Expression of osteopontin in calcified coronary atherosclerotic plaques

Advanced atherosclerosis is often associated with dystrophic calcification and remodeling of extracellular matrix of vascular wall. Recently many studies have documented a general relationship between calcification and severity of coronary disease, and discussed the feasibility of electron beam computed tomography for detecting and quantifying the coronary artery calcification in the patients. The present study investigated the expression and the localization of osteopontin, one of noncollagenous bone matrix protein, within the calcified coronary arteries. Autopsy-derived coronary artery specimens were scanned and reconstructed to visualize the pattern of coronary calcification using a novel microscopic computed tomography technique. The localization of the osteopontin were evaluated by immunohistochemial stain with LF7. The present study showed that the pattern of coronary calcification is variable and the expression of osteopontin is localized mainly to calcified lesion. The smooth muscle cells in addition to macrophage expressed osteopontin protein in human coronary atherosclerotic plaques. Soluble osteopontin released near to the sites of vascular calcification may represent an adaptive mechanism aimed at regulating the process of vascular calcification.

Sandwich capture ELISA by a murine monoclonal antibody against a genus-specific LPS epitope for the detection of different common serotypes of salmonellas

A sandwich capture ELISA based on a murine monoclonal antibody against a genus-specific epitope in the outer core region of the Salmonella lipopolysaccharide is described for the detection of different common serotypes of salmonellas. Four h broth cultures of seven standard and 24 wild strains of salmonellas were all detected by the capture ELISA while overnight broth cultures of 21 non-salmonella standard strains were all negative. The capture ELISA detected 1 ng/ml of Ra lipopolysaccharide, 10(6)/ml of a smooth wild strain of Salm. typhimurium, and 1120 cells of Salm. heidelberg after enrichment culture for 4 h.

Overweight and its association with aortic pressure wave reflection after exercise

BACKGROUND

Obesity is associated with arterial stiffening, left ventricular (LV) hypertrophy, and diastolic dysfunction. However, there is no data regarding dynamic changes in arterial hemodynamics with exercise in overweight subjects. We hypothesized that overweight women would show a different exercise response in wave reflection compared with lean women.

METHODS

A total of 59 overweight and 68 lean nondiabetic women (mean age 63 ± 7 years) underwent symptom-limited supine bicycle exercise testing with simultaneous two-dimensional and Doppler echocardiography. Central hemodynamics including central aortic pressure and augmentation index (AIx) were obtained at rest and immediately after peak exercise using radial artery tonometry.

RESULTS

Overweight women showed a higher LV mass index (lean vs. overweight; 40.2 ± 10.2 vs. 45.3 ± 11.0 g/m(2.7), P = 0.007) and a lower early diastolic mitral annular velocity (6.3 ± 1.8 vs. 5.5 ± 1.6 cm/s, P = 0.013) than lean women. Although the two groups did not differ in peripheral and central hemodynamics including AIx (36.3 ± 11.7 vs. 36.8 ± 10.2%, P = 0.830) and AIx normalized for heart rate 75/min (AIx@75, 30.4 ± 11.5 vs. 30.1 ± 9.9%, P = 0.885) at rest, AIx (20.9 ± 11.5 vs. 27.6 ± 10.4%, P = 0.004) and AIx@75 (25.8 ± 10.2 vs. 31.6 ± 7.7%, P = 0.002) at peak exercise were significantly higher in overweight women. In simple correlation analysis, body mass index (BMI) showed significant correlations with AIx, and AIx@75 at peak exercise, whereas no relationships were found with those parameters at rest. Multiple regression analysis showed that BMI was an independent determinant of AIx@75 at peak exercise (β = 0.28, P = 0.004).

CONCLUSIONS

Despite similar resting peripheral and central hemodynamics, the wave reflection in overweight women after exercise differed from that in lean women. These findings suggest that being overweight is related to higher wave reflection after exercise.

Pulmonary tuberculosis presenting as acute respiratory failure: radiologic findings

PURPOSE

The purpose of this work was to describe the radiologic findings of pulmonary tuberculosis in patients who presented with acute respiratory failure.

METHODS

We included patients who had newly diagnosed active pulmonary tuberculosis and who presented with acute respiratory failure. Initial chest radiographic (n = 17) and high-resolution CT (n = 11) findings of each patient were analyzed retrospectively.

RESULTS

Of 1,010 patients with active pulmonary tuberculosis, 17 patients (1.7%) presented with acute respiratory failure. Nine (53%) of the 17 patients died. The most common initial chest radiographic findings were small nodular lesions (16/17; 94%), consolidation (13/17; 76%), and ground-glass opacity (12/17; 70%). Eleven (69%) of 16 nodular lesions, 9 of 13 (69%) consolidations, and 10 of 12 (83%) ground-glass opacities were bilateral. On HRCT (n = 11), miliary micronodular lesions were seen in 6 patients (55%), whereas bronchogenic spread of tuberculosis with disseminated centrilobular nodules and tree-in-bud appearance was seen in 5 patients (45%). Diffuse areas of ground-glass attenuation were seen in all six patients with miliary nodules and four of five patients with bronchogenic spread of tuberculosis.

CONCLUSION

Patients with pulmonary tuberculosis occasionally present with acute respiratory failure. In this condition, chest radiograph most commonly shows bilateral small nodular lesions mixed with consolidation or ground-glass opacity, whereas HRCT demonstrates findings of miliary or bronchogenic disseminated tuberculosis with diffuse areas of ground-glass attenuation.

Rapid stimulation of 5-lipoxygenase activity in potato by the fungal elicitor arachidonic Acid

The activity of lipoxygenase (LOX) in aged potato tuber discs increased by almost 2-fold following treatment of the discs with the fungal elicitor arachidonic acid (AA). Enzyme activity increased above that in untreated discs within 30 min after AA treatment, peaked at 1 to 3 h, and returned to near control levels by 6 h. The majority of the activity was detected in a soluble fraction (105,000g supernatant), but a minor portion was also associated with a particulate fraction enriched in microsomal membranes (105,000g pellet); both activities were similarly induced. 5-Hydroperoxyeicosatetraenoic acid was the principal product following incubation of these extracts with AA. Antibodies to soybean LOX strongly reacted with a protein with a molecular mass of approximately 95-kD present in both soluble and particulate fractions whose abundance generally corresponded with LOX activity in extracts. LOX activity was not enhanced by treatment of the discs with nonelicitor fatty acids or by branched beta-glucans from the mycelium of Phytophthora infestans. Prior treatment of the discs with abscisic acid, salicylhydroxamic acid, or n-propyl gallate, all of which have been shown to suppress AA induction of the hypersensitive response, inhibited the AA-induced increment in LOX activity. Cycloheximide pretreatment, which abolishes AA elicitor activity for other responses such as phytoalexin induction, did not inhibit LOX activity in water- or elicitor-treated discs but enhanced activity similar to that observed by AA treatment. The elicitor-induced increase in 5-LOX activity preceded or temporally paralleled the induction of other studied responses to AA, including the accumulation of mRNAs for 3-hydroxy-3-methylglutaryl coenzyme A reductase and phenylalanine ammonia lyase reported here. The results are discussed in relation to the proposed role of the 5-LOX in signal-response coupling of arachidonate elicitation of the hypersensitive response.

Effects of electric stimulation on bovine oocyte activation and embryo development in intracytoplasmic sperm injection procedure

PURPOSE

This study was carried out to investigate the efficacy of electric stimulation before and/or after intracytoplasmic sperm injection (ICSI) on bovine oocyte activation and embryo development.

METHODS

The oocytes were treated with electric shock before (B), before and after (B&A), and after (A) sperm injection. In each group, sham ICSI (ICSI-s) was performed to exclude the effect of parthenogenesis (B ICSI-s, B&A ICSI-s, and A ICSI-s). An electric pulse was applied with a single direct current (DC) pulse (0.8 kV/cm, 70 microseconds).

RESULTS

One pronucleus (PN) formation in the B&A ICSI-s group was slightly higher than that found in B and B&A ICSI group; however, the difference was not significant. Two PN formation in B&A ICSI group was higher than that found in sham ICSI groups (P < 0.05). There were no differences among treatment groups in the cleavage rate; however, morulae and blastocyst formation in the B&A embryos was significantly higher than that of other groups (P < 0.05) and got pregnant.

CONCLUSIONS

Electric stimulation before and after injection was an effective method in inducing bovine oocyte activation and in sustaining embryo development to the morulae and blastocyst stage.

17Beta-estradiol inhibits proliferation of cultured vascular smooth muscle cells induced by lysophosphatidylcholine via a nongenomic antioxidant mechanism

OBJECTIVE

Lysophosphatidylcholine (lysoPC), an active component of oxidized low-density lipoprotein, stimulates proliferation of vascular smooth muscle cells (VSMC). We investigated the direct impact of 17beta-estradiol (E2) on the proliferation of VSMC from rat aorta.

RESULTS

VSMC derived from both female and male rats expressed estrogen receptors alpha and beta. Treatments with 1% fetal bovine serum or 5 microM lysoPC increased the incorporation of [3H]-thymidine in VSMC obtained from female rats. 17Beta-E2 did not alter the response to fetal bovine serum, but significantly suppressed the enhanced deoxyribonucleic acid synthesis which had been induced by lysoPC in a dose-dependent manner (10(-4)-10(-6) M). Estrogen also inhibited the proliferation of VSMC from male animals. ICI 182,780, a specific estrogen receptor antagonist, and 17alpha-E2, an inactive form of estradiol, also decreased the mitogenic response to lysoPC in VSMC. In addition, N-acetyl-L-cysteine, a potent antioxidant, inhibited the lysoPC effect. Flow cytometric analysis using the oxidation-sensitive probe 2',7'-dichlorofluorescin diacetate revealed that elevated intracellular formation of reactive oxygen species elicited with lysoPC was depressed significantly by 17beta-E2, ICI 182,780, or 17alpha-E2 as well as by N-acetyl-L-cysteine.

CONCLUSION

17Beta-E2 inhibits in vitro VSMC proliferation induced by lysoPC via a nongenomic antioxidant mechanism.

After facial nerve damage, regenerating axons become aberrant throughout the length of the nerve and not only at the site of the lesion: an experimental study

After facial nerve trauma, aberrant regeneration is associated with synkinesis. Animal models of mechanical nerve guides or reparative cell transplants at the site of a lesion have not been shown to improve disorganized regeneration. We examined whether this is because regenerating axons become disorganized throughout the length of the nerve and not only at the site of the lesion. In rats (n = 12), retrograde fluorescent tracer techniques were used to establish that most of the temporal branch fibres were carried in the superior half of the facial nerve trunk. In two further groups of rats (n = 24) a complete proximal facial nerve lesion was made, and the nerve immediately repaired by suture. After 4 weeks, at a second operation, the superior half of the facial nerve trunk was cut, either proximal or distal to the original lesion, and retrograde tracers were applied to distal branches of the nerve. It was possible to localize the points at which regenerating fibres became aberrant in their course by studying the number of labelled motoneurons in the facial nucleus after application of the tracer to the temporal branch of the nerve: this was similar in the distal and proximal hemisection groups, suggesting that aberrant axonal development occurred throughout the length of the nerve. Future strategies aimed at improving the organization of regeneration need to provide guidance cues not only at the site of the lesion as previously thought, but also throughout the length of the nerve.

Evidence for autocrine inhibition of gonadotropin-releasing hormone (GnRH) gene transcription by GnRH in hypothalamic GT1-1 neuronal cells

To examine whether an ultrashort feedback mechanism of gonadotropin-releasing hormone (GnRH) operates at the level of gene transcription, we studied the effects of GnRH analogs on GnRH promoter activity and GnRH mRNA level in hypothalamic GT1-1 neuronal cells. Treatment of GT1-1 cells with buserelin, a GnRH agonist, or native GnRH for 24 h significantly decreased GnRH promoter activity and its mRNA level, whereas that with GnRH antagonists, antide or [D-Phe2,D-Ala6]-GnRH, showed no effect. The inhibitory effects of buserelin on GnRH gene transcription and GnRH mRNA level were dose-related, and a significant inhibition was observed in cells treated with buserelin at concentrations higher than 0.1 microM. Time-course experiments showed that significant decreases in GnRH promoter-driven luciferase activity and GnRH mRNA level were observed within 12 h and sustained up to 48 h. Moreover, treatment with GnRH agonist for 12 h significantly decreased the transcription rate of the mouse GnRH gene, as revealed by nuclear run-on transcription assay. The promoter analysis with the 5'-deletional constructs demonstrated that cis-acting elements important for GnRH autoregulation by GnRH agonist reside within -854 bp upstream from the transcription start site. These data clearly demonstrate that GnRH can exert autocrine regulation at the level of GnRH gene transcription.

Hepatocellular carcinoma: correlation between vascular endothelial growth factor level and degree of enhancement by multiphase contrast-enhanced computed tomography

RATIONALE AND OBJECTIVES

To determine whether vascular endothelial growth factor (VEGF) is a histopathological factor influencing contrast enhancement of hepatocellular carcinoma (HCC) on computed tomography (CT).

METHODS

Twenty-two nodular HCCs underwent multiphase helical CT and surgery. Tumor size, histological grading of differentiation, and type of hepatitis were evaluated. Tumor attenuation was graded as hyperattenuated, isoattenuated, and hypoattenuated. Immunohistochemical staining with anti-VEGF antibody was performed and scored as weak, intermediate, or strong. Spearman's rank correlation test was used.

RESULTS

Tumors ranged from 1.0 to 12.0 cm (mean 5.1 cm). The degree of enhancement during the hepatic arterial phase was significantly correlated with VEGF expression. Size was negatively correlated with VEGF expression and the degree of enhancement, but histological grade and type of hepatitis were not correlated with VEGF expression, tumor size, or degree of enhancement.

CONCLUSIONS

In HCC, VEGF expression is correlated with the degree of contrast enhancement during arterial-phase CT.

Perinatal survivin is essential for the establishment of pancreatic beta cell mass in mice

AIMS/HYPOTHESIS

Pancreatic beta cells undergo dynamic remodelling during the perinatal period, with enhanced neogenesis, proliferation and apoptosis observed. The molecular mechanisms responsible for these processes have yet to be elucidated. Survivin is an inhibitor of apoptosis, first described as being exclusively expressed in tumour and embryonic tissues with regulatory functions in mitosis and apoptosis. The aim of the present study was to define the essential physiological role of survivin in the pancreas.

METHODS

The expression profile of survivin was assessed in the mouse pancreas, and we generated a Pdx1 promoter-driven Survivin (also known as Birc5) knockout mouse using the Cre-loxP recombination system to determine the essential physiological function of survivin in the pancreas.

RESULTS

Survivin is transiently expressed in mouse pancreatic islets during the embryonic and neonatal periods. Targeted deletion of Survivin in the pancreas resulted in a significant decline in beta cell mass throughout the perinatal period, leading to glucose intolerance in the adult. Survivin-deficient islets showed decreased cell proliferation as a result of a delay in cell cycle progression with perturbations in cell cycle proteins. Survivin did not, however, play an essential role in beta cell apoptosis either during the physiological remodelling period or in response to streptozotocin. Islet development, islet architecture, microvasculature and apoptosis were not affected by the absence of survivin in the pancreas.

CONCLUSIONS/INTERPRETATION

Survivin expression in the pancreatic islets during the perinatal remodelling period is essential for the establishment of beta cell mass through cell cycle regulation.

Comparative performances of an HTLV-I/II EIA and other serologic and PCR assays on samples from persons at risk for HTLV-II infection

BACKGROUND

HTLV-I and HTLV-II are related exogenous pathogenic human retroviruses. Until recently, ELISAs based on HTLV-I antigens have been used to screen for the presence of HTLV-I or -II antibodies. The HTLV-I-based assays have not been as sensitive in detecting antibodies to HTLV-II as in detecting antibodies to HTLV-I. The Abbott HTLV-I/HTLV-II ELISA uses a combination of HTLV-I and HTLV-II antigens to detect antibodies to the whole HTLV group. The performance of this ELISA was compared to that of several HTLV-I-based serologic assays and an HTLV-II PCR assay in cohorts of South American Indians and New York City IV drug users (IVDUs) in whom HTLV-II is endemic.

STUDY DESIGN AND METHODS

Sera from 429 South American Indians and New York City IVDUs were evaluated for HTLV antibodies by the use of three ELISAs (rgp21-enhanced HTLV-I/II, Cambridge Biotech; Vironostika HTLV-I/II, Organon Teknika; and HTLV-I/HTLV-II, Abbott), and a Western blot (WB) assay. Peripheral blood leukocyte DNA from each person was analyzed for HTLV-I and HTLV-II pol DNA via PCR. The HTLV-II PCR-positive samples were further subtyped via cloning and sequencing and/or oligomer restriction.

RESULTS

Two hundred four samples (48%) were positive for HTLV-II by serologic and/or PCR assays. All of the positive samples from the Indians and approximately one-third of the positive samples from the IVDUs were of the HTLV-IIB subtype. Comparative analyses indicate that the sensitivity and specificity of the various assays were: PCR, 98 and 100 percent; Abbott HTLV-I/HTLV-II, 78 and 95 percent; Cambridge Biotech HTLV-I/II, 76 and 96 percent; Vironostika HTLV-I/II, 71 and 98 percent; and WB, 73 and 100 percent, respectively.

CONCLUSION

There were no significant differences among the sensitivities and specificities of the HTLV-I/II ELISAs (p values, 0.056-0.438). The WB and PCR assays were much more specific than the other serologic assays (p</=0.03). However, the PCR assay is significantly (p<0.001) more sensitive than any of the serologic assays in the detection of HTLV-II infection. Thus, optimal detection of HTLV-II infection would seem to require both serologic and DNA PCR assays.

The biological significance of phospholipase C beta 1 gene mutation in mouse sperm in the acrosome reaction, fertilization, and embryo development

PURPOSE

We carried out this study to evaluate the biological significance of phospholipase C beta 1 gene mutation in mouse sperm in the acrosome reaction, fertilization, and embryo development.

METHODS

Study subjects were divided into two groups according to the sperm [intact phospholipase C (PLC) beta 1 and PLC beta 1-/- C57BL/6J x CBA F1 mouse sperm] used. The positive acrosome reaction rate labeled with fluorescein isothiocyanate-Pisum sativum agglutinin, the fertilization rate, and the rate of embryos developed to the stage of morula or blastocyst in the two groups were compared.

RESULTS

The mouse sperm null for the PLC beta 1 gene showed a lower acrosome reaction rate than control sperm (69.2 vs 50.9%, P < 0.05). And the fertilization rate and the rate of embryos developed to the stage of morula or blastocyst were also lower in the group using PLC beta 1-/- mouse sperm compared to the intact group (P < 0.05; 73.5 vs 51.8% and 15.7 vs 4.3%, respectively).

CONCLUSIONS

Mutation of the PLC beta 1 gene in the mouse sperm reduces the acrosome reaction rate, fertilization rate, and embryo development rate, which may be the etiologic factors responsible for the low reproductive rate of PLC beta 1-/- mouse.

The anticonvulsant activities of functionalized N-benzyl 2-acetamidoacetamides. The importance of the 2-acetamido substituent

Recent studies have demonstrated that substituted N-benzyl 2-acetamidoacetamides provide significant protection against maximal electroshock (MES)-induced seizures in mice and rats. In this study, we investigated whether the 2-acetamido moiety was necessary for anticonvulsant activity. Ten derivatives of the known anticonvulsant, N-benzyl 2-acetamido-2-phenyl-acetamide were prepared in which the 2-acetamido group was replaced by hydrogen, methyl, oxygen, and halogen substituents. Evaluation of these compounds in the MES-induced seizure test demonstrated that both the hydroxy and the methexy compounds provided full protection against MES-induced seizures in mice given ip at 100 mg/kg. Moreover, evaluation of the individual stereoisomers for the hydroxy compound showed that the principal activity resided in the (R)-isomer. These findings demonstrated that the 2-acetamido substituent is important but not obligatory for the prevention of MES-induced seizures. Further supporting evidence was provided by comparing the pharmacological activities of N-benzyl 2,3-dimethoxypropionamide with N-benzyl 2-acetamido-3-methoxypropionamide. The ED50 value for the former in the MES test was 30 mg/kg (i.p.), which compared favorably with phenobarbital (ED50 = 22 mg/kg), but the ED50 value for N-benzyl 2-acetamido-3-methoxypropionamide was 8.3 mg/kg.

Comparison of inflammatory markers and angiographic outcomes after implantation of sirolimus and paclitaxel-eluting stents

OBJECTIVE

We compared the degree of systemic inflammation and its relation to the angiographic outcomes after drug-eluting stent (DES) implantations.

METHODS

We implanted a single DES in 79 stable angina patients (50 men; 60.4 (9.5) years of age; sirolimus-eluting stent (SES), n = 38; paclitaxel-eluting stent (PES), n = 41). The high-sensitivity C-reactive protein (hs-CRP) and interleukin 6 (IL-6) levels were determined before and at 24 hours, 72 hours, and 4 weeks after the percutaneous coronary intervention (PCI). An angiography and intravascular ultrasound (IVUS) were performed.

RESULTS

The hs-CRP and IL-6 levels at baseline did not differ between the two groups. The hs-CRP increased significantly from baseline at 24 hours and 72 hours after the PCI in both groups and there was a significant increase in the IL-6 level at 24 hours after the PCI in both groups. However, there was no significant difference between the two groups in any of the hs-CRP or IL-6 measurements. At follow-up, the late lumen loss was significantly higher in the PES group than in the SES group (0.57 (0.56) mm vs 0.28 (0.58) mm, respectively, p = 0.020). The neointimal hyperplasia (NIH) volume in the PES group was significantly higher than that in the SES group (23.1 (22.7) vs 3.8 (7.1) mm(3), respectively, p = 0.000). The percentage luminal volume reduction was higher in the PES group than in the SES group (18.9 vs 3.9%, p = 0.002). The absolute values or change in the inflammatory markers did not correlate with the NIH or stent volume reduction.

CONCLUSIONS

Our study showed that the benefits obtained from the SES, which reduce neointimal proliferation, are not probably mediated by the attenuation of the systemic inflammatory markers hs-CRP or IL-6.

A rare case of vomiting: fourth ventricular B-cell lymphoma

We document the case of a 69-year-old man presenting with 6 weeks of intractable vomiting. Magnetic Resonance Imaging showed a homogenously enhancing mass in the caudal fourth ventricle. Surgical exploration and biopsy was performed and pathological examination demonstrated a high-grade B-cell lymphoma. The lesion was a primary tumour in an immuno-competent patient. Despite the increasing incidence of primary central nervous system lymphomas this is believed to be only the third ever case to have occurred at this rare site. We suggest that primary B-cell lymphoma should be considered with homogenous lesions of the fourth ventricle.

SMI-32 antibody against non-phosphorylated neurofilaments identifies a subpopulation of cultured cortical neurons hypersensitive to kainate toxicity

SMI-32, an antibody against a non-phosphorylated neurofilament epitope identifies a subpopulation of human cortical neurons preferentially lost in Alzheimer's or Huntington's disease. In murine cortical cultures SMI-32 labeled a small subset of neurons exhibiting enhanced vulnerability to kainate toxicity. Most SMI-32(+) neurons were GABAergic and exhibited kainate-activated Co2+ uptake. Thus expression of Ca2+ permeable AMPA or kainate receptor-gated channels likely underlies the heightened vulnerability of SMI-32(+) cortical neurons to kainate.

Anterior deltoid deficiency in reverse total shoulder replacement

Reverse total shoulder replacement (RTSR) depends on adequate deltoid function for a successful outcome. However, the anterior deltoid and/or axillary nerve may be damaged due to prior procedures or injury. The purpose of this study was to determine the compensatory muscle forces required for scapular plane elevation following RTSR when the anterior deltoid is deficient. The soft tissues were removed from six cadaver shoulders, except for tendon attachments. After implantation of the RTSR, the shoulders were mounted on a custom-made shoulder simulator to determine the mean force in each muscle required to achieve 30° and 60° of scapular plane elevation. Two conditions were tested: 1) Control with an absent supraspinatus and infraspinatus; and 2) Control with anterior deltoid deficiency. Anterior deltoid deficiency resulted in a mean increase of 195% in subscapularis force at 30° when compared with the control (p = 0.02). At 60°, the subscapularis force increased a mean of 82% (p < 0.001) and the middle deltoid force increased a mean of 26% (p = 0.04).

Scapular plane elevation may still be possible following an RTSR in the setting of anterior deltoid deficiency. When the anterior deltoid is deficient, there is a compensatory increase in the force required by the subscapularis and middle deltoid. Attempts to preserve the subscapularis, if present, might maximise post-operative function.

Magnesium-Dependent Promotion of H2O2 Production Increases Ecological Competitiveness of Oral Commensal Streptococci

The pyruvate oxidase (SpxB)-dependent production of H₂O₂ is widely distributed among oral commensal streptococci. Several studies confirmed the ability of H₂O₂ to antagonize susceptible oral bacterial species, including caries-associated Streptococcus mutans as well as several periodontal pathobionts. Here we report a potential mechanism to bolster oral commensal streptococcal H₂O₂ production by magnesium (Mg²⁺) supplementation. Magnesium is a cofactor for SpxB catalytic activity, and supplementation increases the production of H₂O₂ in vitro. We demonstrate that Mg²⁺ affects spxB transcription and SpxB abundance in Streptococcus sanguinis and Streptococcus gordonii. The competitiveness of low-passage commensal streptococcal clinical isolates is positively influenced in antagonism assays against S. mutans. In growth conditions normally selective for S. mutans, Mg²⁺ supplementation is able to increase the abundance of S. sanguinis in dual-species biofilms. Using an in vivo biophotonic imaging platform, we further demonstrate that dietary Mg²⁺ supplementation significantly improves S. gordonii oral colonization in mice. In summary, our results support a role for Mg²⁺ supplementation as a potential prebiotic to promote establishment of oral health-associated commensal streptococci.