The expression of laminin-5 in severe dysplasia/carcinoma in situ and early invasive squamous cell carcinoma: an immunohistochemical study

AIM

The objective of the present study was to detect the immunohistochemical localization of laminin-5 in the subepithelial basement membrane and to investigate the integrity of the basement membrane in cases of severe dysplasia/carcinoma in situ and early invasive squamous cell carcinoma.

METHODS

Tissue samples of 55 filed (25-early invasive squamous cell carcinoma; 25-severe dysplasia/carcinoma in situ;5-normal buccal mucosa as controls) cases were collected from the archives of Oral Pathology Department. Routine staining and Immunostaining for laminin-5 (Biogenex) was carried out on the sections. The immunohistochemical localization and integrity of the basement membrane protein isoform laminin-5 was studied in formalin fixed paraffin embedded sections of severe dysplasia/CIS and early invasive squamous cell carcinoma (EISCC). Chi square test was used for statistical analysis. P values <0.05 were considered statistically significant.

RESULTS

The immunostaining of laminin-5 as observed under light microscope ranged from continuous to complete absence. The laminin-5 staining pattern was more often continuous in severe dysplasia/CIS and discontinuous or absent in EISCC. A statistical comparison between different scores of laminin-5 staining in severe dysplasia/CIS and early invasive squamous cell carcinoma showed a highly significant 'P' value (0.0001).

CONCLUSION

The status of basal lamina, laminin-5 may provide additional and relevant information about invasive potential of dysplasias. Hence the study of laminin-5 immunohistologically can be regarded as an adjunct to distinguish severe dysplastic lesions from early oral invasive carcinoma.

Assessment of pollutants and gaseous emissions in sewer network in NCT of Delhi

The NCT of Delhi in India handles domestic sewage through a long sewerage networks. The network is into eight divisions. The aim of the present study is to arrive at a correlation between sewage quality and gas emissions in the sewer network of various divisions. This will aid in forewarning the sewer workers about the safety precautions. The health effects due to toxic sewer gases exposure and assessment of hazardous conditions and hazard potential are discussed. The study areas were broadly classified as residential, commercial, industrial and mix (combination of residential & commercial) for comparison. Sewage samples were collected from 1020 sites and analyzed for 10 different physicochemical parameters. The analytical data revealed wide variation in the chemical composition of sewage flowing at various sewerage network sites. Based on comparison with the regulatory standard for discharge in sewers, 89 sites with higher values of BOD and sulphate were marked as critical sites. Subsequently, the concentrations of CH4 and H2S in sewer emissions were determined for the 89 critical sites through onsite monitoring. Samples from 22 sites had significantly higher concentration of CH4 than the LEL and those from 40 sites showed concentrations higher than the LFL. On the other hand, samples from 38 locations showed significantly high H2S concentration, more than permissible limit of 10 ppm. The sewer workers in North East, North West and West region of the metropolis were exposed to hazards from excessive CH4 and H2S emissions, whereas those under South and South West regions were more vulnerable to H2S related risks. The sewer network under North, Central and South poses relatively less hazard with regard to gaseous emissions.

Treatment of refractory organics from membrane rejects using ozonation

The reject water or retentate generated from membrane application for recovery of water from tannery wastewater treatment contains certain refractory organics. These refractory organics are present in substantial quantity in the condensate of reject water also. Hence the treatment of rejects using conventional methods is rather difficult. In this paper, an attempt has been made to treat the reject water from the reverse osmosis (RO) and nano filtration (NF) operation on tannery wastewater using ozonation treatment technique. Ozonation studies on RO and NF rejects indicate that ozone dose of 80 and 100mg/min for 60 and 70 min contact time achieves 59 and 78% chemical oxygen demand (COD) reduction, respectively. The mass balance in ozone indicates the ozone consumption for RO and NF rejects varies from 2.4 to 3.4 and 2.8 to 4.5 g/g of COD removed respectively. The results suggest that ozonation of RO and NF rejects would significantly reduce the refractory organic pollutant loading into the environment from wastewater reuse facility.

A comparative histological analysis of human pulp following direct pulp capping with Propolis, mineral trioxide aggregate and Dycal

BACKGROUND

Permanent teeth pulp exposures have traditionally been treated with calcium hydroxide pulp capping. The aim of this study was to investigate the response of human pulp tissue which were mechanically exposed to a new material, Propolis and compare it with two existing and commonly used pulp capping agents (mineral trioxide aggregate and Dycal).

METHODS

Thirty-six intact human premolars were mechanically exposed. Teeth were divided into six groups of 6 teeth each and were capped with Propolis, mineral trioxide aggregate and Dycal. Final restoration was done with posterior composite resin using light cured glass ionomer cement as a liner. The teeth were then extracted on the 15th or the 45th day and processed for histological evaluation.

RESULTS

Differences in inflammatory response and dentine bridge formation of the exposed pulp to the three different materials were statistically calculated using chi-square test and were found to be non-significant. There was more pulp inflammation in teeth treated with Dycal than with Propolis and MTA on the 15th as well as on the 45th day. Propolis and MTA showed bridge formation in more teeth, and the bridges were in closer proximity to pulp capping material than teeth treated with Dycal on the 45th day.

CONCLUSIONS

The response of pulps to Propolis as a pulp capping agent was comparable to MTA and Dycal.

Removal of basic dyes from aqueous medium using a novel polymer: Jalshakti

Studies were carried out to remove basic dyes such as safranine T, methylene blue, crystal violet, light green, brilliant milling violet and patent blue VS from their aqueous solutions using biodegradable polymeric absorbent material, viz., Jalshakti (JS). Results showed that 93% safranine T, 98% methylene blue and 84% crystal violet were adsorbed on JS relative to their initial concentration (10 mg L(-1)). The optimum pH was found to be 6.0+/-0.5 and smaller size of particle of JS resulted better adsorptive removal of the dyes. IR spectroscopic and potassium ion release studies revealed that basic dyes were selectively removed through adsorption-ion-exchange mechanism involving carboxylic groups and K+ ions of JS.

Intraoral papillary endothelial hyperplasia: case discussion with supportive histochemistry and immunohistochemistry

An intraoral mass of eight months duration in a six year-old girl was diagnosed as papillary endothelial hyperplasia. Histologically, the tissue was characterized by the unusual endothelial cell proliferation, which is significant, as papillary endothelial hyperplasia resembles angiosarcoma and possible over-treatment thereafter. Clarification of this unusual lesion based on histological findings with supportive histochemical staining and immunohistochemistry in the light of clinico-pathological correlation is discussed. This lesion warrants better documentation of the clinical behavior with regular monitoring.

Physico-chemical treatment of wastewater from clusters of small scale cotton textile units

Small scale industries can not own individual wastewater treatment facility due to non-availability of land and skilled manpower for operation and maintenance of wastewater treatment plants. A centralized wastewater treatment facility for clusters of small scale industries is appropriate. This concept is gaining popularity in recent years. In India, various textile process operations are undertaken by individual small scale units. The wastewater generated at these units is conveyed to a common effluent treatment facility comprising of equalization, flocculation-clarification, activated sludge process, secondary clarification and finally discharge into inland surface water bodies. The wastewater from small scale cotton textile processing units was highly coloured and alkaline with average BOD and COD concentration of 205 and 790 mg l(-1), respectively. Due to the presence of several dyes, particularly reactive dyes, the biological treatment is often found less effective. Therefore, applicability of various physico-chemical treatment methods needs to be investigated in pursuit of an alternative to biological treatment of textile wastewater. A physico-chemical treatment scheme, involving chemical coagulation-sedimentation, dual media filtration, activated carbon adsorption followed by chemical oxidation was investigated in this paper. The quality of final treated wastewater in terms of BOD and COD was 18-24 and 230-240 mg l(-1), respectively through this scheme. A scheme of treatment comprising coagulation-sedimentation, dual media filtration, activated carbon, chemical oxidation may be considered as an alternative to biological treatment of textile wastewater.

Photocatalytic degradation of 2-chlorophenol: a study of kinetics, intermediates and biodegradability

The kinetics of photocatalytic (TiO(2)/UV) degradation of 2-chlorophenol (2-CP), characterization of intermediates and induction of biodegradability in treated chlorophenol solutions is reported. Approximately 95% of the 2-CP is removed in approximately 2h at pH 5 and 0.2g TiO(2)l(-1) when the 2-CP concentration is < or =100mgl(-1); the pseudo-first-order rate constant (k) is estimated to be 0.0183 min(-1). GC-MS analyses detected phenol, catechol, hydroxyhydroquinone (HHQ), and chlorohydroquinone (CHQ) intermediates during the short irradiation time (<1h); however two other higher carbon intermediates 2-hydroxy-benzaldehyde (HB) and [1.1'-biphenyl]-2,2'-diol (BPD) are found as major intermediates over longer irradiation times. The biochemical oxygen demand (BOD) of treated 2-CP solutions improved substantially. A tentative mechanistic pathway to explain formation of higher carbon intermediates is presented.

The endopolyphosphatase gene: essential in Saccharomyces cerevisiae

Endopolyphosphatases (Ppn1) from yeast and animal cells hydrolyze inorganic polyphosphate (poly P) chains of many hundreds of phosphate residues into shorter lengths. The limit digest consists predominantly of chains of 60 (P(60)) and 3 (P(3)) P(i) residues. Ppn1 of Saccharomyces cerevisiae, a homodimer of 35-kDa subunits (about 352-aa) is of vacuolar origin and requires the protease activation of a 75-kDa (674-aa) precursor polypeptide. The Ppn1 gene (PPN1) now has been cloned, sequenced, overexpressed, and deleted. That PPN1 encodes Ppn1 was verified by a 25-fold increase in Ppn1 when overexpressed under a GAL promoter and also by several peptide sequences that match exactly with sequences in a yeast genome ORF, the mutation of which abolishes Ppn1 activity. Null mutants in Ppn1 accumulate long-chain poly P and are defective in growth in minimal media. A double mutant of PPN1 and PPX1 (the gene encoding a potent exopolyphosphatase) loses viability rapidly in stationary phase. Whether this loss is a result of the excess of long-chain poly P or to the lack of shorter chains (i.e., poly P(60) and P(3)) is unknown. Overexpression of the processed form of Ppn1 should provide a unique and powerful reagent to analyze poly P when the chain termini are unavailable to the actions of polyPase and poly P kinase.

Evaluation of mast cells in oral lichen planus and oral lichenoid reaction

Recent attention has been directed towards the role of mast cells in the pathogenesis of oral lichen planus. Mast cells are responsible for trafficking of inflammatory cells into the connective tissue that in turn helps in progression and maintenance of the chronicity of oral lichen planus. In the present study we have evaluated the mast cell count and its cell types using toluidine blue stain, in oral lichen planus and compared it with oral lichenoid reactions. We have observed an increase in mast cell count in both these conditions in comparison to normal mucosa. Also, a significant difference in the types of mast cells in oral lichen planus and oral lichenoid reactions has been noted, possibly suggesting that the role of mast cell is different in these conditions.

Evaluation of immunoglobulin G synthesizing plasma cells in periapical granuloma and cyst

Immunoglobulin synthesizing plasma cells for IgG were quantitated in 20 periapical granulomas and 20 periapical cysts, using unlabelled antibody peroxidase-antiperoxidase complex method. Result showed that immunoglobulin G producing plasma cells were predominant in periapical cyst as compared with periapical granuloma. A statistical significant relation was observed between these two lesions.

Immunofluorescence in oral lichen planus and oral lichenoid reaction. A review

Oral lichen is a mucocutaneous disorder, which presents a confusing array of patterns and forms. Despite the reported differences between the classical lichen planus and lichenoid reaction, several reports have concurred with this lack of distinguishing features. As of yet there is no specific test for lichenoid reaction, although resolution and recurrence of lichenoid reaction on withdrawal and exposure to the drug is probably diagnostic. Thus when the clinical and histopathologic evaluation cannot confirm the diagnosis satisfactorily, the use of immunofluorescent examination is of great importance. Early diagnoses of these conditions are more likely with adjunctive use of immunofluorescent examination. Further, this tool may provide an insight into the pathogenesis of these disorders.

Treatment of phosphoric acid plant wastewater using Fenton's reagent and coagulants

The results of treatability studies viz., Fenton reaction and physico-chemical (coagulation) treatment using lime, alum, Fe salts and polyaluminium chloride (PAC) performed on wastewater generated from a unit manufacturing technical grade phosphoric acid are reported. Due to low biochemical oxygen demand (BOD) chemical oxygen demand (COD) ratio and very low pH, this wastewater is not amenable for biological treatment. The treatability studies indicated that it is possible to remove 75-80% COD using Fenton's reagent at optimum doses of 1.0 g/L FeSO4 and 2 ml of 30% H2O2. Simultaneously, significant quantities of suspended solids, phosphate and fluoride are also removed. Polyaluminium chloride is found to be more effective towards suspended solids (SS), COD, phosphate and fluoride removal, when compared to other coagulants used in the present study. Addition of an anionic polyelectrolyte (Magnafloc 156) to PAC improved the performance further. A treatment scheme that consists of neutralization (pH 4) + Fenton's reagent + neutralization (pH 7.5) + PAC/Magnafloc 156 is found to be effective in treating phosphoric acid plant wastewater to meet marine discharge standards.

Inorganic polyphosphate: a molecule of many functions

Inorganic polyphosphate (poly P) is a chain of tens or many hundreds of phosphate (Pi) residues linked by high-energy phosphoanhydride bonds. Despite inorganic polyphosphate's ubiquity--found in every cell in nature and likely conserved from prebiotic times--this polymer has been given scant attention. Among the reasons for this neglect of poly P have been the lack of sensitive, definitive, and facile analytical methods to assess its concentration in biological sources and the consequent lack of demonstrably important physiological functions. This review focuses on recent advances made possible by the introduction of novel, enzymatically based assays. The isolation and ready availability of Escherichia coli polyphosphate kinase (PPK) that can convert poly P and ADP to ATP and of a yeast exopolyphosphatase that can hydrolyze poly P to Pi, provide highly specific, sensitive, and facile assays adaptable to a high-throughput format. Beyond the reagents afforded by the use of these enzymes, their genes, when identified, mutated, and overexpressed, have offered insights into the physiological functions of poly P. Most notably, studies in E. coli reveal large accumulations of poly P in cellular responses to deficiencies in an amino acid, Pi, or nitrogen or to the stresses of a nutrient downshift or high salt. The ppk mutant, lacking PPK and thus severely deficient in poly P, also fails to express RpoS (a sigma factor for RNA polymerase), the regulatory protein that governs > or = 50 genes responsible for stationary-phase adaptations to resist starvation, heat and oxidant stresses, UV irradiation, etc. Most dramatically, ppk mutants die after only a few days in stationary phase. The high degree of homology of the PPK sequence in many bacteria, including some of the major pathogenic species (e.g. Mycobacterium tuberculosis, Neisseria meningitidis, Helicobacter pylori, Vibrio cholerae, Salmonella typhimurium, Shigella flexneri, Pseudomonas aeruginosa, Bordetella pertussis, and Yersinia pestis), has prompted the knockout of their ppk gene to determine the dependence of virulence on poly P and the potential of PPK as a target for antimicrobial drugs. In yeast and mammalian cells, exo- and endopolyphosphatases have been identified and isolated, but little is known about the synthesis of poly P or its physiologic functions. Whether microbe or human, all species depend on adaptations in the stationary phase, which is truly a dynamic phase of life. Most research is focused on the early and reproductive phases of organisms, which are rather brief intervals of rapid growth. More attention needs to be given to the extensive period of maturity. Survival of microbial species depends on being able to manage in the stationary phase. In view of the universality and complexity of basic biochemical mechanisms, it would be surprising if some of the variety of poly P functions observed in microorganisms did not apply to aspects of human growth and development, to aging, and to the aberrations of disease. Of theoretical interest regarding poly P is its antiquity in prebiotic evolution, which along with its high energy and phosphate content, make it a plausible precursor to RNA, DNA, and proteins. Practical interest in poly P includes many industrial applications, among which is the microbial removal of Pi in aquatic environments.

Glandular odontogenic cyst. A rare entity with aggressive biological behaviour. A case report

Glandular Odontogenic cyst is an apparently rare jaw cyst characterised by typical histopathological features, propensity to reach large size and high rate of local recurrence, if not adequately treated. Identification of this cyst as a separate entity is important because of the difference in biological behaviour. We report a case of Glandular Odontogenic cyst occurring in maxilla.

Inorganic polyphosphate is required for motility of bacterial pathogens

The ppk gene encodes polyphosphate kinase (PPK), the principal enzyme in many bacteria responsible for the synthesis of inorganic polyphosphate (polyP) from ATP. A null mutation in the ppk gene of six bacterial pathogens renders them greatly impaired in motility on semisolid agar plates; this defect can be corrected by the introduction of ppk gene in trans. In view of the fact that the motility of pathogens is essential to invade and establish systemic infections in host cells, this impairment in motility suggests a crucial and essential role of PPK or polyP in bacterial pathogenesis.

Inorganic polyphosphate regulates responses of Escherichia coli to nutritional stringencies, environmental stresses and survival in the stationary phase

The molecular mechanisms responsible for polyP accumulation in E. coli remain largely obscure. Based on the available data, a tentative model is proposed (Fig. 1; Ault-Riché et al. 1998). Inhibition by (p)ppGpp of PPX interrupts the dynamic balance between the synthesis of polyP by PPK and its hydrolysis by PPX, accounting for polyP accumulation. However, mutants lacking PhoB, the response regulator of the Pho regulon, fail to accumulate polyP even in the face of high levels of (p)ppGpp. Clearly, PhoB is required in some undefined manner. With regard to osmotic stress, the pathway to polyP accumulation is also distinct from the one identified with the activation of envZ and the associated changes in membrane functions. A tentative scheme attempting to describe the metabolic turnover of polyP is given in Fig. 4. [figure: see text] In adaptations to stress, cells must coordinate major changes in the rates of transcription, translation, and replication as well as make choices in the genes expressed (Kolter et al. 1993). PolyP could provide activated phosphates or coordinate an adaptive response by binding metals and/or specific proteins. Accumulation of polyP in E. coli and other organisms is commonly assumed to provide a reservoir of energy convertible to ATP. This seems implausible because of the turnover of ATP which consumes only a fraction of a second (Chapman and Atkinson 1977). Thus, other functions for polyP need to be considered, among them a regulatory role. PolyP, even at very low levels, is essential in E. coli for adaptations in stationary phase and for survival (Rao and Kornberg 1996). As a polyanionic polymer, polyP has chemical similarities to DNA and RNA in interactions with basic domains of proteins. Further investigation of the cellular location of polyP, its state of metabolic availability and identification of its binding partners are needed. In view of the ubiquity of polyP in eukaryotic cells (including dynamic turnover in the nuclei of some mammalian cells), studies similar to those undertaken in E. coli may reveal comparable functions.

Inorganic polyphosphate in Escherichia coli: the phosphate regulon and the stringent response

Escherichia coli transiently accumulates large amounts of inorganic polyphosphate (polyP), up to 20 mM in phosphate residues (Pi), in media deficient in both Pi and amino acids. This transient accumulation is preceded by the appearance of nucleotides ppGpp and pppGpp, generated in response to nutritional stresses. Mutants which lack PhoB, the response regulator of the phosphate regulon, do not accumulate polyP even though they develop wild-type levels of (p)ppGpp when subjected to amino acid starvation. When complemented with a phoB-containing plasmid, phoB mutants regain the ability to accumulate polyP. PolyP accumulation requires high levels of (p)ppGpp independent of whether they are generated by RelA (active during the stringent response) or SpoT (expressed during Pi starvation). Hence, accumulation of polyP requires a functional phoB gene and elevated levels of (p)ppGpp. A rapid assay of polyP depends on its adsorption to an anion-exchange disk on which it is hydrolyzed by a yeast exopolyphosphatase.

CCTV study of cemental annulations in determining the age from single tooth

Cementum in human tooth is a hard tissue in its root deposited around dentin in layers throughout the life. Microscopically each layer is seen as a set of alternating dark and light bands and called as Cemental Annulations. Intact teeth obtained from subjects of either sex and of known ages processed by ground sectioning manually and mounted on a glass slide. The cemental annulations were then counted by light microscope using CCTV Screen, at the junction of cervical with middle third of root. Age was then determined by adding the eruption age in years of tooth in study to the annulations counted. This was found to be matching with actual age almost to an accuracy of +/- 1-2 years.

Inorganic polyphosphate and the induction of rpoS expression

Inorganic polyphosphate [poly(P)] levels in Escherichia coli were reduced to barely detectable concentrations by expression of the plasmid-borne gene for a potent yeast exopolyphosphatase [poly(P)ase]. As a consequence, resistance to H2O2 was greatly diminished, particularly in katG (catalase HPI) mutants, implying a major role for the other catalase, the stationary-phase KatE (HPII), which is rpoS dependent. Resistance was restored to wild-type levels by complementation with plasmids expressing ppk, the gene for PPK [the polyphosphate kinase that generates poly(P)]. Induction of expression of both katE and rpoS (the stationary-phase sigma factor) was prevented in cells in which the poly(P)ase was overproduced. Inasmuch as this inhibition by poly(P)ase did not affect the levels of the stringent-response guanosine nucleotides (pppGpp and ppGpp) and in view of the capacity of additional rpoS expression to suppress the poly(P)ase inhibition of katE expression, a role is proposed for poly(P) in inducing the expression of rpoS.

Inorganic polyphosphate supports resistance and survival of stationary-phase Escherichia coli

The Escherichia coli mutant (ppk) lacking the enzyme polyphosphate kinase, which makes long chains of inorganic polyphosphate (poly P), is deficient in functions expressed in the stationary phase of growth. After 2 days of growth in a medium limited in carbon sources, only 7% of the mutants survived compared with nearly 100% of the wild type; the loss in viability of the mutant was even more pronounced in a rich medium. The mutant showed a greater sensitivity to heat, to an oxidant (H2O2), to a redox-cycling agent (menadione), and to an osmotic challenge with 2.5 M NaCl. After a week or so in the stationary phase, mutant survivors were far fewer in number and were replaced by an outgrowth of a small-colony-size variant with a stable genotype and with improved viability and resistance to heat and H2O2; neither polyphosphate kinase nor long-chain poly P was restored. Suppression of the ppk feature of heat sensitivity by extra copies of rpoS, the gene encoding the RNA polymerase sigma factor that regulates some 50 stationary-phase genes, further implicates poly P in promoting survival in the stationary phase.

Genetically altered levels of inorganic polyphosphate in Escherichia coli

The ppk gene encoding polyphosphate kinase (PPK), the enzyme in Escherichia coli that makes long chains of polyphosphate (polyP) reversibly from ATP, was disrupted by insertion of a kanamycin resistance gene. Expression of the exopolyphosphatase gene (ppx) immediately downstream of ppk in the operon was likewise disrupted. Cells were also transformed with a high-copy-number plasmid bearing ppk. Genetically altered polyP levels were estimated in cell extracts by the PPK conversion of ADP to ATP. PolyP levels (microgram/10(11) cells) near 2.0 were reduced in the ppk(-)-ppx- mutants to 0.16 and increased more than 100-fold (e.g. 220) in cells transformed with multiple copies of ppk. Mutant cells, lacking the long polyP chains, showed a growth lag following dilution of a stationary-phase culture. PolyP-deficient cells exhibit a striking phenotype in their failure to survive in stationary phase and loss of resistance to heat (55 degrees C) and to oxidants (42 mM H2O2). High polyP levels are also associated with reduced survival.

Effect of glpT and glpD mutations on expression of the phoA gene in Escherichia coli

In vivo 31P nuclear magnetic resonance analysis of Escherichia coli cells showed that the intracellular concentration of P(i) remained constant in wild-type and in a glpT mutant strain whether the cells were grown on excess (2 mM) P(i) or sn-glycerol-3-phosphate as a phosphate source. The function of the phoA promoter (measured by beta-galactosidase activity in a phoA-lacZ fusion strain) was repressed when glpT+ cells were utilizing sn-glycerol-3-phosphate as the sole source of phosphate. These cells were devoid of alkaline phosphatase activity. However, the phoA promoter was fully active in a glpT mutant. These results indicated that the repression of the enzyme synthesis was not due to a variation in the level of cytoplasmic P(i) but was due to the P(i) excreted into the periplasm and/or to the medium.

Role of PhoU in phosphate transport and alkaline phosphatase regulation

The negative regulatory function of PhoU in alkaline phosphatase (AP) was suggested by the behavior of K10 phoU35 carrying a missense mutation whose product was detected by immunoblotting. To define more clearly the regulatory function of this protein for the synthesis of AP, we constructed a null mutation. The constitutive synthesis of AP in this phoU deletion strain confirmed the negative role of PhoU. However, the expression of the PhoU protein from an isopropyl-beta-D-thiogalactopyranoside-inducible promoter had no effect on the repression of AP synthesis. Furthermore, the involvement of PhoU in free-Pi uptake was demonstrated. These results provide evidence that PhoU participates in Pi transport and in the regulatory role of the phosphate-specific transport system.

Molecular aspects of phosphate transport in Escherichia coli

Escherichia coli transports inorganic phosphate (Pi) by the low-affinity transport system, Pit. When the level of the external Pi is lower than 20 microM, another transport system, Pst, is induced with a Kt of 0.25 microM. An outer-membrane porin, PhoE, with a Km of about 1 microM is also induced. The outer membrane allows the intake of organic phosphates which are degraded to Pi by phosphatases in the periplasm. The Pi-binding protein will capture the free Pi produced in the periplasm and direct it to the transmembrane channel of the cytoplasmic membrane. The channel consists of two proteins, PstA and PstC, which have six and five transmembrane helices, respectively. On the cytoplasmic side of the membrane the channel is linked to the PstB protein, which carries a nucleotide (probably ATP)-binding site. PstB probably provides the energy required by the channel to free Pi. The Pst system has two functions in E. coli: (i) the transport of Pi, and (ii) the negative regulation of the phosphate regulon (a complex of 20 proteins mostly related to organic phosphate transport). It is remarkable that these two functions are not related, since the repressibility of the regulon depends on the integral structure of Pst (PiBP + PstA + PstC + PstB) and not on the Pi transported. Another gene of the pst operon, phoU, produces a protein involved in the negative regulation of the Pho regulon, but the mechanism of this function has not been explained. Thus the regulatory function of the Pst system remains obscure. Its basal level, present when Pi is abundant, is sufficient to repress the Pho regulon but the negative regulatory function is lost upon Pi starvation.

Mandibular canine index--a clue for establishing sex identity

A preliminary study for establishing sex identity by Mandibular Canine Index is described. Seven hundred and sixty six individuals from a South Indian population of either sex, ranging in age from 15 to 21 years, with fully errupted, healthy and non-worn mandibular permanent canines were studied. The data collected was analysed statistically. Accurancy of sex determination identity was found to be 84.3% in the male and 87.5% in the female. The method is simple and inexpensive to conduct and therefore can be applied in Forensic Odontology, as a method for establishing sex identity.

Utilization by Escherichia coli of a high-molecular-weight, linear polyphosphate: roles of phosphatases and pore proteins

We observed that wild-type Escherichia coli utilized a linear polyphosphate with a chain length of 100 phosphate residues (poly-P100) as the sole source of phosphate in growth medium. A mutation in the gene phoA of alkaline phosphatase or phoB, the positive regulatory gene, prevented growth in this medium. Since no alkaline phosphatase activity was detected outside the wild-type cells, the periplasmic presence of the enzyme was necessary for the degradation of polyphosphate. A 90% reduction in the activity of periplasmic acid phosphatase with a pH optimum of 2.5 (delta appA mutants) did not affect polyphosphate utilization. Of the porins analyzed (OmpC, OmpF, and PhoE), the phoB-inducible porin PhoE was not essential since its absence did not prevent growth. To study how poly-P100 diffused into the cells, we used high-resolution 31P nuclear magnetic resonance (31P NMR) spectroscopy. The results suggest that poly-P100 entered the periplasm and remained in equilibrium between the periplasm and the medium. When present individually, porins PhoE and OmpF facilitated a higher permeability for poly-P100 than porin OmpC did. The degradation of polyphosphate by intact cells of E. coli observed by 31P NMR showed a time-dependent increase in cellular phosphate and a decrease in polyphosphate concentration.

Nucleotide pool in pho regulon mutants and alkaline phosphatase synthesis in Escherichia coli

The intracellular nucleotide pool of Escherichia coli W3110 reproducibly changes from conditions of growth in phosphate excess to phosphate starvation, with at least two nucleotides appearing under starvation conditions and two nucleotides appearing only under excess phosphate conditions. Strains bearing a deletion of the phoA gene show the same pattern, indicating that dephosphorylation by alkaline phosphatase is not responsible for the changes. Strains with mutations in the phoU gene, which result in constitutive expression of the pho regulon, show the nucleotide pattern of phosphate-starved cells even during phosphate excess growth. These changes in nucleotides are therefore due to phoU mutation but not to alkaline phosphatase constitutivity. In fact, a phoR (phoR68) mutant strain has the patterns of the wild type in spite of being constitutive for alkaline phosphatase. That these nucleotides might be specific signals for pho regulon expression was supported by the fact that the two nucleotides appearing under phosphate starvation induced the synthesis of alkaline phosphatase in repressed permeabilized wild-type cells under conditions of phosphate excess.

Amount and chain length of polyphosphates in Escherichia coli depend on cell growth conditions

Anaerobiosis induced an accumulation of polyphosphates (poly Pi) in a phosphate-rich medium by an alkaline-phosphatase constitutive mutant of Escherichia coli. The total poly Pi content was maximum at around 6 h of anaerobic growth. Both trichloroacetic acid- and NaOH-soluble poly Pi were found to be present. The acid-soluble fraction consisted mainly of a linear polymer of about 20 +/- 5 phosphate units, whereas the alkali-extractable poly Pi fraction contained at least four molecular species of higher chain length as determined by gel filtration. The majority of poly Pi extracted at 6 h had lower chain lengths than those extracted from cells incubated for 24 h. In vivo 31P nuclear magnetic resonance spectra of E. coli cells as a function of growth conditions were consistent with the in vitro extract results.