Scanning electron microscopic analysis of 5% glycolic acid as a novel alternative to 17% ethylenediaminetetraacetic acid in root biomodification: An in vitro study.

Background: Nonsurgical periodontal therapy results in the formation of a smear layer which inhibits tissue regeneration. Root biomodification (RB) using various agents has been tried for the enhancement of new attachment formation. However, no substantial therapeutic advantages of currently available root conditioning agents have been reported emphasizing the need for additional biologically acceptable agents. Glycolic acid (GA) due to its antimicrobial nature and ability of initiation and proliferation of fibroblasts may potentially modify root surface enabling regeneration. Materials and Methods: Eighty specimens from 40 single-rooted teeth were treated with 17% ethylenediaminetetraacetic acid (EDTA) and 5% GA and scanning electron microscopy analysis was done. The micrographs were examined for the evaluation of smear layer removal, total number of dentinal tubules, total number of patent dentinal tubules, mean diameter and surface area of dentinal tubules, and dentin erosion. Statistical analysis was done using unpaired t-test for intergroup comparison. Results: The efficacy of smear layer removal (P = 0.01) and dentin erosion (P = 0.042) was significantly better in the GA group. Both the groups showed no difference in dentinal tubule-related parameters. Conclusion: GA showed improved RB with greater smear layer removal and lesser dentin erosion, indicating its use as a potent alternative to the conventional EDTA root conditioning.

Knowledge, attitude, and practice of teledentistry in periodontal diagnosis: Is it the required upgrade to conventional periodontics?

Background: Teledentistry which is similar to telemedicine has emerged as a new tool for various dental disciplines. Teleperiodontics is a branch of telehealth which focuses on the application of digital communication technology into the field of periodontics without demanding a specialist presence. An early detection and diagnosis of periodontal conditions can not only treat the disease in its early stage but also prolong the health of the periodontium, thereby improving the overall quality of life of an individual. However, teledentistry has not penetrated into the field of periodontics to a level it has to in providing periodontal care. Hence, the aim of this questionnaire study was to assess the knowledge, attitude, and application of teleperiodontics into everyday practice among the dental surgeons at various levels. Materials and Methods: An electronic questionnaire consisting of 29 close-ended questions including sections assessing the knowledge, attitude, and practice of teledentistry and teleperiodontics was sent to dental colleges present in East and West Godavari districts of Andhra Pradesh. Results: A total of 350 responses were received and 80.57% dental surgeons were aware about teledentistry, and a total of 74% dental surgeons were likely to prescribe oral hygiene aids and medication for temporary management of periodontal conditions. Conclusion: Teleperiodontics is an emerging science whose knowledge, attitude, and application are yet to be explored.

Role of Medicinal Herbs in Periodontal Therapy: A Systematic Review.

Aims and Objectives: The use of medicinal herbs to prevent gingival and periodontal diseases has become increasingly popular due to their anti-inflammatory and antioxidant properties. This systematic review aims to provide the current literature to validate the traditional use of medicinal herbs in the management of gingival and periodontal diseases. Materials and Methods: An online literature search was conducted to identify research papers published from 2010 to 2022 in three major scientific databases, PubMed, Scopus, and Web of Science, in June 2022. Original research studies, case reports, and systematic reviews on medicinal plants' application in oral health care were selected to be included in this systematic review. Only high-quality articles identified in the quality assessment were included for evidence synthesis. Results: Initial keyword research yielded 726 free-text articles published between 2010 and 2022. Of these, 14 articles (8 research papers and 6 reviews) were included for evidence synthesis. The review's findings indicate that the antibacterial property of medicinal plants is due to their alkaline nature and prevents plaque and calculus formation by maintaining acid-alkali balance in saliva. Various parts of medicinal plants help maintain periodontal health. Glycyrrhiza glabra, Ficus religiosa, and Plantago major effectively inhibit primary plaque colonizers and periodontal pathogens. Medicago sativa, Aloe barbadensis Miller, and Trifolium pratense have excellent applications in treating periodontal diseases. Mangifera indica, Pongamia pinnata, the husk of Cocos nucifera, the root of G. glabra and Curcuma longa, leaves of Psidium guajava and Azadirachta indica, fruits of Citrus medica and Punica granatum, Ocimum Moringa oleifera extract, and pomegranate peel extract can serve as a promising alternative in managing chronic gingivitis. Conclusion: The anti-inflammatory, antioxidant, antibacterial, and astringent action of extracts obtained from various parts of medicinal plants make them effective in reducing gingival and periodontal diseases. Herbal medicine may be a viable alternative to contemporary pharmaceuticals as an adjuvant to scaling and root planning procedures.

Clinical outcomes of root coverage using porcine-derived collagen matrix with modified coronally advanced tunnel technique (MCAT) in multiple gingival recessions in smokers - a randomized controlled clinical trial.

OBJECTIVES: Root coverage (RC) is an integral part in management of gingival recessions. Unlike isolated recessions, treating multiple recessions is the most challenging scenario especially in smokers who have reported reduced RC in terms of quantity and stability. Modified coronally advanced tunnel (MCAT) technique due to its improved vascularity along with use of porcine-derived collagen matrix (PDCM) (Mucograft™) with its bilayered dense collagen matrix may be a predictable alternative to conventional gold standard subepithelial connective tissue graft (SCTG). The purpose of this study was to compare the results of RC achieved using PDCM and SCTG with the MCAT approach in the treatment of multiple gingival recessions in smokers. METHODOLOGY: This is a prospective randomized controlled clinical study registered under clinical trial registry (CTRI no. CTRI/2020/03/024238) including 28 patients with 64 recession defects. Smokers (≥ 10 cigarettes/day for ≥ 5 years) fulfilling the inclusion criteria were randomized into the SCTG and PDCM groups which were treated with SCTG using MCAT and PDCM using MCAT technique, respectively. Recession depth (RD), recession width (RW), width of keratinized tissue (WKT), thickness of keratinized gingiva (TKG), and %RC were assessed at baseline, 3, and 6 months. Complete RC (CRC) at 3 and 6 months, RC aesthetic scores (RCES) at 6 months. RESULTS: Both groups showed significant improvement in all clinical parameters. Intergroup comparison of root coverage parameters in smokers showed better performance of the PDCM group in terms of RD, %RC, TKG, WKT, CRC (45.06%), and RCES (p < 0.001) compared to the SCTG group. Time taken for surgical procedure and visual analog pain scores were significantly lesser in the PDCM group. CONCLUSION: PDCM showed good predictable results in terms of all RC parameters compared to SCTG and thus may be used as a predictable alternative to SCTG for RC in smokers. CLINICAL SIGNIFICANCE: PDCM can be used as a potential alternative to gold standard subepithelial connective tissue graft in smokers with better patient compliance.

Evaluation of feed utilization, immune response and disease resistance in striped catfish, Pangasianodon hypophthalmus (Sauvage 1878) fed with a novel Aeromonas hydrophila biofilm vaccine.

Striped catfish, Pangasianodon hypophthalmus was immunized with Biofilm (BF) and Free cell (FC) of Aeromonas hydrophila vaccine at 1010 CFU g-1 for 20 days and monitored for growth parameters, immune responses and disease resistance up to 60 day post vaccination (dpv). Pangasius catfish in the BF vaccinated group had considerably higher growth and feed utilization than the FC vaccinated and unvaccinated groups (p < 0.05). Biofilm vaccinated group showed a significant increase (p < 0.05) in the mean weight gain (46.91 ± 0.59) than the FC (35.94 ± 0.21) and unvaccinated group (34.92 ± 0.35). The vaccinated fishes were challenged with A. hydrophila at 107 CFU/ml. Significant higher relative percentage survival (RPS) was recorded with BF (84.21 ± 1.49%) compared to that with FC (33.33 ± 1.21%). Polyclonal antibody-based ELISA was used to quantify the antibody titre. BF vaccinated group showed significantly higher antibody titer compared to other treatments (p < 0.05). Moreover, higher haematological parameters recorded in the present study were differentially stimulated by the oral administration of A. hydrophila biofilm vaccine. The mean total protein, albumin, and globulin levels of the BF vaccine groups were significantly higher (p < 0.05) than the mean total protein, albumin, and globulin contents of the unvaccinated group. Furthermore, biochemical stress parameters (SGPT, SGOT) in the vaccinated groups showed an incremental trend in the early days of the experimental period. However, the values were significantly lower (p < 0.05) in the biofilm group on 20 dpv onwards indicating improved health condition. Vaccinated BF fishes showed gut associated lymphoid tissues (GALT) within the laminar propria of mid gut. But in FC group fishes showed less aggregation of lymphoid cells. The unvaccinated control fish had no lymphoid cell aggregation in their intestines. The findings of the current research suggested that biofilm vaccine has the capability to be one of the potential oral vaccines in striped catfish against A. hydrophila infection.

Synthesis, spectral characterization, crystal structure and computational investigation of 2-formyl-6-methoxy-3-carbethoxy quinoline as potential SARS-CoV inhibitor.

The recent COVID-19 outbreak caused by the novel coronavirus SARS-CoV-2 has an immense impact on global health and economy. Although vaccines are being used, urgent need of drugs based on natural products with high efficacy and safety is a pressing priority. Quinoline alkaloids are well known for their therapeutic action against malaria; initially, it was tried against Coronaviruses. It is a basic vital scaffold to design drugs with required biological and pharmacological activities. In this present study, a new quinoline compound was synthesized and characterized by spectroscopy techniques. Crystal structure was established by SCXRD analysis and data is used as an input to perform various computations. Additionally, using state-of-the-art quantum computational techniques, the geometry optimization and calculation of UV-Vis spectrum of 2F6M3CQ were performed at B3LYP/6-311G* level of theory. The optimized molecular geometric parameters as well as UV-Vis spectrum values are found to be in good agreement with their respective experimental results. The visualization of 3-D plots of FMO and MEP indicated the structure and reactivity trends of 2F6M3CQ molecule. Molecular docking methods were utilized to find the drug ability of 2F6M3CQ with Mproprotein of SARS-CoV-2. There were many intermolecular interactions between Mpro protein and 2F6M3CQ molecule which lead to good binding energy (-5.5 kcal/mol) between them which was found to be better than the binding energy of chloroquinine molecule (-4.5 kcal/mol) as studied under same docking protocols. Finally, drug likeness and ADME properties of 2F6M3CQ were also analyzed. There is no violation found for RO5 in our 2F6M3CQ compound. ADME analysis shows drug like properties of compound 2F6M3CQ which predicts that it might be a potential candidate for inhibition of SARS-CoV-2.

First report of the infectious spleen and kidney necrosis virus (ISKNV) infection in ornamental fishes in India.

Infectious spleen and kidney necrosis virus (ISKNV), a member of family iridoviridae, reported for the first time in a wide range of ornamental fish species in India. Significant mortalities during the year 2018-19 were reported from a number of retailers in the region with various clinical signs. The samples of moribund, dead and apparently healthy ornamental fishes were collected from retailers, located in three districts of Karnataka, India. Out of 140 fish samples, 16 samples (11.42%) representing 10 different fish species were found positive to ISKNV by OIE listed primers and same samples were reported to amplify the major capsid protein (MCP) gene of ISKNV. Further, sequence analysis of MCP gene showed that all strains detected in this study were closely related to other documented isolates from different countries with an identity ranging from 98.76% to 100%. Further, they clustered in the clade of ISKNV, during the phylogenetic analysis. The sequence similarity was high (99.94%) to ISKNV strains from Japan, Australia and Malaysia. This is the first report of an ISKNV infection in India. Moreover, out of 10 ISKNV-positive fish species, three species were reported positive to ISKNV for the first time in the world. Further, the in vitro experiment showed the growth of virus in Asian sea bass cell line, which is a natural host of ISKNV. Therefore, considering the lethal nature of megalocytiviruses to infect a vast range of species, proper biosecurity measures need to be taken to control these emerging pathogens.

Effect of e-learning methods on Dental education: An observational study.

BACKGROUND: The progress in the usage of technology in hardware, software, and cost-effective Internet connectivity enable the availability of science-related information and its usage in all the developing countries. Hence, in this practical world, there should be a need to implement effective and affordable dental education strategies to attain oral health for all in the coming years. OBJECTIVE: The aim of this study is to reduce the need to teach theory-based, on-site classes, e-learning came into existence. E-learning for dental education may alleviate the burden of severe health worker shortages and deliver affordable access to high-quality dental education. METHODOLOGY: Evaluation and assessment methods were done to know the effectiveness of e-learning in dental education by conducting continuing dental education on newer materials and methods, assignments/formative assessments and by open discussions of case descriptions and their treatment modalities through Edmodo app in our dental institute. Effect on knowledge, skills, attitudes, and satisfaction levels of dental students compared to other traditional methods. RESULTS: Dental e-learning has the capacity to develop into a leading-edge to strengthen clinical training skills among dental students by conducting continuing dental education, assignments, formative assessments, case descriptions, and their treatment modalities through e-learning are the best ways to improve quantity and quality in dental education. CONCLUSION: The probable prospective of e-learning could be innovative or revolutionary because this helps in both theoretical-related and clinical-related advancements, and it is possible only with e-learning in developing countries to meet the quality in education.

Estimation of superoxide dismutase levels in saliva and gingival crevicular fluid among smokers and non-smokers in periodontitis patients - An Observational Study.

BACKGROUND: Smoking, which is an important risk factor for periodontitis, induces oxidative stress in the body and causes an imbalance between reactive oxygen species (ROS) and antioxidants, such as superoxide dismutase (SOD). The present study was done to quantify and compare the level of SOD enzyme levels in gingival crevicular fluid (GCF) and saliva among smokers and nonsmokers. METHODOLOGY: One hundred and thirty-five individuals in the age range of 20-55 years, including 45 light smokers, 45 heavy smokers, and 45 nonsmokers (controls), were selected and the clinical parameters recorded were plaque index, probing depth, and attachment loss. Smokers were divided into light smokers (<10 cigarettes/day) and heavy smokers (>10 cigarettes/day) and into three subgroups: healthy, mild periodontitis, and moderate periodontitis. GCF and saliva samples were collected then SOD levels were analyzed using spectrophotometric assay. RESULTS: The mean levels of SOD in the GCF and saliva of smokers were decreased compared to controls. Intra- and inter-group analyses showed a significant reduction in the levels of SOD in the GCF and saliva of heavy smokers compared to light smokers and the control group. CONCLUSIONS: There was a progressive reduction in SOD levels from healthy nonsmokers to light smokers to heavy smokers.

Evaluation of biofilm of Vibrio anguillarum for oral vaccination of Asian seabass, Lates calcarifer (BLOCH, 1790).

The present study evaluated the biofilm (BF) of Vibrio anguillarum for oral vaccination of Asian seabass, Lates calcarifer. An 80-day experiment was carried out in circular fiber-reinforced plastic (FRP) tanks using free cell (FC) and BF of Vibrio anguillarum with triplicate in each. Heat-inactivated FC and BF cells at 107, 1010 and 1013 CFU/g fish/d were fed to fish for 20 days, agglutination antibody titer estimated at each 10 days interval up to 60-day post vaccination. As compared to FC and control there was a significant increase in agglutinating antibody titer in the biofilm vaccinated fishes. Among the 3 doses, BF at 1010 cfu/g fish/d was considered the ideal dose for vaccination. Relative percentage survival (RPS) was higher in biofilm vaccinated fish (85.4%) compared to that with free cells (27.0%). The study demonstrated the better performance of V. anguillarum biofilm oral vaccine compared that with free cell vaccine in L. calcarifer. The study further supports better performance of biofilm vaccine model with one more bacterial pathogen in a high carnivore fish.

Estimation of superoxide dismutase levels in saliva and gingival crevicular fluid among smokers and non-smokers in periodontitis patients - an observational study

Background: Smoking, which is an important risk factor for periodontitis, induces oxidative stress in the body and causes an imbalance between reactive oxygen species (ROS) and antioxidants, such as superoxide dismutase (SOD). The present study was done to quantify and compare the level of SOD enzyme levels in gingival crevicular fluid (GCF) and saliva among smokers and nonsmokers. Methodology: One hundred and thirty-five individuals in the age range of 20­55 years, including 45 light smokers, 45 heavy smokers, and 45 nonsmokers (controls), were selected and the clinical parameters recorded were plaque index, probing depth, and attachment loss. Smokers were divided into light smokers (<10 cigarettes/day) and heavy smokers (>10 cigarettes/day) and into three subgroups: healthy, mild periodontitis, and moderate periodontitis. GCF and saliva samples were collected then SOD levels were analyzed using spectrophotometric assay. Results: The mean levels of SOD in the GCF and saliva of smokers were decreased compared to controls. Intra- and inter-group analyses showed a significant reduction in the levels of SOD in the GCF and saliva of heavy smokers compared to light smokers and the control group. Conclusions: There was a progressive reduction in SOD levels from healthy nonsmokers to light smokers to heavy smokers

Development and standardization of a monoclonal antibody-based rapid flow-through immunoassay for the detection of Aphanomyces invadans in the field.

A monoclonal antibody-based flow-through immunoassay (FTA) was developed using a nitrocellulose membrane placed on the top of adsorbent pads enclosed in a plastic cassette with a test zone at the center. The FTA could be completed within 10 min. Clear purple dots against a white background indicated the presence of Aphanomyces (A.) invadans. The FTA limit of detection was 7 µg/mL for A. invadans compared to 56 µg/mL for the immunodot. FTA and polymerase chain reaction (PCR) could detect A. invadans in fish tissue homogenates at a 10(-11) dilution compared to a 10(-8) dilution by immunodot. In fish suffering from natural cases of epizootic ulcerative syndrome (EUS) collected from Mangalore, India, FTA and PCR could detect A. invadans in 100% of the samples compared to 89.04% detected by immunodot. FTA reagents were stable and produced expected results for 4 months when stored at 4~8°C. This rapid test could serve as simple and cost-effective on-site screening tool to detect A. invadans in fish from EUS outbreak areas and in ports during the shipment of live or frozen fish.

Eosinophils stimulate fibroblast DNA synthesis.

Fibrosis complicates a number of chronic inflammatory diseases and occurs in some conditions following chronic hypereosinophilic syndromes. We assessed whether eosinophils might be a source of fibrogenic factors. Extracts of human and guinea pig cell populations enriched for eosinophils contained substances that stimulated tritiated thymidine incorporation by human fibroblasts. Supernatants derived from resting eosinophils and extracts prepared from eosinophil granules also contained fibrogenic factors. Our findings demonstrate a new potential role for eosinophils and suggest a causal relationship between tissue eosinophilia and scar formation in certain parasitic conditions.

Phosphorylation and dephosphorylation of soluble proteins in human eosinophils.

The effect of phorbol 12-myristate 13-acetate (PMA), calcium ionophore (A23187), opsonized zymosan (OZ), and N-formylmethionyl-leucyl-phenylalanine (f-Met-Leu-Phe) on protein phosphorylation was examined in purified eosinophils (eos) isolated from human peripheral blood. Eos were prelabeled with [32P]orthophosphate, stimulated with several activating agents for varying periods of time. The soluble proteins were then analyzed by one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and autoradiography. In resting eos, there was phosphorylation of endogenous soluble proteins with molecular weights of 12, 16, 21, 40, and 66 kilodaltons (kDa). PMA, a potent activator of oxidative metabolism, induced phosphorylation of 19-, 40-, and 67-kDa proteins. A23187, a strong degranulating stimulus, caused phosphorylation of 40-, 53-, and 67-kDa proteins. OZ, a relatively weak stimulus for eos function, caused phosphorylation of 30-34-, 59-, 67-, and 93-kDa proteins. In addition, all the above stimuli caused a time-dependent dephosphorylation of 21-kDa protein. In contrast, f-Met-Leu-Phe caused neither phosphorylation of new proteins nor dephosphorylation of preexisting eos proteins. These findings demonstrate that selected stimuli affect phosphorylation of soluble eos protein. These results also suggest that phosphorylation of specific proteins in eos is an intermediary step in external stimulus-induced cell activation, which may involve many different cell functions.

Activated human eosinophils synthesize new proteins.

In order to study the biochemical consequences of prolonged in vitro activation of human blood eosinophils, aqueous whole cell lysates, cell-free supernatants from resting eosinophils, and cells activated with opsonized zymosan, calcium ionophore (A23187), N-formylmethionylleucylphenylalanine (fMet-Leu-Phe), and phorbol 12-myristate 13-acetate (PMA) were analyzed by polyacrylamide gel electrophoresis (PAGE). In comparison to resting eosinophils, opsonized zymosan-activated eosinophil extracts demonstrated altered protein composition on both the native PAGE and sodium dodecyl sulfate (SDS) -PAGE. Three new polypeptides of apparent molecular mass 24 kDa, 43 kDa and 60 kDa appeared on SDS-PAGE gels when opsonized zymosan-activated eosinophil extracts were electrophoresed. In contrast, extracts from fMet-Leu-Phe, A23187, and PMA-activated eosinophils demonstrated neither altered polypeptide composition nor new polypeptides. Opsonized zymosan also induced the incorporation of L-[35S]methionine into eosinophil proteins and this was completely blocked by pretreating the cells with cycloheximide. This finding suggests that eosinophils activated by certain stimuli synthesize new proteins. These newly synthesized proteins, which are freely secreted into the medium during cell activation, may possess important immunological functions.

Human lymphocyte-eosinophil interactions. I. Modulation of phytohemagglutinin-induced lymphocyte proliferation by eosinophils.

Do eosinophils modulate lymphocyte function? This question was studied by examining the effect of purified eosinophils (eos) on lectin-induced human lymphocyte proliferation. Intact resting or zymosan-stimulated eos or their extracts were cocultured with phytohemagglutinin-stimulated mononuclear cells in vitro and [3H]thymidine uptake was measured at 72 hr. Zymosan-stimulated eos consistently suppressed (up to 90%) the lectin-induced proliferative response by a noncytotoxic mechanism. Freeze-thaw extracts from zymosan-stimulated eos also significantly suppressed lymphocyte proliferation to a similar degree. The amount of suppression was directly proportional to the number of eos or the amount of extract added to the lymphocyte cultures. Intact resting eos and their extracts occasionally exhibited suppressive effects (up to 40%) on lymphocyte proliferation; this suppression, however, was always less than that of activated eos or their extracts. Eos pretreated with the protein synthesis inhibitor, pactamycin, exhibited significantly less suppressive activity, suggesting that a protein was responsible in part for the reduction in proliferation. The addition of superoxide dismutase or catalase to the eos-mononuclear cell cocultures did not reduce the amount of suppression observed, thus making it unlikely that active oxygen products were involved in the mechanism of suppression. Heating extracts from stimulated eos to 80 degrees C for 30 min resulted in partial loss of suppressive activity while extensive dialysis of the extracts had no effect. The studies reported here provide evidence that a nondialyzable and heat sensitive factor(s) produced by stimulated eos may exert feedback inhibition of lymphocyte function.

Purification and physicochemical, kinetic and immunological properties of allosteric serine hydroxymethyltransferase from monkey liver.

The homogeneous serine hydroxymethyltransferase purified from monkey liver, by the use of Blue Sepharose affinity chromatography, exhibited positive homotropic co-operative interactions (h = 2.5) with tetrahydrofolate and heterotropic interactions with L-serine and nicotinamide nucleotides. The enzyme had an unusually high temperature optimum of 60 degrees C and was protected against thermal inactivation by L-serine. The allosteric effects were abolished when the monkey liver enzyme was purified by using a heat-denaturation step in the presence of L-serine, a procedure adopted by earlier workers for the purification of this enzyme from mammalian and bacterial sources. The enzyme activity was inhibited completely by N5-methyltetrahydrofolate, N5-formyltetrahydrofolate, dichloromethotrexate, aminopterin and D-cycloserine, whereas methotrexate and dihydrofolate were partial inhibitors. The insoluble monkey liver enzyme-antibody complex was catalytically active and failed to show positive homotropic co-operative interactions with tetrahydrofolate (h = 1) and heterotropic interactions with NAD+. The enzyme showed a higher heat-stability in a complex with its antibody than as the free enzyme. These results highlight the pitfalls in using a heat-denaturation step in the purification of allosteric enzymes.

Inhibition of monkey liver serine hydroxymethyltransferase by Cibacron Blue 3G-A.

Cibacron Blue 3G-A inhibited monkey liver serine hydroxymethyltransferase competitively with respect to tetrahydrofolate and non-competitively with respect to L-serine. NADH, a positive heterotropic effector, failed to protect the enzymes against inhibition by the dye and was unable to desorb the enzyme from Blue Sepharose CL-6B gel matrix. The binding of the dye to the free enzyme was confirmed by changes in the dye absorption spectrum. The results indicate that the dye probably binds at the tetrahydrofolate-binding domain of the enzyme, rather than at the 'dinucleotide fold'.

Regulation of monkey liver serine hydroxymethyltransferase by nicotinamide nucleotide.

The positive homotropic binding of tetrahydrofolate to monkey liver serine hydroxymethyltransferase was abolished on preincubating the enzyme with NADH and NADPH. NAD+ was a negative heterotropic effector, whereas NADP+ was without effect. The allosteric effects of nicotinamide nucleotides on the serine hydroxymethyltransferase, reported for the first time, lead to a better understanding of the regulation of the metabolic interconversion of folate coenzymes.