hb affinity) towards sea-level values. The results in P indicate that this variable increases towards sea level values in the F2 generation. We conclude that in the Andean chicken, a relative "newcomer" to high altitude (no more than 500 years), neither the Hb affinity for oxygen nor the eggshell permeability are invariable indicators of HA adaptation, in contrast with other native high altitude mammals and birds.

Hypoxia- and normoxia-induced reversibility of autonomic control in Andean guinea pig heart

We herein describe the regulation of cardiac receptors in a typical high-altitude native animal. Heart rate response to isoproterenol (HRIso) (beats.min-1.mg Iso.kg-1) and atropine, the density of beta-adrenergic (beta AR) and muscarinic (M2) receptors, and the ventricular content of norepinephrine (NE) and dopamine (DA) were studied in guinea pigs (Cavia porcellus). Animals native to Lima, Peru (150 m) were studied at sea level (SL) and after 5 wk at 4,300-m altitude (SL-HA). Animals native to Rancas [Pasco, Peru (4,300 m)] were studied at high altitude (HA) and after 5 wk at SL (HA-SL). HA animals had a lower HRIso, maximum number of beta AR binding sites (Bmax), beta AR dissociation constant (Kd), NE, and DA (P < 0.05) and a higher M2 Bmax (P < 0.001) when compared with the SL group. HA-SL showed an increase of the HRIso, beta Ar Kd, and NE (P < 0.05) and a decrease of the M2 Bmax and Kd (P < 0.0001) when compared with the HA group. The present study demonstrates the differential regulation and reversibility of the autonomic control in the guinea pig heart.

Hemoglobin affinity and structure in high-altitude and sea-level carnivores from Peru

We compared hemoglobin affinity (P50) and structure of high altitude (HA) carnivores with populations of the same species or genus living at sea level (SL). P50 was measured in cats, pumas and foxes. It differed in animals occupying both niches. SL: cat 29.3 torr, puma 36.3 torr, fox 26.2 torr; HA: cat 22.5 torr, puma 31.1 torr, fox 18.5 torr. Heme and globins were fractionated by HPLC. Puma and fox hemoglobins also showed structural differences. P50 is lower in genotypically HA-adapted species studied and can differentiate SL and HA populations of the same species.

Mucocutaneous and soft tissue infections caused by Xanthomonas maltophilia. A new spectrum

OBJECTIVE

To describe the mucocutaneous and soft tissue infections caused by Xanthomonas maltophilia in patients with cancer.

DESIGN

A retrospective 15-month clinical study.

SETTING

Academic, referral-based cancer center.

PATIENTS

Of 237 patients with X. maltophilia isolated from all sites during the 15-month study period, 114 patients were judged to have true X. maltophilia infections. Only patients with mucocutaneous and soft tissue infections were included in the study.

RESULTS

17 (15%) of the 114 patients with X. maltophilia infection had mucocutaneous and soft tissue infections: Six patients had metastatic cellulitis, 5 had primary cellulitis usually associated with catheter use, and 6 had infected mucocutaneous ulcers. The metastatic cellulitis consisted of previously undescribed multiple, hard, tender nodules with surrounding and distant cellulitis (5 patients) or ecthyma gangrenosum (1 patient). Four of these patients died of the infection. Metastatic cellulitis and mucocutaneous infections occurred in hospitalized, neutropenic patients who received broad-spectrum antibiotics (beta-lactams, quinolones), often with in vitro activity against the infecting organisms. Response usually correlated with recovery from myelosuppression and administration of trimethoprim-sulfamethoxazole with or without ticarcillin-clavulanate. Catheter removal contributed to response in the treatment of primary cellulitis.

CONCLUSIONS

Mucocutaneous and soft tissue infections caused by X. maltophilia are not uncommon, and X. maltophilia can cause metastatic nodular skin lesions that mimic disseminated fungal infections. It also causes serious morbidity and high mortality in patients with metastatic skin nodules and can cause superinfections in patients receiving broad-spectrum beta-lactam or quinolone antibiotics to which the organisms are susceptible when the infections develop. Catheter removal contributes to a favorable outcome in patients with catheter-associated cellulitis without bacteremia. Xanthomonas maltophilia infection should be added to the differential diagnosis of mucocutaneous or soft tissue infection in patients with cancer. Trimethoprim-sulfamethoxazole with or without ticarcillin-clavulanate is the current treatment of choice for culture-proven infections, but early empiric therapy may improve outcome.

[Endoscopic resolution of acute dilatation of the colon secondary to edema of colonic anastomosis]

Acute colonic dilation due to anastomotic edema is rare and is not always solved with conservative treatment. Endoscopic colonic decompression was carried out in 3 patients completing the procedure with a transrectal drainage. No complications resulted from the procedure and all 3 patients did well, once motility was re-established.