Acute changes in the concentrations of prostaglandin F2α (PGF) and cortisol in uterine and ovarian venous blood during PGF-induced luteolysis in cows.

Prostaglandin F2α (PGF) is considered to be the main luteolysin in cattle. We have previously demonstrated that cortisol (Cr) suppresses PGF production in non-pregnant bovine endometrium. This study was carried out to test whether exogenous PGF increases ovarian and/or uterine PGF production and to determine the temporal relationship between PGF and Cr in ovarian and uterine circulations during PGF-induced luteolysis in cows. Catheters were inserted into the ovarian vein (OV), uterine vein (UV) and jugular vein (JV) of 10 cows on Day 9 of the oestrous cycle (Ovulation = Day 0) for frequent blood collection. On Day 10, the cows were divided randomly into two groups and treated with a luteolytic dose of a PGF analogue (cloprostenol) or saline solution. Blood samples were collected at -0.25, 0, 0.25, 0.5, 1 and 2 h and then at 2-h intervals until 12 h after treatment (0 h). The basal concentrations of PGF and Cr in OV and UV plasma were not significantly different. Injection of a PGF analogue induced more than twofold increases in the levels of PGF between 0.25 and 1 h in UV plasma, but not in OV plasma. PGF increased (p < 0.05) the concentrations of Cr in OV, UV and JV plasma between 0.5 and 1 h. The Cr levels in OV, UV and JV plasma were similar. The PGF levels in UV plasma decreased after Cr reached its highest levels. The overall results suggest that the uterus rather than the ovary increases PGF production in response to PGF injection. Based on the temporal changes of PGF and Cr in the ovarian and uterine circulations, Cr may act to reduce uterine PGF production in non-pregnant cows in vivo.

Mechanical stress generated by orthodontic forces on apical root cementum: a finite element model.

OBJECTIVES: 1) To determine the mechanical stress generated at the root apex during different types of tooth movement using a finite element model of an ideal, human maxillary central incisor. 2) To determine the relationship of thickness of cementum and the magnitude of mechanical stress at the root apex. DESIGN: Computer simulation. SETTING AND SAMPLE POPULATION: Not applicable, computer simulation. EXPERIMENTAL VARIABLES: Tooth and investing tissue layers (enamel, dentin, cementum, pulp, periodontal ligament, and alveolar bone). OUTCOME MEASURE: Von Mises and maximum principal stresses. RESULTS: Increasing the apical thickness of cementum increases the amount of mechanical stress. CONCLUSION: A finite element model incorporating all layers of a human maxillary central incisor has been developed. This model was used to determine the location and magnitude of mechanical stress generated for all regions of the tooth, PDL, and enclosed alveolar bone, when orthodontic forces are applied to the tooth. Mechanical stresses were found to increase at the root apex with increasing thickness of apical cementum.

Infant mortality in Louisiana--identifying the risks.

The state of Louisiana consistently has one of the five highest infant mortality rates in the nation and the racial disparity within the state is glaring. The purpose of this paper is to analyze the state's linked birth and death infant data set for the birth cohort of 1990-1998, and to identify the "at risk" population. We have analyzed data from the 1990 to 1998 birth and infant death cohort in Louisiana to determine mothers' characteristics that are associated with infant death. These include extremely young and old ages, unmarried marital status, lower levels of education, and prenatal care. A mother's race is also associated with higher future mortality for her infant, with black mothers and their infants being at greater risk than white ones. Because the infant mortality rate is higher for black infants than for white ones, Louisiana's higher infant mortality rate can be seen as a result of the higher proportion of black births. Main concerns in reducing infant mortality rates include reducing incidence of low birth weights specifically among black births primarily by providing adequate prenatal care.