Perfusion fixation of rat molar pulp tissue for light microscopy

abstract – Molar pulp tissue of 42 rats was subjected to cardiac perfusion fixation or to immersion fixation with glutaraldehyde and formaldehyde. The importance of variations in pressure and duration of cardiac perfusion was studied. The results indicated that the perfusion method was superior to immersion fixation. Best preservation of the tissues was obtained when perfusion was performed with 1.7% glutaraldehyde for 10–12 min under a pressure of 130 cmH₂O, and leaving the animals for 4 h, without immersion fixation. Also perfusion with formaldehyde resulted in good preservation, provided the solutions were prepared from paraformaldehyde powder. In contrast, solutions made from commercial stock solutions of formaldehyde gave inferior results. For sections stained with hematoxylin-eosin, perfusion with glutaraldehyde was preferable, while perfusion with formaldehyde showed increased sensitivity in demonstration of dentinal tubules stained with alcian blue at pH 3.6. It is suggested that in future studies on rat pulp tissue, perfusion with glutaraldehyde and formaldehyde should replace immersion fixation.     

Diagnosis of intrauterine infection by demonstration of antibody-coated bacteria in the amniotic fluid

Summary. Immunofluorescence examination of amniotic fluid for the occurrence of antibody-coated bacteria was carried out in 72 consecutive women with premature rupture of the fetal membranes to assess this method in the diagnosis of intrauterine infection. Antibody-coated bacteria were demonstrated in 11 women with clinical signs of intrauterine infection, histological amnionitis and heavy growth of one bacterial species. The presence of intrauterine infection was considered possible in another 14 women. One patient had no clinical signs of infection, but positive histological and bacteriological evidence; anti-body-coated bacteria were demonstrated in this patient, but not in the remaining 13 women. In 47 women clinical, histological and bacteriological signs of intrauterine infection were absent, and examinations for antibody-coated bacteria were negative in all of them. It is concluded that the demonstration of antibody-coated bacteria in amniotic fluid indicates the presence of intrauterine infection, and the examination may in some cases be positive before the appearance of clinical signs of infection.