Heme compound II models in chemoselectivity and disproportionation reactions.

Heme compound II models bearing electron-deficient and -rich porphyrins, [FeIV(O)(TPFPP)(Cl)]- (1a) and [FeIV(O)(TMP)(Cl)]- (2a), respectively, are synthesized, spectroscopically characterized, and investigated in chemoselectivity and disproportionation reactions using cyclohexene as a mechanistic probe. Interestingly, cyclohexene oxidation by 1a occurs at the allylic C-H bonds with a high kinetic isotope effect (KIE) of 41, yielding 2-cyclohexen-1-ol product; this chemoselectivity is the same as that of nonheme iron(iv)-oxo intermediates. In contrast, as observed in heme compound I models, 2a yields cyclohexene oxide product with a KIE of 1, demonstrating a preference for C[double bond, length as m-dash]C epoxidation. The latter result is interpreted as 2a disproportionating to form [FeIV(O)(TMP+˙)]+ (2b) and FeIII(OH)(TMP), and 2b becoming the active oxidant to conduct the cyclohexene epoxidation. In contrast to 2a, 1a does not disproportionate under the present reaction conditions. DFT calculations confirm that compound II models prefer C-H bond hydroxylation and that disproportionation of compound II models is controlled thermodynamically by the porphyrin ligands. Other aspects, such as acid and base effects on the disproportionation of compound II models, have been discussed as well.

Acute post traumatic portal venous thrombosis associated with shattered spleen: A case report.

Post-traumatic portal venous thrombosis is a rare event, and is usually seen in association with penetrating injuries. Portal venous thrombosis following blunt abdominal trauma is extremely rare with only few reports in the literature, some associated with underlying coagulation disorders. We report multidetector computed tomography findings in a case of blunt abdominal trauma with otherwise normal coagulation profile, which showed shattered spleen and MDCT evidence of acute thrombosis in the right branch of the portal vein. To the best of our knowledge, this is the first documented report of acute portal venous thrombosis in association with shattered spleen.

Dioxygen Activation and O-O Bond Formation Reactions by Manganese Corroles.

Activation of dioxygen (O2) in enzymatic and biomimetic reactions has been intensively investigated over the past several decades. More recently, O-O bond formation, which is the reverse of the O2-activation reaction, has been the focus of current research. Herein, we report the O2-activation and O-O bond formation reactions by manganese corrole complexes. In the O2-activation reaction, Mn(V)-oxo and Mn(IV)-peroxo intermediates were formed when Mn(III) corroles were exposed to O2 in the presence of base (e.g., OH-) and hydrogen atom (H atom) donor (e.g., THF or cyclic olefins); the O2-activation reaction did not occur in the absence of base and H atom donor. Moreover, formation of the Mn(V)-oxo and Mn(IV)-peroxo species was dependent on the amounts of base present in the reaction solution. The role of the base was proposed to lower the oxidation potential of the Mn(III) corroles, thereby facilitating the binding of O2 and forming a Mn(IV)-superoxo species. The putative Mn(IV)-superoxo species was then converted to the corresponding Mn(IV)-hydroperoxo species by abstracting a H atom from H atom donor, followed by the O-O bond cleavage of the putative Mn(IV)-hydroperoxo species to form a Mn(V)-oxo species. We have also shown that addition of hydroxide ion to the Mn(V)-oxo species afforded the Mn(IV)-peroxo species via O-O bond formation and the resulting Mn(IV)-peroxo species reverted to the Mn(V)-oxo species upon addition of proton, indicating that the O-O bond formation and cleavage reactions between the Mn(V)-oxo and Mn(IV)-peroxo complexes are reversible. The present study reports the first example of using the same manganese complex in both O2-activation and O-O bond formation reactions.

Magnetic Resonance Imaging (MRI) Depiction of Robert's Uterus: A Rare Müllerian Duct Anomaly Presenting with Cyclical Pain in Young Menstruating Woman.

BACKGROUND: Robert's uterus is a very rare müllerian duct anomaly which is characterised by septate uterus with obstruction of a one-sided cavity and formation of hematometra. Therefore, patients present with cyclical abdominal pain during menstruation along with normal menstrual flow. CASE REPORT: We present magnetic resonance imaging (MRI) findings in a case of Robert's uterus in a young woman. CONCLUSIONS: Robert's uterus is a very rare anomaly which can be very well characterized by magnetic resonance imaging (MRI). MRI can also show any associated hematometra and endometriomas complicating this condition and aid in the institution of appropriate management in such cases.

Tunneling Effect That Changes the Reaction Pathway from Epoxidation to Hydroxylation in the Oxidation of Cyclohexene by a Compound I Model of Cytochrome P450.

The rate constants of the C═C epoxidation and the C-H hydroxylation (i.e., allylic C-H bond activation) in the oxidation of cyclohexene by a high-valent iron(IV)-oxo porphyrin π-cation radical complex, [(TMP•+)FeIV(O)(Cl)] (1, TMP = meso-tetramesitylporphyrin dianion), were determined at various temperatures by analyzing the overall rate constants and the products obtained in the cyclohexene oxidation by 1, leading us to conclude that reaction pathway changes from the C═C epoxidation to C-H hydroxylation by decreasing reaction temperature. When cyclohexene was replaced by deuterated cyclohexene (cyclohexene-d10), the epoxidation pathway dominated irrespective of the reaction temperature. The temperature dependence of the rate constant of the C-H hydroxylation pathway in the reactions of cyclohexene and cyclohexene-d10 by 1 suggests that there is a significant tunneling effect on the hydrogen atom abstraction of allylic C-H bonds of cyclohexene by 1, leading us to propose that the tunneling effect is a determining factor for the switchover of the reaction pathway from the C═C epoxidation pathway to the C-H hydroxylation pathway by decreasing reaction temperature. By performing density functional theory (DFT) calculations, the reaction energy barriers of the C═C epoxidation and C-H bond activation reactions by 1 were found to be similar, supporting the notion that small environmental changes, such as the reaction temperature, can flip the preference for one reaction to another.

Portal Annular Pancreas: A Rare and Overlooked Anomaly.

BACKGROUND: Portal annular pancreas is a rare pancreatic developmental anomaly which is often overlooked at imaging, and often diagnosed retrospectively when it is detected incidentally at the time of surgery. Although the anomaly itself is asymptomatic, it becomes important in cases where pancreatic resection/anastomosis is planned, because of varying ductal anatomy, risk of ductal injury and increased risk of postoperative pancreatic fistula formation. CASE REPORT: We present imaging findings in a case of portal annular pancreas in a 45-year-old male patient. CONCLUSIONS: Portal annular pancreas is a rare and often neglected pancreatic anomaly due to a lack of awareness of this entity. With the advent of MDCT and MRI, accurate preoperative diagnosis of this condition is possible.

Chemical shift magnetic resonance imaging in differentiation of benign from malignant vertebral collapse in a rural tertiary care hospital in North India.

INTRODUCTION: Magnetic resonance imaging (MRI) is the modality of the first choice for evaluation of vertebral compression/collapse. Many MRI qualitative features help to differentiate benign from malignant collapse. We conducted this study to look for a quantitative difference in chemical shift values in benign and malignant collapse using dual-echo gradient echo in-phase/out-phase imaging. MATERIALS AND METHODS: MRI examinations of a total of 38 patients were retrospectively included in the study who had vertebral compression/collapse with marrow edema in which final diagnosis was available at the time of imaging/follow-up. Signal intensity value in the region of abnormal marrow signal and adjacent normal vertebra was measured on in phase/out phase images. Signal intensity ratio (SIR) was measured by dividing signal intensity value on opposite phase images to that on in phase images. SIR was compared in normal vertebrae and benign and malignant vertebral collapse. RESULTS: There were 21 males and 17 females with mean age of 52.4 years (range 28-76 years). Out of total 38 patients, 18 were of benign vertebral collapse and 20 of malignant vertebral collapse. SIR in normal vertebrae was 0.30 ± 0.14, 0.67 ± 0.18 in benign vertebral collapse, and 1.20 ± 0.27 in malignant vertebral collapse with significant difference in SIR of normal vertebrae versus benign collapse (P < 0.01) and in benign collapse versus malignant collapse (P < 0.01). Assuming a cutoff of <0.95 for benign collapse and ≥0.95 for malignant collapse, chemical shift imaging had a sensitivity of 90% and specificity of 94.4%. CONCLUSION: Chemical shift imaging is a rapid and useful sequence in differentiating benign from malignant vertebral collapse with good specificity and sensitivity.

An Evaluation of Retentive Ability and Deformation of Acetal Resin and Cobalt-Chromium Clasps.

AIM: To compare the retentive ability and deformation of Acetal resin with Cobalt-Chromium clasps via Insertion Removal apparatus after subjecting them to stimulate clinical use. MATERIALS AND METHODS: Materials used for this study are commercially available Cobalt-Chromium alloy namely Wironit, Bego, Germany and Acetal resin namely Biodentaplast, Bredent, Germany. The test samples were divided into two major groups based on the type of materials used in the study. Each major group is further subdivided into two sub groups based on the retentive undercut depths used to engage the clasps. So a total of 20 specimens were prepared, comprising of 5 specimens in each sub group. Then the specimens were tested for retention force and deformation. RESULTS: The results of this study indicate that acetal resin clasps are resistant to deformation and may offer a clinical advantage over the conventional metal clasps. The retentive force of acetal resin clasps did not decrease over the cycling periods. This would be attributed to the resilient nature of acetal resin. Under the conditions of the present study cobalt chromium clasps lost retentive force within 730 cycles of placement and removal and continued to lose retentive force during the remaining test period. CONCLUSION: This invitro study demonstrated that retentive force of cobalt chromium clasp is superior to that of Acetal resin for removable partial dentures. As acetal resin clasps exhibits greater flexibility and long term retentive resiliency, it can be used for removable partial dentures where aesthetics or periodontal health is a primary concern.

Spectrum of MDCT Findings in Bowel Obstruction in a Tertiary Care Rural Hospital in Northern India.

INTRODUCTION: Multidetector Computed Tomography (MDCT) provides clinically and surgically important information in bowel obstruction. It can depict the severity, level and cause of obstruction. AIM: To depict the spectrum of MDCT findings in cases of small and large bowel obstruction. MATERIALS AND METHODS: Contrast enhanced MDCT examination of 50 patients were retrospectively included in the study who had evidence of clinical as well as MDCT evidence of bowel obstruction and in whom surgical/clinical follow-up for final diagnosis was available. CT scan was done in all the patients with Ingenuity CT (128 slice MDCT, Philips Medical Systems). The axial sections were reconstructed in coronal and sagital planes to determine site and cause of bowel obstruction. RESULTS: There were 34 males and 16 females patients in this study with mean age of 28.4 years. The level of obstruction was in small bowel in 39 patients (76.67%) and large bowel in 11 patients (23.33%). Adhesive bands were the cause of Small Bowel Obstruction (SBO) in 17 patients (43.5% of SBO patients). The most common CT signs in adhesive band SBO were beak sign (seen in 70.6% patients) and fat notch sign (52.9% patients). Five cases of SBO were secondary to benign stricture. Matted adhesions were the cause of obstruction in 3 patients. All these patients showed transition zone in pelvis with positive small bowel faeces sign. Two patients with SBO due to adhesive band had evidence of closed loop obstruction with evidence of gangrenous gut on surgery. Large Bowel Obstruction (LBO) was seen in 11 patients. Most common cause of LBO was primary colonic malignancy, accounting for 7 patients (63.6%). In one patient, the cause was direct invasion of hepatic flexure by carcinoma of gall bladder. Other causes of LBO were pelvic adhesions, faecal impaction and ischaemic stricture. CONCLUSION: SBO is more common than LBO with adhesive bands being the most common cause of SBO. MDCT is very useful for depicting site and cause of obstruction and any associated complications.

Magnetic resonance imaging depiction of acquired Dyke-Davidoff-Masson syndrome with crossed cerebro-cerebellar diaschisis: Report of two cases.

Acquired Dyke-Davidoff-Masson syndrome, also known as hemispheric atrophy, is characterized by loss of volume of one cerebral hemisphere from an insult in early life. Crossed cerebellar diaschisis refers to dysfunction/atrophy of cerebellar hemisphere which is secondary to contralateral supratentorial insult. We describe magnetic resonance imaging findings in two cases of acquired Dyke-Davidoff-Masson syndrome with crossed cerebro-cerebellar diaschisis.

Additional merit of coronal STIR imaging for MR imaging of lumbar spine.

INTRODUCTION: Back pain is a common clinical problem and is the frequent complaint for referral of lumbar spine magnetic resonance imaging (MRI). Coronal short tau inversion recovery sequence (STIR) can provide diagnostically significant information in small percentage of patients. MATERIALS AND METHODS: MRI examinations of a total of 350 patients were retrospectively included in the study. MR sequences were evaluated in two settings. One radiologist evaluated sagittal and axial images only, while another radiologist evaluated all sequences, including coronal STIR sequence. After recording the diagnoses, we compared the MRI findings in two subsets of patients to evaluate additional merit of coronal STIR imaging. RESULTS: With addition of coronal STIR imaging, significant findings were observed in 24 subjects (6.8%). Twenty-one of these subjects were considered to be normal on other sequences and in three subjects diagnosis was changed with the addition of coronal STIR. Additional diagnoses on STIR included sacroiliitis, sacroiliac joint degenerative disease, sacral stress/insufficiency fracture/Looser's zones, muscular sprain and atypical appendicitis. CONCLUSION: Coronal STIR imaging can provide additional diagnoses in a small percentage of patients presenting for lumbar spine MRI for back pain. Therefore, it should be included in the routine protocol for MR imaging of lumbar spine.

Correlation of qualitative and quantitative MRI parameters with neurological status: a prospective study on patients with spinal trauma.

INTRODUCTION: Spinal trauma is relatively more common in young active individuals. Although its mortality is low, it is an important cause of long term disability. Magnetic resonance imaging (MRI) can accurately depict presence and extent of spinal cord injury (SCI) in these patients. This study was aimed to look for various qualitative and quantitative MRI findings which are predictive of initial neurological deficit in patients with spinal trauma and final outcome on follow-up. MATERIALS AND METHODS: The present study was conducted on 50 patients with suspected acute cervical or dorsal spinal trauma presenting for MRI study. American Spinal Injury Association (ASIA) motor score was used for assessing neurological status at the time of presentation, at the time of discharge/2weeks and at 3-6 months follow up. Various MRI qualitative and quantitative parameters were evaluated for correlation with severity of spinal injury. RESULTS: Normal baseline MRI (pattern 0) was seen in 12 subjects and was associated with incomplete SCI in 4 subjects (ASIA grade D) followed by complete recovery in all patients on follow-up examination. Pattern I (haemorrhage) was associated with complete spinal cord injury. Pattern II (oedema) was associated with incomplete SCI and good functional recovery on follow up.Pattern III (contusion) was associated with intermediate severity of injury. Compression and transection patterns were associated with complete neurological deficit at presentation and increased mortality at subsequent follow-up. All the three quantitative parameters i.e. lesion length,maximum (bony) canal compromise (MCC), maximum spinal cord compression (MSCC) were significantly increased in patients with complete SCI as compared to those with incomplete SCI. The best predictors for baseline ASIA score were MCC, cord oedema and cord haemorrhage. For the final ASIA score, the best predictors were baseline ASIA score and cord haemorrhage. CONCLUSION: MRI is excellent imaging modality for detecting and assessing severity of spinal trauma. In our study, presence of cord haemorrhage, MCC and cord oedema were best predictors of baseline neurological status at presentation, whereas baseline ASIA score and cord haemorrhage were best predictors of final neurological outcome.

Cystic adventitial disease of popliteal artery with significant stenosis.

Cystic adventitial disease of popliteal artery is a rare condition of unknown etiology which usually presents in middle-aged men. We present Doppler and computed tomography angiography findings in a case of cystic adventitial disease with significant obstruction of popliteal artery, with secondary narrowing of popliteal vein.

A hospital based epidemiological study of snakebite in Western Development Region, Nepal.

Snakebite is an important and serious medical problem throughout the entire terai region of Nepal. But comprehensive study of snakebite epidemiology in Western Development Region of Nepal is scarce. We described the status of snakebite situation in the region based on retrospective data retrieved from 10 snakebite treatment centers during June 2011 to February 2012. We reported six thousand and nine hundred ninety three snakebites in 2008-2010. Of all, we found 640 (9%) cases envenomed and received anti-venom therapy. We recorded the highest number of snakebites in July, August and September, which account 57% of all snakebite victims, during 15.00 and 21.00 h. People aged 11-20 years were mostly victimized by snakebite as compared to other age groups. Female suffered more than male. The average requirement of polyvalent snake anti-venom was 16 vials. Overall, case fatality rate was 13%.

Full term broad ligament pregnancy through a Cesarean scar.

A broad ligament pregnancy is an extremely rare condition. Diagnosis is often missed and finally made during laparotomy. We present a case which remained undiagnosed throughout her pregnancy till she reached term and unfortunately had intrauterine foetal demise when she reported to our hospital. On clinical suspicion, ultrasound and magnetic resonance imaging evaluation was done which picked up the diagnosis of abdominal pregnancy. On laparotomy a broad ligament pregnancy was found with a rent in the previous Cesarean scar towards the gestational sac in the broad ligament.

Aorto-esophageal fistula secondary to penetrating atherosclerotic ulcer.

Aorto-esophageal fistula (AEF) is a rare and life threatening condition, which can be rapidly fatal. More than half of such cases are secondary to aortic aneurysm rupture. There are only two previous reports describing AEF caused by penetrating atherosclerotic ulcer. We present multidetector computed tomography findings in a case of AEF secondary to penetrating atherosclerotic ulcer.