Glucose oxidase as label in histological immunoassays with enzyme-amplification in a two-step technique: coimmobilized horseradish peroxidase as secondary system enzyme for chromogen oxidation

Nerve reinnervation and itch behavior in a rat burn wound model

In this study, we investigated whether postburn itch in rats, after a full thickness burn, is correlated to the nervous reinnervation of the burn wound area. For this purpose, we determined scratching duration (expressed as second/hour) at 24 hours, 2, 4, 8, and 12 weeks postburn and combined this with immunohistochemistry for protein gene product 9.5 (PGP9.5) to identify all nerve fibers, calcitonin gene related peptide (CGRP) to identify peptidergic fibers, tyrosine hydroxylase (TH) for sympathetic fibers, and growth-associated protein 43 (GAP-43) for regrowing fibers. We found a modest, but highly significant, increase in scratching duration of all burn wound rats from 3 to 12 weeks postburn (maximally 63 ± 9.5 second/hour compared to sham 3.1 ± 1.4 second/hour at 9 weeks). At 24 hours postburn, all nerve fibers had disappeared from the burn area. Around 4 weeks postburn PGP 9.5- and CGRP-immunoreactive nerve fibers returned to control levels. TH- and GAP-43-IR nerve fibers, which we found to be almost completely colocalized, did not regrow. No correlation was found between scratching duration and nervous reinnervation of the skin. The present results suggest that in rat, like in human, burn wound healing will induce increased scratching, which is not correlated to the appearance of nervous reinnervation.

Long-term follow-up of peptidergic and nonpeptidergic reinnervation of the epidermis following sciatic nerve reconstruction in rats

OBJECT

Peripheral nerve injuries are a commonly encountered clinical problem and often result in long-term functional deficits. The current gold standard for transected nerves is an end-to-end reconstruction, which results in the intermittent appearance of neuropathic pain.

METHODS

To improve our understanding of the relation between this type of reconstruction and neuropathic pain, the authors transected and immediately end-to-end reconstructed the sciatic nerve in rats. The effect of this procedure on neuropathic pain, as measured by thermal and mechanical hypersensitivity at 4 different time points (5, 10, 20, and 30 weeks), was related to the density of peptidergic and nonpeptidergic fiber innervation in the glabrous skin of rats' hind paws.

RESULTS

Thermal hypersensitivity occurring 20 weeks after reconstruction was accompanied by a significant increase in peptidergic epidermal fibers. However, the lesion-induced reduction in the density of nonpeptidergic epidermal fibers remained decreased at all experimental time points. Moreover, temporal collateral sprouting by undamaged saphenous nerve was visualized using the recently revised Evans blue extravasation technique. Strikingly, as the sciatic nerve repopulated rats' hind paw, the saphenous nerve withdrew to its original territory.

CONCLUSIONS

The authors conclude that the transient thermal hypersensitivity is related to increased density of epidermal peptidergic fibers, which mainly originate from regenerating fibers. Furthermore, a changed composition in the peptidergic and nonpeptidergic epidermal fibers is demonstrated following end-to-end reconstruction of the sciatic nerve.

An early diagnostic tool for diabetic peripheral neuropathy in rats

The skin’s rewarming rate of diabetic patients is used as a diagnostic tool for early diagnosis of diabetic neuropathy. At present, the relationship between microvascular changes in the skin and diabetic neuropathy is unclear in streptozotocin (STZ) diabetic rats. The aim of this study was to investigate whether the skin rewarming rate in diabetic rats is related to microvascular changes and whether this is accompanied by changes observed in classical diagnostic methods for diabetic peripheral neuropathy. Computer-assisted infrared thermography was used to assess the rewarming rate after cold exposure on the plantar skin of STZ diabetic rats’ hind paws. Peripheral neuropathy was determined by the density of intra-epidermal nerve fibers (IENFs), mechanical sensitivity, and electrophysiological recordings. Data were obtained in diabetic rats at four, six, and eight weeks after the induction of diabetes and in controls. Four weeks after the induction of diabetes, a delayed rewarming rate, decreased skin blood flow and decreased density of IENFs were observed. However, the mechanical hyposensitivity and decreased motor nerve conduction velocity (MNCV) developed 6 and 8 weeks after the induction of diabetes. Our study shows that the skin rewarming rate is related to microvascular changes in diabetic rats. Moreover, the skin rewarming rate is a non-invasive method that provides more information for an earlier diagnosis of peripheral neuropathy than the classical monofilament test and MNCV in STZ induced diabetic rats.

Differential Changes in the Peptidergic and the Non-Peptidergic Skin Innervation in Rat Models for Inflammation, Dry Skin Itch, and Dermatitis

Skin innervation is a dynamic process that may lead to changes in nerve fiber density during pathological conditions. We have investigated changes in epidermal nerve fiber density in three different rat models that selectively produce chronic itch (the dry skin model), or itch and inflammation (the dermatitis model), or chronic inflammation without itch (the CFA model). In the epidermis, we identified peptidergic fibers-that is, immunoreactive (IR) for calcitonin gene-related peptide or substance P—and non-peptidergic fibers—that is, IR for P2X3. The overall density of nerve fibers was determined using IR for the protein gene product 9.5. In all three models, the density of epidermal peptidergic nerve fibers increased up to five times when compared with a sham-treated control group. In contrast, the density of epidermal non-peptidergic fibers was not increased, except for a small but significant increase in the dry skin model. Chronic inflammation showed an increased density of peptidergic fibers without itch, indicating that increased nerve fiber density is not invariably associated with itch. The finding that different types of skin pathology induced differential changes in nerve fiber density may be used as a diagnostic tool in humans, through skin biopsies, to identify different types of pathology and to monitor the effect of therapies.

Immunocytochemistry in the assessment of pS2 protein expression in fine needle aspiration cytology from breast carcinoma

pS2 protein is a cysteine-rich polypeptide, of unknown function, the expression of which is induced in the human cancer cell line MCF-7 by oestrogen. The availability of a murine monoclonal antibody to human pS2 protein has prompted us to evaluate its expression in 47 cases of primary breast carcinoma. Using a double indirect immunoperoxidase technique, we compared the expression of pS2 protein in fine needle aspiration (FNA) cytology smears with that in formalin-fixed, paraffin-embedded sections from subsequently excised tumours from the same patients. We also compared the expression of pS2 protein and oestrogen receptor (ER) status using immunocytochemical assay (ER-ICA) in formalin-fixed, paraffin-embedded sections from 22 primary breast carcinomas. We found the application of immunocytochemistry in the assessment of pS2 protein expression in FNA cytology to be a reliable and cost-effective technique, having a sensitivity of 84% and a specificity of 100%. There was also a good correlation between the expression of pS2 protein and ER status.