Rapid characterization of carbapenem-resistant Enterobacterales by multiplex lateral flow assay and detection of ceftazidime-avibactam-aztreonam synergy

PURPOSE

The choice of antibiotics for treatment of Carbapenem-Resistant Enterobacterales (CRE) is increasing becoming limited due to co-expression of Metallo-beta-lactamases (MBL) along with other carbapenemases in these isolates. The study aimed to investigate the occurrence of CRE and to determine the in-vitro synergy and clinical outcomes of Ceftazidime-Avibactam and Aztreonam combination in CRE infections in adult Intensive Care Units (ICUs).

METHODS

79 CRE isolates recovered from adult ICUs during January to March 2023 were tested by O.K.N.V.I. RESIST-5, a lateral flow multiplex assay for rapid detection of OXA-48-like, NDM, IMP, VIM, and KPC carbapenemases. Ceftazidime-Avibactam MIC was determined by microbroth dilution method and in vitro synergy between Ceftazidime-Avibactam and Aztreonam was assessed by Modified E-test/disc diffusion method for these isolates.

RESULTS

The study revealed 7.5 % occurrence of CRE in our hospital, with high occurrence of NDM (n = 42, 53.1 %) and OXA-48-like (n = 63, 79.7 %) carbapenemase. Production of more than one type of carbapenemases was found in 44 isolates. A total of 57 isolates (72 %) had Ceftazidime-Avibactam resistance and 44 of them displayed Ceftazidime-Avibactam and Aztreonam in-vitro synergy. Successful clinical outcome was observed in two patients who received Ceftazidime-Avibactam and Aztreonam combination therapy for 7 days or more.

CONCLUSIONS

Despite the preponderance of Ceftazidime-Avibactam resistant CRE expressing NDM and OXA-48-like carbapenemase in our hospital, 77.2 % of them displayed in-vitro synergy of Ceftazidime-Avibactam with Aztreonam. It emphasizes the potential therapeutic utility of this combination in CRE strains showing coproduction of MBL and serine carbapenemases. Greater therapeutic potential of Ceftazidime-Avibactam and Aztreonam combination was observed with extended duration of therapy. However, further clinical evidence is needed to establish the efficacy of this combination and consider other factors that influence treatment outcomes.

Signet cell rectal carcinoma with prostatic involvement detected by FAPI-04 PET-MRI fusion

A 60-year-old male patient diagnosed with mucinous adenocarcinoma of lower third of rectum underwent abdominoperineal resection and permanent colostomy followed by adjuvant chemotherapy. Response evaluation with F-18 FDG PET-CT showed a complete metabolic response. After 6 months, CEA levels started increasing and clinically a recurrence was suspected. A restaging FDG PET-CT showed no obvious malignant disease. Patient presented again within a month with complaints of urinary retention and haematuria. CEA levels were further elevated, and Ga-68 FAPI-04 (FAPI) PET-CT was performed. FAPI PET-CT revealed prostatic and seminal vesicle disease involvement. Additionally, an MRI of pelvis was done and fused with FAPI PET for confirmation of prostatic involvement.

Synthesis, Spectral, Solvent Dependent Linear and Nonlinear Optical Characteristics of (E)-N-(3-(3-(4(dimethylamino)phenyl)acryloyl) phenyl)quinolone-2-carboxamide

This paper presents the synthesis of novel organic compound (E)-N-(3-(3-(4(dimethylamino)phenyl)acryloyl)phenyl)quinolone-2-carboxamide, also known as Quinolinecarboxamide Chalcone (QCC) using aldol condensation and carboxamide formation method. The organic sample QCC was examined by FT-IR, ¹H NMR, ¹³C NMR and mass spectroscopic techniques, respectively. Linear and third-order nonlinear optical (TNLO) properties of QCC dissolved in polar solvents such as DMSO, DMF and Ethanol have also been studied. The order of nonlinear refractive index and nonlinear absorption coefficient of QCC was measured to be 10^-11 m²/W and 10^-5 m/W. The nonlinear refractive index (n₂) of QCC was attributed to negative nonlinearity due to self-defocusing effect, and nonlinear absorption coefficient (β) indicates the behaviors of saturable absorption (SA) and reverse saturable absorption (RSA). The real and imaginary features of the TNLO susceptibility (χ⁽³⁾) of QCC in polar solvents were calculated to be the order of 10^─7 esu. The spectral characteristics of solvent on TNLO susceptibility of QCC were discussed. The results divulged that the synthesized organic compound is a novel nonlinear optical (NLO) material for applications in photonics and optoelectronics.

Functional variations between Mesenchymal Stem Cells of different tissue origins: A comparative gene expression profiling

BACKGROUND

Mesenchymal Stem Cells (MSCs), regardless of the tissue sources, are considered as excellent candidates for cellular therapy as they are immune-privileged cells containing a multitude of therapeutic functions that aid in tissue regeneration and repair. For the effective application of these cells in cell therapy, it is important to understand and characterize their biological functions.

OBJECTIVES

The present study attempts to characterize the variations in multipotent function such as cell surface antigen levels, proliferation, differentiation and stemness (pluripotency) potential of MSCs isolated from foetal [wharton's jelly (WJ), foetal and maternal side of placenta (PF and PM)] and adult tissue sources [bone marrow (BM) and adipose tissue (AT)] using gene expression by real time PCR (qRT-PCR).

RESULTS

Amongst the different tissue sources, PM, PF and AT-MSCs exhibited significant increase (p < 0.001, p < 0.001 and p < 0.01 respectively) in CD 73 expression and therefore could have a role in immunomodulation. WJ-MSCs exhibited superior proliferation potential based on growth curve, PCNA and Wnt gene expression. BM-MSCs were superior in exhibiting trilineage differentiation. Enhanced stemness potential (Oct 4 and Nanog) was observed for both BM and WJ-MSCs. In addition, BM and WJ-MSCs expressed high levels of CD 90 making them suitable in bone repair and regeneration.

CONCLUSION

Thus to conclude, out of the five different sources tested, BM an adult source and WJ-MSCs a foetal source were superior in exhibiting most of the biological functions indicating that these sources may be suitable candidates for cell repair and regeneration studies.

MUC2 and MUC5AC Expression in Colon Cancer: A Preliminary Report from South India

Background: There is scanty data from India regarding MUC protein expression from colorectal cancers (CRC) among Indian patients. Aim of the Study: The aim of this study is to assess the alterations in the expression of MUC2 and MUC5AC in 25 patients with CRC by site of the tumor location and differentiation at histology. Materials and Methods: Patients with proven adenocarcinoma of the colon alone were included for the study. Biopsy specimens obtained from tumorous lesions in the colon were classified based on histopathology as well differentiated, moderately, and poorly differentiated adenocarcinoma. Immunohistochemistry was done in the 4 μm thick sections to identify the expression of MUC2 and MUC5AC mucins. Results: MUC2 was uniformly expressed with near similar intensity while MUC5 was moderately (56%) to highly expressed (36%) in mucinous tumors. In nonmucinous tumors, MUC2 was least expressed (68%) with a significant expression on MUC5AC (88%). Except for rectosigmoid growth which had greater expression of MUC5AC (31%), both proximal and distal carcinomas had significant MUC2 and MUC5AC expression. Conclusion: MUC2 and MUC5AC are expressed in colonic cancers, the former showing mildtomoderate expression and the latter moderatetointense expression. The expression is more in mucinous adenocarcinoma.

An Interesting Case of a Movement Disorder

Neuroacanthocytosis is a genetic neurodegenerative disorder with syndromes of variable inheritance. These hyperkinetic movement disorders are reported to be very rare. It is associated with choreiform movements, orofacial and lingual dyskinesias and acanthocytes on peripheral smear and normolipoproteinemia. Here we present a similar case.

Isolation, expansion and characterisation of mesenchymal stem cells from human bone marrow, adipose tissue, umbilical cord blood and matrix: a comparative study

The multipotent and immunosuppressive capacities of mesenchymal stem cells (MSCs) attract several scientists worldwide towards translational research focusing on treatment of diseases including liver failure. Though MSC's have been isolated from different sources, researchers do not concur on the best source for expansion and clinical translation. In this study, we have compared the isolation, proliferation and expansion of MSCs from umbilical cord blood (UCB), Wharton's Jelly (WJ), bone marrow (BM) and adipose tissue (AT). MSCs were isolated by density gradient separation from UCB, BM and AT and by both enzymatic and explant method for WJ. The MSCs are characterized by their ability to adhere to plastic, expression of positive (CD105, CD73, CD90, CD29, CD44) and negative (CD45, CD14, CD34) markers by flow cytometry and also by their in vitro adipogenic, osteogenic and chondrogenic differentiation. This comprehensive study clearly shows that WJ is better than UCB both in terms of rapidity, yield and ease of procedure. AT and BM are autologous sources for MSC's but the specimen collection involves cumbersome and painful procedures and an invasive approach. However being autologous, they are safe and probable candidates for therapeutic future applications.

Hematological changes following early ligation of splenic artery during splenectomy in shunt surgery for portal hypertension

OBJECTIVE AND BACKGROUND DATA

Reduction in cellular elements of blood, secondary to hypersplenism is an established component of non-cirrhotic portal hypertension. Prior transfusion of blood or blood components is frequently required for safe surgical intervention. Due to thrombocytopenia, epidural catheter insertion for effective and durable analgesia is not possible. The aim of the present study was to objectively demonstrate the gain in blood components following early ligation of splenic artery for splenectomy in shunt surgery.

METHODS

From Jan 2008 to July 2010, 30 patients underwent elective proximal spleno renal shunt for portal hypertension, for various indications and were analyzed prospectively. We followed the standard protocol of ligating the splenic artery in situ, first in the lesser sac. Proximal spleno shunt was done. After the surgical procedure and before extubation, an epidural catheter was placed for effective and durable analgesia. 5ml of venous blood was drawn in the following order of sequence: prior to induction of anesthesia, immediately after the ligation of splenic artery, 30 minutes after ligation of splenic artery and 30 minutes after splenectomy. Samples were sent for complete hemogram and values were analyzed in respective order. Patients requiring transfusion of blood or blood components during surgery were excluded from the study.

RESULTS

30 patients (M - 9, F- 21) with mean age of 29.4 years (11-60 years) were analyzed (NCPF- 20, EHPVO- 9, cirrhosis- 1). We objectively demonstrated a significant gain in RBCs (p = 0.016) and platelets (p = 0.000) using this standard protocol. As there were no intrinsic abnormalities in RBCs, red blood cell indices (MCV, MCH, MCHC) showed no changes as expected (p-0.9).

CONCLUSION

By following this standard protocol, in addition to reduction in blood loss there was a significant gain in RBCs and platelets. This gain allows the surgeon to perform the surgical procedure safely and the anesthetist to secure an epidural catheter immediately after surgery for effective and durable analgesia without prior transfusion.

Peri-operative outcomes for pancreatoduodenectomy in India: a multi-centric study

BACKGROUND

There have been an increasing number of reports world-wide relating improved outcomes after pancreatic resections to high volumes thereby supporting the idea of centralization of pancreatic resectional surgery. To date there has been no collective attempt from India at addressing this issue. This cohort study analysed peri-operative outcomes after pancreatoduodenectomy (PD) at seven major Indian centres.

MATERIALS AND METHODS

Between January 2005 and December 2007, retrospective data on PDs, including intra-operative and post-operative factors, were obtained from seven major centres for pancreatic surgery in India.

RESULTS

Between January 2005 and December 2007, a total of 718 PDs were performed in India at the seven centres. The median number of PDs performed per year was 34 (range 9-54). The median number of PDs per surgeon per year was 16 (range 7-38). Ninety-four per cent of surgeries were performed for suspected malignancy in the pancreatic head and periampullary region. The median mortality rate per centre was four (range 2-5%). Wound infections were the commonest complication with a median incidence per centre of 18% (range 9.3-32.2%), and the median post-operative duration of hospital stay was 16 days (range 4-100 days).

CONCLUSIONS

This is the first multi-centric report of peri-operative outcomes of PD from India. The results from these specialist centers are very acceptable, and appear to support the thrust towards centralization.

Post pancreaticoduodenectomy haemorrhage: outcome prediction based on new ISGPS Clinical severity grading

OBJECTIVE & BACKGROUND DATA: Mortality following pancreatoduodenectomy (PD) has fallen below 5%, yet morbidity remains between 30 and 50%. Major haemorrhage following PD makes a significant contribution to this ongoing morbidity and mortality. The aim of the present study was to validate the new International Study Group of Pancreatic Surgery (ISGPS) Clinical grading system in predicting the outcome of post pancreaticoduodenectomy haemorrhage (PPH).

MATERIAL AND METHODS

Between January 1998 and December 2007 a total of 458 patients who underwent Whipple's pancreaticoduodenectomy in our department were analysed with regard to haemorrhagic complications. The onset, location and severity of haemorrhage were classified according to the new criteria developed by an ISGPS. Risk factors for haemorrhage, management and outcome were analysed.

RESULTS

Severe PPH occurred in 14 patients (3.1%). Early haemorrhage (<24 hours) was recorded in five (36%) patients, and late haemorrhage (>24 hours) in nine (64%) patients. As per Clinical grading of ISGPS 7 (50%) belongs to Grade C and 7 (50%) belongs to Grade B. Haemostasis was attempted by surgery in 10 (71%) patients; angioembolisation was successful in two (14%) and endotherapy in one (7%) patient. The overall mortality is 29%(n=4). Age >60 years (p=0.02), sentinel bleeding (p=0.04), pancreatic leak (p=0.04) and ISGPS Clinical grade C (p=0.02) were associated with increased mortality.

CONCLUSION

Early haemorrhage was mostly managed surgically with better outcome when endoscopy is not feasible. Late haemorrhage is associated with high mortality due to pancreatic leak and sepsis. ISGPS Clinical grading of PPH is useful in predicting the outcome.

Alpha-fetoprotein as a tumor marker in hepatocellular carcinoma: investigations in south Indian subjects with hepatotropic virus and aflatoxin etiologies

OBJECTIVES

The prevalence of hepatitis B virus (HBV) is reportedly the main cause of hepatocellular carcinoma (HCC) in India, where hepatitis C virus (HCV)-associated HCC is believed to be relatively less prevalent. We verified the usefulness of alpha-fetoprotein (AFP) as a tumor marker and analyzed the influence of viral etiology on AFP levels in HCC.

METHODS

Of a total of 1012 cases with liver disease, 202 were investigated for the presence of AFP (142 HCC cases, 30 cirrhosis cases, and 30 chronic liver disease (CLD) cases). In addition, serum samples from 30 healthy patients, 30 hepatitis B surface antigen (HBsAg) carriers, and 30 acute viral hepatitis cases were included as controls. AFP was quantitatively determined using a commercial ELISA (Quorum Diagnostics, Canada). Out of the 142 HCC cases screened for AFP, aflatoxin B1 (AFB1) detection was carried out in 38 HCC cases using an in-house immunoperoxidase test.

RESULTS

In HBV and HCV co-infected HCC cases, the AFP positivity was 85.7%. In HBV alone-associated HCC, the positivity was 62.9%, and 54.5% of AFB1 positive HCC cases showed AFP positivity. In HBV and HCV negative HCC cases, the positivity was 20.5%, and in HCV-associated HCC it was 17.6%. The HBV/HCV co-infected group and HBV alone positive HCC cases had significantly elevated levels of AFP. When AFP positivity was analyzed based on the marker profile of HBV, 89.7% of AFP positive cases were HBV-DNA positive.

CONCLUSIONS

The overall positivity pattern of AFP in HCC does indicate that higher levels of AFP are observed with hepatitis virus positivity, especially with HBV. Further studies must be carried out to correlate the serum levels of AFP with the size, number, and degree of differentiation of HCC nodules.

Prevalence of aflatoxin B1 in liver biopsies of proven hepatocellular carcinoma in India determined by an in-house immunoperoxidase test

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related death in the world. The incidence of HCC in India is reportedly low and varies from 0.2 to 1.9 %. Aflatoxins, secondary metabolites produced by Aspergillus flavus and Aspergillus parasiticus, are potent human carcinogens implicated in HCC. The prevalence of aflatoxin B1 (AFB1) as co-carcinogen was analysed using an in-house immunoperoxidase test in 31 liver biopsies and 7 liver-resection specimens from histopathologically proven HCC, and in 15 liver biopsies from cirrhosis patients (control group). Serum was tested for hepatitis B and C serological markers using commercial assays, and for AFB1 using an in-house ELISA with a sensitivity of approximately 1 ng ml(-1) for AFB1. In spite of positive AFB1 immunostaining in HCC cases, all serum specimens, from both HCC and the control groups, were AFB1-negative. There were 18 (58.1 %) HCC cases that revealed AFB1 in liver biopsies; 68.8 % (n=11) of non-B non-C hepatitis cases with HCC and 46.1 % (n=6) of the hepatitis B surface-antigen-positive subjects were positive for AFB1. Out of the two hepatitis B/hepatitis C virus co-infected cases, one was positive for AFB1. Of seven tumour-resection samples, six were positive for AFB1. Only one case revealed AFB1 in the non-tumour area of the resected material. Thus AFB1 staining was significantly associated with tumour tissue (P=0.03). Aflatoxins proved to have a significant association with HCC in this peninsular part of the subcontinent. The impact seems to be a cumulative process, as revealed by the AFB1 deposits in HCC liver tissue, even though the serum levels were undetectable.

Solitary extra-hepatic hilar peribiliary cyst presenting with obstructive jaundice: a case report

Peribiliary cyst is a poorly recognized and under-reported clinico-pathologic entity around the biliary tree. Peribiliary cysts are cystic dilatations of obstructed peribiliary glands, which are normal elements of the biliary tract. They are generally asymptomatic and rarely cause biliary obstruction. They are usually discovered incidentally at autopsy or in explants following liver transplantation. A 59-year-old male patient presenting with obstructive jaundice due to a large extra-hepatic hilar peribiliary cyst is reported here. We briefly discuss its differential diagnoses such as bile duct cyst, liver cyst or lymph cyst, and its management. Radiological imaging demonstrated a solitary large (5 cm) well-defined, smooth, thin walled cystic lesion at the porta hepatis paralleling but not communicating with the bile duct. A wide cyst de-roofing was performed and histological examination of the cystic wall revealed an inflammatory cyst. The patient made an uneventful recovery and remained asymptomatic with normal liver function tests 36 months postoperatively.

Level of oxidative stress in the red blood cells of patients with liver cirrhosis

BACKGROUND & OBJECTIVE

Liver cirrhosis is associated with gastrointestinal haemorrhage and oesophageal variceal bleeding. Altered platelet functions has been reported to be a cause of bleeding complication. We carried out this study to find out the level of oxidative stress in the red blood cells of patients with liver cirrhosis.

METHODS

Fifty patients admitted with the complication of liver cirrhosis (with bleeding complications, n=30 and without bleeding complications, n=20) were included in the study. Age and sex matched normal healthy volunteers (n=45) served as controls. The levels of oxyhaemoglobin and methaemoglobin were assayed in the red blood cells. Oxidative stress markers such as lipid peroxides, lipid hydroperoxides and nitric oxide were determined along with enzymatic antioxidants. Membrane bound adenosine triphosphatases, cytosolic glucose-6-phosphate dehydrogenase and NADHmethaemoglobin reductase were also measured. The levels of cholesterol and total phospholipids were assessed in red blood cell membrane. The osmotic fragility of red blood cells was monitored using different concentrations of sodium chloride.

RESULTS

The level of methaemoglobin was significantly higher (P < 0.001) in the red blood cells of liver cirrhotic patients with bleeding complication compared to that of non bleeding patients. The activity level of NADH-methaemoglobin reductase was significantly lower (P<0.001) compared to that of normal subjects. Levels of oxidative stress markers including nitric oxide were found to be higher in patients. The levels of enzymatic antioxidants were low except of glutathione peroxidase. The activity levels of adenosine triphosphatases were also found to be significantly lower (P<0.001) in patients compared to normal subjects. A significant alteration (P<0.05) was found in membrane cholesterol/phospholipid ratio of cirrhotic bleeders. Osmotic fragility of red blood cells was also altered in patients.

INTERPRETATION & CONCLUSION

In cirrhotic condition red blood cells are subjected to severe oxidative stress with significant alterations in the membrane properties.

Role of retrograde dilatation in the management of pharyngo-esophageal corrosive strictures

Pharyngo-esophageal corrosive stricture is a complex clinical scenario. If an esophageal opening cannot be found orally through endoscopy, a retrograde approach with a mini-laparotomy and gastrostomy should be attempted. This study primarily aimed at defining the role of preoperative retrograde dilatation of pharyngo-esophageal corrosive strictures. A retrospective analysis of 51 cases of pharyngo-esophageal corrosive strictures identified between 1997-2005 was performed. The demographic details were analyzed. The details of the injury to the pharynx either in isolation or in combination were noted and the management details were recorded. In 21 patients preoperative retrograde dilatation was considered and the technique was successful in 14 (Group I). In seven the technique failed (Group II) and these patients underwent transhiatal resection and gastric pull-through and/or retrosternal pharyngocoloplasty. In Group I patients the postoperative stay was significantly less than in Group II (12 +/- 2.03 days vs. 18 +/- 4.32 days; p = 0.001) Recurrent aspiration, respiratory tract infections, choking sensation and the need for tracheostomy were less frequent in Group I. The overall functional assessment was good in Group I. For treatment of pharyngo-esophageal obstruction, if antegrade dilatation is not possible due to technical reasons, retrograde dilatation is a viable option before opting for organ replacement/bypass procedures. There is no best replacement of the native organ to maintain quality of life.

Transabdominal modified devascularization procedure with or without esophageal stapler transection--an operation adequate for effective control of a variceal bleed. Is esophageal stapler transection necessary?

BACKGROUND

In Japan, the original Sugiura procedure reported favorable results in non-cirrhotic patients but in the West, the modified Sugiura procedure is not widely accepted because of high rebleeding, morbidity, and mortality in cirrhotics. We retrospectively analyzed the efficacy of our modified Sugiura procedure i.e., devascularization with/without esophageal transection combined with salvage endotherapy and pharmacotherapy for control of a variceal bleed.

MATERIALS AND METHODS

Between January 1999 and December 2004, 912 patients with variceal bleeding were treated. Of these, 66 (7.2%) patients were subjected to surgery after failed endotherapy/propranolol. Among these 66 patients, 52 had transabdominal devascularization (16 emergency, 36 elective); 14 patients underwent devascularization with esophageal stapler transection (group I), and 38 patients had devascularization without esophageal stapler transection (group II). Another 14 patients underwent elective end-to-side proximal splenorenal shunt surgery.

RESULTS

Postoperative mortality was 7.1% in group I, 10.5% in group II (P>0.05). Mortality for emergency surgery was 31.2% (5/16) but there were no deaths in the elective surgery group. Overall morbidity was 57.1% in group I and 21.0% in group II (P<0.05). The rates of variceal rebleeding were 7.1% and 7.8%; residual varices were 30.7% and 32.3%; recurrent varices were 7.6% and 5.8% following the group I and group II procedures, respectively, over a mean follow-up period of 39.9 (7-2) months. Esophageal transection-related morbidity (leak, stricture, and bleeding) was 21.4% (3/14) in group I.

CONCLUSIONS

Devascularization without esophageal stapler transection is a safe and effective procedure for adequate (urgent and long-term) control of variceal bleeding with similar results and less morbidity when compared to devascularization with esophageal transection in cirrhotic patients, as well as non-cirrhotic patients.

Effect of ursodeoxycholic acid on copper induced oxidation of low density lipoprotein

The aim of this study was to investigate copper (Cu++) induced oxidation state of LDL isolated from obstructive jaundice (OBJ) patients with hyperlipidemia and the effect of UDCA on the same. LDL was isolated and oxidation was induced by 5 mM CuSO4 with/without UDCA at different concentrations. LDL oxidation was assessed at different time intervals in terms of conjugated dienes, hydroperoxides and 'thiobarbituric acid reacting substances' (TBARS). The change in the level of endogenous LDL alpha-tocopherol was also monitored simultaneously. The oxidisability of LDL isolated from OBJ patients was significantly higher and showed a steep increase in the level of conjugated diene formation without any lag phase. In normal samples the oxidation proceeded slowly with a lag phase. This was also evidenced by the level of formation of hydroperoxides and TBARS. The basal level of LDL alpha-tocopherol was significantly low in OBJ samples. UDCA was found to delay the oxidation of LDL in a dose dependent manner. The consumption of alpha-tocopherol was found to be minimum in the presence of UDCA. The results of this investigation show that there is a high susceptibility of LDL to oxidation in OBJ cases and this may be due to low endogenous LDL alpha-tocopherol content. UDCA minimizes LDL oxidation in dose dependent manner, which is an additional evidence for its antioxidant nature.

Structural studies of the biomineralized species of calcified pancreatic stones in patients suffering from chronic pancreatitis

The pancreatic stones (Pancreatic calculi) collected from patients suffering from chronic calcific pancreatitis were studied in a view to explore the constituents involved in the calcification. The calcified stones were characterized by XRD, EPR and IR spectroscopic techniques. The detailed studies indicate that these stones consist of calcium carbonate as a major component, besides phosphates and other protein content. The presence of aragonite phases in the biomineralized stones is also discussed. The EPR spectra gave an evidence of the presence of traces of manganese in different oxidation states, which is used as one of the EPR probes in the present work. The samples were sintered at different temperatures to remove all the organic matter, and their EPR spectra have been studied to obtain detailed information regarding the changes in the symmetry of these stone samples. The X-irradiated sample was also characterized by EPR and the resonance signals are attributed to freely rotating CO(2)(-) radicals. The infrared spectrum reveals the presence of many organic bands corresponding to the protein amides.

Acquired volvulus following Nissen fundoplication

Nissen fundoplication is the procedure of choice for the management of gastroesophageal reflux disease. We report a case of acquired gastric volvulus following open fundoplication. The mechanism of formation and correction of the volvulus is discussed.

Surgical practice in symptomatic and asymptomatic gallstone disease

AIMS

To determine the surgical practice in individuals with symptomatic and asymptomatic gallstone disease using a questionnaire survey.

METHODS

A questionnaire was sent to 724 patients with gallstone disease. Details of symptoms, duration of illness, nature of treatment including surgery, color of gallstones retrieved and postoperative follow-up particulars were obtained.

RESULTS

The study group included 225 (54%) men; there was a rising trend of prevalence of gallstones in men with increasing age (p<0.05). A third of the patients (142 [34%]) were symptomatic. The mean duration of symptoms was 12.1 months. One hundred and ninety seven patients (48%), including 90 asymptomatic ones, underwent cholecystectomy. Most patients (92.5% of those symptomatic and 76.6% of those asymptomatic) underwent cholecystectomy within one year of diagnosis. Eight asymptomatic patients underwent surgery 3 years or more after diagnosis. The predominant color of stones retrieved was black or brown (57%) or mixed (39%).

CONCLUSIONS

A majority of patients with gallstone disease had cholecystectomy within one year of diagnosis. Black or brown pigment stones were the dominant types of gallstones.

Predicting the composition of gallstones by infrared spectroscopy

AIM

To determine the composition of gallstones in South India by comparing visual assessment with graphic interpretation of infrared spectra.

METHODS

Infrared spectroscopy (IRS) was used in qualitative analysis of 168 gallstones from Tamilnadu, Kerala and Karnataka and compared with visual interpretation. The spectrum of cholesterol, calcium bilirubinate and calcium carbonate for each stone was correlated with visual inspection.

RESULTS

Fifty four percent of gallstones were of pigment variety, 43% were of mixed and the remaining 3% were cholesterol gallstones as categorised by visual interpretation. Based on infrared spectrocopic interpretation the percentages were 58%, 39% and 2% respectively. There was a good agreement between the visual inspection and IRS in classification of gallstones (Kappa value 85%; 95% CI 77-93%).

CONCLUSION

Visual inspection of gallstones can predict the composition of gallstone with good accuracy and was comparable to infrared spectroscopic interpretation.

A 21-kDa C-terminal fragment of protein-disulfide isomerase has isomerase, chaperone, and anti-chaperone activities

A catalyst of disulfide formation and isomerization during protein folding, protein-disulfide isomerase (PDI) has two catalytic sites housed in two domains homologous to thioredoxin, one near the N terminus and the other near the C terminus. The thioredoxin domains, by themselves, can catalyze disulfide formation, but they are unable to catalyze disulfide isomerizations (Darby, N. J. and Creighton, T. E. (1995) Biochemistry 34, 11725-11735). A 21-kDa, C-terminal fragment of PDI (amino acids 308-491), termed weePDI, comprises the C-terminal third of the molecule. The kcat for ribonuclease oxidative folding by weePDI is 0.26 +/- 0.02 min-1, 3-fold lower than the wild-type enzyme but indistinguishable from the activity of a full-length mutant of PDI in which both active site cysteines of the N-terminal thioredoxin domain have been mutated to serine. Eliminating the ability of weePDI to escape easily from covalent complexes with substrate by mutating the active site cysteine nearer the C terminus to serine has a large effect on the isomerase activity of weePDI compared with its effect on the full-length enzyme. weePDI also displays chaperone and anti-chaperone activity characteristic of the full-length molecule. As isolated, weePDI is a disulfide-linked dimer in which the single cysteine (Cys-326) outside active site cross-links two weePDI monomers. The presence of the intermolecular disulfide decreases the activity by more than 2-fold. The results imply that the functions of the core thioredoxin domains of PDI and other members of the thioredoxin superfamily might be modified quite easily by the addition of relatively small accessory domains.

Subunit structure of rod cGMP-phosphodiesterase

The rod cGMP phosphodiesterase (PDE) is the G-protein-activated effector enzyme that regulates the level of cGMP in vertebrate photoreceptor cells. Rod cGMP PDE is generally viewed as a heterotrimeric protein composed of catalytic alpha and beta subunits ( approximately90 kDa each) and two copies of the inhibitory subunit gamma ( approximately 10 kDa). However, the possibility that rod PDE could exist as distinct isoforms, such as alphaalphagamma2 and betabetagamma2 has not been ruled out. We have studied this question using cross-linking of PDE subunits with maleimidobenzoyl-N-hydroxysuccinimide ester and para-phenyldimaleimide. The cross-linking resulted in major products with molecular mass of 100 and 150 kDa, a doublet at approximately 180-190 kDa, and a doublet at approximately 210-220 kDa. Cross-linked products were analyzed using polyclonal-specific anti-PDEalphabeta, anti-PDEalpha, anti-PDEbeta, or anti-PDEgamma antibodies. The anti-PDEalpha and anti-PDEalphabeta antibodies recognized all the cross-linked products, whereas anti-PDEbeta and anti-PDEgamma antibodies did not interact with the 150-kDa band, indicating that the composition of this band is most likely alphaalpha. Similar analysis of cross-linked products of trypsin-treated PDE preparations revealed bands that are likely formed by PDEbeta subunit. The molecular size of holo-PDE and trypsin-activated PDE were studied using analytical ultracentrifugation in order to determine if oligomerization of PDE could account for the cross-linking of identical PDE subunits. The sedimentation analysis of both holo-PDE and ta-PDE revealed homogeneous samples with molecular masses of approximately220 and approximately150 kDa, respectively. These results indicate that PDE is likely a mixture of the major species alphabetagamma2, minor species alphaalphagamma2, and possibly betabetagamma2. Our data are consistent with the detection of low PDE activity in the rd mouse, which lacks any functional PDEbeta subunit.

Involvement of Neurospora mitochondrial tyrosyl-tRNA synthetase in RNA splicing. A new method for purifying the protein and characterization of physical and enzymatic properties pertinent to splicing

The Neurospora CYT-18 protein, the mitochondrial tyrosyl-tRNA synthetase, functions in the splicing of group I introns. Here, bacterially expressed CYT-18 protein, purified by a new procedure involving polyethyleneimine precipitation to remove tightly bound nucleic acids, was used to characterize properties pertinent to RNA splicing. Analytical ultracentrifugation and other methods showed that the CYT-18 protein is an asymmetric homodimer. The measured frictional ratio, f/fo = 1.55, corresponds to an axial ratio of 10 for a prolate ellipsoid or 12 for an oblate ellipsoid. Like bacterial TyrRSs, the CYT-18 protein exhibits half-sites reactivity, each homodimer having one active site for tyrosyl adenylation and RNA splicing. The splicing activity of CYT-18 was unaffected by aminoacylation substrates at concentrations used in aminoacylation reactions, whereas the TyrRS activity was inhibited by physiological concentrations of the splicing cofactor GTP, as well as CTP or UTP, or by low concentrations of a group I intron RNA. Kinetic measurements suggest that the binding of CYT-18 to a group I intron substrate is a two-step process, with an initial biomolecular step that is close to diffusion limited (3.24 +/- 0.03 x 10(7) M-1s-1) followed by a slower conformational change (0.54 +/- 0.07 s-1). After CYT-18 binding, splicing occurs at a rate of 0.0025 s-1, within 6-fold of the rate of self-splicing of the Tetrahymena large rRNA intron in vitro. The Kd for the complex between the CYT-18 protein and a group I intron substrate, calculated from koff/kon, was < 0.3 pM, substantially lower than determined by presumed equilibrium measurements [Guo, Q., & Lambowitz, A. M. (1992) Genes Dev. 6, 1357-1372]. As a result of this tight binding, the CYT-18 protein functions stoichiometrically in in vitro splicing reactions due to its extremely slow dissociation from the excised intron RNA. The very tight binding of the CYT-18 protein to the intron RNA raises the possibility that specific mechanisms exist for dissociating the protein from the excised intron in vivo.

Construction of a dimeric repressor: dissection of subunit interfaces in Lac repressor

Formation of the lactose repressor tetramer is postulated to involve two subunit interfaces, one primarily contributing to monomer-monomer assembly to dimer and the second to dimer-dimer association to tetramer. The latter interface requires a heptad repeat of three leucines at the C-terminus of lac repressor that is presumed to form an abbreviated coiled-coil motif [Chakerian, A. E., Tesmer, V. M., Manly, S. P., Brackett, J. K., Lynch, M. J., Hoh, J. T., & Matthews, K. S. (1991) J. Biol. Chem. 266, 1371-1374; Alberti, S., Oehler, S., von Wilcken-Bergmann, B., Krämer, H., & Müller-Hill, B. (1991) New Biol. 3, 57-62; Chen, J., & Matthews, K. S. (1992) J. Biol. Chem. 267, 13843-13850]. To strengthen the dimer-dimer interface, this motif was extended by the addition of one and two leucine heptad repeat units to the C-terminus by site-specific insertion mutagenesis. The tetrameric products displayed operator and inducer affinity essentially indistinguishable from the wild-type repressor. In order to probe the effect of the elongated coiled-coil on assembly of the repressor tetramer, the other of the two postulated subunit interfaces was disrupted by introducing a point mutation (Y282D) that yields a monomeric protein in the wild-type background. Both elongated mutant repressors were able to assemble into dimeric species, apparently due to the strengthened subunit association at the C-terminal region compared to the wild-type repressor. These results further confirm the role of a coiled-coil structure in the formation of tetramer in the lac repressor.(ABSTRACT TRUNCATED AT 250 WORDS)