Induction of proliferating cell nuclear antigen (PCNA)-immunoreactive cells in goldfish retina following intravitreal injection with 6-hydroxydopamine

1. The dopaminergic neurotoxin, 6-hydroxydopamine (6-OHDA), was injected intravitreally into the eyes of juvenile (5- to 6-cm) goldfish. 2. Proliferation of rod neuroblasts caused by 6-OHDA (2 micrograms in 2 microliters saline) was detected in retinal wholemounts by immunofluorescence for proliferating cell nuclear antigen (PCNA) 3, 7, 14, 20, or 30 days after injection. 3. The injected dose of 6-OHDA was sufficient to cause permanent loss of dopaminergic interplexiform and serotonergic amacrine cells in the injected eye but not in the contralateral control eye. 4. 6-OHDA increased the density (mm-2) of PCNA-ir cells in the outer nuclear layer (ONL) of the injected eye to 2.65 times the initial density 20-30 days after injection, and it increased the density of PCNA-ir cells in the ONL of the contralateral, untreated eye, equally but after a delay of less than or equal to 7 days with respect to the injected eye. 5. 6-OHDA also increased the density of PCNA-ir cells in the inner nuclear layer (INL) to greater than 20 times the initial density 7 days after injection, followed by a rapid decline almost to control levels by 14 days after injection. 6. The sequence of responses to 6-OHDA, with PCNA-ir cells first scattered in the ONL and then clustered in the INL, suggests that neuroblasts from the ONL migrate to the INL to compensate for toxin-induced cell loss. 7. Double staining for 5-bromodeoxyuridine (BrUdR; a thymidine analogue) and PCNA, carried out on 7 days after intravitreal injection with 6-OHDA, showed that 77% of all PCNA-ir cells in the outer nuclear layer had been in S phase during the previous 24 hr. 8. Immunoreactivity for PCNA was found to be a valid marker for rod neuroblasts which have entered S phase within 1-2 days before sampling and was shown to be especially convenient for investigating the distribution of proliferating cells in whole mounts. 9. In controls injected unilaterally with saline or saline plus 1% dimethyl sulfoxide (DMSO), the differences in densities of PCNA-ir rod precursor nuclei 2-30 days after injection vs. day 0 (uninjected) were statistically insignificant in both injected and uninjected eyes (Negishi et al., 1991). Therefore the local effect of injecting 6-OHDA was due to 6-OHDA itself, not to mechanical damage or nonspecific actions of foreign substances.(ABSTRACT TRUNCATED AT 400 WORDS)     

Anal‐fin ray morphology indicates sexual maturity in Brevimyrus niger (Teleostei,Mormyridae)

This osteological survey of 249 specimens of Brevimyrus niger ranging in size from 44 to 137 mm standard length (L_S) demonstrated that developmental changes in anal‐fin morphology can serve as a predictor of sexual maturity in this species. Anal‐fin ray bases begin to expand when fish reach c. 90 mm L_S at which size and above there were roughly equal numbers of individuals observed with expanded and unmodified anal‐fin bases, reflecting a 1:1 sex ratio.     

Synthesis and post-translational processing of proenkephalin in light- and dark- adapted chicken retinas

Synthesis and post-translational processing of retinal proenkephalin in response to the light or darkness were studied in newly hatched chickens using chromatography, enzymatic digestion (trypsin-carboxypeptidase B) and radioimmunoassay. We found that the concentration of free [Met⁵]-enkephalin in crude retinal extracts increased with the time in the light and decreased in the dark. This effect was directly dependent on illumination, rather than the consequence of an endogenous circadian rhythm. In contrast, the total amount of cryptic [Met⁵]-enkephalin (in larger enkephalin-containing polypeptides) remained constant in all stages of the light/dark cycle. We also showed that the relative amounts of cryptic [Met⁵]-enkephalin stored at different molecular weights remained constant, and that the concentrations of three identified proenkephalin-derived peptides, [Met⁵]-enkephalin, [Leu⁵]-enkephalin and [Met⁵]-enkephalin-Arg⁶-Phe⁷, were higher in the light-adapted than in the dark-adapted retina; but the relative amounts (ratios) of the three proenkephalin-derived peptides stored in the light and in the dark were equal. These data are consistent with the hypothesis that synthesis and processing of proenkephalin proceed at a constant rate and with similar pattern independent of illumination or adaptation, whereas the processed enkephalins are released preferentially in the darkness and accumulated in the light.     

Effects of inflammatory cytokine IL-27 on the activation of fibroblast-like synoviocytes in rheumatoid arthritis

Introduction  

Interleukin (IL)-27 is a novel member of the IL-6/IL-12 family cytokines that are produced early by antigen-presenting cells in T helper (Th)1-mediated inflammation. Elevated expression of IL-27 has been detected in the synovial membranes and fluid of rheumatoid arthritis (RA).     

A tale of timing and transport

Excitatory and inhibitory synapses show long-term plasticity, but spike timing-dependent plasticity was seen only at excitatory connections. No longer. In this issue of Neuron, Woodin et al. demonstrate that coincident pre- and postsynaptic activity acts on the neuronal K+/Cl- cotransporter KCC2 to shift the reversal potential for Cl- and thus alters the effectiveness of GABAergic synapses.     

Immunohistochemical identification of calcitonin gene-related peptide and substance P in nerves of the bovine parathyroid gland

Summary Although peptide neurotransmitters have been shown to modulate hormone secretion in many glands, there are very few studies of neurotransmitters in the parathyroid gland. Bovine parathyroid glands were collected at a local abattoir, fixed with paraformaldehyde, sectioned using a cryostat, and stained by indirect immunohistochemistry for calcitonin gene-related peptide and substance P. We were able to positively identify both neuropeptides. Nerve fibres containing calcitonin gene-related peptide and substance P were identified in contact with the tunica media of arteries and arterioles and dispersed throughout the stroma of the gland. While many of the fibres encircled parenchymal lobules, no intimate contact with the peripheral chief cells was observed. All immunoreactive fibres were found to contain both neuropeptides. Since calcitonin gene-related peptide and substance P are vasodilators, they may increase blood flow within the gland. In addition, the neuropeptides may diffuse from perilobular nerve fibres into the parenchyma, thereby modulating secretion of parathyroid hormone.