The significance of low first trimester serum progesterone in ongoing early pregnancies presenting as pregnancies of unknown location.

OBJECTIVES: The primary objective of this study was to ascertain whether there is association between low initial serum progesterone, sonographic parameters and clinical outcomes in women presenting with pregnancies of unknown location (PUL), which are found to be ongoing at their follow up scans in the first trimester. STUDY DESIGN: This was a non-interventional retrospective cohort study of 1056 patients spanning a 14-year period, conducted in the Early Pregnancy Unit (EPU) of an inner-city teaching hospital. Patients who had an ongoing singleton first trimester pregnancy after presenting with PUL were identified and categorised as having low progesterone if it was 32 nmol/l or lower. The crown-rump length (CRL), mean gestational sac diameter (MGSD) and gestational sac volume (GSV) were measured when the embryo was first seen, and the pregnancy outcome recorded. RESULTS: Pregnancies with low progesterone tended to have smaller gestational sacs (GS) on follow up scan (p = 0.001) and the sac was smaller than expected for a given CRL (p = 0.000). There was no ultrasound parameter that was characteristic of low progesterone. The observation of a smaller than expected MGSD for a given CRL remained even when only pregnancies with normal outcomes were analysed. Clinical outcome data were available for 854 (80.9 %) women. Overall, 81.4 % (n = 34/43) of pregnancies with low progesterone resulted in livebirth, compared to 91.7 % (n = 744/811) livebirths in pregnancies with higher levels (p = 0.0454). CONCLUSION: Pregnancies with low progesterone tend to have a smaller GS compared to those with a higher progesterone, and the GSs are smaller than expected for a given CRL. The current study shows that women with low progesterone at the start of pregnancy remain at higher risk of miscarriage, even when the pregnancy is initially found to be viable in the first trimester. These pregnancies also tend to be associated with the sonographic finding of a smaller GS than expected for a given gestational age, regardless of eventual outcome.

Detection of breastfeeding and weaning in modern human infants with carbon and nitrogen stable isotope ratios.

Carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) stable isotope ratios were longitudinally measured in fingernail and hair samples from mother-infant pairs where infants were exclusively breastfed (n = 5), breast- and formula-fed (n = 2), or exclusively formula-fed (n = 1) from birth. All exclusively breastfed infants had a dual enrichment in carbon ( approximately 1 per thousand) and nitrogen ( approximately 2-3 per thousand) when compared to maternal values. In contrast, breast- and formula-fed subjects had reduced enrichments compared to exclusively breastfed subjects, and the exclusively formula-fed infant showed no increase in delta(13)C or delta(15)N values. This finding of a carbon trophic level effect in breastfeeding infants suggests that (13)C-enrichments of approximately 1 per thousand in archaeological populations are not necessarily the result of the consumption of C(4)-based weaning foods such as maize or millet. During the weaning process, the delta(13)C results for breastfed infants declined to maternal levels more rapidly than the delta(15)N results. This suggests that delta(13)C values have the potential to track the introduction of solid foods into the diet, whereas delta(15)N values monitor the length of time of breast milk consumption. These findings can be used to refine the isotopic analysis of breastfeeding and weaning patterns in past and modern populations.

Cuspal deformation and fracture resistance of teeth with dentin adhesives and composites.

This study investigated the effect of polymerization shrinkage of posterior composite (Herculite) on the dimensions and fracture strength of human maxillary premolars with a phosphonate-ester DBA (Bondlite) and a second DBA comprised of 4-META with MMA/TBB (Superbond). The individual role of etched enamel and nonetched dentin bonding was also studied with high-copper amalgam used as a control. Two sizes of preparation isthmus were designated for evaluation of the effect of the polymerization contraction on weakened teeth. The following conclusions were drawn. 1. Narrow intracoronal tooth preparations were significantly stronger than wider, expansive preparations. There was no difference among the narrow isthmus preparations restored with amalgam or acid etching and composite. 2. There was a significant expansion in tooth dimension when MOD cavities were restored with amalgam. 3. Teeth with narrow isthmus preparations using composite bonded with Bondlite adhesive to etched enamel demonstrated a significant contraction compared with Superbond DBA. 4. Composite restorations using Superbond DBA in wide MOD cavities significantly improved the fracture strength of maxillary premolars. 5. Superbond DBA with composite restorations benefited the tooth in dimensional change and fracture strength. 6. There was a positive correlation between the fracture strength and tooth dimension.

Effects of maturation and priming on audiogenic seizure thresholds in mice.

The rise and fall of audiogenic seizure vulnerability were followed in three lines of mice selected for brain/body weight ratio and in the heterogeneous stock from which they were derived. Over a period of 12 to 24 days, susceptibility increased and then declined. Subjects retested after a 2-day interval were more susceptible, but this priming effect declined steadily. Differences in seizure threshold varied unsystematically among the lines. No sex differences in susceptibility were found. Mice who seized were heavier on the average than nonseizers of the same age and line. It is proposed that mice with a slower development rate are less susceptible to the stimulus used to evoke seizures. If so, rapid development may tend to lower the threshold of audiogenic seizures in mice.

The use of an intermediate resin in the acid-etch procedure: retentive strength, microleakage, and failure mode analysis.

Three composite resin systems, one conventional (Concise) and two microfilled (IsoPast and Silar), used with and without an intermediate resin (Concise Enamel Bond), were evaluated with and without thermal stress for in vitro retentive strength and sealing ability to acid-etched human enamel. All three materials yielded significantly different shear strength values. The use of an intermediate resin significantly improved both the shear strength and resistance to microleakage of Silar, while no differences were observed for Concise and IsoPast. The thermocycling procedure did not generally or consistently affect the results. The failure mode of the three acid-etched composite resins was studied by evaluation of the failure surface and by describing the percentage of enamel, composite, and interface which were present. The use of an intermediate resin did not significantly influence the failure mode, and the correlation between the failure mode and retentive strength, although significant was low. The study confirmed the importance of adequate wetting action of a resin on the etched enamel to ensure proper bonding.

Development of susceptibility to audiogenic seizures in DBA/2J and Rb mice: toward a systematic nomenclature of audiogenic seizure levels.

A systematic nomenclature of levels of audiogenic seizures has been proposed and applied to describe the developmental changes in susceptibility in Rb-1, Rb-2 and DBA/2J mice.

The ability of foods to stain two composite resins.

In this bench study, coffee and soy sauce stained composite resin restorations to a significantly greater degree than did tea or cola beverage. Generally, the greatest degree of staining with all samples occurred during the first week of the study time. The stain penetration was superficial and was estimated to be 5 mu or less.

The fracture strength of amalgam overlying base materials.

Conclusions reached within the constraints of this study showed the following: 1. Fracture strength of Class II amalgam restorations decreased as the thickness of the bases increased. 2. Fracture strengths of amalgam restorations based with different thicknesses of zinc phosphate cement underline with 0.5 mm Dycal were not different from each other. 3. The strength of the restorations varied with the type of base. Zinc phosphate cement is equal to no base and superior to zinc phosphate cement plus Dycal, which is equal to Dycal. Dycal is superior to Cavitec, which is the same as Cavitec plus Dycal. 4. The base materials did not fracture. The amalgam restorations were stronger over a base with a higher modulus of elasticity, indicating that modulus of elasticity of a base is more important than compressive strength in supporting an amalgam restoration. 5. There is no advantage (no improvement in resistance to fracture of the amalgam restoration) to be gained from placing zinc phosphate cement over Dycal. 6. When a calcium hydroxide liner is not needed, the cements with a higher modulus of elasticity, such as zinc phosphate cement and reinforced ZOE, will provide for stronger amalgam restorations than Cavitec and unreinforced ZOE.