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Fixing specimens properly
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history of facial trauma or breathing habits and difficulties, took clinical photographs, and carried out rhinoscopy. Cephalometric analysis was obtained from standard radiographs. Total nasal resistance was measured by anterior active rhinometry. Comparison within and between twins suggested that anterior septal deformity resulted in a underdevelopment of the cartilaginous part of the nose and a shortened anteroposterior dimension of the maxilla. There was no effect on the vertical dimension of the face, which was therefore thought to be genetically determined. The vertical dimension was the variable most related to nasal resistance-the shorter the maxillary height the greater the resistance. These workers believe that facial morphology is influenced by the development of the anterior cartilaginous septum rather than by secondary effects of altered nasal resistance. While there remains some doubt about the role of the nasal septum in facial development, most surgeons adopt a conservative approach to surgery on the septum in children. It is generally agreed that septal cartilage should be preserved and realigned rather than resected and that surgery should be carried out only on those with pronounced deformity or severe nasal obstruction. Cooper BC. Nasorespiratory function and orofacial development. Otolaryngol Clin N Am 1989; 22: 413-41. 2. Linder-Aronson S. Adenoids: their effect on mode of breathing and nasal airflow and their relationship to characteristics of the facial skeleton and the dentition. Acta Otolaryngol Suppl 1970; 265 (suppl). 3. Bresolin D, Shapiro GG, Shapiro PA, et al. Facial characteristic of children who breathe through the mouth. Pediatrics 1984; 73: 622-25. 4. Moss ML, Salentum L. The primary role of functional matrices in facial growth. Am J Orthod 1969; 55: 566. 5. Harvold EP. Primate experiments on oral respiration. Am J Orthod 1981; 1.
79: 359-72. 6. Linder-Aronson S. Respiratory function in relation to facial morphology and the dentition. Br J Orthod 1979; 6: 59-71. 7. Brain DW, Rock WP. The influence of nasal trauma during childhood on growth of the facial skeleton. J Laryngol Otol 1983; 97: 917-23. 8. Grymer LF, Melsen B. The morphology of the nasal septum in identical twins. Laryngoscope 1989; 99: 642-46. 9. Haight JSJ, Cole Ph. The site and function of the nasal valve. Laryngoscope 1983; 93: 49-55. 10. Grymer LF, Pallisgaard C, Melsen B. The nasal septum in relation to the development of the nasomaxillary complex: a study in identical twins. Laryngoscope 1991; 101: 863-68.
Fixing specimens properly Fixation of specimens is a complex chemical process; the aim is to preserve tissue in a condition closely resembling the living state, from which reproducible histological sections may be obtained. Autolysis and bacterial contamination are prevented with very little alteration to tissue shape and volume or to the relations of its constituent components. Tissues are usually fixed before microscopy; efficient fixation is essential for accurate histological assessment. Most fixatives penetrate tissues slowly. The commonest primary fixative is 4% formaldehyde solution, which penetrates only 3-8 mm in 24 hours.1 Small specimens measuring less than 1 cm in diameter will fix by simple diffusion. Larger specimens must be
or perfused to assist the Clinicians may be tempted to cut into the process.2.3 specimen to see for themselves, but shrinkage and distortion can then make life more troublesome for the pathologist. Speedy transfer to the laboratory is better. Clinicians can also help by indicating the orientation-for example, difficulties in handling small mucosal biopsy specimens can be reduced if the fresh tissue is attached to paper card before fixation. Complex and fragmented specimens such as cone biopsies of the cervix should be fixed pinned to cork board with suitable markers for accurate interpretation.2,3 For specialised procedures such as renal and muscle biopsies, experienced staff must be on hand to deal with specimens when they are still fresh. Pathologists, clinicians, and theatre and laboratory personnel need to cooperate so that the most appropriate fixative is used for each specimen. There is often a conflict between the requirements of routine histology and specialised techniques such as electron
sliced, partly dissected,
immunohistochemistry, hormone receptor assays, and tissue culture. Although most specimens can be treated with a standard fixative at the time of surgical removal, some techniques require fresh, snap-frozen, or immediately fixed tissue. Specimens requiring special attention should be identified in advance, as should those that require non-standard or secondary fixation.2,3 Common examples are the use of Bouin’s fixative for testicular biopsy specimens and glutaraldehyde for tissues requiring electron microscopy. Primary fixation can affect histological interpretation. Fixation may cause changes in tissue volume and various artifacts.3Delayed fixation affects the numbers of observable mitotic figures in tissues,4 and so may influence the systems of mitosis-counting that are used in the diagnosis of malignancy in uterine smooth muscle turnours5 and to provide prognostic indices in other tumours.Since fixatives can directly influence the immunoreactivity of tissue antigens, evaluation of immunohistochemistry may come to depend on detailed knowledge of tissue fixation and preparation.7,8 Proper fixation is important. microscopy,
1. Baker JR. 1960.
Principles of biological microtechnique. London: Methuen,
Kennedy A. Basic techniques in diagnostic histopathology. Edinburgh: Churchill Livingstone, 1977: 1-11. 3. Hopwood D. Fixation and fixatives. In: Bancroft JD, Stevens A. Theory and practice of histological techniques. Edinburgh: Churchill Livingstone, 1982: 21-42. 4. Cross SS, Start RD, Smith JHF. Does delay in fixation affect the number of mitotic figures in processed tissue? J Clin Pathol 1990; 43: 597-99. 5. Silverberg SG. Reproducibility of the mitosis count in the histologic diagnosis of smooth muscle tumors of the uterus. Hum Pathol 1976; 7: 2.
451-54. 6. Baak JPA. Mitosis counting in tumors. Hum Pathol 1990; 21: 683-85. 7. Leong AS, Gilham PN. The effects of progressive formaldehyde fixation on the preservation of tissue antigens. Pathology 1989; 21: 266-68. 8. Pelstring RJ, Allred DC, Esther RJ, Lampkin SR, Banks PM.
Differential
antigen preservation during tissue autolysis. Hum Pathol
1991; 22: 237-41.
history of facial trauma or breathing habits and difficulties, took clinical photographs, and carried out rhinoscopy. Cephalometric analysis was obtained from standard radiographs. Total nasal resistance was measured by anterior active rhinometry. Comparison within and between twins suggested that anterior septal deformity resulted in a underdevelopment of the cartilaginous part of the nose and a shortened anteroposterior dimension of the maxilla. There was no effect on the vertical dimension of the face, which was therefore thought to be genetically determined. The vertical dimension was the variable most related to nasal resistance-the shorter the maxillary height the greater the resistance. These workers believe that facial morphology is influenced by the development of the anterior cartilaginous septum rather than by secondary effects of altered nasal resistance. While there remains some doubt about the role of the nasal septum in facial development, most surgeons adopt a conservative approach to surgery on the septum in children. It is generally agreed that septal cartilage should be preserved and realigned rather than resected and that surgery should be carried out only on those with pronounced deformity or severe nasal obstruction. Cooper BC. Nasorespiratory function and orofacial development. Otolaryngol Clin N Am 1989; 22: 413-41. 2. Linder-Aronson S. Adenoids: their effect on mode of breathing and nasal airflow and their relationship to characteristics of the facial skeleton and the dentition. Acta Otolaryngol Suppl 1970; 265 (suppl). 3. Bresolin D, Shapiro GG, Shapiro PA, et al. Facial characteristic of children who breathe through the mouth. Pediatrics 1984; 73: 622-25. 4. Moss ML, Salentum L. The primary role of functional matrices in facial growth. Am J Orthod 1969; 55: 566. 5. Harvold EP. Primate experiments on oral respiration. Am J Orthod 1981; 1.
79: 359-72. 6. Linder-Aronson S. Respiratory function in relation to facial morphology and the dentition. Br J Orthod 1979; 6: 59-71. 7. Brain DW, Rock WP. The influence of nasal trauma during childhood on growth of the facial skeleton. J Laryngol Otol 1983; 97: 917-23. 8. Grymer LF, Melsen B. The morphology of the nasal septum in identical twins. Laryngoscope 1989; 99: 642-46. 9. Haight JSJ, Cole Ph. The site and function of the nasal valve. Laryngoscope 1983; 93: 49-55. 10. Grymer LF, Pallisgaard C, Melsen B. The nasal septum in relation to the development of the nasomaxillary complex: a study in identical twins. Laryngoscope 1991; 101: 863-68.
Fixing specimens properly Fixation of specimens is a complex chemical process; the aim is to preserve tissue in a condition closely resembling the living state, from which reproducible histological sections may be obtained. Autolysis and bacterial contamination are prevented with very little alteration to tissue shape and volume or to the relations of its constituent components. Tissues are usually fixed before microscopy; efficient fixation is essential for accurate histological assessment. Most fixatives penetrate tissues slowly. The commonest primary fixative is 4% formaldehyde solution, which penetrates only 3-8 mm in 24 hours.1 Small specimens measuring less than 1 cm in diameter will fix by simple diffusion. Larger specimens must be
or perfused to assist the Clinicians may be tempted to cut into the process.2.3 specimen to see for themselves, but shrinkage and distortion can then make life more troublesome for the pathologist. Speedy transfer to the laboratory is better. Clinicians can also help by indicating the orientation-for example, difficulties in handling small mucosal biopsy specimens can be reduced if the fresh tissue is attached to paper card before fixation. Complex and fragmented specimens such as cone biopsies of the cervix should be fixed pinned to cork board with suitable markers for accurate interpretation.2,3 For specialised procedures such as renal and muscle biopsies, experienced staff must be on hand to deal with specimens when they are still fresh. Pathologists, clinicians, and theatre and laboratory personnel need to cooperate so that the most appropriate fixative is used for each specimen. There is often a conflict between the requirements of routine histology and specialised techniques such as electron
sliced, partly dissected,
immunohistochemistry, hormone receptor assays, and tissue culture. Although most specimens can be treated with a standard fixative at the time of surgical removal, some techniques require fresh, snap-frozen, or immediately fixed tissue. Specimens requiring special attention should be identified in advance, as should those that require non-standard or secondary fixation.2,3 Common examples are the use of Bouin’s fixative for testicular biopsy specimens and glutaraldehyde for tissues requiring electron microscopy. Primary fixation can affect histological interpretation. Fixation may cause changes in tissue volume and various artifacts.3Delayed fixation affects the numbers of observable mitotic figures in tissues,4 and so may influence the systems of mitosis-counting that are used in the diagnosis of malignancy in uterine smooth muscle turnours5 and to provide prognostic indices in other tumours.Since fixatives can directly influence the immunoreactivity of tissue antigens, evaluation of immunohistochemistry may come to depend on detailed knowledge of tissue fixation and preparation.7,8 Proper fixation is important. microscopy,
1. Baker JR. 1960.
Principles of biological microtechnique. London: Methuen,
Kennedy A. Basic techniques in diagnostic histopathology. Edinburgh: Churchill Livingstone, 1977: 1-11. 3. Hopwood D. Fixation and fixatives. In: Bancroft JD, Stevens A. Theory and practice of histological techniques. Edinburgh: Churchill Livingstone, 1982: 21-42. 4. Cross SS, Start RD, Smith JHF. Does delay in fixation affect the number of mitotic figures in processed tissue? J Clin Pathol 1990; 43: 597-99. 5. Silverberg SG. Reproducibility of the mitosis count in the histologic diagnosis of smooth muscle tumors of the uterus. Hum Pathol 1976; 7: 2.
451-54. 6. Baak JPA. Mitosis counting in tumors. Hum Pathol 1990; 21: 683-85. 7. Leong AS, Gilham PN. The effects of progressive formaldehyde fixation on the preservation of tissue antigens. Pathology 1989; 21: 266-68. 8. Pelstring RJ, Allred DC, Esther RJ, Lampkin SR, Banks PM.
Differential
antigen preservation during tissue autolysis. Hum Pathol
1991; 22: 237-41.