Lynn H. Larkin

Nerve entrapment in the lateral pterygoid muscle

The posterior trunk of the mandibular division of the trigeminal nerve normally descends deep to the lateral pterygoid muscle. In three of 52 dissections the three main branches of the posterior trunk (lingual, inferior alveolar, and auriculotemporal nerves) were observed to pass through the medial fibers of the lower belly of the lateral pterygoid muscle. The mylohyoid and anterior deep temporal nerves also were observed to pass through the lateral pterygoid muscle in other specimens. These nerve entrapments in the infratemporal fossa provide new information concerning the anatomic and clinical relationships between the mandibular nerve and the lateral pterygoid muscle. These findings support the hypothesis that a spastic condition of the lateral pterygoid muscle may be causally related to compression of an entrapped nerve that lead to numbness, pain, or both in the respective areas of nerve distribution.

Discomalleolar and anterior malleolar ligaments: Possible causes of middle ear damage during temporomandibular joint surgery

Damage to structures within the middle ear during surgical manipulation of the temporomandibular joint (TMJ) has been reported. Two structures are proposed as possible intermediaries in this trauma: the discomalleolar ligament (DML), which passes from the malleus to the medial retrodiscal tissue of the TMJ, and the anterior malleolar ligament (AML), which connects the malleus with the lingula of the mandible via the sphenomandibular ligament (SML). It has been hypothesized that when tension is applied to the DML and/or AML, the resulting movement of the malleus could cause damage to the tympanic membrane and associated structures. The objective of this study was to determine whether tension applied to the DML and/or the AML could cause movement of the malleus. With the use of a superior medial approach through the middle cranial fossa, the ligaments connecting the malleus with the mandible were examined in 52 adult/human cadaveric half-heads. Tension applied directly to the SML resulted in movement of the malleus in three specimens. Similar tension applied to the DML did not cause movement of the malleus. Histologic evidence showed a continuity of fibers between the SML and AML. When the mandibular condyle was distracted inferiorly, tension was demonstrated in the SML. The results indicate that the AML via the SML has the potential to cause middle ear damage and is more likely to do so than the DML.

Muscle attachment to the lateral aspect of the articular disk of the human temporomandibular joint

OBJECTIVE To investigate the anatomic attachments to the lateral aspect of the anterior band of the human temporomandibular joint articular disk. MATERIAL AND METHODS Sixteen human cadaver half-heads were dissected and examined macroscopically. RESULTS No direct attachment was observed between the deep masseter muscle and the temporomandibular joint articular disk. In one specimen, a small band of the anterior temporalis muscle was directly attached to the lateral aspect of the temporomandibular joint disk; whereas, on the same specimen, the attachment of the superior belly of the lateral pterygoid muscle was a comparatively large band. In another specimen, the lateral pterygoid muscle passed in an anterolateral direction. CONCLUSIONS The masseter muscle has no functional significance in the biomechanics of temporomandibular joint disk displacement. The anterior temporalis muscle may have functional significance when it is accompanied by an anterolaterally divergent lateral pterygoid muscle.

PURIFICATION OF RELAXIN FROM THE PLACENTA OF THE RABBIT

The studies conducted to date dealing with isolation and characterization of relaxin in the pregnant animal have concerned mainly the ovary, e.g., pig,l shark,2 and COW.^ Although relaxin has recently been detected in the uterus of the pregnant guinea pig,c relaxin from only one nonovarian tissue, the human placenta, has been isolated and partially ~haracterized.~ Previous studies by Zarrow and Rosenberg8 and Larkin et d9 have indicated that the placenta of the rabbit was a source of relaxin and these reports provided the basis for the following studies.

Human relaxin inhibits division but not differentiation of 3T3-L1 cells.

For the first time, we demonstrate here the ability of human relaxin to block cell division. During the induction of differentiation of 3T3-L1 fibroblasts to adipocytes, the cells typically undergo two rounds of cell division followed by accumulation of lipid droplets and expression of insulin-stimulated glucose transport as the cells attain the adipocyte phenotype. Human relaxin added during induction had no effect on the development of the adipocyte phenotype or insulin-stimulated glucose transport. However, it blocked cell division at a half-maximal concentration of 1.25 nM, well within physiological range. This could be reversed by the addition of antibodies specific for human relaxin. Thus relaxin joins a select number of hormones with growth inhibitory properties such as transforming growth factor-beta (TGF beta) and mammastatin. Potentially, this is an important but until now unidentified function of relaxin. Unlike other inhibitory polypeptides, like TGF beta, relaxin does not prevent differentiation but rather uncouples it from cell division.

Chemistry of bovine relaxin.

The physiological role of relaxin (relaxation of pelvic ligaments and cervical softening) demonstrated in other species makes the potential use of this hormone appealing to the cattle industry.

Cytochemical detection of carbohydrate and immunocytochemical detection of relaxin in the same secretory granule.

We administered estradiol and progesterone to spayed guinea pigs, with resultant accumulation of secretory granules in endometrial gland cells. By initially employing protein A-colloidal gold immunolocalization of relaxin, followed by cytochemical staining of carbohydrate with the thiocarbohydrazide-silver proteinate method on the same section, we showed clearly that the secretory granules were composed of a central core containing relaxin and a cortex of carbohydrate-rich material. Use of normal rabbit serum rather than relaxin antiserum, and omission of periodic acid, demonstrated the specificity of the technique.