Lateral pterygoid muscle: a three-dimensional analysis of neuromuscular partitioning.

The lateral pterygoid (LP) has been implicated in temporomandibular joint (TMJ) pathology. Few studies have examined muscle architecture of the superior (SLP) and inferior (ILP) heads of LP; moreover, the pattern of intramuscular innervation is poorly defined. The purpose of this study was to determine patterns of intramuscular innervation of LP using 3D modeling. The superior and lateral aspects of LP were exposed in 10 embalmed cadaveric specimens. Nerves entering the muscle, all branches of the mandibular nerve (V(3) ), were followed intramuscularly in short segments and sequentially digitized. Muscle volume, surrounding bone, and the TMJ disc were also digitized. The data were reconstructed into 3D models (Maya®) that were used to determine patterns of intramuscular innervation. It was found that the SLP had independent sources of innervation to each of the quadrants in its superior part (masseteric/posterior deep temporal/middle deep temporal/buccal) and one primary source of innervation (buccal) to the quadrants of the inferior part. This difference in innervation is significant as the superior part attaches to the TMJ disc-capsule complex, whereas the inferior part attaches to the mandibular condylar neck. Differing sites of attachment and sources of innervation for each part suggests that movement of the TMJ disc-capsule complex, independent of the condyle, may be possible. The buccal nerve supplied both the medial and lateral quadrants of the ILP, with the medial quadrants receiving additional innervation from V(3) muscular branches. Results of this study could be used to direct EMG/ultrasound studies of LP function as related to TMJ disorders.

Fetal toxicity caused by excessive maternal dietary calcium.

The effects of diet-induced maternal hypercalcemia on fetal development were studied in the CD 1 mouse. Female mice were maintained for two weeks on high calcium diets and then mated. The resulting litters were surgically removed one day prior to term and compared to control litters of untreated mice. Fetuses from the treated litters showed significantly lower birth weights and higher frequencies of missing calcification centres in the developing skeletons and dentitions. In addition, centres that had begun to calcify were not as advanced as corresponding centres in the control series. It appears that high calcium intake during pregnancy is fetotoxic and results in decreased fetal weight and retarded skeletal and dental calcification.

Prenatal hamster development following maternal administration of PGE2 at midterm.

The effects of PGE2 on embryonic and fetal development were studied in the golden Syrian hamster. Pregnant hamsters were treated on day 8 of gestation with either 0.2, 0.5, 0.75, or 1.0 mg/kg PGE2 delivered I.P. and the near term litters were compared to those of untreated and vehicle treated controls. Fetuses from the treated litters showed significantly higher frequencies of mortality, lower weights, malformations, and missing ossification centres in comparison to control litters. The results demonstrate that PGE2 is teratogenic in the hamster and the developing neural tube and the fetal skeleton are particularly susceptible to the effects of this teratogen.

Mesometrial smooth muscle in the mouse: its control of uterine blood flows.

The form and function of the mesometrial smooth muscle and the interposed mesometrial branches and tributaries of the uterine vessels were studied in the nonpregnant and pregnant mouse to see whether contractions of mesometrial muscle alter uterine blood flows. Histological sections of mouse uterine horn demonstrated that the outer longitudinal layer of myometrium extends onto the mesometrium and sandwiches the mesometrium and its vessels as a bilaminar myometrial extension (BME). The BME ends midway across the mesometrium as a free edge. Cleared specimens, perfused with silicone rubber, revealed that the mesometrial branches and tributaries of the uterine vessels formed longitudinally communicating looping arcades between adjacent mesometrial vessels. Comparisons with human dissections and uterine histological sections revealed similar patterns of mesometrial smooth muscle and mesometrial blood vessels. BME activity and its control of mesometrial blood flow were studied by transillumination of the surgically exposed mesometria of anesthetized day 12 pregnant mice. Observed contractions of the BME coincided precisely with uterine contractions measured at the cervix and the BME contractions diminished or stopped venous outflow particularly in the midhorn regions. Arterial flows seemed to be unaffected and were diminished or halted only during infrequent forceful and sustained contractions. Trapped venous outflow passed up or down the venous arcades to escape through less restricted mesometrial veins. Uterine and BME contractions normally take place throughout gestation. It is possible that abnormally long and forceful contractions may compromise the embryo or fetus.

Factors of human skeletal craniofacial morphology.

Thirty cephalometric measurements representing craniofacial depth, height, and width were obtained from lateral and posterior rediographs of 66 boys, 8 years of age. A multivariate factor analysis was performed on these measurements in an effort to locate specific areas of variability within the craniofacial complex. Twelve uncorrelated factors were extracted which account for 91% of the total variance and these were identified as: 1) retrognathic facial type, 2) anterior dentoalveolar height, 3) maxillary body length, 4) cranial base and facial width, 5) mandibular ramus height, 6) anterior maxillary body height, 7) mandibular length, 8) cranial vault height, 9) vertical position of the condyles, 10) cranial vault and clivus length, 11) bigonial width, and 12) cranial vault width.