Lymph and interstitial fluid dynamics in labial gingival tissues of sheep.

Lymphatic drainage and circulation in periodontal tissues have been cited as important components of host defence and pathogenic mechanisms, but quantitative data are sparse because of the technical difficulties associated with small animal lymphatic studies. However, the lymphatic vessels draining the periodontal tissues and surrounding region are sufficiently large in sheep to permit surgical placement of lymphatic catheters. Consequently, lymph and recirculating lymphocytes can be continuously collected and this permits the quantitative assessment of local immune responses in these tissues. We have studied the lymphatic drainage pathways from the labial gingival tissues in sheep by two methods. First, in a series of anatomical studies (n = 6), a complex of Evan's blue dye and albumin was injected into the labial gingival tissues. One hour after injection the animals were sacrificed and the submandibular and cervical regions were dissected to expose the stained lymphatics. This anatomical study demonstrated 2 major drainage pathways: 1) cervical lymph ducts and; 2) efferent prescapular lymphatics. Secondly, to compare the relative importance of these two drainage pathways, radiolabeled protein (125I-albumin) was injected directly into the gingival tissues and its appearance in the cervical and prescapular lymph was measured (n = 7). Despite the technical difficulties encountered in the experiments, data collected showed that over 7.5 h, 64.7% of the injected protein was recovered in the prescapular and cervical lymph vessels (31.8 +/- 6.5% and 32.9 +/- 8.5%, respectively). In addition, 11.9 +/- 2.1% of the injected protein was transported to the blood by routes not involving the cannulated cervical and prescapular lymph vessels. With most of the remaining radiolabeled protein (17.9 +/- 4.9%) recovered from the injection site, we were able to account for approximately 95% of the injected protein. This study suggests that the lymph drainage from this region in the sheep model could provide one of the best described closed and contained systems and thus, could be a useful system for future continuous monitoring of inflammatory responses during experimental periodontal diseases.

Reduction in peripheral nerve allograft antigenicity with warm and cold temperature preservation.

Lymphocyte migration into fresh and preserved peripheral nerve allografts was assessed to determine the effects of preservation time, preservation temperature, and graft harvest technique on the immunologic response to the peripheral nerve allograft. Peroneal nerve was harvested from either live or cadaveric (tissue) donors and stored as 1.5-cm segments at 5 degrees C or 37 degrees C for 1, 3, 5, or 7 days. Each of nine outbred ewes then received multiple segments of peroneal autograft, fresh allograft, and preserved nerve allograft implants. Lymphocyte migration was studied 7 days after implantation by intravenous injection of autologous 111In-labeled lymphocytes and quantified by gamma counter. Lymphocyte migration into fresh allografts (7212 +/- 1575) increased an average of 4.1 times over fresh autograft tissue (1758 +/- 421; p < 0.05). Short-term preservation (24 hours) at both temperatures enhanced lymphocyte migration into pretreated allograft tissue (12684 +/- 2575 at 5 degrees C, 8751 +/- 1577 at 37 degrees C) as compared with fresh allograft (7212 +/- 1575). Conversely, 7 days of pretreatment at both 5 degrees C (3586 +/- 1421) and 37 degrees C (1570 +/- 414) resulted in migration values not significantly different from autograft. No statistically significant difference was seen between grafts harvested from live (5710 +/- 1651) versus cadaveric (tissue) donors (4013 +/- 832) after 5 days of cold preservation.

Repeated exposure to silicone gel can induce delayed hypersensitivity.

The possible immunologic reactivity of silicone gel remains speculative and controversial. In this laboratory, a quantitative lymphocyte localization assay has been developed and well studied using pure lymphocytes collected by the technique of lymph vessel cannulation in sheep. The kinetics of antigen-specific immune responses (e.g., tuberculin reaction) in this model are well described and accepted. Using the known parameters regarding the response to purified protein derivative and the classic adjuvant Freund's Complete Adjuvant, this study was designed to identify the possible antigen-specific immunologic response, in the form of delayed-type hypersensitivity, after repeated exposure to silicone gel. Pure lymphocytes were collected by cannulating the efferent vessel of a subcutaneous lymph node in four groups of primed sheep which, 30 days previously, had received intradermal injections of 0.9% saline (negative controls; n = 6), Freund's Complete Adjuvant only (positive controls; n = 6), silicone gel (n = 7), or Freund's Complete Adjuvant homogenized with silicone gel (n = 7) in an attempt to induce sensitization. Multiple (1040) intradermal skin tests were performed using silicone gel, purified protein derivative, and 0.9% saline. After the skin lesions had developed for 48 hours, 5 x 10(8) lymphocytes were labeled in vitro with indium-111, returned intravenously, and allowed to circulate for 3 hours. Sheep were euthanized, the skin lesions were removed, and the radioactivity was counted in a gamma spectrometer. The radioactivity in each skin lesion is considered a measure of lymphocyte accumulation. The occurrence of augmented accumulation after reexposure to an antigen is a hallmark of delayed-type hypersensitivity. The purified protein derivative and saline lesions functioned as positive and negative controls, with counts per minute (cpm +/- standard error) of 2404 +/- 478 (Freund's Complete Adjuvant group) and 149 +/- 21 (saline group), respectively. Significantly greater (p = 0.0021) radioactivity was found in the silicone gel sites (310 +/- 35) in the silicone gel-primed group and the Freund's Complete Adjuvant plus silicone gel group (453 +/- 44; p = 0.0004) than in normal skin in each group. These data suggest that it may be possible to induce an antigen-specific lymphocyte-mediated response to silicone gel.

Occupational exposure to hand vibration in northern Ontario gold miners.

Nineteen underground gold mine drillers who operate vibration equipment and a control group of 16 gold mill workers without vibration exposure were evaluated. Assessment included static two-point discrimination, moving two-point discrimination, vibration threshold, and cutaneous pressure threshold. Provocative tests, including Tinel, pressure, and Phalen signs, were performed at the carpal and cubital tunnels. Mean age of the miners was 35 years, and the mean age of the control group was 31 years. The mean time of vibration exposure was 14 years. Numbness, pain, and weakness was reported in 12 miners and 1 control subject. Symptoms of vibration white finger were found in 16 miners and 3 control subjects. The miners had a higher incidence of positive provocative tests at the carpal and cubital tunnels and higher cutaneous pressure thresholds than the control group. Significantly higher vibration thresholds were found in the miners versus the control subjects. A correlation between years of vibration exposure and vibration threshold was found.