Improved tolerance to salinity and low temperature in transgenic tobacco producing glycine betaine

Glycine betaine is an osmoprotectant found in many organisms, including bacteria and higher plants. The bacterium Escherichia coli produces glycine betaine by a two-step pathway where choline dehydrogenase (CDH), encoded by betA, oxidizes choline to betaine aldehyde which is further oxidized to glycine betaine by the same enzyme. The second step, conversion of betaine aldehyde into glycine betaine, can also be performed by the second enzyme in the pathway, betaine aldehyde dehydrogenase (BADH), encoded by betB. Transformation of tobacco (Nicotiana tabacum), a species not accumulating glycine betaine, with the E. coli genes for glycine betaine biosynthesis, resulted in transgenic plants accumulating glycine betaine. Plants producing CDH were found to accumulate glycine betaine as did F1 progeny from crosses between CDH- and BADH-producing lines. Plants producing both CDH and BADH generally accumulated higher amounts of glycine betaine than plants producing CDH alone, as determined by 1H NMR analysis. Transgenic tobacco lines accumulating glycine betaine exhibited increased tolerance to salt stress as measured by biomass production of greenhouse-grown intact plants. Furthermore, experiments conducted with leaf discs from glycine betaine-accumulating plants indicated enhanced recovery from photoinhibition caused by high light and salt stress as well as improved tolerance to photoinhibition under low temperature conditions. In conclusion, introduction of glycine betaine production into tobacco is associated with increased stress tolerance probably partly due to improved protection of the photosynthetic apparatus.

Mechanisms of heavy-metal sequestration and detoxification in crustaceans: a review

This review is an update of information recently obtained about the physiological, cellular, and molecular mechanisms used by crustacean organ systems to regulate and detoxify environmental heavy metals. It uses the American lobster, Homarus americanus, and other decapod crustaceans as model organisms whose cellular detoxification processes may be widespread among both invertebrates and vertebrates alike. The focus of this review is the decapod hepatopancreas and its complement of metallothioneins, membrane metal transport proteins, and vacuolar sequestration mechanisms, although comparative remarks about potential detoxifying roles of gills, integument, and kidneys are included. Information is presented about the individual roles of hepatopancreatic mitochondria, lysosomes, and endoplasmic reticula in metal sequestration and detoxification. Current working models for the involvement of mitochondrial and endoplasmic reticulum calcium-transport proteins in metal removal from the cytoplasm and the inhibitory interactions between the metals and calcium are included. In addition, copper transport proteins and V-ATPases associated with lysosomal membranes are suggested as possible sequestration processes in these organelles. Together with several possible cytoplasmic divalent and trivalent anions such as sulfate, oxalate, or phosphate, accumulations of metals in lysosomes and their complexation into detoxifying precipitation granules may be regulated by variations in lysosomal pH brought about by bafilomycin-sensitive proton ATPases. Efflux processes for metal transport from hepatopancreatic epithelial cells to the hemolymph are described, as are the possible roles of hemocytes as metal sinks. While some of the cellular processes for isolating heavy metals from general circulation occur in the hepatopancreas and are beginning to be understood, very little is currently known about the roles of the gills, integument, and kidneys in metal regulation. Therefore, much remains to be clarified about the organs and mechanisms involved in metal homeostasis in decapod crustaceans.

FSP95, a testis-specific 95-kilodalton fibrous sheath antigen that undergoes tyrosine phosphorylation in capacitated human spermatozoa

Protein tyrosine phosphorylation has been associated with both capacitation and motility of mammalian sperm. During capacitation, human spermatozoa undergo tyrosine phosphorylation of a characteristic set of proteins, only one of which has thus far been cloned and localized. We report here the sequence of a fibrous sheath protein of 95 kDa (FSP95) that undergoes tyrosine phosphorylation during capacitation of human spermatozoa and has similarity to sperm A-kinase anchor proteins (AKAPs). FSP95 is both auto- and iso-antigenic in humans as it is recognized by sera containing antisperm antibodies from infertile men and women. The 853-residue protein has a calculated molecular weight of 94.6 kDa and an isoelectric point (pI) of 6.0, and it contains multiple potential phosphorylation sites for protein kinase C and casein kinase II as well as one potential tyrosine kinase phosphorylation site at amino acid 435. The sequence has amino acid homology to mouse sperm fibrous sheath AKAP82 (pro-mAKAP82, 34% identity) and to human sperm fibrous sheath AKAP82 (pro-hAKAP82, 32% identity). The gene encoding FSP95 has 5 exons separated by 4 introns and is located on chromosome 12 at locus p13.3. Northern analysis detected a single transcript of approximately 3.0 kilobases, and Northern dot blot analysis of 50 human tissues revealed FSP95 mRNA expression only in testis. By employing sperm immobilization, indirect immunofluorescence, and immunoelectron microscopy with antisera to purified recombinant FSP95, the protein was localized to the ribs of the fibrous sheath in the principal piece of the sperm tail. FSP95 is the second fibrous sheath protein to be cloned, sequenced and localized in human spermatozoa.

D-glucose transport in decapod crustacean hepatopancreas

Physiological mechanisms of gastrointestinal absorption of organic solutes among crustaceans remain severely underinvestigated, in spite of the considerable relevance of characterizing the routes of nutrient absorption for both nutritional purposes and formulation of balanced diets in aquaculture. Several lines of evidence attribute a primary absorptive role to the digestive gland (hepatopancreas) and a secondary role to the midgut (intestine). Among absorbed organic solutes, the importance of D-glucose in crustacean metabolism is paramount. Its plasma levels are finely tuned by hormones (crustacean hyperglycemic hormone, insulin-like peptides and insulin-like growth factors) and the function of certain organs (i.e. brain and muscle) largely depends on a balanced D-glucose supply. In the last few decades, D-glucose absorptive processes of the gastrointestinal tract of crustaceans have been described and transport mechanisms investigated, but not fully disclosed. We briefly review our present knowledge of D-glucose transport processes in the crustacean hepatopancreas. A discussion of previous results from experiments with hepatopancreatic epithelial brush-border membrane vesicles is presented. In addition, recent advances in our understandings of hepatopancreatic D-glucose transport are shown, as obtained (1) after isolation of purified R-, F-, B- and E-cell suspensions from the whole organ by centrifugal elutriation, and (2) by protein expression in hepatopancreatic mRNA-injected Xenopus laevis oocytes. In a perspective, the applicability of these novel methods to the study of hepatopancreatic absorptive function will certainly improve our knowledge of this structurally complex organ.

Experience with different treatment modules in hidradenitis suppuritiva: a study of 106 cases

BACKGROUND

Hidradenitis suppuritiva, a disease of the apocrine sweat glands, has always been a challenging area to the plastic and reconstructive surgeon. The aetiology is idiopathic and medical treatment offers temporary relief only. Radical surgical excision, therefore, is the mainstay of active management.

AIM

To present and evaluate a series of 106 patients of hidradenitis suppuritiva treated in the regional plastic surgery unit of southeast Scotland between January 1990 and December 2000.

PATIENTS

Median age at onset was 36 years (range 17-70 years). The patients were predominantly females (88.78%) and heavy smokers (98.1%). Median age before active surgical intervention was six years (range 1-30 years). The patients were divided into a mild group (n=64) and a severe group (n = 42). All patients had broad-spectrum antibiotics and multiple incision and drainage procedures before referral from general practitioners, dermatologists or general surgeons. One hundred sites were managed by primary closure (mostly in the 'mild' group); 29 resurfaced with split skin grafts and 14 with local, fasciocutaneous or musculocutaneous flaps (mostly in the 'severe' group). Median postoperative follow-up period was three years (range 1-7 years).

RESULTS

In the 'primary closure' series, recurrence rate requiring at least one secondary operation was 69.88%. There was no recurrence, no serious complications and no revision operations in the 'graft' and the 'flap' series.

CONCLUSION

A high index of suspicion is required before contemplating primary closure in hidradenitis suppuritiva, even in the ' mild' variety. This condition should always be treated aggressively by radical excision of all hair-bearing areas and reconstructed with a graft or a flap.

Autoantibodies in sclerosing cholangitis against a shared peptide in biliary and colon epithelium

BACKGROUND/AIMS

A strong association exists between ulcerative colitis and primary sclerosing cholangitis (PSC). Previously, the presence of a unique epitope shared by colon and biliary epithelial cells was shown by using the novel monoclonal antibody (MAb) 7E12H12 developed against a colonic epithelial protein. In the present study, the presence of circulating autoantibody in PSC against this peptide was examined.

METHODS

Sera from 16 patients with PSC, 13 with primary biliary cirrhosis, 6 with secondary biliary stricture, and 6 with chronic liver diseases and 10 normal subjects were used. An inhibition immunoperoxidase assay using the 7E12H12 MAb was developed against sections of bile duct and gallbladder. Sera were also examined in an enzyme-linked immunosorbent assay (ELISA) against the gallbladder extract enriched in 7E12H12-reactive protein.

RESULTS

About two thirds of the sera from patients with PSC blocked the binding of 7E12H12 MAb on the bile duct and gallbladder, whereas non-PSC sera did not. In the ELISA, 93% of PSC sera had circulating immunoglobulin G antibodies against the enriched gallbladder extract. The reactivity of sera from the PSC group was significantly (P < 0.01 to P < 0.0001) higher than in each of the non-PSC groups.

CONCLUSIONS

Sera from patients with PSC contains autoantibodies against a cross-reactive peptide shared by colon and biliary epithelial cells.

Learning disabilities and poor motivation to achieve due to prolonged iodine deficiency

The effect of prolonged iodine deficiency on learning and motivation was studied. One hundred male children--matched for age, socioeconomic status, and formal education--were selected from both severely iodine-deficient (SID) and mildly iodine-deficient (MID) villages. Mean urinary iodine excretion was significantly lower in the SID than in the MID group (219.84 +/- 57.52 compared with 449.14 +/- 32.31 nmol/L, P < 0.001). The serum thyroxine concentration was significantly lower (90.36 +/- 6.46 compared with 123.70 +/- 15.42 nmol/L, P< 0.001) and serum thyroid-stimulating hormone (TSH) was significantly higher in the SID group than in the MID group (6.23 +/- 0.34 compared with 4.85 +/- 0.28 mU/L, P< 0.01). The children were administered maze, verbal, and pictorial learning tasks and a test of motivation. The results showed that SID children are slow learners compared with MID children. In both groups the rate of learning over trials was superior in younger (aged 9-12 y) children although the initial performance of older (aged 12-15 y) children was better (P < 0.01). SID children scored significantly lower than MID children on the achievement motivation scale (P < 0.01). The results are suggestive of neural impairment as well as poor sociopsychologic stimulation, resulting in learning disability and lowered achievement motivation. Unless iodine nutrition is improved in the community as a whole, these abnormalities may prevent millions of children from the SID areas from achieving their full potential even if learning opportunities are made available to them.

Comparison of cartilage scoring and cartilage sparing otoplasty – A study of 203 cases

The Edinburgh experience of different methods of otoplasty techniques in 203 patients (406 ears) over a five-year period is reviewed.

MATERIALS AND METHODS

The patients were divided into three groups - Group A (anterior cartilage scoring), Group B (cartilage sparing in the fashion of posterior suturing) and Group C (posterior suturing refined with posterior fascial flap). Demographic details, operation technique, operation time, grade of the surgeon, suture materials, early and late complications, recurrence and revision rates, patients' and physicians' comments at the follow-up clinic were retrieved from the case notes. The pre- and the post-operative photographs were assessed by a blinded lay observer and a physician and scored on a visual analogue scale. Median follow-up was 11 months.

RESULTS

The recurrence rate was 11.0%, 8.0% and 4.8% in Groups A, B and C, respectively (p = 0.0214). Complications were more common in Group A (8.8%) and Group B (7.9%) compared to Group C (1.2%) (p = 0.0208). The cosmetic result was judged best in Group C. In our experience, cartilage-sparing otoplasty refined with the post-auricular fascial flap results in significantly reduced complication rate and improved aesthetic outcome.

Depolarization of mitochondrial membrane potential is the initial event in non-nucleoside reverse transcriptase inhibitor efavirenz induced cytotoxicity

Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI) and an active constituent of the highly active antiretroviral therapy regime. It has significantly contributed in control and management of human immunodeficiency virus propagation. However, EFV administration has also led to severe adverse effects, several reports highlighted the role of EFV in mitochondrial dysfunction and toxicity but the molecular mechanism has been poorly understood. In present study, human hepatoma cells Huh 7.5 were treated with clinically relevant concentrations of EFV and parameters like cytotoxicity, mitochondrial transmembrane potential, mitochondrial morphology, cytochrome c release, mitochondria-mediated apoptosis, mtDNA and mtRNA levels and EFV distribution into mitochondrial compartment were evaluated to understand sequence of events leading to cell death in EFV-treated cells. EFV at its clinically relevant concentration was significantly toxic after 48 and 72 h of treatments. EFV-mediated toxicity is initiated with the permeabilization of mitochondrial outer membrane and change in mitochondrial membrane potential (Δψm) which triggers a series of events like cytochrome c release, alteration in mitochondrial morphology and mitochondria-mediated apoptosis. Total mitochondrial content is reduced after 48 h of EFV treatment at IC₅₀ concentration which is also reflected in reduced mitochondrial DNA and RNA levels. After detecting EFV in mitochondrial compartment after 12 h of incubation with EFV, we hypothesize that EFV being a lipophilic molecule is internalized into the mitochondrial compartment causing depolarization of Δψm which subsequently leads to a cascade of events causing cell death.

Complement activation in heart diseases. Role of oxidants

Increasing evidence demonstrated that atherosclerosis is an immunologically mediated disease. Myocardial ischemia/reperfusion injury is accompanied by an inflammatory response contributing to reversible and irreversible changes in tissue viability and organ function. Three major components are recognized as the major contributing factors in reperfusion injury. These are: (1) molecular oxygen; (2) cellular blood elements (especially the neutrophils); and (3) components of the activated complement system. The latter two often act in concert. Endothelial and leukocyte responses are involved in tissue injury, orchestrated primarily by the complement cascade. Anaphylatoxins and assembly of the membrane attack complex contribute directly and indirectly to further tissue damage. Tissue damage mediated by neutrophils can be initiated by complement fragments, notably C5a, which are potent stimulators of neutrophil superoxide production and adherence to coronary artery endothelium. The complement cascade, particularly the alternative pathway, is activated during myocardial ischemia/reperfusion. Complement fragments such as the anaphylatoxins C3a and C5a, are produced both locally and systematically, and the membrane attack complex is deposited on cell membranes and subsequent release of mediators such as histamine and platelet activating factor (PAF), thereby causing an increase in vascular permeability with concomitant manifestation of cellular edema. Complement increases the expression of CD18 on the neutrophils and increases P-selectin expression on the surface of the endothelium. Mitochondria may be a source of molecules that activate complements during ischemia/reperfusion injury to myocardium, providing therewith a stimulus for infiltration of polymorphonuclear leukocytes. Tissue salvage can be achieved by depletion of complement components, thus making evident a contributory role for the complement cascade in ischemia/reperfusion injury. The complexities of the complement cascade provide numerous sites as potential targets for therapeutic interventions designed to modulate the complement response to injury. The latter is exemplified by the ability of soluble form of complement receptor 1 (sCR1) to decrease infarct size in in vitro models of ischemia/reperfusion injury. The mechanism(s) that initiates complement activation is not clearly known, although loss of CD59 (protectin) from cells compromised by ischemia/reperfusion may contribute to direct damage of the coronary vascular bed by the terminal complement complex. Therapeutic approaches to ischemia/reperfusion injury in general, and especially those involving complements, are at the very beginning and their potential benefits have still to be adequately evaluated. It may be noted that complement activation has both positive and negative effects and, therefore, might be modulated rather than abruptly blunted.

Current practice in surveillance strategy for patients with Barrett's oesophagus in the UK

BACKGROUND

Many guidelines exist regarding the surveillance of patients with Barrett's oesophagus. There are limited data, however, with regard to whether practitioners follow these guidelines.

METHODS

We assessed current surveillance practice amongst members of the British Society of Gastroenterology using a simple 11-question anonymous survey, mailed to 300 randomly selected members from the British Society of Gastroenterology Handbook.

RESULTS

Two hundred and three of the 300 (68%) responded, 76% considering that surveillance was worthwhile. In those who considered surveillance to be worthwhile, 83% used sub-selection based on age, the length of Barrett's oesophagus or the presence of ulcer or stricture. Patients with Barrett's oesophagus of < 3 cm (short-segment) were considered to be inappropriate for surveillance by 62%. Forty-one per cent reported following the 'advised' recommendations of four-quadrant biopsies every 2 cm, whereas 44% followed a 'random and suspicious areas only' protocol. Marked variation was reported in the re-endoscope interval for both low- and high-grade dysplasia. Only 55% reported that two experienced pathologists reviewed all biopsies showing high-grade dysplasia.

CONCLUSIONS

Despite the existence of multiple guidelines for Barrett's surveillance, clinical practice varies widely in the UK. This may be due to a lack of knowledge or because gastroenterologists remain unconvinced by the quality of the current evidence of its value. These results have implications for studies attempting to collate data from multiple centres.

The frequency of silencing in Arabidopsis thaliana varies highly between progeny of siblings and can be influenced by environmental factors

In a collection of 111 transgenic Arabidopsis thaliana lines, silencing of the nptII gene was observed in 62 (56%) of the lines and three distinct nptII-silencing phenotypes were identified. Two T-DNA constructs were used, which differed in distance and orientation of the marker gene relative to the border sequences. Comparison of the sets of lines generated with each vector, indicate that the T-DNA construct configuration influence the incidence of lines displaying silencing, as well as the distribution of silencing phenotypes. Twenty lines were investigated more thoroughly. The frequency of silencing varied between siblings in 19 lines, including three lines containing a single T-DNA copy. The last line showed 100% silencing. The gus gene present in both constructs could be expressed in the presence of a silenced nptII gene. Investigation of methylation at a single site in the pnos promoter revealed partial methylation in multi-copy lines, but no methylation in single-copy lines. For 16 lines, the overall frequencies of silencing differed significantly between control plants and plants exposed to temperature stress; in 11 of these lines at the 0.1% level. In several cases, the frequency of silencing in progeny of stress-treated plants was higher than for the control group, while other lines showed higher frequencies of kanamycin-resistant progeny for the stress-treated sibling plants.

Safety and efficacy of non-steroidal anti-inflammatory drugs to reduce ileus after colorectal surgery

BACKGROUND

Ileus is common after elective colorectal surgery, and is associated with increased adverse events and prolonged hospital stay. The aim was to assess the role of non-steroidal anti-inflammatory drugs (NSAIDs) for reducing ileus after surgery.

METHODS

A prospective multicentre cohort study was delivered by an international, student- and trainee-led collaborative group. Adult patients undergoing elective colorectal resection between January and April 2018 were included. The primary outcome was time to gastrointestinal recovery, measured using a composite measure of bowel function and tolerance to oral intake. The impact of NSAIDs was explored using Cox regression analyses, including the results of a centre-specific survey of compliance to enhanced recovery principles. Secondary safety outcomes included anastomotic leak rate and acute kidney injury.

RESULTS

A total of 4164 patients were included, with a median age of 68 (i.q.r. 57-75) years (54·9 per cent men). Some 1153 (27·7 per cent) received NSAIDs on postoperative days 1-3, of whom 1061 (92·0 per cent) received non-selective cyclo-oxygenase inhibitors. After adjustment for baseline differences, the mean time to gastrointestinal recovery did not differ significantly between patients who received NSAIDs and those who did not (4·6 versus 4·8 days; hazard ratio 1·04, 95 per cent c.i. 0·96 to 1·12; P = 0·360). There were no significant differences in anastomotic leak rate (5·4 versus 4·6 per cent; P = 0·349) or acute kidney injury (14·3 versus 13·8 per cent; P = 0·666) between the groups. Significantly fewer patients receiving NSAIDs required strong opioid analgesia (35·3 versus 56·7 per cent; P < 0·001).

CONCLUSION

NSAIDs did not reduce the time for gastrointestinal recovery after colorectal surgery, but they were safe and associated with reduced postoperative opioid requirement.

Production of immunoglobulin G and G1 antibodies to cytoskeletal protein by lamina propria cells in ulcerative colitis

BACKGROUND & AIMS

Recent studies suggest an autoantigenic role for tropomyosin-related protein(s) in ulcerative colitis (UC). This study examined whether immunoglobulin G and G1 subclass antibodies against tropomyosins are produced spontaneously by the lamina propria mononuclear cells (LPMCs) that infiltrate the inflamed UC tissue.

METHODS

LPMCs were isolated from colonic biopsy specimens from 29 patients with UC, 15 with colonic Crohn's disease (CD), and 13 with non-inflammatory bowel disease (IBD). The autologous peripheral blood mononuclear cells (PBMCs) were obtained. Cells were cultured in vitro and unstimulated for 10 days. Spontaneous production of immunoglobulin G and G1 antibodies against tropomyosins was measured by enzyme-linked immunosorbent assays using highly enriched tropomyosins from skeletal muscle and colonic mucosa.

RESULTS

The total immunoglobulin G produced by LPMCs from both patients with UC and CD was comparable but higher than from patients with non-IBD (P < 0.05). However, immunoglobulin G antibodies to tropomyosins were higher in patients with UC than in patients with CD (P < 0.04) and non-IBD (P < 0.02). LPMCs from patients with symptomatic UC produced higher immunoglobulin G antibodies to tropomyosins than patients with UC in remission (P < 0.03), symptomatic CD (P < 0.04), and non-IBD (P < 0.02). Immunoglobulin G antibodies to tropomyosins predominantly belonged to immunoglobulin G1 subclass. The autologous PBMCs showed comparable results.

CONCLUSIONS

Immunoglobulin G antibodies predominantly belonging to immunoglobulin G1 subclass and reactive against tropomyosin-related protein(s) are spontaneously produced by LPMCs from the colonic mucosa in patients with UC.

Hyposmotic stress causes ATP release and stimulates Na,K-ATPase activity in porcine lens

Purinergic receptors in lens epithelium suggest lens function can be altered by chemical signals from aqueous humor or the lens itself. Here we show release of ATP by intact porcine lenses exposed to hyposmotic solution (200 mOsm). 18α-glycyrrhetinic acid (AGA) added together with probenecid eliminated the ATP increase. N-ethylmaleimide (200 µM), an exocytotic inhibitor, had no significant effect on ATP increase. Lenses exposed to hyposmotic solution displayed a ~400% increase of propidium iodide (PI) entry into the epithelium. The increased ability of PI (MW 668) to enter the epithelium suggests possible opening of connexin and/or pannexin hemichannels. This is consistent with detection of connexin 43, connexin 50, and pannexin 1 in the epithelium and the ability of AGA + probenecid to prevent ATP release. Na,K-ATPase activity doubled in the epithelium of lenses exposed to hyposmotic solution. The increase of Na,K-ATPase activity did not occur when apyrase was used to prevent extracellular ATP accumulation or when AGA + probenecid prevented ATP release. The increase of Na,K-ATPase activity was inhibited by the purinergic P2 antagonist reactive blue-2 and pertussis toxin, a G-protein inhibitor, but not by the P2X antagonist PPADS. Hyposmotic solution activated Src family kinase (SFK) in the epithelium, judged by Western blot. The SFK inhibitor PP2 abolished both SFK activation and the Na,K-ATPase activity increase. In summary, hyposmotic shock-induced ATP release is sufficient to activate a purinergic receptor- and SFK-dependent mechanism that stimulates Na,K-ATPase activity. The responses might signify an autoregulatory loop initiated by mechanical stress or osmotic swelling.

Biology of the 2Na+/1H+ antiporter in invertebrates

The functional expression of membrane transport proteins that are responsible for exchanging sodium and protons is a ubiquitous phenomenon. Among vertebrates the Na+/H+ antiporter occurs in plasma membranes of polarized epithelial cells and non-polarized cells such as red blood cells, muscle cells, and neurons, and in each cell type the transporter exchanges one sodium for one hydrogen ion, is inhibited by amiloride, and regulates intracellular pH and sodium concentration within tight limitations. In polarized epithelial cells this transporter occurs in two isoforms, each of which is restricted to either the brush border or basolateral cell membrane, and perform somewhat different tasks in the two locations. In prokaryotic cells, sodium/proton exchange occurs by an electrogenic 1Na+/2H+ antiporter that is coupled to a primary active proton pump and together these two proteins are capable of tightly regulating the intracellular concentrations of these cations in cells that may occur in environments of 4 M NaCl or pH 10-12. Invertebrate epithelial cells from the gills, gut, and kidney also exhibit electrogenic sodium/proton exchange, but in this instance the transport stoichiometry is 2Na+/1H+. As with vertebrate electroneutral Na+/H+ exchange, the invertebrate transporter is inhibited by amiloride, but because of the occurrence of two external monovalent cation binding sites, divalent cations are able to replace external sodium and also be transported by this system. As a result, both calcium and divalent heavy metals, such as zinc and cadmium, are transported across epithelial brush border membranes in these animals and subsequently undergo a variety of biological activities once accumulated within these cells. Absorbed epithelial calcium in the crustacean hepatopancreas may participate in organismic calcium balance during the molt cycle and accumulated heavy metals may undergo complexation reactions with intracellular anions as a detoxification mechanism. Therefore, while the basic process of sodium/proton exchange may occur in invertebrate cells, the presence of the electrogenic 2Na+/1H+ antiporter in these cells allows them to perform a wide array of functions without the need to develop and express additional specialized transport proteins. J. Exp. Zool. 289:232-244, 2001.

Vanadium-mediated chemoprotection against chemical hepatocarcinogenesis in rats: haematological and histological characteristics

The trace element vanadium was investigated for its anti-neoplastic role in relation to haematological status, hepatic histopathology and histochemical analysis of glycogen in liver. Its impact on the survival of male Sprague-Dawley rats subjected to a two-stage hepatocarcinogenesis regimen was also assessed. Initiation was performed using a single intraperitoneal injection of diethylnitrosamine (DENA) (200 mg/kg) followed by promotion with phenobarbital (0.05%) in a basal diet. Vanadium supplementation as ammonium monovanadate at 0.5 ppm vanadium in drinking water was given ad libitum throughout the experiment (20 weeks), before the initiation (4 weeks), or during the promotional period (14 weeks). At the end of the study, there was a significant decrease in red blood cell count, haemoglobin content, haematocrit value, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, plasma volume change and total white cell count, with a concurrent alteration in lymphoid:myeloid ratio in DENA control animals compared with their normal counterparts. Vanadium supplementation throughout the study or before the initiation significantly reversed the DENA-induced alterations in most of the haematological indices. A single intraperitoneal injection of DENA also depleted the plasma albumin concentration, raised the plasma globulin content, and decreased the ratio of albumin to globulin. These altered features began to return to normal following vanadium supplementation. Supplementary vanadium also elicited substantial protection against DENA-mediated rat liver carcinogenesis. This was fairly evident from hepatic histology and evaluation of glycogen accumulation by periodic acid-Schiff reaction. The survival of DENA-treated animals was considerably increased in the presence of vanadium. The critical involvement of vanadium in modulating several factors associated with erythropoiesis under carcinogenic challenge may thus have a possible impact on the eventual increased survival of the host.

Upper Airway Obstruction in Children

Children with upper airway obstruction are both unique and variable in their presentation and management, often posing a challenge to the pediatrician. Several anatomical and physiologic peculiarities make a child vulnerable to develop an obstruction of upper airways. The characteristic finding in upper airway obstruction is stridor-inspiratory, biphasic or expiratory. The etiologies vary widely throughout the age groups and according to the mode of presentation. The approach starts with suspicion, mandates careful clinical evaluation of the degree of obstruction and many a times emergency measures precede any investigation or even precise diagnosis. Maintaining an open and stable airway is of the utmost importance, often requiring a team approach of emergency physician, pediatrician, otorhinolaryngologist and pediatric pulmonologist. The commonest condition presenting with upper airway obstruction in pediatric population is viral croup. Croup is a clinical diagnosis in a febrile child, with barking cough and stridor preceded by upper respiratory infection. It is treated with systemic or inhaled steroids and nebulized epinephrine. Epiglottitis and bacterial tracheitis are acute bacterial infections of upper airways, presenting as true airway emergencies. Though the mainstay of therapy is IV antibiotics, the prime concern is maintenance of airway, which frequently requires endotracheal intubation. Rigid bronchoscopy is the procedure of choice for airway foreign bodies, a common cause of upper airway obstruction in children below 3 y of age. Airway malacias are the commonest cause of chronic stridor and are mostly managed conservatively.