Participation of residue F552 in domain III of the protective antigen in the biological activity of anthrax lethal toxin

The protective antigen (PA) component of anthrax toxin translocates the catalytic moieties lethal factor (LF) and edema factor (EF) into the cytosol. The proteolytically activated 63 kDa form of PA (PA63) has the ability to oligomerize and bind LF/EF. PA has four distinct domains performing specialized functions; whereas the function of domains I, II and IV has been well characterized, domain III has no known role in the biological activity of PA. Here we report the role of amino acid residues lining an exposed hydrophobic patch of domain III in the biological activity of PA. The residues Phe552, Phe554, lIe562, Leu566 and lle574 were individually substituted with alanine and the effect was studied. All mutant PA proteins except Phe552Ala were equally active as wild-type PA in exhibiting a toxic phenotype to J774A.1 cells in the presence of LF. Substitution of Ala for Phe552 reduced the ability of PA to intoxicate cells by more than 250-fold. However, Phe552Ala was equally active in receptor binding and susceptibility to trypsin and chymotrypsin as wild-type PA, the activities that have been shown to be essential for the biological activity of PA. This mutated PA protein had a decreased ability to bind LF, oligomerize on cells and to induce release of 86Rb+ from Chinese hamster ovary cells. These results suggest that the residue Phe552 in PA plays an important role in LF binding and oligomerization. Our study provides a basis for further exploration of the biological significance of domain III of PA.

Role of residues constituting the 2beta1 strand of domain II in the biological activity of anthrax protective antigen

Anthrax toxin consists of three proteins, protective antigen, lethal factor and oedema factor. A proteolytically activated 63-kDa fragment of protective antigen binds lethal factor/oedema factor and translocates them into the cytosol. Domain II of protective antigen has been implicated in membrane insertion and channel formation. In the present study, alanine substitutions in 14 consecutive residues of the 2beta1 strand that are highly homologous to the putative membrane interacting segment of Clostridium perfringens iota-b toxin were generated and the effect on the biological activity of protective antigen studied. One of the mutants, Pro260Ala, showed considerably reduced toxicity in combination with lethal factor. The mutant also showed decreased membrane insertion and translocation of lethal factor into the cytosol. The data suggest that Pro260 is important for membrane insertion and translocation by protective antigen.

Anthrax-toxin-mediated delivery of a 19 kDa antigen of Mycobacterium tuberculosis into the cytosol of mammalian cells

PA63, the proteolytically activated 63 kDa fragment of protective antigen (PA, 83 kDa), mediates translocation of lethal factor (LF) and oedema factor into the cytosol. The N-terminal 254 amino acids of LF (LFn) are required for binding to PA63 and mediating translocation of active ligands fused to either the N- or C-terminus. Here we report translocation of a 19 kDa antigen of Mycobacterium tuberculosis into the cytosol of mammalian cells when fused to the C-terminus of LFn (LFn-19kDa). The fusion protein was non-toxic to J774A.1 macrophage cells in combination with PA and retained the ability to bind to PA63 when incubated with Chinese hamster ovary K1 cells. The data show the efficacy of anthrax toxin to mediate translocation of M. tuberculosis antigens into the cytosol of mammalian cells and may prove useful in delivering proteins and peptides carrying immunodominant mycobacterial antigens into the cytosol.

Pseudoexstrophy in a female child

A six-year-old female patient presenting with a swelling in the infraumbilical part of the abdomen, bulging out on straining, was diagnosed to have pseudoexstrophy bladder. The urinary tract was normal. The patient had bifid clitoris. There was no other associated malformation. Surgical repair of abdominal wall defect was done successfully. A new classification of exstrophy variants is proposed.

Intrauterine intussusception--a cause for ileal atresia

A case of ileal atresia consequent to intrauterine intussusception is reported. The baby presented with features of neonatal intestinal obstruction but signs of peritonitis were absent. The intussusception was discovered on gross examination of distal atretic ileal segment. The case was managed successfully by resection and end to back anastomosis. This case is reported to highlight intrauterine intussusception as one of the causes of ileal atresia.

Venous thrombosis associated with the placement of peripherally inserted central catheters

PURPOSE

Peripherally inserted central catheters (PICCs) have become an essential component of the management of an increasing number of patients, including patients who may require hemodialysis. Reported symptomatic venous thrombosis rates associated with PICC lines are based on clinical signs and symptoms and range from 1% to 4%. The purpose of this study is to evaluate the true rate of thrombosis of upper extremity veins after the placement of PICCs and the potential impact on future access in hemodialysis patients.

MATERIALS AND METHODS

A retrospective analysis was performed. Patients who had (i) normal findings during initial venography, (ii) PICC placement, and (iii) who underwent subsequent repeated venography were included. Age, sex, vein cannulated, catheter size, location, and incidence of thrombosis were analyzed.

RESULTS

Three hundred fifty-four PICCs were placed in 119 patients. Of the 144 extremities, 137 had normal findings during initial venography. Of the 137 extremities, 32 developed thrombosis of the cannulated vein (or central veins) after initial PICC placement (23.3%). When all extremities with multiple PICC lines placed were considered, 52 developed thrombosis, for an overall thrombosis rate of 38%. The incidence of thrombosis by site was cephalic 57%, basilic 14%, and brachial 10%. No significant differences were noted in the rates of thrombosis by age, sex, or catheter size.

CONCLUSIONS

There is a relatively high rate of venous thrombosis associated with PICCs, particularly cephalic thrombus. Because of the high rate of thrombosis associated with these catheters, an alternative mode of access should be considered in current or potential hemodialysis patients. All patients with a history of PICC line placement requiring dialysis access should undergo upper extremity venography prior to the placement of permanent access.

Cloning and characterization of secretory tyrosine phosphatases of Mycobacterium tuberculosis

Two genes with sequence homology to those encoding protein tyrosine phosphatases were cloned from genomic DNA of Mycobacterium tuberculosis H(37)Rv. The calculated molecular masses of these two putative tyrosine phosphatases, designated MPtpA and MPtpB, were 17. 5 and 30 kDa, respectively. MPtpA and MPtpB were expressed as glutathione S-transferase fusion proteins in Escherichia coli. The affinity-purified proteins dephosphorylated the phosphotyrosine residue of myelin basic protein (MBP), but they failed to dephosphorylate serine/threonine residues of MBP. The activity of these phosphatases was inhibited by sodium orthovanadate, a specific inhibitor of tyrosine phosphatases, but not by okadaic acid, an inhibitor of serine/threonine phosphatases. Mutations at the catalytic site motif, cysteine 11 of MPtpA and cysteine 160 of MPtpB, abolished enzyme activity. Southern blot analysis revealed that, while mptpA is present in slow-growing mycobacterial species as well as fast-growing saprophytes, mptpB was restricted to members of the M. tuberculosis complex. These phosphatases were present in both whole-cell lysates and culture filtrates of M. tuberculosis, suggesting that these proteins are secreted into the extracellular medium. Since tyrosine phosphatases are essential for the virulence of several pathogenic bacteria, the restricted distribution of mptpB makes it a good candidate for a virulence gene of M. tuberculosis.

P300 event related potential in normal healthy controls of different age groups

P300 event related potential was recorded in 115 healthy controls with a mean age of35.9±14.81 years and a male : female ratio of 72 : 43. There was significant difference in the P300 latency in < 40 years as compared to ≥ 40 years group (p< 0.001). There was no significant difference between males and females. There was a strong positive correlation between age and P300 latency (p< 0.001). The regression equation for P300 latency was Y=287.9+1.492x with an SEE of 20.2 (where Y is the P300 latency in ms, x is the age in years, SEE is the standard error of estimate). There was a negative correlation between age and P300 amplitude which was significant in ≥ 40 years age group while in > 40 years age group it was not significant.

MODERN MANAGEMENT OF INGUINAL HERNIA

Hernia repair is the most commonly performed surgical procedure in male. In the last two decades there have been radical changes in the methods of inguinal hernia repair. This article reviews the various newer options for the repair of inguinal hernia and also discusses the myths and realities about the causes of primary and recurrent inguinal hernia which should bring about a radical change in our surgical practices.

Anthrax toxin-mediated delivery of cholera toxin-A subunit into the cytosol of mammalian cells

The protective antigen (PA) component of anthrax toxin mediates delivery of either lethal factor (LF) or oedema factor into the cytosol of mammalian cells. The N-terminal domain of LF(1-254) (amino acids 1-254 of LF) binds to PA and, when fused to heterologous proteins, delivers such proteins into the cytosol. In the present study, we fused the catalytic subunit of cholera toxin (CT-A) with LF(1-254) and showed that the fusion protein LF(1-254)-CT-A retains ADP-ribosylation activity in solution and increased intracellular cAMP levels in J774A.1 macrophage cells when added together with PA. A mutant fusion protein, in which arginine-7 of CT-A was replaced with lysine, did not show ADP-ribosylation activity in solution and failed to increase cAMP levels in macrophage cells. The data show that LF(1-254)-CT-A retains its catalytic activity in solution as well as when translocated into the cytosol of eukaryotic cells via an alternative pathway to the GM(1) receptor used by CT.

Antifungal activity of bicyclic heterocyclic-1,2-diazole

A novel series of heterocyclic-1,2 diazole namely N1-iso nicotinoyl-5,5'-dimethyl cyclohexane-4-(sulpha/substituted phenylazo)-1,2-diazoles have been synthesized. The compounds were screened for the anti-fungal properties against building fungi. The fungal species used for this purpose were Aspergillus niger and Pencillium frequentans. It was found that out of a series of 25 compounds, fourteen have shown significant fungicidal properties against both the above species. Minimum inhibition concentration was observed between 100 and 200 ppm for most of the compounds.

Intra-abdominal needles: an enigma (a report of two cases)

Ingested sharp metallic bodies perforate the gut surprisingly rarely. Perforation and migration of such a foreign body may be silent. Patients may present with unrelated symptoms and the discovery of foreign body on radiological examination of the abdomen may come as a surprise. History of ingestion is usually difficult to obtain. Foreign bodies after perforation have been reported to migrate to almost any intraabdominal or rarely to even extra-abdominal sites. Migration to the liver, mesentery or the anterior abdominal wall, however, is extremely rare. We report two cases of young women with two ingested needles in each which perforated silently and in one case migrated to the liver and the anterior abdominal wall while in the other they migrated to the mesentery of the small intestine and the anterior abdominal wall.

Multiple neurilemmomas of the penis

A 10-year-old male with multiple small swellings over the shaft of the penis for 2 years was found to have multiple neurilemmomas on histopathologic examination. The case is reported in view of the extreme rarity of the entity.

Repair of a giant omphalocele by a modified technique

Large omphaloceles that contain centrally herniated liver pose challenges to surgical closure, the most significant being the space limitation of the abdominal cavity. In addition, the "pedicled" nature of the liver on the inferior vena cava creates a predisposition to acute hepatic vascular outflow obstruction as the liver is reduced into the abdominal cavity. In such cases, the alternatives include conservative treatment or staged silo reduction. The worst complication of silastic silo (SS) placement is tension and infection of the fascia with disruption of the suture line. Once infection or premature disruption occurs, closure of the defect is difficult or impossible. This case report details a different management technique for a newborn with a giant omphalocele and presents an interesting variation of the usual SS technique that may be helpful in the management of some cases, especially in an emergency. The thick silk sutures applied in the present case absorbed the tension and the silastic sheet prevented the risks of infection and adhesions.

Optimal prefixation of cells to demonstrate apoptosis by the TUNEL method

OBJECTIVE

To determine the optimal fixation method for cultured human ovarian cancer cell line SHIN-3 to document cisplatin-induced apoptosis by the terminal deoxynucleotidyl transferase-mediated biotinylated dUTP nick end-labeling (TUNEL) assay.

STUDY DESIGN

Cisplatin-treated cancer cell suspensions were (1) fixed in 4% buffered formalin for 10 minutes (BF group); (2) treated with 2% Carbowax in 50% ethanol (CW) for 10 minutes and then fixed in 100% ethanol for one hour (CW + ET); or (3) treated with CW for 10 minutes and then fixed in 4% buffered formalin for one hour (CW + BF). Cell morphology, adhesion to the glass slides and TUNEL reactivity were compared among the three groups. The effects of prolonged prefixation of cell suspensions in CW and of the postfixation of cell smears in BF for one, three and seven days were also examined.

RESULTS

CW + BF treatment yielded satisfactory cell morphology, minimum cell loss and an excellent TUNEL reaction. However, prolonged prefixation in CW resulted in cell shrinkage.

CONCLUSION

CW + BF treatment can be widely recommended for use with cytologic preparations for the TUNEL assay.