Enhancing the Embryology teachinglearning experience in the medical curriculum: a faculty & student lookout

It has been identified that most medical students are dissatisfied with current embryology teaching, and they often find embryology learning difficult. The present study was conducted to evaluate the perception of faculty and undergraduate medical students regarding the existing teaching-learning practices in embryology. The present cross-sectional study involved faculty, undergraduate, and postgraduate students engaged in embryology teaching-learning. The study was conducted in two steps. In the first step, the undergraduates were provided with a semi-structured questionnaire that addressed the practices of embryology teaching- learning in the current medical curriculum. The responses were recorded using a Likert scale. In the second step, the participants were invited to answer an open-ended question on improving the teaching-learning practices of embryology. The study involved 50 faculty, 232 medical undergraduates, and 15 postgraduate students. Most participants (76.1%) agreed that human embryology is essential in understanding anatomical variations, congenital anomalies, and clinical ailments. Although embryology is interesting to study, it is not easy to comprehend, as stated by most students (52.24%). They also felt that embryology is often neglected while learning Anatomy (70.73%). Ways to improve the embryology teaching-learning practices assessed in step two identified the following themes: image and video-assisted learning, experiential learning, 3D-models assisted learning, case-based learning, specimen-based learning, assessment-based learning, and smallgroup teaching. Embryology teaching-learning is an integral part of the Anatomy curriculum. Therefore, there is a need to reform the existing methodologies of embryology teaching-learning to enhance student engagement. Seeking students and faculty’s perceptions about the current practices of embryology teaching and its impact on their learning becomes useful. This study intents to utilize the feedback gained in improving the process of imparting embryology knowledge and will assist in a positive learning experience for the students.

Hepatoprotective Role of Caesalpenia bonduc: A Histopathological and Biochemical Study

BACKGROUND

Hepatotoxicity is one of the inevitable side effects of long term use of medicines in many different disorders, chronic use of alcohol and in certain infectious disorders. Even though there are few effective drugs to treat such hepatotoxicity, mortality due to hepatotoxicity is increasing day by day. Therefore, in search of alternative and more effective medicine we found that Caesalpenia bonduc (CB), a shrub grows in hotter places of south Asia has been effectively used to treat such hepatotoxicity in folk medicine.

AIM

AIM of the study is to scientifically evaluate the hepatoprotective nature of aqueous extract of CB using Carbon tetrachloride(CCl4) induced hepatotoxic rat model. Materials and Methods and Result: Elevated levels of blood ALT, AST and ALT enzymes were found in CCl4 induced hepatotoxic rat models. Treating these animals with CB either prior or after the induction of hepatotoxicity, shows significant decrease in the levels of ALP, AST, and ALT in their blood in comparison with the untreated hepatotoxic group. Additionally, histologically, hepatotoxic rats show necrotic changes & vacuolation in their hepatocytes, altered hepatic architecture and congested hepatic sinusoids. However, such histopathological adverse changes were minimized when these animals treated with CB.

CONCLUSION

Results of the present study indicate that CB acts as both preventive and curative hepatoprotector.

Ovarian development in Wistar rat treated prenatally with single dose diisobutyl phthalate

Phthalates are a class of industrial compounds with an array of toxicological properties used in day to day life. Diisobutyl phthalate on (DIBP) is used as an additive to keep the plastics soft or flexible (plasticizer) in nitrocellulose plastic, nail polish, explosives, lacquer manufacturing etc. Although DIBP exposure in humans is generally low, people in adhesive industries and pharmaceutical industries are exposed to higher levels. The aim of this study was to determine the effect of single dose of DIBP on developing ovary of Wistar rat. One hundred and eight adult pregnant Wistar rats were divided into control and experimental groups. Rats in experimental group were given DIBP on day 10, 12 and 14 of gestation at 0.375, 0.75 and 1.25 ml/kg body weight dose intraperitoneally in a single dose. Sections of ovaries collected on day 21 of gestation were stained with hematoxylin and eosin and examined and Masson's trichrome histologically. Sections belonging to the control group showed the presence of oocytes in clusters separated by thin fibrous septa. Degeneration oocytes, empty follicles surrounded by follicular cells without gonocytes in the center were observed in ovarian stroma. Blood vessels in the ovarian stroma were prominent and congested. Around a bunch of follicles total architectural disarray was observed although on special staining fibrosis was not evident. As pregnant women are constantly exposed, effect of DIBP on ovary of a developing fetus would denote the long term consequence in future generations (Fig. 5, Ref. 39).

Randomized, controlled clinical study to evaluate efficacy of novel indigenously designed controlled release flurbiprofen gel system for management of periodontal diseases

Background:

This randomized, controlled clinical study was planned to evaluate the use of anti-inflammatory drug flurbiprofen in the form of locally delivered controlled release gel in the treatment of periodontal disease.

Materials and Methods:

The flurbiprofen gel was indigenously prepared in the concentration of 0.3%. The 30 patients with localized periodontal pockets measuring ≥5 mm were randomly divided into three groups. The groups received flurbiprofen gel, flurbiprofen gel after prophylaxis, and placebo gel after oral prophylaxis, respectively. The clinical parameters for plaque and gingival inflammation were evaluated at baseline, 7^th day, and 14^th day.

Results:

The results of the study suggested the statistically significant (P < 0.05) improvement in the gingival status of the patients with the use of flurbiprofen gel as an adjunct to scaling and root planing as compared to oral prophylaxis or gel alone.

Conclusion:

The data demonstrated that the additional use of local drug delivery of flurbiprofen through gel media enhances the positive effects of scaling and root planing and helps in faster resolution of the inflammation.

Rabbit as an animal model for experimental research

Animal experimentation is carried out in consultation with the veterinary wing but it is essential that be familiar with experimental protocols of animal model to be able to design an approriate study. This is more so in place where the veterinary facilities are not easily available.Span Rabbits are commonly used as subjects for screening implant material. They have gained favour for their numerous advantages even though they should be ideally used prior to testing in a larger animal model. Though experimentation on rabbits seems to be easy there are many pitfalls. Our endeavor in this article is to integrate all the data about maintaining rabbits as a model and to critically analyze it on the basis of our experimentation.

Comparison of immuno-phenotypes of stem cells from human dental pulp and periodontal ligament

It has been established that human dental pulp and periodontal ligament contain a population of mesenchymal stem cells (MSCs). However, the phenotypic analysis in terms of putative stem cell markers expressed by these stem cell populations is incomplete. It is relevant to understand whether stem cells derived from closely related tissues are programmed differently. The aim of the present study is to analyze whether these stem cells depict distinct characteristics by gaining insight into differences in their immunophenotype. Dental pulp and periodontal ligament tissue samples were obtained from extracted impacted wisdom teeth. Cell cultures were analyzed for surface and intracellular markers by indirect immunoflourescence. Detailed immunophenotype analysis was carried out by flow cytometry using relevant markers. The present study data shows dental pulp stem cells (DPSCs) and periodontal ligament stem cells (PDLSCs) expressed embryonic stem (ES) cell markers Oct-4, Nanog and mesodermal marker Vimentin by indirect immunoflourescence. PDLSCs, however, had a weak expression of Nanog. Immunophenotyping revealed strong expression of MSC markers (CD73, CD90) in DPSCs and PDLSCs. Differences were observed in expression of stemness-related markers. DPSCs displayed increased percentages of SSEA4, CD13 and CD166 and decreased CD9 expression compared to PDLSCs. Both stem cells express common MSC markers, different levels of expression suggests there might be more than one stem cell population existing within these tissues which differ in their embryonic status, and DPSCs are a more primitive stem cell population in comparison to PDLSCs.

Nerve loop around the axillary vessels by the roots of the median nerve a rare variation in a south Indian male cadaver: a case report

INTRODUCTION

Median nerve is normally formed by the union of medial and lateral root arising from the medial and the lateral cords of the brachial plexus respectively. However, variations in the formation and its relation with the axillary vessels are not uncommon. Therefore, knowledge of the variations in the nerve formation and course is useful for the clinicians during surgery and for differential diagnosis of uncommon clinical conditions.

CASE PRESENTATION

During the routine dissection in the department of anatomy, Kasturba Medical Collage, Manipal, India, we found unique anatomical variations in the formation and the course of the roots of the median nerve forming the neural loops around the axillary artery and vein.

CONCLUSION

Here we report the detailed description of these variations along with its clinical, embryological relevance and review of literature.

Petroleum ether extract of Cissus quadrangularis (Linn.) enhances bone marrow mesenchymal stem cell proliferation and facilitates osteoblastogenesis

OBJECTIVE

To evaluate the effects of the petroleum ether extract of Cissus quadrangularis on the proliferation rate of bone marrow mesenchymal stem cells, the differentiation of marrow mesenchymal stem cells into osteoblasts (osteoblastogenesis) and extracellular matrix calcification. This study also aimed to determine the additive effect of osteogenic media and Cissus quadrangularis on proliferation, differentiation and calcification.

METHODS

MSCs were cultured in media with or without Cissus quadrangularis for 4 weeks and were then stained for alkaline phosphatase. Extracellular matrix calcification was confirmed by Von Kossa staining. marrow mesenchymal stem cells cultures in control media and osteogenic media supplemented with Cissus quadrangularis extract (100, 200, 300 microg/mL) were also subjected to a cell proliferation assay (MTT).

RESULTS

Treatment with 100, 200 or 300 microg/mL petroleum ether extract of Cissus quadrangularis enhanced the differentiation of marrow mesenchymal stem cells into ALP-positive osteoblasts and increased extracellular matrix calcification. Treatment with 300 microg/mL petroleum ether extract of Cissus quadrangularis also enhanced the proliferation rate of the marrow mesenchymal stem cells. Cells grown in osteogenic media containing Cissus quadrangularis exhibited higher proliferation, differentiation and calcification rates than did control cells.

CONCLUSION

The results suggest that Cissus quadrangularis stimulates osteoblastogenesis and can be used as preventive/ alternative natural medicine for bone diseases such as osteoporosis.

Petroleum ether extract of Cissus quadrangularis (LINN) stimulates the growth of fetal bone during intra uterine developmental period: a morphometric analysis

OBJECTIVE

The aim of the present study was to analyze the effect Cissus quadrangularis plant petroleum ether extract on the development of long bones during the intra-uterine developmental stage in rats.

METHODS

Pregnant rats (n=12) were randomly assigned into either a control group (n=6) or a Cissus quadrangularis treatment (n=6) group. Pregnant rats in the Cissus quadrangularis group were treated with Cissus quadrangularis petroleum ether extract at a dose of 500 mg/kg body weight from gestation day 9 until delivery. The animals in the control group received an equal volume of saline. Newborn pups were collected from both groups for alizarin red S - alcian blue staining to differentiate ossified and unossified cartilage. The ossified cartilage (bone) was morphometrically analyzed using Scion image software.

RESULTS

Morphometric analysis revealed that the percentage of the total length of ossified cartilage (bone) in pups born to treated dams was significantly higher (P<0.001- -0.0001) than that of the control group.

CONCLUSION

The results of the present study suggest that maternal administration of Cissus quadrangularis petroleum ether extract during pregnancy can stimulate the development of fetal bone growth during the intra-uterine developmental period.

Salvaging a tooth with a deep palatogingival groove: an endo-perio treatment – a case report

AIM

To describe the diagnosis and management of tooth 22 with a necrotic pulp and severe periodontal destruction associated with a deep palatogingival groove extending to the root apex.

SUMMARY

Palatogingival grooves are uncommon in maxillary lateral incisors, but when present may contribute to the pathogenesis of periodontal and endodontic lesions. In the present case, the prognosis was considered poor, as the patient presented with a deep probing defect, advanced bone loss and grade III mobility of tooth 22. Root canal treatment was performed, followed by periodontal surgery, during which the groove was conditioned and sealed with conventional glass-ionomer cement and the osseous defect filled with indigenously prepared hydroxyapatite. The 18 month post-operative follow up showed substantial resolution of the osseous defect with gain in attachment and decreased tooth mobility.

KEY LEARNING POINTS

Teeth with deep palatogingival grooves may be significantly compromised with severe periodontal and periapical bone loss. Following thorough evaluation, the careful application of endodontic and periodontal surgical procedures may restore satisfactory function.

Oral malodor: a review of the literature

Oral malodor or halitosis is any unpleasant odor emerging from the mouth that is detected by others. Many patients experience extreme discomfort and embarrassment and therefore seek help for this problem. Oral causes, such as poor oral hygiene, periodontal disease, tongue coating, food impaction, unclean dentures, faulty restorations, and dry mouth, are far more common than nonoral causes of malodor. Management may include simple measures such as scaling and root planing, instructions in oral hygiene, tongue cleaning, and mouth rinsing. This paper reviews the current knowledge, etiology, diagnosis, and possible treatment strategies for oral malodor. Emphasis is placed on the recognition of the dental hygienist as a specialist in aspects of patient care and instruction, which relate to the prevention and control of oral malodor.

LC determination and pharmacokinetics of meloxicam

A simple and rapid HPLC assay method for the estimation of meloxicam in plasma was developed. The method totally eliminated the solvent extraction procedure. The plasma proteins were precipitated using perchloric acid (70%) and acetonitrile mixture (1:1 v/v) and the supernatant was directly injected to the HPLC system. The separation was achieved on a Lichrospher C18 5 micron (125x4.0 mm) analytical column with a mobile phase of sodium acetate buffer (pH 3.3, 170 mmol):acetonitrile (62:38 v/v) mixture. Detection was by UV detector at 355 nm. The retention time observed for meloxicam and piroxicam (internal standard) were at 6.0 and 4.0 min, respectively. The response was linear over a range of 50-1500 ng x ml(-1) in human plasma. The method was simple, specific, precise and accurate. The method was also used for the bioequivalence study of meloxicam formulation in healthy, human, Indian, male volunteers.

Slit signaling promotes the terminal asymmetric division of neural precursor cells in the Drosophila CNS

The bipotential Ganglion Mother Cells, or GMCs, in the Drosophila CNS asymmetrically divide to generate two distinct post-mitotic neurons. Here, we show that the midline repellent Slit (Sli), via its receptor Roundabout (Robo), promotes the terminal asymmetric division of GMCs. In GMC-1 of the RP2/sib lineage, Slit promotes asymmetric division by down regulating two POU proteins, Nubbin and Mitimere. The down regulation of these proteins allows the asymmetric localization of Inscuteable, leading to the asymmetric division of GMC-1. Consistent with this, over-expression of these POU genes in a late GMC-1 causes mis-localization of Insc and symmetric division of GMC-1 to generate two RP2s. Similarly, increasing the dosage of the two POU genes in sli mutant background enhances the penetrance of the RP2 lineage defects whereas reducing the dosage of the two genes reduces the penetrance of the phenotype. These results tie a cell-non-autonomous signaling pathway to the asymmetric division of precursor cells during neurogenesis.

Sloppy paired acts as the downstream target of wingless in the Drosophila CNS and interaction between sloppy paired and gooseberry inhibits sloppy paired during neurogenesis

Wingless (Wg) and other Wnt proteins play a crucial role in a number of developmental decisions in a variety of organisms. In the ventral nerve cord of the Drosophila embryo, Wg is non-autonomously required for the formation and specification of a neuronal precursor cell, NB4-2. NB4-2 gives rise to a well-studied neuronal lineage, the RP2/sib lineage. While the various components of the Wg-signaling pathway are also required for generating NB4-2, the target gene(s) of this pathway in the signal-receiving cell is not known. In this paper, we show that sloppy paired 1 and sloppy paired 2 function as the downstream targets of the Wg signaling to generate the NB4-2 cell. Thus, while the loss-of-function mutations in wg and slp have the same NB4-2 formation and specification defects, these defects in wg mutants can be rescued by expressing slp genes from a heterologous promoter. That slp genes function downstream of the Wg signaling is also indicated by the result that expression of slp genes is lost from the neuroectoderm in wg mutants and that ectopic expression of wg induces ectopic expression of slp. Finally, previous results show that Gooseberry (Gsb) prevents Wg from specifying NB4-2 identity to the wg-expressing NB5-3. In this paper, we also show that gsb interacts with slp and prevents Slp from specifying NB4-2 identity. Overexpression of slp overcomes this antagonistic interaction and respecifies NB5-3 as NB4-2. This respecification, however, can be suppressed by a simultaneous overexpression of gsb at high levels. This mechanism appears to be responsible for specifying NB5-3 identity to a row 5 neuroblast and preventing Wg from specifying NB4-2 identity to that cell.

Cell division genes promote asymmetric interaction between Numb and Notch in the Drosophila CNS

Cell intrinsic and cell extrinsic factors mediate asymmetric cell divisions during neurogenesis in the Drosophila embryo. In the NB4-2-&gt;GMC-1-&gt;RP2/sib lineage, one of the well-studied neuronal lineages in the ventral nerve cord, the Notch (N) signaling interacts with the asymmetrically localized Numb (Nb) to specify sibling neuronal fates to daughter cells of GMC-1. In this current study, we have investigated asymmetric cell fate specifications by N and Nb in the context of cell cycle. We have used loss-of-function mutations in N and nb, cell division mutants cyclinA (cycA), regulator of cyclin A1 (rca1) and string/cdc25 phosphatase (stg), and the microtubule destabilizing agent, nocodazole, to investigate this issue. We report that the loss of cycA, rca1 or stg leads to a block in the division of GMC-1, however, this GMC-1 exclusively adopts an RP2 identity. While the loss of N leads to the specification of RP2 fates to both progeny of GMC-1 and loss of nb results in the specification of sib fates to these daughter cells, the GMC-1 in the double mutant between nb and cycA assumes a sib fate. These epistasis results indicate that both N and nb function downstream of cell division genes and that progression through cell cycle is required for the asymmetric localization of Nb. In the absence of entry to metaphase, the Nb protein prevents the N signaling from specifying sib fate to the RP2/sib precursor. These results are also consistent with our finding that the sib cell is specified as RP2 in N; nb double mutants. Finally, our results show that nocodazole-arrested GMC-1 in wild-type embryos randomly assumes either an RP2 fate or a sib fate. This suggests that microtubules are involved in mediating the antagonistic interaction between Nb and N during RP2 and sib fate specification.

Segment polarity genes in neuroblast formation and identity specification during Drosophila neurogenesis

The relatively simple central nervous system (CNS) of the Drosophila embryo provides a useful model system for investigating the mechanisms that generate and pattern complex nervous systems. Central to the generation of different types of neurons by precursor neuroblasts is the initial specification of neuroblast identity and the Drosophila segment polarity genes, genes that specify regions within a segment or repeating unit of the Drosophila embryo, have emerged recently as significant players in this process. During neurogenesis the segment polarity genes are expressed in the neuroectodermal cells from which neuroblasts delaminate and they continue to be expressed in neuroblasts and their progeny. Loss-of-function mutations in these genes lead to a failure in the formation of neuroblasts and/or specification of neuroblast identity. Results from several recent studies suggest that regulatory interactions between segment polarity genes during neurogenesis lead to an increase in the number of neuroblasts and specification of different identities to neuroblasts within a population of cells.

Evaluation of efficacy of Sofscale. A clinical and SEM study

Efficacy of Sofscale in the case of removal of calculus from the root surface as claimed by manufacturers was evaluated in the present study. 32 patients suffering from chronic periodontitis, having calculus deposits in the lower incisors were selected for the study. A double blind study was conducted to evaluate the ease with which calculus could be removed. In the second part of study, a SEM study of the root surface subjected to root planing alone and root planing after application of Sofscale was done to see whether any remnants of calculus was left behind. In the double blind study conducted on 32 patients, it was found in 21 patients, calculus could be removed with greater ease and less time in experimental area compared to the control. 17 patients were able to correctly identify the product side as easier to Sofscale. Patients did not complain of increased sensitivity of teeth or discomfort following application of Sofscale. Under SEM the root surface after root planing showed the presence of smear layer whereas after Sofscale application root surface appeared devoid of smear layer. No other significant difference were noticed between the root surfaces.

The posterior determinant gene nanos is required for the maintenance of the adult germline stem cells during Drosophila oogenesis

In a variety of tissues in eukaryotes, multipotential stem cells are responsible for maintaining a germinal population and generating a differentiated progeny. The Drosophila germline is one such tissue where a continuous supply of eggs or sperm relies on the normal functioning of stem cells. Recent studies have implicated a possible role for the posterior determinant gene nanos (nos) in stem cells. Here, I report that nanos is required in the Drosophila female germline as well as in the male germline. In the female, nos is required for the functioning of stem cells. In nos mutants, while the stem cells are specified, these cells divide only a few times at the most and then degenerate. The loss of germline stem cells in nos mutant mothers appears to be due to a progressive degeneration of the plasma membrane. Furthermore, following germ cell loss, the germaria in the nos mutant mothers appear to carry on massive mitochondrial biogenesis activity. Thus, the syncytia of such germaria are filled with mitochondria. In the male germline, the male fertility assay indicates that nos appears to be also required for the maintenance of stem cells. In these mutant males, spermatogenesis is progressively affected and these males eventually become sterile. These results indicate novel requirements for nos in the Drosophila germline.

Efficacy of minocycline as a root conditioner in comparison to citric acid and tetracycline. An in vitro evaluation

This study compared the root surface characteristics produced by Minocycline HCl, Citric acid and Tetracycline HCl. when used as a root conditioner. This study included 5 groups of 10 extracted teeth each with advanced periodontal disease. Diseased root surfaces of group B,C,D and E were planed with Gracy curets and solutions of Citric acid, Tetracycline HCl, Monocycline Hcl and Tween 80 of PH 2.5, were applied to the surface in respective groups with cotton pellets for 5 mts. Group A was not subjected to root planning or application of any root conditioner and was used as a control. The teeth in all five groups were then washed, sectioned processed and examined under scanning electron microscope. These results revealed that the surfaces of acid treated sites differed from each other and with specimens treated sites differed from each other and with specimens treated with root panning alone. The efficacy of Minocycline and tetracycline in the removal of smear layer and exposure of dentinal tubules were comparable and Minocycline HCl though not as effective as Citric acid can probably be recommended in view of its antibactrial activity, anti collagense and substantivity properties.

frizzled and frizzled 2 play a partially redundant role in wingless signaling and have similar requirements to wingless in neurogenesis

The Drosophila Frizzled (Fz) and Frizzled2 (DFz2) proteins function as receptors for Wingless (Wg) in tissue culture cells. While previous results indicate that loss of function for fz has tissue polarity defects, loss-of-function effects of Dfz2 are not known. Here, we have examined the requirements of fz and Dfz2 during neurogenesis. Our results indicate that both Fz and DFz2 function in Wg signaling, and loss of either of the two affects the same subset of neuroblasts as those affected by loss of wg. While these defects are partially penetrant in embryos lacking either fz or Dfz2, the penetrance is significantly enhanced in embryos lacking both. Since the penetrance of the CNS phenotypes is not complete in double mutants, additional components that allow some degree of Wg signaling must exist in vivo.

Local antimicrobial delivery in periodontal therapy

Treatment strategies towards periodontal diseases have evolved to eliminate specific pathogens or suppress destructive host response. The inherent activity of the antibiotic against the target microorganism and various Pharmacokinetic parameters such as potency, permeability, intrinsic efficacy, and substantivity of the drug dictate the success of the therapeutic outcome. However selection of an appropriate delivery system is an important factor. Rapid advances in molecular biology have helped to overcome the disadvantages of systemic and topical applications, by direct placement of antimicrobial agent (s) into subgingival sites, thus minimizing antimicrobial impact on non-oral body sites. As periodontitis is a 'localized' disease condition it is amenable to localized drug treatments. By means of controlled local delivery from within the periodontal pocket, a single administration of a few milligram of an antibacterial agent can maintain therapeutic concentrations within the crevicular fluid for a longer period of time than any other mode of delivery. This paper shall review the different local delivery systems along with the commonly employed drugs through these delivery systems.

Efficacy of Chitra granule and powder (hydroxyapatite) in alveolar bone regeneration in rabbits. A histological evaluation

The reconstruction or restoration of osseous defects caused by inflammatory periodontal disease is a continuing challenge in periodontal therapy. Great strides are being made to this effect using alloplasts such as hydroxyapatite. The present study was designed in Newzealand dwarf rabbits to observe the biologic response of periodontal tissues to synthetically prepared hydroxyapatite in both powder and granule forms by Srichitra Tirunal Institute for Medical Sciences & Technology, Trivandrum and to compare it with that of a commercially available, pure resorbable hydroxyapatite, OsteoGen (HA Resorb). The test materials were implanted in the artificially created bonydefects in the mandible via an intraoral approach. The wounds were allowed to heal upto 26 weeks postimplantation. The clinical evaluation at 12 weeks and 26 weeks postimplantation revealed neither any evidence of inflammation, infection or abscess formation nor any exposure or exfoliation of test materials. The histological examination of the implant sites at 12 and 26 weeks postimplantation revealed varying extent of formation of new osseous tissue and periodontal fibers. A comparison between test materials and control suggested that Chitra granules exhibit a relatively greater potential for newbone and periodontal fibre formation.

Cell-cell signaling during neurogenesis: some answers and many questions

Development of a multicellular organism requires that cells communicate with each other in order to regulate their growth, organize into tissues and coordinate their function. This cell-cell communication is mediated by signals cells receive (or send) between each other and from the environment. The signaling can be a short range remote signaling (through secreted signaling molecules), contact signaling (via plasma membrane bound molecules, gap junctions) or a long range signaling (through hormones). In this article, I have reviewed the recent advances on the role of cell-cell signaling in the development of the embryonic nervous system of the fruitfly Drosophila melanogaster and discussed some of the open questions raised by these studies. It discusses the contributions of the neurogenic genes Notch and Delta and the signaling pathways controlled by wingless, patched and hedgehog in neuroblast formation, neuroblast identity specification and neuroblast lineage elaboration.

Metastasis to maxillary gingiva from carcinoma of breast. A case report

A rare case of metastatic infiltrating duct carcinoma involving gingiva in relation to maxillary left canine-premolar of a 40 year old female is presented. The unilateral gingival enlargement in canine-premolar region was quite unusual. Pertinent history and histological examination revealed that the tumor was a metastatic carcinoma, the primary lesion of which was in the breast. The differential diagnosis of gingival enlargements is discussed in this paper. The resemblance of this mass to an inflammatory hyperplastic condition reflects the need for a detailed case history and examination.

Establishment of stem cell identity in the Drosophila germline

In the adult Drosophila ovary the continuous production of eggs depends upon a small group of stem cells located at the anterior tip of the germarium. These stem cells divide asymmetrically to self renew and to generate a cystoblast, which in females is committed to the oocyte differentiation pathway. While much is known about the development of poststem cell cystoblasts, little is known about when stem cells are formed or how their identity is initially established. To investigate these questions we have used the P-M hybrid dysgenesis syndrome as a tool for ablating the "pre-stem cell" progenitors of the stem cells. Our experiments indicate that the pre-stem cells in females assume stem cell identity during the early pupal stage. Our results also suggest a model in which at least two pre-stem cells must be present within an ovariole for the specification of stem cell fate. When only a single pre-stem cell is sequestered by an ovariole, this cell does not assume stem cell identity, but instead follows the cystoblast-cystocyte differentiation pathway.

Requirement for engrailed and invected genes reveals novel regulatory interactions between engrailed/invected, patched, gooseberry and wingless during Drosophila neurogenesis

During neurogenesis, the transmembrane protein Patched (Ptc) promotes a wingless (wg)-mediated specification of a neuronal precursor cell, NB4-2, by repressing gooseberry (gsb). In this study, novel interactions of these genes with engrailed (en) and invected (inv) during neurogenesis have been uncovered. While in row 4 cells Ptc represses gsb and wg, in row 5 cells en/inv relieve Ptc repression of gsb by a non-autonomous mechanism that does not involve hedgehog (hh). This differential regulation of gsb leads to the specification of NB5-3 and NB4-2 identities to two distinct neuroblasts. The uncoupling of the ptc-gsb regulatory circuit also enables gsb to promote Wg expression in row 5 cells. Our results suggest that the en/inv--&gt;ptc--&gt;gsb--&gt;wg pathway uncovered here and the hh--&gt;wg are distinct pathways that function to maintain wild-type level of Wg. Our results also indicate that Hh is not the only ligand for Ptc and similarly Ptc is not the only receptor for Hh.

The patched signaling pathway mediates repression of gooseberry allowing neuroblast specification by wingless during Drosophila neurogenesis

The Drosophila signaling molecule Wingless (Wg) plays crucial roles in cell-cell communications during development. In the developing nervous system, a previous study has shown that Wg acts non-autonomously to specify the fate of a specific neuronal precursor, NB4-2 (Q. Chu-LaGraff and C. Q. Doe (1993) Science 261, 1594–1597). The lack of autocrine specification of NB4-2 in Wg-expressing cells suggests that the response to Wg is spatially restricted, presumably through the activity of the Wg-receptor. I show that two other proteins, a transcription factor Gooseberry (Gsb) and a transmembrane protein Patched (Ptc), participate in the Wg-mediated specification of NB4-2 by controlling the response to the Wg signal. In gsb mutants, Wg-positive NB5-3 is transformed to NB4-2 in a Wg-dependent manner, suggesting that Gsb normally represses the capacity to respond to the Wg signal. In ptc mutants, Gsb is ectopically expressed in normally Wg-responsive cells, thus preventing the Wg response and consequently the correct specification of NB4-2 does not take place. This conclusion is supported by the observation that NB4-2 can be specified in gsb;ptc double mutants in a Wg-dependent manner. Moreover, ectopic expression of Gsb from the hsp7O-gsb transgene also blocks the response to the Wg signal. I propose that the responsiveness to the Wg signal is controlled by sequential negative regulation, ptc--&gt;gsb--&gt;Wg receptor. The timing of the response to Gsb suggests that the specification of neuroblast identities takes place within the neuroectoderm, prior to neuroblast delamination.

Clinical significance of furcation anatomy of the maxillary first premolar: a biometric study on extracted teeth

Multirooted teeth in which chronic periodontitis has progressed to involve the furcation present special problems in treatment. The apical placement of furcation, narrow furcation entrance, concavities on the root surface, and the undesirable root configuration make instrumentation and plaque control difficult. Furcation involvement, when present in maxillary first premolars in particular, presents a poor prognosis as the furcation opens mesiodistally. This study on 100 extracted maxillary first premolars is an attempt to determine the frequency of bifurcation, the proximity of bifurcation to cemento-enamel junction, the depth of concavities on the root trunk and the furcal aspect of root, the diameter of furcation entrance, and the extent of root divergence.

The GAGA factor is required in the early Drosophila embryo not only for transcriptional regulation but also for nuclear division

The GAGA protein of Drosophila was first identified as a stimulatory factor in in vitro transcription assays using the engrailed and Ultrabithorax promoters. Subsequent studies have suggested that the GAGA factor promotes transcription by blocking the repressive effects of histones; moreover, it has been shown to function in chromatin remodeling, acting together with other factors in the formation of nuclease hypersensitive sites in vitro. The GAGA factor is encoded by the Trithorax-like locus and in the studies reported here we have used the maternal effect allele Trl13C to examine the functions of the protein during embryogenesis. We find that GAGA is required for the proper expression of a variety of developmental loci that contain GAGA binding sites in their upstream regulatory regions. The observed disruptions in gene expression are consistent with those expected for a factor involved in chromatin remodeling. In addition to facilitating gene expression, the GAGA factor appears to have a more global role in chromosome structure and function. This is suggested by the spectrum of nuclear cleavage cycle defects observed in Trl13C embryos. These defects include asynchrony in the cleavage cycles, failure in chromosome condensation, abnormal chromosome segregation and chromosome fragmentation. These defects are likely to be related to the association of the GAGA protein with heterochromatic satellite sequences which is observed throughout the cell cycle.

Periodontal implications of Class II restorations. Clinical and SEM evaluation

30 subjects with class II silver amalgam restorations were studied to evaluate the influence of these restorations on periodontal health of the adjacent region. The incidence of overhangings were noted. The periodontal changes were recorded with the help of indices. The surface of the restoration and the interface between the restoration and the cavity margin were observed on extracted teeth under SEM. The gingival and periodontal status at the site of the restoration were affected by the restoration and the restoration showed a rough surface as compared to the enamel on SEM examination.

Increased activity of porcine pancreatic phospholipase A2 by designed long-range electrostatic stabilisation of the transition state

Stabilisation of the catalytic transition state by long-range charge interactions has been tested with mutagenesis for porcine pancreatic phospholipase A2. Electrostatics calculations were used to determine locations which would interact preferentially with one part of the dipolar charge separation that is believed to develop in the transition state. Experiment shows increased enzyme activity relative to wild-type recombinant enzyme for mutants N97D and N101D, consistent with the design.

The miti-mere and pdm1 genes collaborate during specification of the RP2/sib lineage in Drosophila neurogenesis

We have investigated (i) the role of pdm1, a Drosophila POU gene, during the elaboration of the GMC-1-->RP2/sib lineage and (ii) the functional relationship between pdm1 and the closely linked second POU gene, miti-mere, in this lineage. We show that deletion of pdm1 causes a partially penetrant GMC-1 defect, while deletion of both miti and pdm1 results in a fully penetrant defect. This GMC-1 defect in miti- and pdm1- embryos can be rescued by the pdm1 or miti transgene. Rescue is observed only when these genes are expressed at the time of GMC-1 formation. Overexpression of pdm1 or miti well after GMC-1 is formed results in the duplication of RP2 and/or sib cells. Our results indicate that both genes are required for the normal development of this lineage and that the two collaborate during the specification of GMC-1 identity.

The Drosophila miti-mere gene, a member of the POU family, is required for the specification of the RP2/sibling lineage during neurogenesis

The Drosophila POU gene miti-mere (previously known as pdm2) has a complex spatial and temporal pattern of expression during early development; initially it is expressed in gap-gene-like pattern, then in 14 stripes and finally in a subset of the cells in the developing CNS and PNS. To study the function of this gene during development, we generated a ‘synthetic anti-morphic mutation’ by expressing a truncated version of the miti protein from a constitutive hsp83 and an inducible hsp70 promoter. We show that these delta miti transgenes behave like classical antimorphic mutations. Using these dominant negative transgenes, together with deletions and a duplication for the gene, we show that miti is required during segmentation and neurogenesis. We have also used temperature-shift experiments with the hsp70 delta miti transgene to demonstrate that miti function in segmentation is distinct and separable from its function during neurogenesis. In segmentation, miti appears to be required in the specification of the segments A2 and A6. In the CNS, miti is required for the elaboration of the NB4-2--&gt;GMC-1--&gt;RP2/sib lineage. miti is initially required in this lineage to establish the identity of the parental ganglion mother cell, GMC-1. miti must then be down-regulated to allow the asymmetric division of GMC-1 into the RP2 and its sibling cell.

The activity of porcine pancreatic phospholipase A2 in 20% alcohol/aqueous solvent, by experiment and electrostatics calculations

The activity of porcine pancreatic phospholipase A2 (pla2), measured at pH 8, is reduced when methanol or ethanol is added to the aqueous solution. Finite difference electrostatics calculations were used to study the effect of modelling mixed solvents on the pKas of histidine 48 and the amino-terminal group, both of which influence the pH-dependence of catalysis. Calculations and experiment indicate that these pKa values cannot account for the activity reduction. Charge separation in the transition state is destabilized in 20% alcohol solvent relative to 100% aqueous solvent. The calculated values, which are combinations of stabilizing and destabilizing contributions, are in qualitative agreement with experiment. Saturating dielectric theory is used to model solvent water ordering in a high electric field, and water dielectric structure is assumed to dominate at the 20% alcohol level. The observed agreement demonstrates the utility of transition state stabilization theory and continuum solvent modelling. It is further suggested that electrostatic effects on kcat contribute to the pH-dependence of activity around pH 7, and to previously reported activity changes for charge mutants.

Changes in activity of porcine phospholipase A2 brought about by charge engineering of a major structural element to alter stability

We have modified the stability of porcine phospholipase A2 by charge engineering. The mutations are situated at the N-terminal of a major helix and are N89D and N89D/E92Q. This engineering has significantly altered the activity of the enzyme to aggregated and monomeric substrates. A N89D/E92K mutant is more stable but considerably less active than wild type. An N89D mutant is more stable and of similar activity to wild type. The substantial change in activity may be due to direct interaction of residue 92 with aggregated substrate or may be via second calcium binding. Second calcium binding may be more probable as activity against monomers is also affected. Additional calcium binding may therefore be an important way of manipulating the activity of phospholipase A2.

A novel method for the purification of porcine phospholipase A2 expressed in E. coli

Porcine phospholipaseA2 expressed in E. coli as a fusion protein was isolated, renatured and specifically cleaved by trypsin as described in (1). Active phospholipaseA2, was purified to homogeneity on a column of PBE-94 over a pH region 7.4-4.5. Using this method, several phospholipase A2 mutant enzymes have now been purified in a single step and all behaved identically during chromatofocusing. The method will therefore be extremely useful not only for those interested in understanding the structure-function relationships of phospholipaseA2 but also for preparing the enzyme in large quantities for industrial and pharmaceutical purposes.

Modification of the stability of phospholipase A2 by charge engineering

Electrostatic interactions play an important role in stabilizing the folded conformation of globular proteins. Here we predict the change in stability of charge engineered mutants, construct these mutants and compare the predicted change in stability with that observed. The change in stability was correctly predicted for two of the three mutants and the factors responsible for the discrepancy between observation and prediction for the third mutant are discussed.

Study of the mode of action and site-specificity of the endo-(1----4)-beta-D-glucanases of the fungus Penicillium pinophilum with normal, 1-3H-labelled, reduced and chromogenic cello-oligosaccharides

The modes of action of the five major endo-(1----4)-beta-D-glucanases (I, II, III, IV and V) purified from Penicillium pinophilum cellulase were compared by h.p.l.c. analysis, with normal, 1-3H-labelled and reduced cello-oligosaccharides and 4-methylumbelliferyl glycosides as substrates. Significant differences were observed in the preferred site of cleavage even when substrates with the same number of glycosidic bonds were compared. Thus, although endoglucanase I was unable to attack normal cello-oligosaccharides shorter than degree of polymerization 6, it hydrolysed reduced cellopentaose to yield cellotriose and cellobi-itol, and it produced cellotriose and 4-methylumbelliferyl glucoside from 4-methylumbelliferyl cellotetraoside. Endoglucanase IV hydrolysed [1-3H]cellotriose but did not attack either cellotri-itol or 4-methylumbelliferyl cellobioside. These and other anomalous results indicated clearly that modification of the reducing glycosyl residue on the cello-oligosaccharides induces in an apparent change in the mode of action of the endoglucanases. It is suggested that, although cello-oligosaccharide derivatives are useful for differentiating and classifying endoglucanases, conclusions on the mechanism of cellulase action resulting from these measurements should be treated cautiously. Unequivocal information on the mode of endoglucanase action on cello-oligosaccharides was obtained with radiolabelled cello-oligosaccharides of degree of polymerization 3 to 5. Indications that transglycosylation was a property of the endoglucanases were particularly evident with the 4-methylumbelliferyl cello-oligosaccharides. Turnover numbers for hydrolysis of the umbelliferyl cello-oligosaccharides were calculated, and these, along with the other analytical data collected on the products of hydrolysis of the normal, reduced and radiolabelled cello-oligosaccharides, suggested that the various endoglucanases had different roles to play in the overall hydrolysis of cellulose to sugars small enough to be transported through the cell membrane.

Calcium-binding affinity and calcium-enhanced activity of Clostridium thermocellum endoglucanase D

Clostridium thermocellum endoglucanase D (EC 3.2.1.4: EGD), which is encoded by the celD gene, was found to bind Ca2+ with an association constant of 2.03 x 10(6) M-1. Ca2+ stimulated the activity of EGD towards swollen Avicel by 2-fold. In the presence of Ca2+, the Kd of the enzyme towards p-nitrophenyl-beta-D-cellobioside and carboxymethylcellulose was decreased by 4-fold. Furthermore, Ca2+ increased the half-life of the enzyme at 75 degrees C from 13 to 47 min. Since the 3' sequence of celD encodes a duplicated region sharing similarities with the Ca2+-binding site of several Ca2+-binding proteins, a deleted clone was constructed and used to purify a truncated form of the enzyme which no longer contained the duplicated region. The truncated enzyme was very similar to EGD expressed from the intact gene with respect to activity, Ca2(+)-binding kinetics and Ca2+ effects on substrate binding and thermostability. Thus the latter parameters do not appear to be mediated through the duplicated conserved region.

The mechanism of fungal cellulase action. Synergism between enzyme components of Penicillium pinophilum cellulase in solubilizing hydrogen bond-ordered cellulose

Studies on reconstituted mixtures of extensively purified cellobiohydrolases I and II and the five major endoglucanases of the fungus Penicillium pinophilum have provided some new information on the mechanism by which crystalline cellulose in the form of the cotton fibre is rendered soluble. It was observed that there was little or no synergistic activity either between purified cellobiohydrolases I and II, or, contrary to previous findings, between the individual cellobiohydrolases and the endoglucanases. Cotton fibre was degraded to a significant degree only when three enzymes were present in the reconstituted enzyme mixture: these were cellobiohydrolases I and II and some specific endoglucanases. The optimum ratio of the cellobiohydrolases was 1:1. Only a trace of endoglucanase activity was required to make the mixture of cellobiohydrolases I and II effective. The addition of cellobiohydrolases I and II individually to endoglucanases from other cellulolytic fungi resulted in little synergistic activity; however, a mixture of endoglucanases and both cellobiohydrolases was effective. It is suggested that current concepts of the mechanism of cellulase action may be the result of incompletely resolved complexes between cellobiohydrolase and endoglucanase activities. It was found that such complexes in filtrates of P. pinophilium or Trichoderma reesei were easily resolved using affinity chromatography on a column of p-aminobenzyl-1-thio-beta-D-cellobioside.

Sporotrichum thermophile Growth, Cellulose Degradation, and Cellulase Activity

The activity of components of the extracellular cellulase system of the thermophilic fungus Sporotrichum thermophile showed appreciable differences between strains; β-glucosidase (EC 3.2.1.21) was the most variable component. Although its endoglucanase (EC 3.2.1.4) and exoglucanase (EC 3.2.1.91) activities were markedly lower, S. thermophile degraded cellulose faster than Trichoderma reesei . The production of β-glucosidase lagged behind that of endoglucanase and exoglucanase. The latter activities were produced during active growth. When growth was inhibited by cycloheximide treatment, the hydrolysis of cellulose was lower than in the control in spite of the presence of both endoglucanase and exoglucanase activities in the culture medium. Degradation of cellulose was a growth-associated process, with cellulase preparations hydrolyzing cellulose only to a limited extent. The growth rate and cell density of S. thermophile were similar in media containing cellulose or glucose. A distinctive feature of fungal development in media incorporating cellulose or lactose (inducers of cellulase activity) was the rapid differentiation of reproductive units and autolysis of hyphal cells to liberate propagules which were capable of renewing growth immediately.