Extended trans-septal approach for mitral valve surgery: Our early experience

Background Extended trans septal (ETS) approach for mitral valve surgery often divides the artery to the Sino-Atrial node. The clinical implication of this is contentious. We analyzed our early results with ETS approach. Methods Between June 1998 and September 2003 eleven patients underwent mitral valve surgery by ETS approach. Six were females. Age ranged from 19 years to 67 years (median 40 years). Six underwent mitral valve replacement (MVR). Four underwent aortic and mitral (double) valve replacement (DVR). One had mitral valve repair. Three had additional procedures (tricuspid valve repair=1, Coronary artery bypass=1, Aorto bifemoral graft=1). Cardiopulmonary bypass ranged from 64 minutes to 77 minutes (median 72 minutes) for MVR and 112 minutes to 178 minutes (median 140 minutes) for DVR. Aortic cross clamp times ranged from 39 minutes to 52 minutes (median 47 minutes) for MVR and 74 minutes to 120 minutes (median 95 minutes) for DVR. Results There was no mortality or morbidity attributed to the ETS approach. One early death in emergency DVR was due to heart failure. Three patients needed seqeuntial pacing in the immediate post-operative period. Nine out of ten survivors were back to their preoperative rhythms on hospital discharge (6 sinus rhythm; 3 atrial fibrillation). One patient with preoperative trifascicular block who underwent reoperation to fix a paravalvular mitral leak needed a permanent pacemaker (VVI). The follow-up ranged from 1 month to 64 months (median 6 months) and is 100% complete. There was no late death or new arrhythmia. Conclusions Extended trans septal approach is safe. It gives excellent exposure of the mitral valve. division of the sinus node artery is not deleterious in the short to intermediate term. Presented at the 50th Annual Meeting of IACTS. New Delhi, Feb. 2004.     

Effect of the external donors on the polymerization of 4-methyl-1-pentene with high activity MgCl2/TiCl4 catalytic system

In order to find out correlations between the structure of an external donor and the obtained polymer, the effects of different external donors on the activity and stereospecificity of the MgCl₂/TiCl₄ catalytic system in the bulk polymerization of 4-methyl-1-pentene (4MP) were carefully studied. Different silane compounds of the structure R_nSi(OR')_4-n (where: n = 1–3, R = alkyl/phenyl, R = alkyl) and Al(i-Bu)₃ (TIBA) were used as external donors and cocatalyst, respectively. The effect of the donor/TIBA mole ratio on the activity and stereospecificity of the catalytic system was studied. Some major effects were observed for the three different external donors, namely, Me₃Si(OMe), Me₂Si(OMe)₂, and Me₃Si(OBu)₃, in the 4MP polymerization process. It was observed that the effect of the external silane donor on the polymerization strongly depends upon the size of the alkoxy and hydrocarbon (alkyl/phenyl) groups which are attached to the silicon atom. A selective deactivation of the non-stereospecific centers, as well as a transformation of the non-stereospecific into isospecific centers, is assumed to occur. On the basis of the obtained results and literature data available for the propene polymerization, the concept of structural conformity between the ligand-surrounded active center and the monomer molecule was carried forward.     

It May Seem Inflammatory,but Some T Cells Are Innately Healing to the Bone

Among the most significant developments to have taken place in osteology over the last few decades is an evolution from treating and viewing bone disorders primarily through an endocrine lens to instead seeing them as metabolic disorders that interface at the molecular and cellular level with the immune system. Osteoimmunology was officially born in response to accumulating evidence that the immune system is integrally involved in bone remodeling, but much of the early work focused on the role of conventional αβ T cells in driving bone loss. There is, however, emerging data indicating that innate lymphocytes, in particular γδ T cells, may in fact be important for bone regeneration. We first observed that bisphosphonate‐associated osteonecrosis of the jaw (ONJ), a rare but serious adverse drug effect characterized by nonhealing necrotic bone tissue of the mandible or maxilla, was linked to a deficiency in a subset of γδ T cells found in human peripheral blood. Patients who developed ONJ while on bisphosphonate therapy not only lacked the main subset of circulating γδ T cells, but they also all had underlying conditions that compromised their immune integrity. A number of recent studies have unraveled the role of γδ T cells (and lymphocytes sharing their characteristics) in bone regeneration—particularly for fracture healing. These findings seem to contradict the prevailing view of such “inflammatory” T cells as being bone degenerative rather than restorative. This viewpoint melds together the emerging evidence of these so‐called inflammatory T cells in bone remodeling and healing—showing that they are not in fact “all bad to the bone.” © 2016 American Society for Bone and Mineral Research.     

Risk of acute pancreatitis with incretin-based therapy: a systematic review and updated meta-analysis of cardiovascular outcomes trials

ABSTRACT

Background

The link of acute pancreatitis (AP) with Incretin based therapies (IBTs) in type 2 diabetes has existed since United States Food and Drug Administration alert in 2010. This issue still remains unresolved due to conflicting results among studies.     

A clinical trial of 7 alpha-methyl-19-nortestosterone implants for possible use as a long-acting contraceptive for men

Several preparations of testosterone and its esters are being investigated alone or in combination with other gonadotropin-suppressing agents as possible antifertility agents for men. We studied the effectiveness of 7 alpha-methyl-19-nortestosterone (MENT) as an antispermatogenic agent in men. MENT has been shown to be more potent than testosterone and to be resistant to 5 alpha-reduction. For sustained delivery of MENT, we used a system consisting of ethylene vinyl acetate implants containing MENT acetate (Ac), administered subdermally. Thirty-five normal volunteers were recruited in 3 clinics and were randomly assigned to 1 of 3 doses: 1 (12 men), 2 (11 men), or 4 (12 men) MENT Ac implants. The initial average in vitro release rate of MENT Ac from each implant was approximately 400 micro g/day. Implants were inserted subdermally in the medial aspect of the upper arm under local anesthesia. The duration of treatment was initially designed to be 6 months. However, in 2 clinics the duration of treatment was extended to 9 months for the 2-implant group and to 12 months for the 4-implant group. Dose-related increases in serum MENT levels and decreases in testosterone, LH, and FSH levels were observed. Effects on sperm counts were also dose related. None of the subjects in the 1-implant group exhibited oligozoospermia (sperm count, <3 million/ml). Four subjects in the 2-implant group became oligozoospermic, 2 of whom reached azoospermia. Eight subjects in the 4-implant group reached azoospermia, with 1 exhibiting oligozoospermia, whereas 2 were nonresponders. Side effects generally seen with androgen administration, such as increases in erythrocyte count, hematocrit, and hemoglobin and a decrease in SHBG, were also seen in this study and were reversible. Changes in lipid parameters were moderate and transient. Liver enzymes showed small changes. This study demonstrates that MENT Ac, when administered in a sustained release fashion via subdermal implants, can inhibit spermatogenesis over a prolonged period after a single administration and has the potential to be used as a male contraceptive.     

Isoelectronic perturbations to f-d-electron hybridization and the enhancement of hidden order in URu2Si2

Electrical resistivity measurements were performed on single crystals of URu_2–xOs_xSi₂ up to x = 0.28 under hydrostatic pressure up to P = 2 GPa. As the Os concentration, x, is increased, 1) the lattice expands, creating an effective negative chemical pressure P_ch(x); 2) the hidden-order (HO) phase is enhanced and the system is driven toward a large-moment antiferromagnetic (LMAFM) phase; and 3) less external pressure P_c is required to induce the HO→LMAFM phase transition. We compare the behavior of the T(x, P) phase boundary reported here for the URu_2-xOs_xSi₂ system with previous reports of enhanced HO in URu₂Si₂ upon tuning with P or similarly in URu_2–xFe_xSi₂ upon tuning with positive P_ch(x). It is noteworthy that pressure, Fe substitution, and Os substitution are the only known perturbations that enhance the HO phase and induce the first-order transition to the LMAFM phase in URu₂Si₂. We present a scenario in which the application of pressure or the isoelectronic substitution of Fe and Os ions for Ru results in an increase in the hybridization of the U-5f-electron and transition metal d-electron states which leads to electronic instability in the paramagnetic phase and the concurrent formation of HO (and LMAFM) in URu₂Si₂. Calculations in the tight-binding approximation are included to determine the strength of hybridization between the U-5f-electron states and the d-electron states of Ru and its isoelectronic Fe and Os substituents in URu₂Si₂.

The heavy-fermion superconducting compound URu2Si2 is known for its second-order phase transition into the so-called “hidden-order” (HO) phase at a transition temperature T0 ≈17.5 K. Extensive investigation of the phase space in proximity to the HO phase transition has provided a detailed picture of the electronic and magnetic structure of this unique phase (1–42). However, more than three decades after the initial characterization of URu2Si2 (1–3), the order parameter for the HO phase is still unidentified.Most perturbations to the URu2Si2 compound have the effect of suppressing HO. The application of an external magnetic field (H) suppresses the HO phase (41, 43) and many of the chemical substitutions (x) at the U, Ru, or Si sites that have been explored significantly reduce T0, even at modest levels of substituent concentration (44–52). At present, only three perturbations are known to consistently enhance the HO phase in URu2Si2: 1) external pressure P, 2) isoelectronic substitution of Fe ions for Ru, and 3) isoelectronic substitution of Os ions for Ru. Upon applying pressure P, the HO phase in pure URu2Si2 is enhanced (6) and the system is driven toward a large-moment antiferromagnetic (LMAFM) phase (53). The HO→LMAFM phase transition is identified indirectly by a characteristic “kink” at a critical pressure Pc ≈1.5 GPa in the T0 (P) phase boundary (18, 53, 54) and also directly by neutron diffraction experiments, which reveal an increase in the magnetic moment from μ ∼ (0.03±0.02)μB/U in the HO phase to μ ∼ 0.4 μB/U in the LMAFM phase (13, 55, 56).Recent reports indicate that the isoelectronic substitution of Fe ions for Ru in URu2Si2 replicates the T0(P) behavior in URu2Si2 (57–59). An increase in x in URu2−xFexSi2 enhances the HO phase and drives the system toward the HO→LMAFM phase transition at a critical Fe concentration xc ≈0.15 (58, 60). The decrease in the volume of the unit cell due to substitution of smaller Fe ions for Ru may be interpreted as a chemical pressure, Pch, where the Fe concentration x can be converted to Pch (x) (57, 59). In addition, the induced HO→LMAFM phase transition in URu2−xFexSi2 occurs at combinations of x and P that consistently obey the additive relationship: Pch(x) + Pc ≈1.5 GPa (57, 59). These results have led to the suggestion that Pch is equivalent to P in affecting the HO and LMAFM phases (58, 59).Reports of the isoelectronic substitution of larger Os ions for Ru have shown that an increase in x in URu2−xOsxSi2 1) expands the volume of the unit cell, thus creating an effective negative chemical pressure (Pch ≤0); 2) enhances the HO phase; and 3) drives the system toward a similar HO→LMAFM phase transition at a critical Os concentration of xc ≈0.065 (60–62). These results are contrary to the expectation that a negative Pch would lead to a suppression of HO and complicate the view of chemical pressure as a mechanism affecting the evolution of phases in URu2Si2.In this paper, we report on the behavior of the T(x, P) boundary for the URu2−xOsxSi2 system based on ρ(T) measurements of single crystals of URu2−xOsxSi2 as a function of Os concentration x and applied pressure P. The T(x, P) phase boundary observed here for the URu2−xOsxSi2 system (57–59) is compared to that of the URu2−xFexSi2 system and also with the behavior of T(P) in pure URu2Si2. As an explanation for the enhancement of HO toward the HO→LMAFM phase transition, we suggest a scenario in which each of the perturbations of Os substitution, Fe substitution, and pressure P favors delocalization of the 5f electrons and increases the hybridization of the uranium 5f-electron and transition metal (Fe, Ru, Os) d-electron states. To avoid an ad hoc explanation of the effect of increasing the Os concentration x in URu2−xOsxSi2, compared to the effects of pressure P and Fe substitution, we explain how pressure P, Fe substitution, and Os substitution are three perturbative routes to enhancement of the U-5f- and d-electron hybridization. The importance of the 5f- and d-electron hybridization to the emergence of HO/LMAFM is presented in the context of the Fermi surface (FS) instability that leads to a reconstruction and partial gapping of the FS during the transition from the paramagnetic (PM) phase to the HO and LMAFM phases (2, 6, 20, 22, 24–26, 37, 38, 63).In an effort to further understand the effect of isoelectronic substitution on the 5f- and d-electron hybridization, calculations in the tight-binding approximation were made for compounds from the series UM2Si2 (M = Fe, Ru, and Os). The calculations indicate that the degree of hybridization is largely dependent on the magnitude of the difference between the binding energy of the localized U-5f electrons and that of the transition metal d electrons.     

Diffusion tensor imaging analysis of rheumatoid arthritis patients with neuropsychiatric features to determine the alteration of white matter integrity due to vascular events

Clinical Rheumatology - The pathophysiology of neuropsychiatric manifestations in rheumatoid arthritis is not well known. The magnetic resonance imaging of the brain in rheumatoid arthritis...