Hydroxyapatite and their use as coatings in dental implants: a review

At present, no standard manufacturing guideline exists for depositing hydroxyapatite (HA) on implant surfaces. Although animal and in vitro studies have reported on the benefits of using HA-coated implants as well as the risks of dissolution, these short-term studies did not demonstrate that the dissolution of the HA coating leads to a loss of implants. In addition, many in vivo and clinical studies did not include the chemical and structural characterization of the coatings, and thus comparisons between studies are difficult. In the clinics, the recommendation is that HA-coated screw implants be used for the anterior maxilla and posterior mandible where the bone depth exceeds 10 mm and when the cortical layer is thinner and spongiosia is less dense. In the posterior maxilla or when the cortical layer is very thin with low density, the use of HA-coated cylindrical implants is recommended. However, there are concerns for using HA-coated implants. The clinician needs to take into consideration the enhanced bacterial susceptibility of HA coatings compared with titanium implants. In addition, the clinician needs to consider the possible failure of HA coatings as a result of coating-substrate interfacial fracture. Finally, besides the surgical skills, it is also important that the clinical investigators be well versed with the materials characterization needed for HA-coated implants, the problems associated with the current HA coatings, and the indications for use. In addition, the correlation between well characterized coatings and their effect on bone formation rate and long-term implant success, coating-implant interfacial strength, and alternative superior coating process need to be investigated further.

Curing potential of dual-polymerizable resin cements in simulated clinical situations

STATEMENT OF PROBLEM

Little is known about the ability of dual-polymerizable resin cements to polymerize when they are used in various clinical scenarios.

PURPOSE

This study was conducted to determine whether any of 6 commercially available dual-polymerizable resin cements should be classified as an "all-purpose" resin cement.

MATERIAL AND METHODS

. Chemical conversion values (C=C converted to C-C, or the extent of the curing reaction) of 6 commercially available dual-polymerizable resin cements were determined with infrared spectroscopy in 5 clinically relevant scenarios. Scenarios included: using each cement in a dual-polymerizable mode (mixing of 2 pastes); light polymerizing curing through Mylar sheets (dual-Mylar), which served as the control; light polymerizing through 3-mm porcelain (dual-3 mm); and no exposure to light (dual-no light). The single-component light-polymerizable product was also tested as follows: exposed directly through Mylar (light-Mylar) or exposed through 3 mm of porcelain (light-3 mm). Results. For each product, dual-Mylar treatment yielded the highest conversion value of all treatments (control for each product). For all products, dual-3 mm conversion was at least 97% of control and equivalent to control, with the exception of Lute-It!. Dual-no light conversion was less than control treatment but at least 86% of control for all products except for Variolink II (62% of control). For all products in dual-no light mode, except Choice and Variolink II, conversion was at least equal to the light-Mylar values. Only 1 product (Variolink II) did not demonstrate increased conversion values for dual-Mylar compared with light-Mylar treatments. For most other products (Calibra, Insure, and Lute-It!), conversion values for light-3 mm were significantly less than for light-Mylar. Conversion values for Nexus, Choice, and Variolink II were equivalent between light-Mylar and light-3 mm treatments.

CONCLUSION

The choice of a dual-polymerizable cement should be based on its intended use because not all products polymerize adequately in every clinical situation. Although no cement met the stated criteria for an "all-purpose" cement, those tested did produce a range of product-specific results.

Long-term results of duodenectomy with highly selective vagotomy in the treatment of complicated duodenal ulcers

BACKGROUND

Highly selective vagotomy and complete circular or partial duodenectomy have been applied to complicated duodenal ulcer for many years. These procedures seem to provide better clinical results than truncal vagotomy and antrectomy.

METHODS

A retrospective analysis was conducted of 120 patients with complicated duodenal ulcer who underwent surgical treatment between 1986 and 1999. Patients with obstruction were treated with either circular complete (17) or partial duodenectomy (3) combined with highly selective vagotomy or truncal vagotomy and antrectomy (37). Those with perforation were treated primarily with highly selective vagotomy and partial duodenectomy, highly selective vagotomy alone, or truncal vagotomy and pyloroplasty. Every patient was followed up either by a clinic visit (75%) or questionnaire to determine the presence of ulcer pain, dumping, diarrhea, vomiting, weight loss, and Visick grade.

RESULTS

Long-term follow-up of patients treated with duodenectomy and highly selective vagotomy for obstruction showed that 94% had sustained weight gain whereas more than half of those treated with truncal vagotomy and antrectomy had weight loss. In patients with perforation, duodenectomy and highly selective vagotomy offered no advantage over highly selective vagotomy alone.

CONCLUSIONS

Highly selective vagotomy and complete circular or partial duodenectomy provide fewer sequelae and better weight gain long term than truncal vagotomy and antrectomy for patients with obstructing duodenal ulcers.

Metabolism-resistant bradykinin antagonists: development and applications

Bradykinin plays many roles in normal and pathological physiology, but rapid enzymatic degradation made elucidation of its functions extremely difficult. Development of effective degradation-resistant antagonists made it possible to delineate these roles and to open the way for development of new drugs to control pathology due to excess production of bradykinin. Presently available peptide bradykinin antagonists are extremely potent, are completely resistant to enzymatic degradation, and are orally available. Non-peptide bradykinin antagonists have also been discovered. Development of bradykinin antagonists as drugs for cancer, inflammation and trauma is anticipated.

Novel approach to measure composite conversion kinetics during exposure with stepped or continuous light-curing

PURPOSE

The objective of this research was to evaluate a novel approach to monitor the polymerization reaction during a light-curing exposure by using infrared (IR) spectroscopy.

MATERIALS AND METHODS

An IR spectrometer was equipped to use an attenuated total reflectance (ATR) element as an IR-active substrate. The uncured composite (Herculite XRV, Shade A2, Kerr, Orange, California) was placed against the crystal, and the IR spectrum was continuously obtained during various exposure scenarios. The degree of conversion and the maximum rate of reaction were monitored at 0 mm (top surface), 1 mm, 2 mm, and 3 mm beneath the surface. The exposure conditions included continuous 40-second or 60-second exposures at 100% intensity (800 mW/cm2) or a stepped output of 10 seconds at 17% maximal output (133 mW/cm2) followed by full output for the remainder of the 40-second or 60-second exposure (Elipar Highlight, ESPE, Norristown Pennsylvania). The results were analyzed using MANOVA with appropriate post hoc tests (p < or = .05).

RESULTS

For 40-second exposures, the peak conversion rates were significantly reduced (p < .05) when using the stepped exposure mode compared to the continuous exposure: 40-second top surface: stepped = 5.5%/s +/- 0.4, continuous = 10.5%/s +/- 1.0; 1 mm step = 3.6%/s +/- 0.4, continuous mode = 4.8%/s +/- 0.2. The same trend was noted when using the 60-second exposure. Equivalent conversion values (p > .05) beneath the surface between stepped and continuous exposure modes at similar depths 60 seconds after light initiation were only attained at 3 mm 4 for the 40-second exposure. However, using the 60-second exposure, equivalent conversion values between step and continuous exposure modes at similar depths were obtained. Even with a reduced conversion rate at the surface using the stepped cure mode, polymerization shrinkage forces were sufficient to debond the specimens from the test crystal after only 20 seconds into the exposure. This result indicated that stress development in the curing composite was non-uniform, and stress values developed at the surface of the restoration were the greatest.

CLINICAL SIGNIFICANCE

Stepped intensity curing for the ESPE Highlight unit was shown to produce significantly lower conversion rates at the surface and at 1-mm depths, but longer exposure times were still required to provide conversion values equivalent to continuous exposure.

Synergistic effects of new chemopreventive agents and conventional cytotoxic agents against human lung cancer cell lines

Non-small cell lung cancer (NSCLC) cells have constitutively high expression of cytosolic phospholipase A2 (cPLA2) and cyclooxygenase (COX) 2. These NSCLC cells also have increased prostaglandin expression (PGE2). Many lung cancers also express 12-lipoxygenase RNA and 12-lipoxygenase protein and biosynthesize 12(S)-hydroxyeicosatetraenoic acid, which correlates with their metastatic potential. Several studies have demonstrated that COX-1 and COX-2 inhibitors could inhibit the in vitro growth of human lung cancer cell lines. In this report, we evaluated the growth-inhibitory effects of sulindac sulfide, a COX-1 and COX-2 inhibitor; exisulind (sulindac sulfone), a novel proapoptotic agent that does not inhibit COX enzymes; and nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor on human lung cancer cell lines. We compared these effects with those of 13-cis-retinoic acid, a chemoprevention agent, and with the cytotoxic chemotherapeutic agents paclitaxel and cisplatin, alone or in combination. Our goal was to develop new chemoprevention and treatment strategies. Each of the six agents tested inhibited the in vitro growth of three NSCLC and three SCLC cell lines at the highest concentration. Paclitaxel was the most potent agent (IC50 = 0.003-0.150 microM); sulindac sulfide, NDGA, and 13-cis-retinoic acid had intermediate potency (IC50 = 4-80 microM), and cisplatin and exisulind were the least potent (IC50 = 150-500 microM). Combination studies showed synergistic interactions for sulindac sulfide, exisulind, and NDGA with paclitaxel, cisplatin, and 13-cis-retinoic acid, regardless of drug-resistance phenotype. At high concentrations, the combination of 13-cis-retinoic acid and each of the five other drugs resulted in a strong synergistic effect. These studies provide a rationale for chemoprevention (exisulind +/- retinoic acid +/- NDGA) and therapeutic (exisulind +/- paclitaxel +/- cisplatin) studies in patients at risk for, or with, lung cancer.

Evaluation of different methods for cleaning and preparing occlusal fissures

The effectiveness of different methods for cleaning and preparing occlusal fissures before placing sealants was evaluated. Extracted mandibular molars received such treatments as brushing, pumicing, bur preparing, and air abrasion before application of fissure sealants. FluroShield fissure sealant was then applied to the occlusal fissures. Specimens were subjected to thermo-cycling and then immersed in a 10% solution of methylene blue, and finally sectioned. The sections were examined and photographed in a stereomicroscope, and the dye penetration was recorded using a scoring system. The results indicated that only the control (brushing with a dry brush) and the pumicing groups demonstrated dye penetration to the base of the sealant. Teeth prepared with the #1/4 round bur and air abrasion demonstrated a better seal in evaluated fissures. For this study, those three groups (occlusal fissures prepared with the #1/4 round bur and two air abrasion methods), demonstrated significantly better sealing (P < 0.01) than the control group and the other groups tested.

Bradykinin antagonists: present progress and future prospects

Bradykinin (BK) antagonist peptides have been powerful tools for delineating roles of kinins in both normal and pathological physiology and offer promise of drug development for a variety of inflammatory conditions and cancers. At the present time, potent peptide antagonists are available that are either specific for BK B1 or B2 receptors, or are effective on both receptor classes. Non-peptide BK B2 antagonists are now being announced and are under investigation in several companies. The best peptide B1-B2 peptide antagonist is stable against all kininases, is orally available, and has a very long lifetime in vivo. Certain dimers of this antagonist, as well as several smaller molecules, are active against several cancers, both in vitro and in vivo.

Radiopacity of tantalum oxide nanoparticle filled resins

OBJECTIVES

Radiopacity of composite resins allows radiographic distinction of existing restorations and recurrent caries. Current composites must be supplemented with heavy metal-containing glasses or minerals to achieve a desired radiopacity. The purpose of this study was to evaluate the radiopacity of Tantalum oxide (Ta2O5) filled resins at varying percentage loadings.

METHODS

Methacrylate functionalized Ta2O5 nanoparticles (< 50 nm) in methanol-dissolved or powder forms were mixed into either glycerol dimethacrylate (GDMA) or a bisGMA, TEGDMA, bisEMA mixture (GTE). Specimens were made in a split brass mold (2 x 2 x 15 mm) and compared with an aluminum stepwedge (99.5% pure Al) and a dentin slice of the same thickness. Kodak Ultraspeed periapical X-ray film on a lead plate at a target distance of 45 cm was exposed at 70 kVp and 10 mA, for 0.5 s and processed automatically. Optical density was measured (n = 3) with an RMI Processor Control Densitometer. Radiopacity was calculated as percent relative linear attenuation coefficient (Alpha). ANOVA and Student-Newman-Keuls comparisons were used to determine significance at the 95% confidence level.

RESULTS

Radiopacity increased significantly with Ta2O5 loading (p = 0.001). Ta2O5 nanoparticle filled resins enter the optimal range of diagnostic detectability (alpha = 150-250) at 50 wt.% and approach equivalence with enamel at approximately 70 wt.%.

SIGNIFICANCE

The introduction of tantalum oxide nanoparticle filler has potential as a miscible component of a resin composite to provide radiopacity for microfiller-type restorative materials and to circumvent the need for hydrolysis-prone glass reinforcing fillers.

Evidence that a prominent cavity in the coiled coil of HIV type 1 gp41 is an attractive drug target

Synthetic C peptides, corresponding to the C helix of the HIV type 1 (HIV-1) gp41 envelope protein, are potent inhibitors of HIV-1 membrane fusion. One such peptide is in clinical trials. The crystal structure of the gp41 core, in its proposed fusion-active conformation, is a trimer of helical hairpins in which three C helices pack against a central coiled coil. Each C helix shows especially prominent contacts with one of three symmetry-related, hydrophobic cavities on the surface of the coiled coil. We show that the inhibitory activity of the C peptide C34 depends on its ability to bind to this coiled-coil cavity. Moreover, examining a series of C34 peptide variants with modified cavity-binding residues, we find a linear relationship between the logarithm of the inhibitory potency and the stability of the corresponding helical-hairpin complexes. Our results provide strong evidence that this coiled-coil cavity is a good drug target and clarify the mechanism of C peptide inhibition. They also suggest simple, quantitative assays for the identification and evaluation of analogous inhibitors of HIV-1 entry.

Effects of recombinant neutral endopeptidase (EC 3.4.24.11) on the growth of lung cancer cell lines in vitro and in vivo

Many lung cancers are stimulated by an autocrine/paracrine system of neuroendocrine peptide hormones. Attempts to block this autocrine growth pathway by interactions with specific ligand-receptor binding using monoclonal antibodies and peptide-specific antagonists have been largely unsuccessful because of the heterogeneity of hormone production and receptor expression. In the normal lung, neutral endopeptidase (NEP; CD10, CALLA, enkephalinase, and EC 3.4.24.11) plays a physiological role in degrading biologically active peptides, including all peptides implicated in autocrine growth stimulation of lung cancer. Cigarette smoke decreases the activity of NEP, indicating that the lack of NEP contributes to the dysregulation of the peptide autocrine system. The cloning of the human NEP gene allowed for production of sufficient quantities of recombinant NEP (rNEP) to evaluate its role in inhibiting the growth of lung cancer cells. In this study, we evaluated the ability of rNEP to inactivate the peptides involved in lung cancer signal transduction and to inhibit the growth of lung cancer cells as well as normal lung cells in vitro and in vivo in athymic nude mice. We showed that the growth inhibition of lung cancer cells by rNEP was related to the dose and schedule. Continuous exposure to high doses was required for growth inhibition. These studies confirm the importance of NEP in this autocrine pathway.

Short-term efficacy and tolerability of combination therapy with lovastatin and acipimox in Chinese patients with type 2 diabetes mellitus and mixed dyslipidemia

In type 2 diabetes, it is not uncommon to find an elevated serum triglyceride and/or reduced high-density lipoprotein (HDL) cholesterol levels; elevated total cholesterol levels often occur as well. To evaluate the short-term efficacy and tolerability of combination therapy with lovastatin and acipimox in Chinese patients with type 2 diabetes who have mixed dyslipidemia, an open-label 6-month trial was conducted. All patients had type 2 diabetes (n = 33) with total cholesterol > or = 6.2 mmol/L and fasting triglyceride > or = 2.8 mmol/L, which had been confirmed twice and persisted for at least 12 weeks after introduction of diet control. After a 4-week run-in period, they were given lovastatin 40 mg daily at night for 12 weeks. Acipimox 250 mg three times a day was then added for a further 12 weeks. After 12 weeks of treatment with lovastatin alone, improvement was observed in total cholesterol (21% reduction), triglyceride (32% reduction), low-density lipoprotein (LDL) cholesterol (5.5% reduction), HDL cholesterol (11.6% elevation), apolipoprotein A-I (4.6% elevation), and apolipoprotein B (20.5% reduction). The addition of acipimox to lovastatin for an additional 12 weeks further reduced serum total cholesterol, triglyceride, LDL cholesterol, and apolipoprotein B, but this additional decrease was not statistically significant. However, HDL cholesterol and apolipoprotein A-I levels were significantly increased by the addition of acipimox (a 14.2% and 9.0% elevation, respectively). Serum creatine phosphokinase increased slightly after 12 weeks of lovastatin but decreased to a concentration similar to baseline after 12 weeks of combination treatment. No patients reported muscle pain or weakness or other side effects. Combination treatment with lovastatin and acipimox appears to be a safe and effective therapy in patients with type 2 diabetes and mixed dyslipidemia, and has particular benefit in elevating serum HDL cholesterol and apolipoprotein A-I levels.

The mouse formin (Fmn) gene: abundant circular RNA transcripts and gene-targeted deletion analysis

BACKGROUND

Mutations in the mouse formin (Fmn) gene result in limb deformities and incompletely penetrant renal aplasia. A molecular genetic approach was taken to characterize novel circular RNAs from the Fmn gene and to understand the developmental effects of gene-targeted mutations.

MATERIALS AND METHODS

RT-PCR and ribonuclease protection analyses were done to characterize the circular RNA transcripts arising from the Fmn gene. Two lines of mice with gene-targeted deletions of specific Fmn exons, namely exon 4 or exon 5, were generated and analyzed.

RESULTS

In our analysis of formin cDNAs, we discovered a class of transcripts in which the exon order is reversed such that downstream exons are joined to the acceptor end of a specific exon that lies 5' to them in the genome. RT-PCR and ribonuclease protection analyses indicate that these transcripts are circular and are the major transcripts arising from this locus in adult brain and kidney. To gain insight into the biological function of these transcripts, we have systematically deleted the relevant exons using gene-targeted homologous recombination. The resulting mice fail to produce circular transcripts, but appear to produce normal amounts of the linear RNA isoforms from this locus. While these deficient mice have normal limbs, they display variably penetrant renal aplasia characteristic of other mutant formin alleles.

CONCLUSIONS

Our results demonstrate novel circular transcripts arising from the Fmn gene. Moreover, their high levels of expression suggest that they are not products of aberrant splicing events, but instead, may play important biological roles. Mice with gene-targeted deletions of Fmn exons 4 or 5 lack these circular transcripts and have an incompletely penetrant renal agenesis phenotype. While the biologic function of circular Fmn RNA transcripts is not entirely known, our work suggests their possible involvement in kidney development.

Crystal structure of the simian immunodeficiency virus (SIV) gp41 core: conserved helical interactions underlie the broad inhibitory activity of gp41 peptides

The gp41 subunit of the envelope protein complex from human and simian immunodeficiency viruses (HIV and SIV) mediates membrane fusion during viral entry. The crystal structure of the HIV-1 gp41 ectodomain core in its proposed fusion-active state is a six-helix bundle. Here we have reconstituted the core of the SIV gp41 ectodomain with two synthetic peptides called SIV N36 and SIV C34, which form a highly helical trimer of heterodimers. The 2.2 A resolution crystal structure of this SIV N36/C34 complex is very similar to the analogous structure in HIV-1 gp41. In both structures, three N36 helices form a central trimeric coiled coil. Three C34 helices pack in an antiparallel orientation into highly conserved, hydrophobic grooves along the surface of this coiled coil. The conserved nature of the N36-C34 interface suggests that the HIV-1 and SIV peptides are functionally interchangeable. Indeed, a heterotypic complex between HIV-1 N36 and SIV C34 peptides is highly helical and stable. Moreover, as with HIV-1 C34, the SIV C34 peptide is a potent inhibitor of HIV-1 infection. These results identify conserved packing interactions between the N and C helices of gp41 and have implications for the development of C peptide analogs with broad inhibitory activity.

Fluoride release from fissure sealants

This 30-day study, compared the amounts and patterns of fluoride release from 5 commercially available fluoride-containing pit and fissure sealants: FluroShield, Helioseal-F, Ultraseal XT, Baritone L3, and Teethmate-F; Delton without fluoride, was used as control. Disc-shaped samples of each sealant were immersed in distilled water and the fluoride release was measured periodically until day 30. All the fluoridated sealants tested released measurable fluoride throughout the test period in a similar pattern: the greatest amount of fluoride was released in the first 24 hours after mixing, fell sharply on the second day and decreased slowly for the last days. On day one, Baritone L3 released significantly more fluoride than all other materials. Teethmate-F released the highest amount of fluoride during all the other time intervals from day 2, until day 30.

The effect of sprue design on the marginal accuracy of titanium castings

The purpose of this study was to measure the effects of sprue number and position on cast titanium crown margins. Twenty-four complete veneer crown wax patterns were fabricated on a stainless steel die with a 30 degrees bevel finish line. Twelve wax patterns were sprued with one 8-gauge wax sprue and the remaining 12-gauge double sprued. All patterns were invested with a phosphate bonded investment. Castings were made with a titanium casting machine following the manufacturer's instructions and using commercially pure titanium (> 99.5%) ingots. The castings were than carefully cleansed and the margins were examined with indirect impression technique. Data were analysed with an ANOVA and the Student's t-test with confidence level at 95%. The results revealed that the marginal discrepancy for the double sprueing group (32.1 +/- 12.8 microm) has significantly less discrepancy (P < 0.001) than the single sprueing group (49.8 +/- 16.4 microm). There was no statistically significant differences in marginal discrepancy between locations within the sprueing techniques (P > 0.05). An improvement in the degree of casting accuracy of titanium crown was indicated by the double sprue design used in this investigation.

Reconstructing hominid Y evolution: X-homologous block, created by X-Y transposition, was disrupted by Yp inversion through LINE-LINE recombination

The human X and Y chromosomes share many blocks of similar DNA sequence. We conducted mapping and nucleotide sequencing studies of extensive, multi-megabase homologies between Yp and Xq21, which do not recombine during male meiosis. We confirmed and built upon previous evidence that a Yp inversion had occurred during evolution: a single contiguous segment of Xq21 is homologous to two non-contiguous segments of Yp. We precisely defined and sequenced the inversion breakpoints, obtaining evidence that the inversion was mediated by recombination between LINE-1 elements in otherwise non-homologous regions. This inversion appears to have followed a single transposition of an approximately 4 Mb segment from the X to the Y chromosome. These events jointly account for the present arrangement of Yp-Xq21 homologous sequences. Based on Southern blotting studies of primates and of humans drawn from diverse populations, we conclude that both the X-Y transposition and the subsequent, LINE-mediated Yp inversion occurred after the divergence of hominid and chimp lineages but before the radiation of extant human populations. This evolutionary scenario is consistent with our finding of 99.3 +/- 0.2% nucleotide identity between the X and Y chromosomes within the transposed region, which suggests that the transposition occurred approximately 3-4 million years ago, near the time of emergence of Homo . Comparative sequencing of the entire human X and Y chromosomes may reveal a succession of transpositions, inversions and other rearrangements underlying the complex pattern of sequence similarities between the present-day sex chromosomes. With the possible exception of cubitus valgus, phenotypic features of Turner syndrome are absent in individuals monosomic for Yp-Xq21 homologous sequences, suggesting that most of the critical 'Turner genes' are found elsewhere on the X and Y chromosomes.

Anti-growth factor therapy for lung cancer

Lung cancers are the leading cause of cancer death in developed countries. In the USA, lung cancer accounts for 29% of all cancer deaths. The cure rate for lung cancer is low (14%) because the cancer spreads early and because chemotherapy cannot cure metastatic disease. In small cell lung cancer (SCLC) two-thirds of patients present with metastatic disease in a distant organ (stage IV). In non-small cell lung cancers (adenocarcinoma, squamous carcinoma, large cell carcinoma) one-third present with metastatic disease. Initial chemotherapy produces high response rates in both SCLC (85%-90% response rate) and NSCLC (50% response rate) but response duration is short and drug resistance develops rapidly. Growth factors play an important role in the pathogenesis and the progression of lung cancers. Knowledge of the role of these growth factors, their receptors and their signal pathways has produced new therapeutic targets. Compounds developed toward these targets have completed preclinical testing and are now in clinical trials. Some of these compounds are active in both drug sensitive and drug resistant lung cancers. They also produce synergistic growth inhibition when combined with cytotoxic chemotherapeutic agents. Thus, these compounds may provide a new way to overcome drug resistance in lung cancer.

Pituitary-adrenal response in preterm very low birth weight infants after treatment with antenatal corticosteroids

Antenatal corticosteroids have been widely used for the prevention of respiratory distress syndrome in preterm neonates, yet little is known about their effects on the hypothalamic-pituitary-adrenal axis in these infants. We prospectively evaluated pituitary-adrenal function in 61 preterm (< 32 gestational weeks), very low birth weight (< 1500 g) infants on days 7 and 14 of life using the human CRH stimulation test. The baseline and poststimulation plasma ACTH and serum cortisol concentrations did not differ significantly between infants whose mothers received no antenatal corticosteroids, and those whose mothers received 1-2 doses or > 2 doses (mean 7.2 doses) of prenatal dexamethasone (P = > 0.12). The number of doses of dexamethasone and the time intervals between the last dose of drug and delivery did not significantly affect the pituitary-adrenal responsiveness on days 7 and 14 of life. Among infants who did not require mechanical ventilation at the time of the human CRH test, significantly higher plasma ACTH (P < 0.014) and lower serum cortisol concentrations (P < 0.02) were found on day 14 than on day 7. In contrast, none of the poststimulation hormone concentrations were significantly different in ventilated infants between days 7 and 14. The relationship between the blood hormone concentrations in each time epoch (day 7 and day 14) and possible confounding factors including gestational and postconceptional age, birth weight, sex, Apgar scores, mode of delivery, single or higher order births, and mode of ventilation were determined. Plasma ACTH concentrations on day 7 were found to be significantly higher in ventilated than in nonventilated infants (P = 0.006). However, none of the aforementioned factors correlated significantly with plasma ACTH concentrations on day 14. Serum cortisol concentrations on day 7 were significantly higher in infants of greater gestational age (P = 0.039) and birth weight (P = 0.013), with lower Apgar scores at 1 and 5 min (P = 0.021 and P = 0.049, respectively), and in those delivered vaginally (P = 0.047). Similarly, serum cortisol concentrations on day 14 were found to be significantly higher in infants with lower Apgar scores at 1 and 5 min (P = 0.011 and P = 0.014, respectively) and in infants requiring mechanical ventilation (P = 0.014). Our results suggest that single or multiple courses of antenatal dexamethasone have no long-lasting suppressive effects on pituitary-adrenal function in preterm, very low birth weight infants. Maturation of pituitary function appears to be more advanced than adrenal function. The organ's ability to respond appropriately to various stressful stimuli indicates that the pituitary-adrenal axis is highly responsive at these early gestational ages.

A substitute for facial replica in mannequin procedures

The use of mannequin exercises has been a teaching tool in the education of dental students. Various commercially available materials to simulate extraoral facial structure form part of this apparatus, also called a "phantom head." It is not always practical, with cost considerations, to replace this external component when unavoidable wear and tear occurs. An alternative that uses a recycled milk carton is presented as an inexpensive substitute.

Pituitary-adrenal suppression and recovery in preterm very low birth weight infants after dexamethasone treatment for bronchopulmonary dysplasia

High dose dexamethasone is frequently used for the treatment of neonatal respiratory conditions and to facilitate weaning from mechanical ventilation in preterm, very low birth weight infants. However, very little is known about the severity, site, and duration of steroid-induced hypothalamic-pituitary-adrenal axis suppression in this category of patients. Twenty-three preterm, very low birth weight infants who received a full 3-week dose-tapering course of dexamethasone were prospectively studied, with a human CRH stimulation test performed at three different times: before the start of steroid treatment (week 0), immediately after the course (week 3), and 4 weeks after stopping dexamethasone (week 7). Plasma ACTH and serum cortisol concentrations were measured at 0 (baseline), 15, 30, and 60 min. Immediately after the steroid course (week 3), both basal and poststimulation plasma ACTH and serum cortisol concentrations were markedly suppressed. The hormone concentrations at 0, 15, 30, and 60 min in week 3 were significantly lower than their corresponding levels in week 0 (P < 0.0001 for both ACTH and cortisol) and week 7 (P < 0.0001 and P < 0.005 for ACTH and cortisol, respectively). In contrast, when the hormone levels in week 7 were compared to their corresponding concentrations in week 0, only the 60 min serum cortisol concentration in week 7 was significantly lower (P = 0.02). The currently used dosage of dexamethasone caused severe pituitary-adrenal suppression immediately after treatment, but substantial recovery of the endocrine axis was observed 4 weeks after discontinuation of therapy. Although the recovery appeared to be earlier with the pituitary center, both pituitary and adrenal glands were capable of mounting a biochemically adequate response to exogenous human CRH stimulation at this stage. Steroid replacement therapy may be desirable at a time of stress in the immediate posttreatment period, but it would seem unnecessary 1 month after stopping dexamethasone treatment.

The role of a single formin isoform in the limb and renal phenotypes of limb deformity

BACKGROUND

Mutations of the murine limb deformity (ld) locus are responsible for a pleiotropic phenotype of completely penetrant limb malformations and incompletely penetrant renal agenesis and/or dysgenesis. The ld locus encodes a complex family of mRNA and protein isoforms.

MATERIALS AND METHODS

To examine the role of one of the more prominent of these isoforms, isoform IV, we specifically eliminated it by gene targeting.

RESULTS

Unlike other mutant ld mice, homozygous mice bearing this isoform IV disruption display incompletely penetrant renal agenesis, but have perfectly normal limbs. Whole mount in situ hybridization demonstrated that this targeted disruption was specific for isoform IV and did not interfere with the expression of other ld isoforms. The isoform IV-disrupted allele of ld does not complement the renal agenesis phenotype of other ld alleles, in a manner consistent with its penetrance, and like the isoform IV-deficient mice, these compound heterozygotes have normal limbs. Sequence analysis of formin isoform IV in other ld mutant alleles did not detect any amino acid changes relative to the strain of origin of the mutant allele.

CONCLUSIONS

Thus, the disruption of isoform IV is sufficient for the renal agenesis phenotype, but not the limb phenotype of ld mutant mice. Structural mutations in this isoform are only one of several genetic mechanisms leading to the renal phenotype, since amino acid changes in this isoform were not detected. These results demonstrate that this gene is limb deformity, and that variable isoform expression may play a role in generating the pleiotropic ld phenotype.

Potent, long-acting bradykinin antagonists for a wide range of applications

Actions of bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg; BK) are mediated by constitutively expressed B2 receptors (which require the full BK peptide chain) and by B1 receptors (which require BK (1-8) as ligand) that are induced in inflammation. BK has many functions in normal and pathological physiology, including initiation of most, if not all, inflammation. BK also evidently functions as an autocrine stimulant for growth of small cell lung cancer (SCLC). A new group of BK antagonists containing the novel amino acid alpha-(2-indanyl)glycine (Igl) provides both broad-spectrum and selective antagonists for all these functions. As examples, D-Arg-Arg-Pro-Hyp-Gly-Igl-Ser-D-Igl-Oic-Arg (B9430) is an extremely potent and long-acting antagonist of both B1 and B2 receptors, is stable against endogeneous kininase enzymes, and is active in various in vivo models, including by intragastric administration. Acylation of B9430 with dehydroquinuclidine-2-carboxylic acid (Dhq) gives B9562, a highly selective B2 antagonist. In contrast, Lys-Lys-Arg-Pro-Hyp-Gly-Igl-Ser-D-Igl-Oic (B9858) is a highly potent and selective B1 antagonist. The dimer of B9430 linked at the amino terminus with suberimide is a potent selectively cytotoxic agent for SCLC cells. Results with these peptides suggest that a new generation of antiinflammatory and anticancer drugs may be at hand.

Potent, long-acting, orally-active bradykinin antagonists for a wide range of applications

Actions of bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg; BK) are mediated by constitutively expressed B2 receptors, that require the full BK peptide chain, and by B1 receptors, induced in inflammation, that use BK(1-8) as ligand. In addition to many physiological and pathophysiological functions, the growth factor activity of BK evidently allows it to act as an autocrine stimulant for small cell lung cancer. A new group of BK antagonists containing the novel amino acid a-(2-indanyl)glycine provides extremely potent broad-spectrum as well as selective antagonists for all these functions.