Given an abstract of a paper, generate a title for this paper such that conveys the key focus of the paper.

Abstract: We examined changes in estrogen receptors (ERs) in endometrial stromal and epithelial cells in cynomolgus macaques during artificially induced menstruation and repair. We used Silastic implants filled with either estradiol (E2) or progesterone (P) to treat spayed animals for 14 days with E2 followed by 14 days of E2 plus P. We then withdrew the P (but not the E2) implants and removed uteri 0, 0.5, 1, 2, 3, 4, 5, 7, and 14 days later. Uterine tissues were assayed biochemically for ER content, fixed for histology and frozen for immunocytochemistry of ER with monoclonal antiestrophilins. On day 0, ER levels in endometrium were low [1330 +/- 201 (n = 9) fmol/mg DNA]. An increase in total receptor was evident by 3-4 days of P withdrawal 2762 +/- 190 (n = 6) fmol/mg DNA; P less than 0.001]. Total receptor concentrations increased linearly with time from 0.5-7 days of P withdrawal (r = 0.88). On day 0, staining for nuclear ER in the glandular epithelium and stroma of zones I, II, and III of the endometrium was negative. Beginning at 12-24 h and continuing through 4 days of P withdrawal, nuclear staining became detectable and increased in intensity only in endometrial stromal fibroblasts and myometrial smooth muscle cells. The glandular epithelium of the endometrium did not develop nuclear staining until 5-7 days of P withdrawal, coincident with a 10-fold increase in the mitotic index of the epithelium of the upper zones. Thus, the increase in endometrial ER levels that occurred during the first 5 days of an induced luteal-follicular transition took place almost exclusively in stromal fibroblasts.
Immunocytochemical localization of estrogen receptors in the macaque endometrium during the luteal-follicular transition.

Abstract: To determine the relative contributions of the atrial and ventricular septa to total cardiac septation in patients with atrioventricular (AV) canal defect, two-dimensional echocardiography was used to measure the length of each portion of the septum in 14 patients with partial AV canal and 13 patients with the complete form of this lesion. Results were compared with similar data from 30 normal children, 10 patients with dilated cardiomyopathy and 11 patients with ostium secundum atrial septal defect. In patients with partial AV canal, the portion of total cardiac length occupied by the atrial septum did not differ from normal (24.8 +/- 9.9% versus 28.7 +/- 7.9%, p greater than 0.05), but there was a deficiency of both AV and ventricular septal tissue, the latter occupying only 48.2 +/- 7.0% of total cardiac length (versus 57.9 +/- 4.1% in normal subjects, p less than 0.05). Similarly, patients with complete AV canal had a normal amount of atrial septal tissue, a deficiency of AV septal tissue and a deficiency of ventricular septal tissue which was even greater than that of patients with a partial defect (39.4 +/- 5.0% versus 48.2 +/- 7.0%, p less than 0.05). Thus, although partial AV canal defect is often called ostium primum atrial septal defect, the amount of atrial tissue is usually normal, the defect being formed by a deficiency of AV and ventricular septal tissue. In the complete form of the lesion, the deficiency of ventricular septal tissue is greater.
Cardiac septation in atrioventricular canal defect.

Abstract: In reconstructing the anterior cruciate ligament (ACL) it is important to place the inner ends of the drill channels correctly, to get the ACL into an isometric position. Anatomic studies demonstrate the value of a modified surgical technique using a special drill guide for standardized positioning of the anterior cruciate substitute. The drill guide consists of a metal frame with one adjustable and one fixed guide tube. Drilling is done from the anteromedial aspect of the tibia, upwards, through the joint space and the femur in a straight line, both channels being drilled in a single procedure. The precision of guided drilling was superior to that of free-hand drilling in positioning the ligament in the correct anatomic place.
A modified technique for anterior cruciate ligament (ACL) surgery using a new drill guide for isometric positioning of the ACL.