Brainstem melanocortin 3/4 receptor stimulation increases uncoupling protein gene expression in brown fat

Central administration of melanocortin 3 and 4 receptor (MC3/4-R) agonists increases energy expenditure, with the hypothalamus commonly held as the primary site of action. It is also clear, however, that MC4-R are expressed in caudal brainstem structures of relevance to the control of energy expenditure. Three experiments investigated whether hindbrain MC-R contribute to the energy expenditure effects of central MC3/4-R agonist treatments; in each, we examined the effect of fourth intracerebroventricular (i.c.v.) administration of a MC3/4-R agonist, MTII (three injections, each separated by 12 h), on uncoupling protein 1 (UCP-1) gene expression in brown adipose tissue (BAT). First, we compared the effects of fourth and third i.c.v. administration of MTII and found that the hindbrain and forebrain treatments were equally effective at elevating UCP-1 mRNA expression in BAT compared with the respective vehicle-treated group results. A second experiment demonstrated that the fourth i.c.v. MTII-induced rise in UCP-1 expression was mediated by sympathetic outflow to BAT by showing that this response was abolished by surgical denervation of BAT. In the third experiment, we showed that chronic decerebrate rats, like their neurologically intact controls, elevated UCP-1 mRNA expression in response to fourth i.c.v. MTII administration. Taken together, the results indicate that: 1) there is an independent caudal brainstem MC3/4-R trigger for a sympathetically stimulated elevation in BAT UCP-1 gene expression, and 2) the MTII-induced rise in UCP-1 expression can be mediated by circuitry intrinsic to the caudal brainstem and spinal cord.

Role of antioxidants in the survival of normal and vitiliginous avian melanocytes

Mutant feather melanocytes from Barred Plymouth Rock (BPR) and White Leghorn (WL) chickens are currently being used as avian models of vitiligo. Feather melanocytes in BPR and WL chickens die prematurely in vivo due to low (50-66%) antioxidant glutathione and superoxide dismutase levels when compared to the wild type Jungle Fowl (JF) melanocytes. Excess superoxide anions, generated by xanthine:xanthine oxidase (X:XO), caused a 15-20% increase in mortality after 1 and 2 hrs. in all three genotypes of in vitro melanocytes as compared to control values that received no X:XO. Overall, the JF wild type melanocytes had the lowest mortality rate, WL melanocytes had the highest mortality rate and the BPR melanocytes had an intermediate mortality rate. Superoxide anion and hydroxyl radical production in the WL feather were double the production in the JF wild type feather. The production of reactive oxygen species in BPR was intermediate to the other two genotypes. In an effort to mimic the low antioxidant levels of the BPR and WL feathers in the JF feather, JF in vitro feather melanocytes were treated with buthionine sulfoximine (BSO), a glutathione synthesis inhibitor. With BSO added to the medium, the JF mortality rates increased by 20-25%, reaching the mortality levels of the mutant BPR melanocytes. The addition of iron to the JF melanocyte X:XO medium increased their mortality rate by 20%, probably via the Fenton reaction. Thus, antioxidants play an extremely important role in both the viability of normal avian melanocytes and the premature death of the vitiliginous avian melanocytes. A working hypothesis, supported in part by the current results, is that the premature death of the mutant melanocytes could be precipitated in the poorly vascularized feather by low antioxidant protection due to both low turnover of tissue fluids which contain SOD and to genetically determined low levels of internal antioxidant protection in these melanocytes. This same mechanistic hypothesis could apply as "a" cause of premature melanocyte cell death in human vitiligo wherein the vitiliginous melanocytes may have a genetic defect in their antioxidant protection system and blood flow to an area may be restricted.

The role of alpha-MSH, its agonists, and C-AMP in in vitro avian melanocytes

Little is known about the effect of alpha-MSH and other melanogenic stimulators on avian melanocytes. Tissue cultures of Barred Plymouth Rock regenerating feather melanocytes were established and the culture medium contained selected concentrations of alpha-MSH and other melanogenic stimulators in Ham's F-10 medium supplemented with antibiotics and 10% new born calf serum. Cultures were maintained at 37 degrees C in 95% air/5% CO2. No increase in melanogenesis over control levels due to the addition of 10(-5) M Forskolin, 10(-4) M IBMX, 10(-3) M c-GMP, and 10(-3) M db-c-AMP was observed in the cultures on days 5 and 7. However, 2.5 (optimum), 5, and 10 micrograms/ml alpha-MSH and 10(-3) M 8-bromo-c-AMP significantly increased melanogenesis over control levels on days 5 and 7. The stimulation of melanogenesis was detectable by a significantly increased number of melanocytes containing numerous stage IV melanosomes. No increase in melanocyte cell number was observed in any of the experimental cultures. The addition of 1, 2 (optimum), or 3 mM calcium did enhance the increased pigmentation effect of 2.5 micrograms/ml alpha-MSH. Two very convincing experiments showed that c-AMP was the second messenger for alpha-MSH in these birds. First, the c-AMP inhibitor, 10(-3) M Rp-c-AMPS, completely inhibited the stimulatory effect of alpha-MSH in these in vitro melanocytes. Second, direct measurements of c-AMP levels in feather tissue showed a significant increase in c-AMP levels 10.min after alpha-MSH treatment. Controls received no alpha-MSH. The results showed that these avian melanocytes have alpha-MSH receptors and were able to respond to the hormone. C-AMP was the second messenger in this system. Apparently db-c-AMP was not able to enter these mature, highly-differentiated cells and c-AMP agonists, Forskolin and IBMX, were also either unable to enter these older cells or, if they did enter the cells, were unable to stimulate c-AMP production. Evidently the more lipophilic 8-bromo-c-AMP was able to enter these cells and stimulate melanogenesis.

Premature avian melanocyte death due to low antioxidant levels of protection: fowl model for vitiligo

Feather melanocytes in the Barred Plymouth Rock (BPR) and White Leghorn (WL) chickens die prematurely in vivo when compared to the wild type Jungle Fowl (JF) chicken. Since these mutant melanocytes live in vitro, an environmental factor in the feather must precipitate their death. Results show that the addition of selected antioxidants, glutathione (GSH) and superoxide dismutase (SOD), can rescue these mutant melanocytes in vitro that have been placed under stress conditions that cause their premature cell death. Measurements of in vivo levels of GSH, catalase, and SOD show no significant difference in catalase activity between the JF, BPR, and WL feathers but do show a significant reduction in GSH activity in both the BPR and WL feathers to approximately 66% of the GSH concentration found in JF feathers. SOD activity in the BPR tissue is reduced significantly to approximately 50% of the JF activity and the WL SOD activity is reduced significantly to approximately 50% of the BPR SOD activity. Preliminary results of measurements of glutathione peroxidase activity indicate there is no difference in the levels of this enzyme in JF, BPR and WL feathers. A working hypothesis, based on current results, is proposed for premature cell death in BPR and WL feather melanocytes. The BPR melanocytes are genetically sensitive due to a defect in their SOD and GSH levels caused by the barring gene (B) and their death, due to reactive species of oxygen radicals, is precipitated in the poorly vascularized feather by the accumulation of oxygen radicals due to the low turnover of tissue fluids. The WL chicken carries the dominant white gene (I) in addition to the B gene. This gene directs the further reduction of the level of SOD and, when combined with the cell death mechanism already present in the BPR chicken, causes the WL feather melanocytes to die much earlier than the BPR feather melanocytes which in turn die much earlier than the wild type JF melanocytes. This same mechanistic hypothesis could apply as a cause of premature melanocyte cell death in human vitiligo wherein the vitiliginous melanocytes may have a genetic defect in their oxygen radical protection system.

Effect of the barring gene on eye pigmentation in the fowl

Pigment cells of the iris, pecten, retinal pigment epithelium, and choroid of the wild-type jungle fowl (JF) and the barred Plymouth rock (BPR) breeds of adult chickens were studied at both light and electron microscopic levels. BPR choroidal tissues had 2.8 times fewer melanophores than the JF choroid, and BPR melanophores also contained 2.4 times fewer melanosomes, which tended to clump together in variously sized clusters. The melanosomes were often irregular in shape, smaller in diameter, and less mature (stage III) than those granules in the JF. The retinal pigment epithelium of both JF and BPR breeds contained a single epithelial layer of columnar cells. Rod-shaped melanosomes were present in the more apical regions of this cell type in both breeds. Both JF and BPR irides contained a multilayered posterior pigmented epithelium of columnar shaped cells that were densely filled with large spherical granules. Intercellular spaces with interdigitating cytoplasmic projections were present between pigment cells of both breeds. The pecten melanophores of both breeds were dendritic with melanosomes that were larger and fewer in numbers than those pigment cells of the iris and choroid. Intercellular spaces were present between cells in both breeds, with numerous villous-like pigment cell extensions. Choroid melanophores contained very little, if any, acid phosphatase activity. Approximately one-half of the retinal pigment epithelial cells observed contained small amounts of diffuse acid phosphatase activity in both breeds. The iris and pecten melanophores of both breeds contained profuse acid phosphatase activity scattered throughout their cytoplasms. Sparse tyrosinase activity was seen in iris and pecten pigment cells, whereas no tyrosine activity was observed in choroid melanophores or in retinal pigment epithelial cells in the two breeds, indicating that little new melanogenesis occurs in adult pigmented eye tissues. The results show that the barring gene reduces the number and melanin content of the choroidal melanophores in homozygous male BPR chickens as compared to the wild-type JF chickens. Whether this gene prevents the initial migration of embryonic neural crest cells (future melanophores) to the choroid or whether some of the choroidal melanophores prematurely degenerate in the embryo of young birds is yet to be determined. If the latter is the case, this choroid system may serve as a model for a genetic hypomelanotic disease such as vitiligo.

A simple method for the establishment of tissue culture melanocytes from regenerating fowl feathers

A quick and simple method for the establishment of tissue cultures of nonembryonic domestic fowl melanocytes was desired. The selected source of these cells was the 14-d-old regenerating feather. Three procedures were compared on the basis of the yield and purity of melanocytes. For the first method, 2 mm of the proximal end of the feather was cut off under sterile conditions and placed immediately in Hanks' balanced salt solution (BSS) containing antibiotics. The feather was split longitudinally and the pulp removed. The tissue was placed pulp side down in several drops of Ham's F12 medium containing 2.5 micrograms/ml Fungizone, 50 micrograms/ml gentamicin, 100 micrograms/ml streptomycin, 100 micrograms/ml penicillin, and 10% fetal bovine serum. After 2 h at 37 degrees C, the tissue was attached to the dish and new medium was added and changed every 3 d thereafter. Cells migrated from the tissue starting on Day 2 and the tissue was removed on Day 5. Large dendritic peripheral cells and small round central cells were seen. Approximately 6.5 X 10(4) cells were present on Day 10 and 8 X 10(4) cells were counted on Day 20. By Day 30, the pigmented melanocytes were large, flat, dendritic cells. Electron microscopy and the use of the dopa reaction indicated that the population of cells was almost entirely melanocytes. The second method used was similar to the first, the only difference being that the feather sheath was also removed and thus only the collar of cells remained. The third method tried was similar to the second with the difference that the collar of cells was gently agitated with 0.25% trypsin for 5, 10, and 20-min intervals at 37 degrees C. The trypsin supernatant fluid was removed by gentle centrifugation and medium plus fetal bovine serum was added to stop tryptic action. The second method showed no advantage over the first. The purity and yield of melanocytes in the third method were lower than in either of the previous two methods. The number of cells desired can be controlled by varying the number of the feather pieces used per culture.

A biochemical study of the carrageenan-induced granuloma in the rat lung

Intralobular injection of carrageenan in the rat lung induced a chronic granulomatous response, characterized by a prolonged accumulation of macrophages within the affected lobe. This was accompanied by moderate but significant increases in lysosomal beta-acetyl glucosaminidase, cathepsin B1, and neutral protease activity. Beta-acetyl glucosaminidase and cathepsin B1 activities peaked on day 16 post carrageenan injection and cathepsin B1 activity peaked again on day 112. These enzyme peaks correlated with previous morphological findings that numerous PMNs and carrageenan-containing macrophages were present in the alveoli on day 16 and on day 112. Lymphocytes and plasma cells were present in the alveoli on day 112 in addition to the numerous carrageenan-filled large macrophages. The caseinolytic enzyme activity was significantly elevated over controls throughout the duration of the experiment but no distinct peaks of activity were observed. Based on determinations of total collagen, insoluble collagen, salt-soluble collagen, acid-soluble collagen, protein, total proline, and specific activity of proline and hydroxyproline, there was biochemical evidence of increased collagen synthesis or collagen accumulation in the inflamed lobes on days 4 to 32 as compared to the control lobes. No evidence was found to indicate an increase of collagen or collagen synthesis after day 32 in the experimental lobes. These results differ from our earlier histological and ultrastructural findings which reported that no increased collagen deposition was observed on any day in this system, even 500 days post carrageenan injection. Lung to body weight ratios of experimental animals were significantly elevated over controls on all days studied.

An ultrastructural study of the macrophages of the carrageenan-induced granuloma in the rat lung

The intralobular injection of 0.17 ml of 2 per cent. carrageenan into the rat lung induced an inflammatory granulomatous response. This inflammation was characterized in the early stages by immediate polymorphonuclear (PMN) leucocyte infiltration into the alveoli. Within 2 days the PMN's began to disappear and were replaced by carrageenan-containing macrophages. Alveolar macrophages actively phagocytised the injected carrageenan and were the dominant cell type in he alveoli for the length of this study (365 days). These low-turnover alveolar macrophages, which with light microscopy stained pinkish-red metachromatically with toludine blue due to their carrageenan content, underwent changes in vacuole morphology as well as changes in size and shape. Throughout the course of this inflammation, these macrophages had carrageenan-containing vacuoles which could be seen undergoing fusion to form larger vacuoles which at times constituted half the size of the entire macrophage cytoplasm. The carrageenan in the vacuoles was an amorphous flocculent appearing material for the initial 14 days but changes to a more fine filamentous form for the remainder of the study. This was probably due to its partial digestion by lysosomal enzymes. The general composition of the cytoplasm remained fairly constant during the 365 days. Pinocytotic vesicles and free ribosomes were abundant and the many mitochondria were small and rounded. Smooth endoplasmic reticulum lysosomes, and Golgi apparati, although not prominent, were present but the most striking feature of the cytoplasm was the presence of numerous lamellar bodies (phagocytosised surfactant). Some of the macrophages increased greatly in overall size (five to seven times) compared to their initial size. A few isolated macrophages could be seen degenerating but no general necrosis was seen. Except for one isolated case, no epithelioid cells were observed in this carrageenan inflammation. Fibrosis, if present at all, was very localised and was only evident at day 340 post-injection. This fibrosis generally involved one or two carrageenan-containing macrophages encapsulated by a few collagen fibres. No widespread fibrosis was ever observed in this study which confirmed earlier histological and biochemical investigations.

A histological study of the carrageenan-induced granuloma in the rat lung

Intralobular injection of 0.17 ml of 2% carrageenan, through a ventral slit in the trachea of rats, induced localised areas of inflammation with a high survival rate. This inflammation was characterised by immediate polymorphonuclear leucocyte (PMN) infiltration into the interstitial and alveolar spaces followed in 4 days by replacement of the PMNs by carrageenan-containing macrophages. Between days 10 to 70, the macrophages rapidly increased in size and accumulated numerous large vacuoles which stained for the presence of carrageenan. Several macrophages were so large that they each filled an entire alveolar space. From days 70 to 205, the macrophage appearance was unchanged except that the staining of their carrageenan-containing vacuoles was less metachromatic with toluidine blue. Fibrosis was first noted at day 205 and consisted of several small granulomas located near large airways and blood vessels. These granulomas had a central area filled with macrophages and a peripheral zone consisting of fibroblasts, new collagen, scattered macrophages and blood vessels. The morphology of the macrophages remained essentially unchanged from days 205 to 500 but by day 500, the macrophages were found only in numerous pockets within the inflamed lobe. They still stained positive for the presence of carrageenan at day 500. The extreme longevity of these macrophages and the lack of significant fibrosis may be due to the "un-naturalness", indigestibility, and low toxicity of the irritant, carrageenan. In addition, their size and numerous vacuoles may have inhibited their movement and subsequent removal from the lung. The paucity of significant fibrosis may be due to the lack or inhibition of a "fibroblast stimulating factor" released by the macrophages or possibly the collagen was degraded as soon as it was synthesised. This carrageenan-induced inflammation is a very suitable for the study of alveolar macrophages but appears to be inappropriate for the study of pulmonary fibrosis.

An ultrastructural study of periderm granules in the regenerating feather of the jungle fowl

Periderm granules in the support cells of regenerating feathers of mature male Jungle Fowls were studied ultrastructurally and histochemically. Histochemical results showed the absence of carbohydrate and lipid, and the presence of protein in the periderm granules. The periderm granules were measured at successive levels of feather regeneration. The mean size of the periderm granules increased significantly as the regenerating feather matured, and this observation was suggestive of a storage function, perhaps of surplus of waste protein. The cells in which the periderm granules are found also contain glycogen. There are numerous desmosomal junctions on their interdigitating plasma membranes. These transient cells may collect waste, provide nutrition, and serve as a protective barrier for the definitive cells of the regenerating feather.