Lymphocytes capable of mediating delayed-type hypersensitivity reactions accumulate within sponge matrix allografts.

The rejection of sponge matrix allografts across H-2 barriers has generally been found to contain specifically sensitized cytotoxic T cells to donor alloantigen. There is one exception: sponge matrix allografts that differ only with respect to class II alloantigens do not contain specifically sensitized cytotoxic T cells. We therefore investigated the capacity of infiltrating cells removed from sponge matrix allografts to generate delayed hypersensitivity reactions after exposure to fresh alloantigen in a footpad assay. Cells infiltrating class I and II allografts were equally capable of eliciting delayed footpad reactions when injected with specific donor alloantigen into the footpads of naive responder strain mice. Allosensitized T-lymphocyte clones of helper or cytotoxic type were also capable of initiating delayed-type hypersensitivity (DTH) reactions in vivo. We conclude that rejecting allografts across class I or II alloantigenic barriers are infiltrated by cells capable of effecting DTH reactions, in addition to their capacity to exert specific helper or specific cytotoxic reactions. The results also support that both helper and cytotoxic T cells can participate in allospecific DTH reactions.

Chronology and histology of exfoliation and eruption of mandibular premolars in dogs.

Exfoliation of third deciduous mandibular premolars and their replacement by the third permanent premolars were compared in young dogs of purebred beagle and mongrel stock. Radiographic and histologic studies showed that eruption of the permanent premolar begins during the 16th postnatal week and is completed in 7 weeks. Root elongation proceeds with eruption, but fibers of the periodontal ligaments are not anchored in alveolar bone and do not attain their final orientation with respect to the long axis of the tooth until final phase of the eruptive period. These data define a predictable system in which various stages in the mechanism of eruption of noncontinuously erupting teeth may be examined experimentally. Furthermore, the observation that these processes are identical in timing and sequence in beagle and mongrel dogs suggests that less expensive, more readily available mongrel dogs can be used for these studies.

Experimental study in the dog of the non-active role of the tooth in the eruptive process.

The role of the tooth in eruption was studied radiographically and histologically after experimental manipulations of the crowns of permanent mandibular premolars in dogs. Crowns were removed and dead crown shells or metal or silicone replicas were substituted into dental follicles just prior to scheduled eruption. These replacements erupted on schedule after formation of the usual eruption pathways and formation of trabecular bone from the base of the bony crypt. Removal of crowns, but without adding replacements, also exhibited these same hallmarks of eruption. We conclude that tooth eruption is a series of metabolic events in alveolar bone characterized by bone resorption and formation on opposite sides of the dental follicle and the tooth does not contribute to this process.

The effect of removing the true dental follicle on premolar eruption in the dog.

Eruption is a highly localized process during which the bone resorption and formation that occur on opposite sides of the tooth are dependent upon the surrounding soft tissues, the true dental follicle externally and the enamel organ internally. To examine the ability of the enamel organ to cause eruption the external layer (dental follicle) was removed just prior to and up to 4 weeks before eruption in 13 mandibular premolars in dogs and eruption followed clinically, radiographically and histologically. None of the teeth without dental follicles erupted but three teeth from which the follicle was separated then replaced did erupt. These data indicate that the enamel organ without the dental follicle cannot support tooth eruption and provide indirect evidence for the central role of the dental follicle, alone or in combination with the enamel organ, in eruption.

Defining the cross-sectional anatomy important to interscalene brachial plexus block with magnetic resonance imaging.

BACKGROUND AND OBJECTIVES: Interscalene brachial plexus block is a useful technique to provide anesthesia and analgesia for the shoulder and proximal upper extremity. The initial needle direction at the interscalene groove has been described as being "perpendicular to the skin in every plane" (1). A cross-sectional (axial) approach may offer a more easily conceptualized directed needle placement. The purpose of this study is to define the cross-sectional anatomy and idealized needle angles important to interscalene brachial plexus block. METHODS: Following IRB approval, 50 patients were studied. Cross-sectional volume coil T1-weighted magnetic resonance images (MRI) were obtained from 50 patients undergoing cervical region imaging for other reasons. At the interscalene groove, a simulated needle path to contact the ventral rami or trunks of the brachial plexus was approximated at the level of C6 or C6-C7 interspace. The angle of this needle path intersecting the sagittal plane was recorded for each patient. RESULTS: The mean angle of the simulated needle path relative to sagittal plane was determined to be 61.1 +/- 6.1 degrees (range, 50-78 degrees). In 13 of 50 (26%) MRI scans, the cervical nerve roots were not visualized at the level of C6 and were measured at the C6-C7 level. CONCLUSIONS: These findings suggest initial needle placement at the interscalene groove should be angled less perpendicularly relative to the sagittal plane than is often observed. A cross-sectional approach enables more practical visualization of initial needle placement. A more accurate initial needle placement may minimize the number of needle passes necessary to contact the nerve roots, thereby more efficiently obtaining a successful block.

Sectional anatomy of the larynx: implications for the transcutaneous approach to endolaryngeal structures.

A transcutaneous, transcricothyroid membrane approach to endolaryngeal structures is used for several techniques such as placement of electrodes for laryngeal electromyography and transcutaneous Teflon injection of the paralyzed vocal fold. The purpose of this study is to examine the sectional anatomy of the larynx with respect to the cricothyroid membrane and describe a suitable transcutaneous approach to endolaryngeal structures. Sixteen whole organ cadaveric larynges were frozen in clear gelatin to facilitate sectioning. Specimens were sectioned in the transaxial, sagittal, and coronal planes as well as 30 degrees, 45 degrees, and 60 degrees from the transaxial plane. For clinical orientation, the transaxial plane was defined as 90 degrees from the most anterior plane of the cricothyroid membrane. Sections were examined and angles and depths of penetration were measured with respect to the transcutaneous approach to endolaryngeal structures.

Transversalis fascia: historical aspects and its place in contemporary inguinal herniorrhaphy.

Since the introduction of the term "fascia transversalis" by Sir Ashley Cooper in 1840, this thin layer of tissue has been discovered, denied, and redefined. The transversalis fascia was originally described as a bilaminar membrane. Although most subsequent descriptions do not reflect this analysis, some authors, especially in the surgical literature, believe that a posterior lamina of the transversalis fascia exists. Others believe that the posterior lamina of the transversalis fascia is, in fact, part of the preperitoneal fascia. The usefulness of the transversalis fascia and its derivatives or analogues; e.g., the crura of the deep inguinal ring, have also been extensively discussed. The aim of this paper is to provide a brief survey of the historical literature concerning the transversalis fascia and a discussion of some of the contemporary views on its morphology and significance in current laparoscopic hernia repair.

Anomalous thymic branch of the right common carotid artery.

A previously unreported anomalous thymic artery that branched from the anterior aspect of right common carotid artery approximately 1 cm above bifurcation of the brachiocephalic artery was found during routine dissection. It traveled inferiorly through a plexus of inferior thyroid veins for 6 cm in front of the brachiocephalic artery and crossed the anterior surface of the trachea where it divided into two branches that supplied the right and left lobes of the thymus. The development and blood supply of the thymus and their clinical anatomy are reviewed.

Cross-sectional anatomy of the pericardial sinuses, recesses, and adjacent structures.

Detailed drawings of four cross sections through the mediastinum which pass through the sinuses and recesses of the pericardial cavity, are presented. The drawings depict the location and extent of the pericardial sinuses, recesses, and their closely associated extrapericardial structures. Two previously unnamed recesses within the serous pericardium are defined and named, one the inferior aortic recess of the transverse sinus and the other, the right pulmonic recess of the transverse sinus. The terminology of the pericardial sinuses and recesses has been inconsistent, and the authors propose a nomenclature for standardizing the names of the recesses of the serous pericardium. Important anatomic pericardial relationships with regard to pericardial effusions and lymphadenopathy are discussed.

Supplemental clinical dissections for freshman gross anatomy.

This paper describes a series of nine short clinically oriented dissection exercises as supplements for freshman gross anatomy courses. These procedures heighten and focus student interest, and they do not extensively lengthen the time required to accomplish the regular dissection assignments. The exercises are: lumbar puncture, anterior approach for shoulder arthroplasty, acromioclavicular dislocation, fenestration of the diaphragm, appendectomy, cholecystectomy, display of the facial nerve as in parotidectomy, posterior approach for hip arthroplasty, and injuries to the knee ligaments and meniscectomy.

Regional control by the dental follicle of alterations in alveolar bone metabolism during tooth eruption.

Tooth eruption is a localized, bilaterally symmetrical series of events which involves resorption and formation of alveolar bone on opposite sides of the tooth and requires the presence of the dental follicle. We examined the effect on eruption of selective surgical removal of parts of the follicle. Removal of either the basal or coronal halves of the follicle prevented eruption. Bone resorption and formation of an eruption pathway did not occur after removal of the coronal part of the follicle and bone formation did not occur after removal of the basal part of the follicle. Exposure and incisions of the follicle had no effect on eruption. We interpret these data to mean that the polarized resorption and formation of alveolar bone that occur around a tooth during eruption are regulated by the adjacent parts of the dental follicle.

Ultrastructure of alveolar bone during tooth eruption in the dog.

Previous work from our laboratories has established that eruption of the permanent mandibular premolars in dogs is dependent upon the presence of the dental follicle and that it involves resorption of alveolar bone and the roots of the deciduous predecessor above and formation of alveolar bone below the developing crown. This study illustrates the topography of the bone surfaces of the crypt by scanning electron microscopy and the ultrastructure of the cells on alveolar bone surfaces during tooth eruption. Above the developing crown where the eruption pathway forms, the bone surface is a pitted sheet, the characteristic topographic feature of bone resorption; between the crown and the mandibular canal, the bone surface has numerous interconnecting trabeculae. Transmission electron microscopy of bone cells lining the eruption pathway area of the crypt showed numerous osteoclasts with adjacent mononuclear cells. Both cell types contained specific, membrane-bound cytoplasmic vesicles shown by the work of others to be characteristic features of osteoclasts and their precursors. Basal trabeculated bone in the crypt was covered by plump osteoblasts. These data show that the metabolic events in alveolar bone associated with tooth eruption have the appropriate cellular and bony surface correlates and that the suspected control of alveolar bone resorption by the dental follicle may be mediated by its recruiting and directing to adjacent bone surfaces the mononuclear precursors of osteoclasts.

Catching up.

The medical school I (S.M.) attended did not require dissection of a cadaver to fulfill the requirements of the anatomy curriculum. I had "learned" human anatomy through lectures, text books, and an atlas, but did no dissection. Although it was difficult doing anatomy that way, I passed basic science exams with high marks and did well on the board exams (NBME). I graduated from medical school with distinction and thought I was well prepared for residency. To my surprise, dissection of the orbit and periorbital regions and cranial cavity were included in my ophthalmology residency and were to pose a challenge for me. I requested the aid of a medical school anatomist to help me face this challenge. Not only did I learn the art of dissection, I gained considerable knowledge in anatomy (much of it clinically relevant), acquired better skill with surgical instruments and enhanced my logical and critical thinking ability. This viewpoint is based upon a diary I kept during my dissection experience.