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Biomedical subjects

J Pettigrew

Publications and source records attributed to J Pettigrew.

12 recordsLinked to original sources
PubMed1995

Organization of somatosensory cortex in monotremes: in search of the prototypical plan.

The present investigation was designed to determine the number and internal organization of somatosensory fields in monotremes. Microelectrode mapping methods were used in conjunction with cytochrome oxidase and myelin staining to reveal subdivisions and topography of somatosensory cortex in the platypus and the short-billed echidna. The neocortices of both monotremes were found to contain four representations of the body surface. A large area that contained neurons predominantly responsive to cutaneous stimulation of the contralateral body surface was identified as the primary somatosensory area (SI). Although the overall organization of SI was similar in both mammals, the platypus had a relatively larger representation of the bill. Furthermore, some of the neurons in the bill representation of SI were also responsive to low amplitude electrical stimulation. These neurons were spatially segregated from neurons responsive to pure mechanosensory stimulation. Another somatosensory field (R) was identified immediately rostral to SI. The topographic organization of R was similar to that found in SI; however, neurons in R responded most often to light pressure and taps to peripheral body parts. Neurons in cortex rostral to R were responsive to manipulation of joints and hard taps to the body. We termed this field the manipulation field (M). The mediolateral sequence of representation in M was similar to that of both SI and R, but was topographically less precise. Another somatosensory field, caudal to SI, was adjacent to SI laterally at the representation of the face, but medially was separated from SI by auditory cortex. Its position relative to SI and auditory cortex, and its topographic organization led us to hypothesize that this caudal field may be homologous to the parietal ventral area (PV) as described in other mammals. The evidence for the existence of four separate representations in somatosensory cortex in the two species of monotremes indicates that cortical organization is more complex in these mammals than was previously thought. Because the two monotreme families have been separate for at least 55 million years (Richardson, B.J. [1987] Aust. Mammal. 11:71-73), the present results suggest either that the original differentiation of fields occurred very early in mammalian evolution or that the potential for differentiation of somatosensory cortex into multiple fields is highly constrained in evolution, so that both species arrived at the same solution independently.

Animals↗
PubMed1991

Cystic ameloblastic fibroma.

A seven-year-old white male presented with an enlarging mass in the mandible which was a cystic ameloblastic fibroma. This case, the third reported in the literature, demonstrated several unusual histopathologic findings and presented several controversies in management.

Child↗
PubMed1990

Intensive nursing care. The ministry of presence.

The nurse's presence offers meaningful support to people in critical care situations. Because crisis and suffering dispirit a person, there is an increased sense of vulnerability, isolation, and alienation, as well as a decreased sense of relationship and being heard in an environment that is already overwhelming, often associated with pain, frightening, and unfamiliar. The nurse's presence can lessen these negative effects of suffering as one comes alongside and enters that suffering by listening and being available in a way that involves self-giving. In this way, the nurse is fully attentive with all of self, as opposed to seeming to be. The idea of being present may be threatening to a nurse because it requires exposing one's vulnerability in order to come alongside one who is already very ragged and exposed. The silence also may be intimidating as the nurse chooses to wait with a person who is in turmoil and wrestling emotionally, mentally, physically, or spiritually. Another challenge for the nurse is confronting traditional attitudes about what it means to "be professional" and "therapeutic." The experience of presence is an awesome privilege humbly received as one realizes the personal cost to the one who chooses to share inner wrestling and brokenness. Presence occurs only with the permission or invitation of the one suffering and only when the nurse is willing to accept the invitation and also be that vulnerable. Because suffering often triggers spiritual wrestling in addition to emotional, mental, and physical pain, the nurse may be invited to come alongside a person in a role that interfaces with that of the chaplaincy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Psychological↗
PubMed1989

Differentiation of radicular cyst and granulomas using computerized tomography.

The purpose of this investigation was to study periapical lesions by means of computerized tomography to ascertain if this noninvasive method could be of value in distinguishing between radicular cysts and granulomas. Periapical radiographs were taken of the teeth of 60 human cadavers. Periapical radiolucencies were seen in conjunction with 33 teeth. Based on the periapical radiographs, an oral radiologist (J.P.) attempted to select 4 granulomas and 4 cysts from the 33 radiolucencies. Computerized tomography was performed on the root tips and the periapical lesions of these 8 teeth. The roots and periapical lesions were then surgically removed and prepared histologically for microscopic examination. In the tomographs, 7 of the periapical lesions had a cloudy appearance with a density similar to each other and to the surrounding soft tissue. In the eighth lesion a homogeneous dark area with a distinctly lower density could be distinguished from surrounding cloudy areas. Histologically, the dark area was shown to be an epithelialized cyst cavity. The other 7 lesions were granulomas. Thus, a cyst could be differentiated from periapical granulomas by computerized tomography because of a marked difference in density between the content of the cyst cavity and granulomatous tissue.

Diagnosis, Differential↗
PubMed1985

Identification of an anteriorly displaced meniscus in vitro by means of three-dimensional image reconstructions.

Computerized tomography has some limitations for diagnosis of internal derangements of the TMJ. The use of three-dimensional image reconstructions of CT data may enhance the diagnostic utility of CT. In a cadaver simulation, three-dimensional imaging was able to demonstrate the location of a displaced meniscus which was not obvious in two-dimensional sections. Location of the meniscus was aided by the use of a "transparency mode" in displaying the data.

Cartilage, Articular↗
PubMed1985

Investigation of the relationship between clinically detected loss of attachment and radiographic changes in early periodontal disease.

A total of 383 students, ages 12-16, were examined clinically to determine periodontal attachment loss by a trained examiner, utilizing standard techniques. 70 of these were selected, for whom bitewing radiographs were available for assessment of early alveolar bone loss by 2 radiologists and a general dentist, utilizing 4 criteria. The results indicate poor agreement between clinical and radiographic diagnoses by the 3 examiners. Variations were also found in the diagnosis of pathologic sites utilizing radiographs. The data indicate that bitewing dental radiographs were a poor screening or diagnostic procedure for the assessment of early periodontal disease in adolescents.

Adolescent↗
PubMed1985

Temporomandibular joint: magnetic resonance imaging.

Magnetic resonance (MR) imaging of the temporomandibular joint was performed in two subjects using a 1.5 T experimental imaging system equipped with a 6.5 cm surface coil antenna. Normal and pathologic anatomy were demonstrated with exquisite detail. Anterior displacement of the joint meniscus was clearly visible in the symptomatic subject, consistent with arthrographic confirmation.

Adult↗
PubMed1984

Three-dimensional imaging and display of the temporomandibular joint.

Despite recent advances in diagnostic radiology, current techniques for radiographic evaluation of the temporomandibular joint continue to present the clinician with difficult problems in interpretation and diagnosis. The use of three-dimensional images reconstructed from computed tomographic (CT) data improves the diagnostic value of conventional CT at no additional risk to the patient and may provide new insights into this complex anatomic structure. A sequence of 1.5 mm CT sections is made with a slice-to-slice spacing of 1.0 mm. These are used to construct a new sequence of slices by mathematical interpolation in which the new slice spacing equals the size of the pixels. Structures to be imaged separately are then masked in the interpolated sections prior to "windowing" for the appropriate tissue density. A special algorithm detects the boundary surface of the selected structure. The surface pixels are assigned gray levels on the basis of their distance and attitude from the observer. When displayed, this produces a simulated three-dimensional image. The image can be rotated and sectioned. Rotations permit otherwise hidden surfaces to be examined. Images of a human temporomandibular joint in vitro are presented to demonstrate (1) the bony components of the joint and their relationships within the joint; (2) the bony components separated to display hidden surfaces; and (3) the joint meniscus in situ and as a separate component.

Cadaver↗
PubMed1973

Kitten visual cortex: short-term, stimulus-induced changes in connectivity.

Single neurons in the kitten visual cortex can be induced to increase their responsiveness to a repeated stimulus applied while the neurons are under observation. These short-term changes are in the same direction as the permanent modifications produced in whole populations of neurons following environmental manipulations during the "critical period" of cortical development, but are less pronounced and probably transient.

Age Factors↗
PubMedDate not supplied

Radiologic techniques used to evaluate the temporomandibular joint; I. Conventional methods.

Symptoms of temporomandibular joint pathology are present in a relatively high proportion of the population. Conventional radiographic techniques used to evaluate the morphology of the joint provide data which may be difficult to interpret. These techniques are reviewed briefly and their interpretational shortcomings are noted. Computed tomography is currently being used by some clinicians to evaluate the joint. This technique may also yield data which are difficult to interpret. Extended processing of CT data to provide three-dimensional images of the joint enhances the technique as a means of diagnosing hard tissue pathology, but despite reports in the literature detailing its use in diagnosing soft tissue pathology, CT is not optimal for this purpose. The introduction of nuclear magnetic resonance imaging provides a means of examining the soft tissues of the joint in either two- or three-dimensional images and has the advantage over all previous techniques in that the patient is not subjected to ionizing radiation during the scan process.

Humans↗