Explainable artificial intelligence prediction-based model in laparoscopic liver surgery for segments 7 and 8: an international multicenter study

BACKGROUND

Artificial intelligence (AI) is becoming more useful as a decision-making and outcomes predictor tool. We have developed AI models to predict surgical complexity and the postoperative course in laparoscopic liver surgery for segments 7 and 8.

METHODS

We included patients with lesions located in segments 7 and 8 operated by minimally invasive liver surgery from an international multi-institutional database. We have employed AI models to predict surgical complexity and postoperative outcomes. Furthermore, we have applied SHapley Additive exPlanations (SHAP) to make the AI models interpretable. Finally, we analyzed the surgeries not converted to open versus those converted to open.

RESULTS

Overall, 585 patients and 22 variables were included. Multi-layer Perceptron (MLP) showed the highest performance for predicting surgery complexity and Random Forest (RF) for predicting postoperative outcomes. SHAP detected that MLP and RF gave the highest relevance to the variables "resection type" and "largest tumor size" for predicting surgery complexity and postoperative outcomes. In addition, we explored between surgeries converted to open and non-converted, finding statistically significant differences in the variables "tumor location," "blood loss," "complications," and "operation time."

CONCLUSION

We have observed how the application of SHAP allows us to understand the predictions of AI models in surgical complexity and the postoperative outcomes of laparoscopic liver surgery in segments 7 and 8.

First Measurement of Hard Exclusive π^{-}Δ^{++} Electroproduction Beam-Spin Asymmetries off the Proton

The polarized cross-section ratio σ_{LT^{'}}/σ_{0} from hard exclusive π^{-}Δ^{++} electroproduction off an unpolarized hydrogen target has been extracted based on beam-spin asymmetry measurements using a 10.2  GeV/10.6  GeV incident electron beam and the CLAS12 spectrometer at Jefferson Lab. The study, which provides the first observation of this channel in the deep-inelastic regime, focuses on very forward-pion kinematics in the valence regime, and photon virtualities ranging from 1.5  GeV^{2} up to 7  GeV^{2}. The reaction provides a novel access to the d-quark content of the nucleon and to p→Δ^{++} transition generalized parton distributions. A comparison to existing results for hard exclusive π^{+}n and π^{0}p electroproduction is provided, which shows a clear impact of the excitation mechanism, encoded in transition generalized parton distributions, on the asymmetry.

First CLAS12 Measurement of Deeply Virtual Compton Scattering Beam-Spin Asymmetries in the Extended Valence Region

Deeply virtual Compton scattering (DVCS) allows one to probe generalized parton distributions describing the 3D structure of the nucleon. We report the first measurement of the DVCS beam-spin asymmetry using the CLAS12 spectrometer with a 10.2 and 10.6 GeV electron beam scattering from unpolarized protons. The results greatly extend the Q^{2} and Bjorken-x phase space beyond the existing data in the valence region and provide 1600 new data points measured with unprecedented statistical uncertainty, setting new, tight constraints for future phenomenological studies.

First Measurement of Λ Electroproduction off Nuclei in the Current and Target Fragmentation Regions

We report results of Λ hyperon production in semi-inclusive deep-inelastic scattering off deuterium, carbon, iron, and lead targets obtained with the CLAS detector and the Continuous Electron Beam Accelerator Facility 5.014 GeV electron beam. These results represent the first measurements of the Λ multiplicity ratio and transverse momentum broadening as a function of the energy fraction (z) in the current and target fragmentation regions. The multiplicity ratio exhibits a strong suppression at high z and an enhancement at low z. The measured transverse momentum broadening is an order of magnitude greater than that seen for light mesons. This indicates that the propagating entity interacts very strongly with the nuclear medium, which suggests that propagation of diquark configurations in the nuclear medium takes place at least part of the time, even at high z. The trends of these results are qualitatively described by the Giessen Boltzmann-Uehling-Uhlenbeck transport model, particularly for the multiplicity ratios. These observations will potentially open a new era of studies of the structure of the nucleon as well as of strange baryons.

Observation of Correlations between Spin and Transverse Momenta in Back-to-Back Dihadron Production at CLAS12

We report the first measurements of deep inelastic scattering spin-dependent azimuthal asymmetries in back-to-back dihadron electroproduction in the deep inelastic scattering process. In this reaction, two hadrons are produced in opposite hemispheres along the z axis in the virtual photon-target nucleon center-of-mass frame, with the first hadron produced in the current-fragmentation region and the second in the target-fragmentation region. The data were taken with longitudinally polarized electron beams of 10.2 and 10.6 GeV incident on an unpolarized liquid-hydrogen target using the CLAS12 spectrometer at Jefferson Lab. Observed nonzero sinΔϕ modulations in ep→e^{'}pπ^{+}X events, where Δϕ is the difference of the azimuthal angles of the proton and pion in the virtual photon and target nucleon center-of-mass frame, indicate that correlations between the spin and transverse momenta of hadrons produced in the target- and current-fragmentation regions may be significant. The measured beam-spin asymmetries provide a first access in dihadron production to a previously unexplored leading-twist spin- and transverse-momentum-dependent fracture function. The fracture functions describe the hadronization of the target remnant after the hard scattering of a virtual photon off a quark in the target particle and provide a new avenue for studying nucleonic structure and hadronization.

Observation of Azimuth-Dependent Suppression of Hadron Pairs in Electron Scattering off Nuclei

We present the first measurement of dihadron angular correlations in electron-nucleus scattering. The data were taken with the CLAS detector and a 5.0 GeV electron beam incident on deuterium, carbon, iron, and lead targets. Relative to deuterium, the nuclear yields of charged-pion pairs show a strong suppression for azimuthally opposite pairs, no suppression for azimuthally nearby pairs, and an enhancement of pairs with large invariant mass. These effects grow with increased nuclear size. The data are qualitatively described by the gibuu model, which suggests that hadrons form near the nuclear surface and undergo multiple scattering in nuclei.These results show that angular correlation studies can open a new way to elucidate how hadrons form and interact inside nuclei.

Smile analysis and face-bow transfer: enhancing aesthetic restorative treatment

The objective of current aesthetic dental treatments are to enhance the patient's smile by improving the overall dental appearance. A detailed analysis of the patient's face as it relates to the three-dimensional position, shape, and color of the teeth is required to improve this appearance. A full frontal and lateral evaluation of the patient's facial form is required to successfully complete on aesthetic smile evaluation. Additional considerations include cephalometry and a thorough dental analysis. This article demonstrates a comprehensive smile analysis technique and its communication to the dental technician.

Anterior implant-supported reconstructions: a prosthetic challenge

Recent investigations have demonstrated that the successful utilization of anterior implant-supported restorations in the maxilla is dependent upon the satisfaction of numerous surgical and prosthodontic criteria. Conservative treatment alternatives that use a provisionalization phase can provide clinical benefits for patients with partial edentulism by guiding tissue maturation following completion of a meticulous surgical procedure. This article demonstrates a series of prosthetic considerations that guide contemporary aesthetic restorations, and highlights the underlying surgical factors related to this treatment.

Anterior implant-supported reconstructions: a surgical challenge

Reconstructive procedures are able to provide improved aesthetics for implant patients who present with anatomical limitations (e.g., vertical or horizontal tissue loss) in the anterior maxilla. Aesthetic results, however, are directly related to the ability of the treatment team to reconstruct the lost bone and soft tissue, place the implant into its proper tridimensional position in the patient's arch, and use precise restorative techniques. This article presents comprehensive treatment steps for the utilization of single-unit and multiple-unit implant-supported restorations in the anterior maxilla.

Nanoleakage at the dentin adhesive interface vs microtensile bond strength

Excessive etching of the dentin may decrease bond strength because the adhesive may fail to completely infiltrate to the base of the over-etched demineralized collagen network. The purpose of the present study was to evaluate the influence of increasing etching times on the microtensile bond strength of Single Bond and the leakage of silver ions within the hybrid layer. After etching occlusal dentin for 15, 30, or 60 seconds with 35% phosphoric acid gel, Single Bond was applied and cured for 10 seconds. Z100 was added and cured for 60 seconds. After 24 hours of water immersion, the teeth were sectioned into slices 0.7 mm thick, and hour-glass-shaped specimens were prepared. Alternate slices were either dried for 30 minutes in air, kept wet, or they were coated with fingernail varnish except for 0.5 mm around the bonded area. Only the varnished samples were then stained with 50% AgNO3. Microtensile bond strength was tested using a Vitrodyne V-1000 universal tester. The samples of the stained group were embedded in self-curing PMMA and polished. All samples were observed with an SEM. Nanoleakage of silver ions was measured by exposure to laser ablation with an inductively connected plasma mass spectrometer and by electron dispersive elemental analysis. Increasing etching times seemed to have a negligible effect on bond strength of Single Bond, producing an average value of ca 38 MPa. However, the silver uptake increased upon prolonged etching times. Short-term results suggest that overetching has no detrimental effect on bond strength values of Single Bond. However, increased silver uptake, depending on the etching time, raises concern about the long-term stability of the bond.

Effect of water content on the physical properties of model dentine primer and bonding resins

OBJECTIVE

Primers and adhesives containing hydroxyethyl methacrylate (HEMA) are placed on moist dentine even though several studies indicate that water may interfere with the polymerization reaction. The purpose of this study was to evaluate the influence of increasing amounts of water on the physical properties of a model dentine primer resin (HEMA) and model dentine bonding resin (a mixture of HEMA and Bis-GMA).

METHODS

Miniature (ca 10 x 0.5 mm (long x thick) hour-glass shaped and parallel-sided specimens were created by casting the monomer or comonomer mixtures into appropriately shaped moulds. The water content was either 0, 5, 9, 17 or 29 vol%. One hour after polymerization, half the specimens were subjected to physical testing under dry conditions. The other half were immersed in water for 24 h and then tested while wet. The ultimate tensile strength (UTS), modulus of elasticity (E), percent elongation at failure, and toughness were calculated.

RESULTS

The properties of the dry-stored primer and bonding resins were not altered by water incorporation up to 9 vol%. Higher water content lowered the physical properties (P < 0.05). Immersion of primers polymers in water for 24 h significantly decreased their properties. Water immersion of the bonding resins was unaffected only for specimens containing 0 or 5 vol% water.

CONCLUSIONS

The plasticizing effects of extrinsic water are far more important than the effects of intrinsic water in poly-HEMA resin. Hybrid layers composed primarily of poly-HEMA would be expected to be more elastic than those made with bifunctional, cross-linked polymer chains.

Perfusing dentine with horse serum or physiologic saline: its effect on adhesion of dentine bonding agents

Freshly prepared dentine specimens of human teeth were perfused with either horse serum or physiologic saline. After application of AllBond2, ART Bond, Syntac or an experimental dentine bonding agent called P-Bond, a composite cylinder was added and cured at the same time. After 1500 thermal cycles with constant imitation of intrapulpal pressure, the shear bond strengths were measured. Resulting shear bond strength values were analysed with Students t-test or Mann-Whitney Test. The values for AllBond2 were not significantly different. The values for ART Bond (P < 0.05) and for Syntac (P < 0.05) were significantly higher if the dentine was perfused with horse serum. For P-Bond (P < 0.001) the values were significantly higher if the dentine was perfused with physiologic saline. According to these results it does not seem to be appropriate to take a clear decision as to which of the two perfusing media investigated might be more suitable to imitate in vivo conditions.

Evaluation of the interface between one-bottle bonding agents and dentin by cryopreparation and low-temperature scanning electron microscopy (LTSEM). A pilot study on perfused dentinal samples

OBJECTIVES

Dentin bonding samples are generally observed in the high vacuum chamber of an electron microscope only after completion of the bonding procedure fixation, dehydration and drying of the specimens. The purpose of this study was to observe the effect of each step in the application of various one-bottle dentin bonding agents (DBA) using cryopreparation followed by low-temperature scanning electron microscopy (LTSEM).

METHODS

Prime&Bond 2.1 (P&B 2.1), Coltène Experimental (Exp.) and Syntac Single Component (Syntac SC) were applied onto perfused dentin of extracted, human third permanent molar teeth. After acid-etching, rinsing and drying, and following the application of the respective resins, the teeth were fractured at random and plunge-frozen in liquid nitrogen before examination under LTSEM. As this method preserves the state of the treated surface at the moment when it is frozen, each step of the application of the DBA can be observed as if it were a 'real-time' procedure.

RESULTS

Acid-etching the dentin resulted in the removal of the smear layer for all materials tested. Those one-bottle DBAs which recommend the application of two consecutive resin layers (P&B 2.1 and Syntac SC) showed incomplete saturation of the dentinal surface after application of the first layer. With Syntac SC the incomplete saturation was more pronounced than with P&B 2.1. The use of Exp. resulted in a much more homogeneous coverage of the dentin despite only one layer of resin having been applied.

CONCLUSION

It is concluded that cryo-preparation followed by LTSEM appears to be a method which allows each stage of the application of DBA to be evaluated.

Aesthetic evolution of anterior maxillary crowns: a literature review

The aesthetics of anterior maxillary restorations and health of the surrounding tissues are primary determinants of the successful outcome of a clinical procedure. Various restorative materials and application techniques have been developed to achieve optimal aesthetics. While early porcelain-fused-to-metal restorations exhibited metal margins, the development of shoulder porcelain margins in the 1980s resulted in a significant aesthetic improvement. Only in the 1990s, however, did all-porcelain restorations finally achieve the strength and complete range of optical characteristics exhibited by the natural dentition.

The dual bonding technique: a modified method to improve adhesive luting procedures

Indirect restorative procedures usually require temporary restorations for protection of the pulp and for restoring the patients esthetic and functional needs. The use of temporary cements, either with or without eugenol, however, considerably decreases the adhesion of the bond on dentin if--according to the conventional technique--such dentin bonding systems are applied once at the moment of final cementation. With a dual application of the dentin bonding agents a considerable increase in bond strength values was discovered. This article presents a modified luting procedure called the "dual bonding technique."

Film thickness of various dentine bonding agents

Curing dentine bonding agents create a film thickness on the surface of teeth which are prepared for all-ceramic crowns. The aim of this study was to investigate if the film thickness of dentine bonding agents (DBAs) is acceptable with the fit of definitive restorations of 50-100 microm. AllBond 2, Syntac, ART Bond, P-Bond (an experimental DBA), and the Primer of AllBond 2 were applied onto teeth which were prepared with standardized all-ceramic crown preparations. The DBAs were applied onto the prepared tooth surfaces according to manufacturers' instructions and under a standardized simulation of intrapulpal pressure. After curing the DBAs, the teeth were cut mesiodistally and orolingually and the film thickness was measured under a light microscope. Only the film thicknesses of AllBond 2 and P-Bond were low enough and, therefore, would enable curing to take place immediately after their application.

Post and core reconstruction for fixed prosthodontic restoration

If the previous restorative therapy or dental caries has resulted in substantial loss of tooth structure, the abutment teeth for fixed prosthodontic restorations require a core reconstruction or a post and core. Small dentin defects can be restored with bonded cores; more extensive dentin defects that are often accompanied by previous endodontic treatment generally require additional support for the core material. A direct procedure with a bonded post is a viable treatment method. The decision to use either light-conducting all-ceramic zirconium or titanium as a post material depends on the aesthetic requirements present. The indications for a cast post and core as an indirect procedure for prosthodontic reconstructions appear to be decreasing. The learning objective of this article is to review the past and current post and core materials and techniques. Indications for core reconstruction with vital teeth and posts and cores for pulpless teeth are discussed.

Effect of cleaning dentine with soap and pumice on shear bond strength of dentine-bonding agents

This in vitro study reports on the cleaning effect of different soaps on the shear bond strength of various dentine-bonding agents. Human teeth were coated with provisional cements for 24 h or for 14 days. After removing the provisional cements with a scaler, the dentinal surface was cleaned with a cotton pellet and non-fluoridated flour of pumice and soap for 10 sec. Different dentine-bonding agents and a luting resin were bonded to the dentinal surface according to manufacturers' instructions with the bonding agent and the composite material being light-cured at the same time. The bonding agents were tested under intrapulpal pressure and with thermal cycling to imitate physiological conditions. Compared with cleaning the dentine with water and pumice, all soaps investigated in this study decreased the shear bond strength values of the tested dentine-bonding agents considerably.

Bond strength of one-bottle dentin bonding agents on human dentin

PURPOSE

To evaluate the shear bond strength of one-bottle dentin bonding agents (DBA's) (Prime & Bond 2.1, ART Experimental, Syntac Single Component) on pressurized human dentin.

MATERIALS AND METHODS

Freshly prepared dentin specimens of human teeth were perfused with horse serum which was diluted 1:5 in physiologic saline. Three different types of surface treatment were evaluated on the freshly prepared dentin. Group 1: One of the three one-bottle DBA's was applied onto freshly prepared dentin together with a cylinder of composite luting resin and cured. Group 2: A provisional cement (Freegenol, without eugenol, or Temp Bond, containing eugenol) was applied first on the dentin surface for 24 h. Only then was one of the three the one-bottle DBA's added onto the dentin together with a cylinder of composite luting resin after cleaning the dentin surface with pumice. Group 3: One of the three one-bottle DBA's was applied first on the dentin surface and light-cured. Then a provisional cement (Freegenol, without eugenol, or Temp Bond, containing eugenol) was added for 24 h. After cleaning with pumice, the respective one-bottle DBA was applied for a second time onto the dentin together with a cylinder of composite luting resin and light-cured. As control for Group 1 (freshly prepared dentin), the two- or three-step DBA's ART Bond and Syntac were used in a similar way. As control for Group 2 (single application of the DBA's after contamination of the dentin with a provisional cement) and Group 3 (dual application of the DBA's with intermediate contamination of the dentin with a provisional cement) the two-step DBA ART Bond was used. After 1500 thermal cycles with constant imitation of intrapulpal pressure, shear bond strengths were measured. Resulting shear bond strength values were displayed by means of a box plot and they were analyzed statistically by Student's t-Test or one-way ANOVA.

RESULTS

Lowest and highest mean shear bond strength values were 0.26 +/- 0.47 MPa (single use of ART Bond with prior application of Temp Bond) and 16.34 +/- 5.02 MPa (dual use of ART Bond with intermediate application of Temp Bond). With respect to the surface treatment significant differences between the DBA's could be found in all groups.

Dentin bond strength of Dyract Cem

PURPOSE

To evaluate the influence of provisional cements and of a dentin bonding agent on the adhesion of a self-curing polyacid-modified resin composite (Dyract Cem) on pressurized human dentin.

MATERIALS AND METHODS

Freshly prepared dentin specimens of human teeth were perfused with physiologic saline. Three different types of surface treatment were evaluated. (1) Dyract Cem was applied to freshly prepared dentin without (Group 1.1) or with (Group 1.2) the respective dentin bonding agent (Prime & Bond 2.0) and cured. (2) Freegenol (Groups 2.1 and 2.2) or Temp Bond (Groups 2.3 and 2.4) were applied first on the dentin surface for 24 hours. Only then was Dyract Cem (with or without Prime & Bond 2.0) added onto the dentin after cleaning the dentin surface with pumice. 3) Prime & Bond 2.0 was applied first on the dentin surface and cured. Then Freegenol (Group 3.1) or Temp Bond (Group 3.2) were added for 24 hours. After cleaning with pumice, Prime & Bond 2.0 was applied for a second time on the dentin (= dual application) and finally Dyract Cem was added. As control, a conventional glass ionomer cement (Ketac-Cem Maxicap; Groups 4.1-4.3) was used in a similar way. After 1,500 thermal cycles with constant imitation of intrapulpal pressure, shear bond strengths were measured. Resulting shear bond strength values were displayed by means of a box plot and they were analyzed statistically by Mann-Whitney, Kruskal-Wallis or one way ANOVA tests.

RESULTS

Lowest and highest mean shear bond strength values were 0.27 +/- 0.42 MPa (Group 2.4; single use of Prime & Bond 2.0 with prior application of TempBond) and 5.84 +/- 3.36 MPa (Group 3.1; dual use of Prime & Bond 2.0 with intermediate application of Freegenol). A clearly significant difference between groups could only be found when a single or dual use of the dentin bonding agent Prime & Bond 2.0 were combined with either Freegenol (Groups 2.1, 2.2 and 3.1; Kruskal-Wallis: P < 0.01) or Temp Bond (Groups 2.3, 2.4 and 3.2; Kruskal-Wallis: P < 0.001) as additional dentin surface treatment.

Effect of provisional cements on the bond strength of various adhesive bonding systems on dentine

Temporization of prepared teeth is needed for protection of the pulp and the restoration of the patients' aesthetic and functional needs. When zinc-oxyphosphate cement is used, eugenol-containing provisional cements are preferred because of their sedative effect to the pulp and because of their acceptable compressive strength. However, prior to definitive adhesive cementation with composite luting resins and dentine bonding agents the use of eugenol-containing provisional cements has to be considered critical because eugenol severely disturbs the polymerization of resinous materials. The purpose of this study was to compare shear bond strength values of various adhesive luting systems on dentine which had been in contact with various provisional cements prior to dentine bonding. The results show that the provisional cements which were used considerably decreased some of the bond strength values of the dentine bonding systems tested. Freegenol and Fermit, however, seem to have beneficial effects on the SBS values of Syntac and ART Bond. The only bonding system which produces acceptably high average SBS values with a eugenol-containing provisional cement was P-Bond.

Dual application of dentin bonding agents: effect on bond strength

PURPOSE

To evaluate the effect of a dual application of dentin bonding agents (DBA) on their shear bond strength on dentin with intermediate application of a provisional cement.

MATERIALS AND METHODS

Freshly prepared flat dentin surfaces of human teeth were coated with a first layer of one of various dentin bonding agents (All-Bond 2, ART Bond, Syntac or an experimental DBA called P-Bond). After curing the DBA, a provisional cement (Temp Bond, Freegenol or Fermit, a soft provisional diacrylate) was applied to the bonded dentin surface. After 24 hours, the provisional cement was removed and the dentin surface scrubbed with pumice. A second application of the same DBA together with a composite cylinder followed. After curing and 1,500 thermal cycles with constant imitation of intrapulpal pressure, shear bond strengths were measured.

RESULTS

Compared to a single application of dentin bonding agents following Temp Bond treatment (SBS in MPa: Syntac: 0.86 +/- 1.75, ART Bond: 0.26 +/- 0.47, P-Bond: 14.90 +/- 4.51) application of DBAs prior to use of Temp Bond as well as after its removal seems to be very beneficial to shear bond strength values (SBS in MPa: Syntac:13.36 +/- 4.70, ART Bond: 16.34 +/- 5.02, P-Bond: 19.04 +/- 2.01). Independent from the provisional cement, the values after serial application of P-Bond provided consistently high bond values which were not statistically different (Kruskal-Wallis, P > 0.05) from values of P-Bond on fresh dentin (18.19 +/- 2.29 MPa). The only exception from these findings in the present study was All-Bond 2. Regardless of the provisional materials used, the bond strength values of All-Bond 2 remained low (maximum SBS with Fermit as intermediate provisional cement: 4.63 +/- 2.91 MPa).

Light transmission of composite luting resins

The final color of all-ceramic restorations is dependent on the surrounding structures and on the ceramic itself. The degree that the layer of the composite luting agent contributes to this final color formation can only be estimated. Based on general optical physics, this paper reports on transmissivity of some commercially available composite luting resins and discusses how these theoretical results apply to clinical situations.

The new In-Ceram Spinell system--a case report

The final color of all-ceramic restorations is mainly dependent on the light-transmission characteristics of the different components of the ceramic material. This article is a report on the improvement in light reflection and light transmission possible with the new In-Ceram Spinell crown system, which provides a natural-looking appearance.

Factors in dentin bonding. Part 1: A review of the morphology and physiology of human dentin

Dentin bonding has been the object of intensive research for many years. If a substance is expected to bond to a natural tooth surface, the morphologic and physiologic characteristics of the substrate determine both the bonding applications and testing methods used.

Gonadal steroids effect similar regulation of gonadotrophin subunit mRNA expression in both male and female rats

Gonadal steroids can act both indirectly via gonadotrophin-releasing hormone (GnRH) and directly on the pituitary to regulate gonadotrophin subunit gene expression. Recent studies to assess a possible direct action at the pituitary have shown that testosterone, when given to males in the absence of endogenous GnRH action, selectively increases FSH-beta mRNA concentrations. Conversely, in females, oestradiol appears to regulate gonadotrophin subunit mRNAs primarily via GnRH. The present study was designed to determine whether these differing results reflect specific actions of the gonadal steroids themselves or different responses of the pituitary gonadotroph cells in males and females. Rats which had been castrated 7 days earlier were given silicone elastomer implants (s.c.) containing oestradiol (plasma oestradiol 68 +/- 4 ng/l) in males or testosterone (plasma testosterone 3.5 +/- 0.3 micrograms/l) in females in the absence or presence of a GnRH antagonist. Seven days later pituitaries were removed and steady-state mRNA concentrations measured by dot-blot hybridization. In males, oestradiol reduced LH-beta and FSH-beta but not alpha mRNA. The antagonist reduced levels of all three subunit mRNAs in males and the addition of oestradiol had no further effect, suggesting that oestradiol regulates gonadotrophin subunit gene expression in males by suppressing GnRH secretion. In females, testosterone reduced all three subunit mRNAs though FSH-beta remained threefold higher than in intact animals. The GnRH antagonist was as effective as testosterone alone and reduced alpha and LH-beta to levels found in intact animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Gonadotropin-releasing hormone pulses: regulators of gonadotropin synthesis and ovulatory cycles

The data reviewed present evidence that the pattern of GnRH secretion is an important factor in the regulation of gonadotropin subunit gene expression, gonadotropin synthesis, and secretion. The information on regulation of mRNA expression by GnRH pulses should be considered with some caution, as the experiments were performed in male rats and may not accurately reflect events in female primates or humans. However, an overall pattern emerges which suggests that common factors may be involved in all mammalian species. If current evidence is correct, and only a single gonadotropin-releasing hormone exists, then mechanisms to differentially regulate the three gonadotropin genes may involve changes in GnRH secretion. Alterations in GnRH pulse frequency and amplitude are recognized by the pituitary gonadotrope cell and could be the mechanism used to effect differential expression of the gonadotropin subunit genes. Differential regulation of subunit gene expression would be expected to be critically important in the establishment of pubertal maturation, and subsequently in the maintenance of ovulatory cycles in women. Our hypotheses, proposing a major role of pulsatile GnRH secretion in the regulation of human reproduction, are summarized in schematic form in Fig. 14 for men and Fig. 15 for women. In utero and during the first few months of life, GnRH is secreted at a relatively fast frequency (approximately 1 pulse/hour). During the first year, GnRH secretion is inhibited and both the amplitude and apparent frequency of pulsatile release is markedly reduced. The mechanisms involved in inhibiting GnRH release remain unclear in humans. Similarly, the mechanisms involved in the disinhibition of GnRH secretion, which first occurs during sleep at the initiation of puberty, are unclear, but in humans do not appear to involve opiates. In males, the increased frequency and amplitude of GnRH secretion favor LH synthesis and release, which in turn stimulates testosterone secretion (Fig. 14). Testosterone acts at the hypothalamus, perhaps through opioid mechanisms, to inhibit GnRH pulse frequency and to maintain a regular pattern of pulses occurring approximately every 90-110 min in adult males. In females, the mechanisms involving alterations in the patterns of GnRH secretion to regulate reproduction appear more complex. This may reflect the need to differentially synthesize and secrete FSH and LH at different times during reproductive cycles to allow orderly follicular maturation and ovulation. As shown in Fig. 15, we hypothesize that the events during the first decade of life and through the initiation of nocturnal GnRH secretion at puberty are similar in both sexes.(ABSTRACT TRUNCATED AT 400 WORDS)

Gonadotropin subunit messenger RNA concentrations after blockade of gonadotropin-releasing hormone action: testosterone selectively increases follicle-stimulating hormone beta-subunit messenger RNA by posttranscriptional mechanisms

Regulation of gonadotropin gene expression by sex steroids may occur via direct effects on the pituitary and/or indirect effects of steroids mediated through hypothalamic GnRH. We aimed to define the effects of testosterone (T) on alpha, LH beta, and FSH beta mRNA expression in the male rat after blockade of GnRH action on the gonadotrope. A water-soluble GnRH antagonist was administered iv to castrate male rats (increased endogenous GnRH secretion) and to castrate T-replaced rats in which gonadotropin subunit mRNAs had been increased by prior treatment with exogenous GnRH pulses. In castrate male rats, GnRH antagonist resulted in a fall in all three subunit mRNAs. Alpha and LH beta declined at slower rates (half-disappearance after 50 and 65 h, respectively), and neither fell to values present in intact rats over 84 h. In contrast, FSH beta mRNA declined more rapidly, with a half-disappearance after 20 h. In castrate T-replaced rats, alpha mRNA declined at a rate similar to that in castrates (half-disappearance after 50 h). LH beta declined more slowly, and the rate of FSH beta decline was markedly prolonged in the presence of T (half-disappearance time increased from 20 to 50 h). These results suggest that T exerts direct effects on FSH beta transcription or mRNA stability which are independent of GnRH action. To assess these possibilities, a long-acting GnRH antagonist (Detirelix) was administered to castrate male rats, which also received T or sham implants 4 days after castration. FSH beta mRNA levels fell during the 4 days of Detirelix alone, but the addition of T on day 4 resulted in a 2-fold rise in FSH beta mRNA, restoring FSH beta mRNA to levels present in intact rats. Serum FSH closely paralleled FSH beta mRNA concentrations. Alpha mRNA was reduced by 25%, and LH beta mRNA concentrations were unchanged in the presence of T. The rate of alpha mRNA transcription was markedly reduced and that of LH beta tended to fall in T-treated rats, but T had no significant effect on the FSH beta transcription rate. Thus, the action of T to increase concentrations of cytosolic FSH beta mRNA appears to be exerted at a posttranscriptional level, possibly via effects of T on FSH beta mRNA stability. This may represent a mechanism by which T can effect differential regulation of gonadotropin subunit mRNA concentrations.

Differential regulation of gonadotropin subunit gene expression by gonadotropin-releasing hormone pulse amplitude in female rats

The role of GnRH in regulating gonadotropin subunit gene expression was examined in adult female rats. Animals were ovariectomized, estradiol implants inserted sc, and jugular cannulae placed into the right atria. On the next day, animals were given GnRH pulses (saline to controls) every 30 min for up to 48 h and alpha, LH beta, and FSH beta mRNA levels measured by hybridization to cDNA probes. To determine the effects of GnRH treatment duration, rats received GnRH pulses (25 ng at 30-min intervals) for 6, 12, 24, and 48 h. FSH beta mRNA was increased (by 92%) after 6 h of pulses and remained elevated through 48 h. alpha mRNA was not increased until 12 h (27% increase) and rose further (57%) by 48 h. LH beta mRNA levels were only transiently increased at 12 h (67%) and values were not different from saline controls after 24 or 48 h. To examine whether the rise in serum PRL which is characteristic of the ovariectomized-estradiol animal model was responsible for the decrease in LH beta mRNA responsiveness to GnRH over longer durations, studies were repeated in bromocriptine-treated animals (0.6 mg sc, twice daily). The results showed similar response patterns for all three subunit mRNAs including the decrease in LH beta after 48 h. A third experiment examined the effect of varying GnRH pulse amplitude (0.5-250 ng/pulse at 30-min intervals) over 12 h. alpha mRNA levels were increased by all GnRH doses greater than 5 ng with maximum responses after 250 ng pulses. LH and FSH beta mRNAs were both elevated by GnRH pulse doses of 0.5-25 ng (P less than 0.05 vs. saline controls). Maximal increases (2-fold) were seen after 5 ng pulses for LH beta and after 15-ng pulses for FSH beta mRNA. These results show that pulsatile GnRH increases FSH beta mRNA more rapidly than alpha or LH beta mRNAs in female rats. In addition, high amplitude GnRH pulses increase only alpha mRNA, whereas both LH beta and FSH beta mRNAs show maximum responses to lower doses. The data suggest that alterations in the amplitude of the GnRH pulsatile signal can exert differential effects on gonadotropin gene expression.

Thyrotoxicosis caused by thyroid cancer

Well-differentiated follicular carcinoma causing thyrotoxicosis is a rare entity. The age and sex distribution is no different from that of other patients with follicular carcinoma, with 87% older than the age of 40 and a female:male ratio of 3:1. The clinical presentation is similar to that of Graves' patients except that evidence of metastatic disease is often present (soft tissue masses, bone pain). The metastases are in the usual locations (bone, lung, mediastinum) and are often bulky. Despite the poor efficiency of iodine uptake and thyroid hormone production, the large tumor mass is capable of producing excessive hormone. Laboratory data confirm the hyperthyroid state, but the occurrence of T3 elevations with normal T4 levels is common, and T3 toxicosis may be missed if only T4 levels are measured. The role of thyroid stimulating immunoglobulins is still evolving, but such stimulators may support the growth of metastatic thyroid carcinoma and promote the development of hyperthyroidism. The treatment of these patients varied. Most had thyroidectomy followed by 131I therapy. Dosimetry allows for the administration of the largest dose of 131I with acceptable side effects. A good response to radioiodine predicted a more favorable outcome. The survival of patients with metastatic thyroid carcinoma causing hyperthyroidism does not differ from euthyroid patients with metastatic follicular disease (10-year survival, 59%).

Gonadotrophin-releasing hormone regulation of gonadotrophin subunit gene expression: studies in tri-iodothyronine-suppressed rats

We have previously shown that a pulsatile gonadotrophin-releasing hormone (GnRH) stimulus can increase steady-state levels of alpha and LH-beta subunit mRNAs in the male rat pituitary. Since alpha subunit is produced in both thyrotroph and gonadotroph cells, the effect of GnRH specifically on gonadotroph alpha gene expression is uncertain. To address this tissue, adult male rats were given injections of tri-iodothyronine (T3; 20 micrograms/100 g body wt, i.p.) daily for 8 days (day 8 = day of death) in order to decrease thyrotroph alpha mRNA levels (+T3 group). Saline injections (i.p.) were given to control animals (-T3group). Three days before GnRH administration, the animals were castrated and testosterone implants inserted s.c., to inhibit endogenous GnRH secretion. GnRH pulses (25 ng/pulse; 30-min interval) were given to freely moving animals (saline pulses to controls) via an atrial cannula for 12,24 or 48 h. Serum LH and FSH were measured before and 20 min after the last GnRH pulse. Pituitary RNA was extracted and alpha, LH-beta, FSH-beta and prolactin mRNA levels were determined by dotblot hybridization using 32P-labelled cDNA probes. Castration and testosterone replacement reduced alpha and LH-beta mRNA levels by 30 and 40% respectively, compared with levels in untreated intact males, but did not decrease FSH-beta concentrations. T3 administration further decreased alpha mRNA to 30% of values seen in intact males, but LH-beta mRNA levels were unchanged. FSH-beta mRNA concentrations were decreased by 23% in T3-treated rats (P less than 0.05 vs intact controls).(ABSTRACT TRUNCATED AT 250 WORDS)

Dose response effects of pulsatile GnRH administration on restoration of pituitary GnRH receptors and pulsatile LH secretion during lactation

Ovariectomized (OVX) rats suckling 8 pups have a complete suppression of pulsatile LH secretion and a decrease in pituitary GnRH receptor (GnRH-R) content. Removing the suckling stimulus for 24 h results in a sharp increase in GnRH-R and a restoration of pulsatile LH secretion. These findings suggest that the suckling stimulus induces a suppression of GnRH secretion, and removal of the suckling stimulus permits the restoration of GnRH secretion. Indeed, if GnRH antiserum is injected at the time of pup removal, the restoration of pituitary GnRH-R and LH secretion is prevented. The present studies were designed to test our hypothesis that the deficits in pituitary gonadotroph function observed during lactation are due to suckling-induced suppression of GnRH. Exogenous GnRH was administered in a pulsatile regimen to OVX lactating rats on days 10 and 11 postpartum, and the effects on pituitary GnRH-R levels, pituitary sensitivity to GnRH, and pulsatile LH secretion were assessed. GnRH doses of 0, 0.5, 2.0 or 5.0 ng/pulse were administered every 50 min for 24 h beginning on day 10. Administration of 0.5 ng GnRH/pulse for 24 h increased GnRH-R from 35 +/- 3 to 63 +/- 8 fmol/pituitary. There was a clear GnRH dose-related upregulation of GnRH-R to approach nonsuckling levels (140-160 fmol/pituitary) with the 5 ng GnRH dose. At the beginning of GnRH administration, the pituitary was very unresponsive to GnRH. Consistent LH pulses were only observed with 5 ng GnRH/pulse.(ABSTRACT TRUNCATED AT 250 WORDS)

Management of massive air embolism during open heart surgery

Two patients in whom a massive bolus of air was introduced into the arterial circuit and ascending aorta during valve replacement and in whom the recovery was complete are presented. The technical details of the management of this serious accident are described.