Amylin and its relation to insulin and lipids in obese children before and after weight loss

Objective: There are limited data concerning the relationships between amylin, weight status, lipids, insulin, and insulin resistance in obese humans. Therefore, the aim was to study these relationships in cross‐sectional and longitudinal analyses. Research Methods and Procedures: Fasting amylin, insulin, glucose, triglycerides, low‐density lipoprotein (LDL)‐ and high‐density lipoprotein (HDL)‐cholesterol, and percentage body fat based on skinfold measurements were determined in 37 obese children (median age, 11.5 years) and compared with 16 lean children of the same age and gender. Furthermore, we analyzed the changes of these variables in the obese children after participating in a one‐year weight loss intervention program. Results: Obese children had significantly (p < 0.01) higher amylin, triglycerides, LDL‐cholesterol, and insulin levels as compared with the lean children. In multiple linear regression analysis, amylin was significantly (p < 0.05) correlated to insulin and triglycerides, but not to age, gender, pubertal stage, or BMI. Changes of amylin correlated significantly (p < 0.001) to changes of insulin (r = 0.54) and triglycerides (r = 0.49), but not to changes of BMI or percentage body fat. Substantial weight loss in 17 children led to a significant (p < 0.05) decrease of amylin, triglycerides, and insulin, in contrast to the 20 children without substantial weight loss. Conclusion: Amylin levels were related to insulin concentrations in both cross‐sectional and longitudinal analyses, suggesting a relationship between amylin and insulin secretion. Amylin levels were reversibly increased in obesity and related to triglyceride concentrations.     

Simultaneous determination of incretin hormones and their truncated forms from human plasma by immunoprecipitation and liquid chromatography-mass spectrometry

The incretins, glucose-dependent insulinotropic peptide (GIP(1-42)) and glucagon-like peptide 1 (GLP-1(7-36)), are involved in regulation of gastric emptying, glucose homeostasis, body fat regulation and the glucose-induced insulin secretion from the endocrine pancreas. After release in the circulation both peptides are rapidly degraded by the exopeptidase dipeptidyl peptidase IV (DP IV) to the inactive polypeptides GIP(3-42) and GLP-1(9-36). In vivo stabilization of the active incretins by orally available DP IV-inhibitors is now widely accepted as a new therapeutic approach in antidiabetic treatment. In order to demonstrate the pharmacodynamic effect of DP IV-inhibitors, it is necessary to measure the plasma levels of active and inactive forms of GIP and GLP-1. We previously described an immunoprecipitation method as sample preparation and concentration in combination with a LC-MS analysis for determination of active and inactive GIP. We could improve the efficiency and suitability of this method by reduction of the necessary sample volume to 1.0 ml and simultaneous measurement of GIP(1-42), GIP(3-42) and GLP-1(7-36), GLP-1(9-36), without loss of sensitivity. An LOQ of approximately 5 and 11 pmol/l was maintained for GIP and GLP-1, respectively.     

Growth regulation and development in Physcomitrella patens: an insight into growth regulation and development of bryophytes

Observations made on the effects of auxin, of cytokinin and of various light treatments on cultures of wild-type Physcomitrella patens , grown either on solid medium or in continuously-replaced liquid medium, have allowed us to suggest probable roles for these factors during the early stages of normal gametophyte development. Further data obtained by studying mutants affected in their responses to one or both types of hormones or to light have supported our model of gametophyte development and enabled us to elaborate it.     

The current status of physiology and biochemistry of brassinosteroids

Brassinolide, first isolated from pollen of rape as a plant growth promoting substance, has been found to be widely distributed in the plant kingdom. Over thirty endogenous analogues, called collectively brassinosteroids, have been isolated and identified. As a new class of plant hormones, brassinosteroids show not only growth promoting activity but also other physiological effects on the growth and development of plants and draw attention as promising chemicals for practical application in agriculture. This review describes the current status of the studies on the natural occurrence, analysis, physiological actions, metabolism and biosynthesis of brassinosteroids.Abbreviations ABA abscisis acid - BR brassinosteroid - GA gibberellin - GC-MS combined gas chromatography-mass spectrometry - GC-SIM combined gas chromatography-selected ion monitoring - HPLC high performance liquid chromatography - IAA indole-3-acetic acid     

Circadian and seasonal variations of physiological and biochemical determinants of acute myocardial infarction

Almost all cardiovascular events occur according to a circadian rhythm with a greater frequency in the morning on waking and when resuming activity, the mechanism and precise triggering events for myocardial infarction (MI) are not yet fully known. Multiple biologic functions show a diurnal and/or seasonal variation that may contribute to adverse cardiac outomes. Exogenous factors may also modulates these variations. The MI peak usually occurs between 07:00 and 12:00 h. This timing corresponds to the concurrent increase in platelet aggregability, blood concentration of cortisol, catecholamines, angiotensin II, myocardial oxygen demand and coagulation activity, while fibrinolytic activity is decreased. In this review paper we will point out the biological rhythms of a number of functions involved in acute myocardial infarction e.g. blood pressure, hormonal determinants, cholesterol, among others.     

激素对植物细胞悬浮培养代谢产物的影响研究进展

激素是调节植物细胞生长发育和代谢产物形成的主要物质。综述了在植物细胞悬浮培养中,激素对细胞生物量和代谢产物含量的影响的研究进展。内容包括外源激素的种类、浓度、配比对悬浮培养细胞生物量和代谢产物含量的影响,内源激素检测技术的发展历程、内源激素的含量变化及其对悬浮培养细胞生物量和代谢产物含量的影响,内源激素和外源激素对植物细胞悬浮培养影响的相互作用关系以及新品种激素影响作用的相关研究。     

多胺与植物激素

本文概述了多胺与植物生长促进剂、生长抑制剂及乙烯的关系,以及它们对植物生长发育、花芽分化、抗逆性及衰老的作用。     

Environmental physiology of the teleostean thyroid gland: a review

Synopsis Recent studies of thyroid hormone function are reviewed as they relate to the environmental physiology of teleost fish. In addition, reports dealing with the apparent interdependence of thyroid gland function with that of other endocrine glands are discussed with emphasis on the interrelated endocrine response associated with changing physiological status of teleosts.Seasonal changes in thyroid gland activity are described in several species. Although seasonal alterations in apparent thyroid status are concomitant with changes in ambient temperature, photoperiod and/or gonadal status, their biological significance is not fully understood and direct relationships are for the most part, not proven. Similarly, most reports of thyroid involvement in gonadal development or maturation are based on indirect evidence of the relationship. The exception to this is a study in immature or hypophysectomized goldfish in which thyroxine (T₄) was shown to promote ovarian development and maturation, possibly acting collateralistically or synergistically with gonadotropin. Even in this study it is not clear whether the T₄ effect is a direct action on the ovarian tissue or an indirect action via the regulation of metabolites necessary for gonad metabolism. Integumentary silvering and retinal porphyropsin formation in salmonids are stimulated by administration of T₄ or thyroid extracts. Administration of T₄ or triiodothyronine (T₃) enhances skeletal and somatic growth in some teleostean species, although the effect on somatic growth is most pronounced when these hormones act synergistically with somatotropin (STH) or androgens. The growth-promoting effects of T₄ and T₃ may be linked to their apparent involvement in lipid, carbohydrate, protein and vitamin metabolism. alterations in apparent thyroid activity concomitant with changes in ambient temperature have been reported (for example correlated with seasonal ambient thermal changes), although there are marked contradictions in data presented by different investigators. Reported temperature-related effects on thyroid function are probably secondary responses of thyroid metabolism to altered temperatures. Evidence of a direct rate of thyroid hormones in the regulation of migration (and associated behavioural modifications), salmonid smoltification, oxygen consumption, and osmotic or ionic regulation although highly suggestive in a number of areas is inconclusive and requires further critical experimental evaluation.The pituitary control (by thyrotropin) of thyroid secretion of T₄ is convincingly shown in several teleosts, and evidence of an inhibitory hypothalamic control of thyrotrop activity is highly suggestive in some species. A thyrotropic effect of somatotropin preparations is well established in several teleostean species; the effect does not appear to be related to contamination of the somatotropin preparations with thyrotropin, and may be an important consideration in explaining the apparently related involvement of T₄ (or T₃) and somatotropin in growth and metabolism. The apparent thyrotropic property of some gonadotropin preparations, shown in several teleostean species, requires further investigation before the doubts regarding hormone preparation purity can be satisfied. Recent studies of effects of prolactin on thyroid function are highly suggestive of an inhibitory role of prolactin in peripheral monodeiodination of T₄ to T₃ which secondarily affects thyroid activity in some species. There is no evidence of a direct involvement of corticotropin, melanotropin or fractions of these molecules on thyroid function in teleosts. Moreover, the little evidence in support of a role of gonadal or adrenocortical steroids in thyroid control is either often contradictory or indirect and needs to be evaluated further.Interlake epizootiological studies of thyroid dysfunction in Great Lakes salmonids provide substantive evidence for the presence of a ubiquitous waterborne goitrogen(s) in the Great Lakes environs. The nature of the goitrogen(s), whether naturally-occurring or a man-introduced toxicant, remains to be determined but the possible existence of waterborne goitrogens in natural water systems and their possible effects on experimental studies of teleostean thyroid function have to be evaluated further. If goitrogens are a common component of aquatic environments their presence could explain some of the data discrepancy among different groups of investigators, and could account for some of the apparent seasonal change in teleost thyroid physiology.     

Display of proceptive behaviors in relation to urinary and fecal progestin levels over the ovarian cycle in female tufted capuchin monkeys

In many primates species, female sexual attractivity is influenced by behavioral cues as well as by nonbehavioral cues (i.e., visual-morphological or chemical signals). Both kinds of cues are usually related to the ovarian cycle and female hormonal state. Female tufted capuchins (Cebus apella) lack any external morphological change in relation to the ovarian cycle and evidence of scent-marking behavior has never been reported. In addition, tufted capuchin males do not routinely investigate the female's body or urine. Instead, capuchin females are extremely active in sexually soliciting the male(s) and their courtship toward them involves a rich behavioral repertoire. In the present study we defined female tufted capuchin proceptivity and investigated its relationship with female reproductive state. Ovarian hormones were measured in urine and fecal samples from four captive females in order to (a) assess their reliability for monitoring female ovarian function and (b) provide information on the timing of the component cycle phases and in particular the periovulatory phase. Measurements of urinary and fecal progestin metabolites provided the best indicator of ovarian cyclicity and for timing of the periovulatory phase. Through a multivariate analysis of the behavioral data set we distinguished four behaviors (eyebrow raising with vocalization, touching-and-running, nuzzling and head cocking) which showed a marked cyclicity (21.3 days) that matched that of urinary progesterone (21.9 days). Data showed that each period of proceptive behaviors was 2.7 +/- 0.8 days long and the day of a defined luteal phase rise in urinary progesterone levels was markedly shifted toward the end of this period. Furthermore, the ejaculations observed always occurred within proceptive periods. The results clearly indicate that female behavior is a good indicator of the periovulatory phase and can enhance female attractivity.     

正常月经周期妇女卵泡液中激素水平的变化

本文测定了24例正常月经妇女在不同时相、不同大小卵泡的卵泡液中雌二醇(E_2)、孕酮(P_0)、雄烯二酮(A)、睾酮(T)、卵泡刺激素(FSH)、黄体生成素(LH)和催乳素(PRL)的含量,并分析其与外周血中相应激素浓度的关系。测定结果显示:小卵泡的卵泡液中E_2、Po,FSH,LH水平低于大卵泡中水平,而A和T水平则相反。排卵前大卵泡中E_2(9815nmol/L),P_0(3316nmol/L),FSH(1.34IU/L)和LH(3.9lIU/L)达最高值。A(280nmol/L)和T(137nmol/L)却较小卵泡中水平低(相应为692nmol/L和176nmol/L)。PRL水平在大小卵泡中无显著性差异。卵泡液中甾体激素水平高于外周血7—20.000倍,FSH、LH水平为外周血的10—80％,PRL水平为60％—3倍。     

Reproduction in the vervet monkey (Cercopithecus aethiops): II. Annual menstrual patterns and seasonality

Menstrual patterns and progesterone levels were monitored for 5 years from a cohort of 28 female vervet monkeys that were individually caged indoors. Three distinct cycle types (short, normal, and prolonged) were defined according to cycle length. Mean length of the normal cycle (32.5 days) and menses duration (4.8 days) are in agreement with previous reports. Prolonged cycles (> 50 days) contributed 20% of the total, with a decreased incidence during the natural peak breeding period. Weekly progesterone measurements indicated that many prolonged cycles were associated with an extended luteal phase, while others were probably due to lack of ovulation. From these data it would appear that the vervet monkey, although not strongly seasonal, does favor a particular time of year for breeding in a colony housed indoors.     

Actions of calcitonin, parathyroid hormone, and prostaglandin E2 on cyclic AMP formation in chicken and rat osteoclasts

The effects of calcitonin, parathyroid hormone, and prostaglandin E2 on cyclic AMP production were studied in osteoclast-rich cultures derived from medullary bone of laying hens and from the long bones of newborn rats. Cyclic AMP was assayed biochemically in replicate cultures, and furthermore, changes in cytoplasmic fluorescence were sought by indirect immunofluorescence with rabbit anti-cyclic AMP and FITC-labelled goat anti-rabbit IgG. Treatment of rat osteoclasts with calcitonin increased cyclic AMP formation as measured biochemically, and this was confirmed by the immunofluorescence method. No such increase took place in chick osteoclasts. Prostaglandin E2 increased cyclic AMP production in both rat and chick osteoclasts as determined by both methods. Since the immunofluorescence method failed to detect a response to parathyroid hormone either in chick or rat osteoclasts, its variable biochemical effects were concluded to be due to actions on contaminating osteoblasts in the cultures. Thus it has been possible with a combined biochemical and immunocytochemical approach to define the cyclic AMP responses to the calcium-regulating hormones in rat and chick osteoclasts. The failure of calcitonin to increase cyclic AMP in chick osteoclasts identifies a need to investigate the nature of calcitonin action on avian osteoclasts, which may contribute to understanding of its actions on mammalian cells.     

Reproductive and metabolic hormones during estrus after fasting in Holstein heifers

The estrous cycles of 23 Holstein heifers were synchronized with three prostaglandin F₂α (PG) injections at 0600 h 11 d apart, designated as Days ?11, 0 and 11. Twelve of the animals were randomly assigned to receive no solid food (Group F) from Day 6 to 14, while the other animals remained on full feed to serve as controls (Group C). Jugular blood samples were collected at 6-h intervals beginning with PG injection at 0600 h on Day 0 until 1800 h on Day 4 and at 0600, 1200 and 1700 h on Day 8 through 10. Samples were collected again at 6-h intervals from PG Day 11 (0600 h) until 1800 h on Day 15. Period 1 was defined as those samples collected from Day 0 through 4.5, Period 2 from Day 7 through 10, Period 3 from Day 11 through 14.25, and Period 4 from Day 14.5 through 15. Plasma growth hormone concentrations were increased (P<0.01) in F as compared with C animals during Periods 2, 3 and 4. Plasma concentrations of prolactin (P<0.01) were decreased in F as compared with C animals during Periods 2 and 3. Plasma urea concentrations were increased (P<0.01) in F as compared with C animals during the first 3 d of the fast (Period 2) but were decreased (P<0.01) during the remainder of the experiment (Periods 3 and 4). Thus, fasting was effective in altering several metabolic parameters. Although plasma progesterone and luteinizing hormone (LH) concentrations remained similar (P>0.05) between F and C animals, plasma estradiol-17β concentrations decreased in F as compared with C animals during Periods 2, 3 and 4. No differences (P>0.05) between F and C animals were found in duration to LH peak after PG injection, estrous behavior, or pregnancy rates. Results from this study indicate that fasting reduced plasma estradiol-17β concentrations during estrus but did not alter occurrence of estrus or pregnancy rate.     

腹腔镜对结直肠癌患者血清基质金属蛋白酶、胃肠激素及应激激素水平的影响

目的:探讨腹腔镜对结直肠癌患者血清基质金属蛋白酶、胃肠激素及应激激素水平的影响。方法:将110例结直肠癌患者纳入本研究,随机分为对照组和观察组,均55例,分别给予对照组和观察组患者开腹手术治疗和腹腔镜手术治疗,对比治疗前后患者的血清基质金属蛋白酶、胃肠激素及应激激素水平。结果:治疗前,两组血清基质金属蛋白酶(Matrix metalloproteinase,MMP)MMP-2、MMP-9、血清胃动素(Motilin,MTL)、胃泌素(Gastrin,GAS)、皮质醇(Cortisol,Cor)、去甲肾上腺素(Noradrenaline,NE)水平比较差异均无统计学意义(P0.05);与组内治疗前相比,两组治疗后血清MMP-2、MMP-9、MTL、GAS水平均显著降低,血清COR、NE水平均显著升高,差异有统计学意义(P0.05);观察组治疗后血清MMP-2、MMP-9、NE、COR水平均明显低于对照组,血清GAS、MTL水平均明显高于对照组,差异对比均有显著性(P0.05)。结论:腹腔镜治疗结直肠癌可有效降低患者血清基质金属蛋白酶水平,促进胃肠功能恢复,减轻机体应激损伤。     

Urinary steroid evaluations to monitor ovarian function in exotic ungulates: VIII. Correspondence of urinary and plasma steroids in the llama (Lama glama) during nonconceptive and conceptive cycles

Ovarian function was evaluated in mature female llamas (n = 2) during seven ovulations in 2 conceptive and 5 nonconceptive ovarian cycles by measuring urinary and plasma hormone concentrations. Ovulation was induced by three different methods; administration of gonadotropin-releasing hormone (GnRH), copulation with a vasectomized male and copulation with an intact male. Plasma estradiol and progesterone concentrations, and urinary concentrations of estrogen conjugates and two progesterone metabolites, pregnanediol-3-glucuronide (PdG), and immunoreactive (iPdG), concentrations were compared to determine their value in monitoring ovarian function. Estrogen concentrations in urine corresponded to estradiol levels in plasma and accurately reflected changes in follicular activity when evaluated over several daily samples. Plasma progesterone and urinary iPdG were reliable indicators of luteal function. These data represent the first comparison of blood and urinary hormone measurements for monitoring the complete ovarian cycle of an ungulate, and demonstrates that either can be used to assess changes in ovarian activity in this species.     

Nutritional regulation of body condition score at the initiation of the transition period in primiparous and multiparous dairy cows under grazing conditions: milk production, resumption of post-partum ovarian cyclicity and metabolic parameters

The objective of this study was to investigate the effect of different body condition score (BCS) at 30 days before calving (-30 days) induced by a differential nutritional management from -100 days until -30 days on productive parameters, the interval to first ovulation and blood parameters in primiparous and multiparous Holstein cows under grazing conditions until 60 days post partum. The experimental arrangement was a randomized complete block design, where cows were blocked according to BW and expected calving date and then randomly assigned to different nutritional treatments from -100 to -30 days relative to calving to induce different BCS. As the assignment of cows to treatments was random, cows had to lose, maintain or gain BCS; thus, different planes of nutrition were offered with approximately 7, 14 or 20 kg dry matter per day. The BCS score was assessed every 15 days and animals were reassigned in order to achieve the desired BCS at -30 days. Only animals that responded to nutritional treatment were considered and this was defined as follows: primiparous and multiparous high cows (PH and MH) had to gain 0.5 points of BCS, primiparous low (PL) had to lose 0.5 points of BCS and multiparous low (ML) had to maintain BCS at least in two subsequent observations from -100 to -30 days. From -30 days to calving, primiparous and multiparous cows (P and M cows) were managed separately and cows were offered a diet once a day. From calving to 60 days post partum, cows of different groups grazed in separate plots a second year pasture. Cows were also supplemented individually with whole-plant maize silage and commercial concentrate. Cows had similar BCS at -100 days and differed after the nutritional treatment; however, all groups presented similar BCS at 21 days post partum. The daily milk production and milk yield at 60 days post partum was higher in M than P cows. The percentage of milk fat was higher in PH cows compared with PL cows. Concentrations of non-esterified fatty acids (NEFA) were affected by the BCS at -30 days within parity, and in PH cows the concentration of NEFA was higher than in PL cows. The concentrations of total protein were higher in M cows. A lower probability of cycling was found in PL than in PH cows (P < 0.05) and in ML than in MH cows (P < 0.05). Treatment affected various endocrine/metabolic profiles according to parity, suggesting that the metabolic reserves signal the productive/reproductive axis so as to induce a differential nutrient partitioning in adult v. first-calving cows.     

Amino acid modifications in canine, equine and porcine pituitary growth hormones, identified by peptide-mass mapping

Modified amino acid residues in porcine, canine and equine growth hormones purified from pituitary glands were characterised by tryptic mapping and high-performance liquid chromatography with on-line coupled electrospray ionisation mass spectrometry (HPLC–ESI-MS) detection. Hormones from all three species showed the same changes. Conversion of Asp¹²⁸ to iso-Asp¹²⁸ was a component of native hormones, while deamidation of Asn¹² and Asn⁹⁸ to Asp and iso-Asp, oxidation of Met⁴, and cyclisation to the pyroglutamyl derivative of Gln¹³⁹, probably occurred in vitro, during isolation, storage or hydrolysis. Porcine and canine hormones had indistinguishable protein fingerprints, confirming the assumption, based on their cDNA sequences, that their mature primary structures are identical.     

Estrogen and prostate cancer: an eclipsed truth in an androgen-dominated scenario

Prostate cancer is the commonest non-skin cancer in men. Incidence and mortality rates of this tumor vary strikingly throughout the world. Although several factors have been implicated to explain this remarkable variation, lifestyle and dietary factors may play a dominant role, with sex hormones behaving as intermediaries between exogenous factors and molecular targets in development and progression of prostate cancer. Human prostate cancer is generally considered a paradigm of androgen-dependent tumor; however, estrogen role in both normal and malignant prostate appears to be equally important. The association between plasma androgens and prostate cancer remains contradictory and mostly not compatible with the androgen hypothesis. Similar evidence apply to estrogens, although the ratio of androgen to estrogen in plasma declines with age. Apart from methodological problems, a major issue is to what extent circulating hormones can be considered representative of their intraprostatic levels. Both nontumoral and malignant human prostate tissues and cells are endowed with key enzymes of steroid metabolism, including 17betahydroxysteroid dehydrogenase (17betaHSD), 5beta-reductase, 3alpha/3betaHSD, and aromatase. A divergent expression and/or activity of these enzymes may eventually lead to a differential prostate accumulation of steroid derivatives having distinct biological activities, as it occurs for hydroxylated estrogens in the human breast. Locally produced or metabolically transformed estrogens may differently affect proliferative activity of prostate cancer cells. Aberrant aromatase expression and activity has been reported in prostate tumor tissues and cells, implying that androgen aromatization to estrogens may play a role in prostate carcinogenesis or tumor progression. Interestingly, many genes encoding for steroid enzymes are polymorphic, although only a few studies have supported their relation with risk of prostate cancer. In animal model systems estrogens, combined with androgens, appear to be required for the malignant transformation of prostate epithelial cells. Although the mechanisms underlying the hormonal induction of prostate cancer in experimental animals remain uncertain, there is however evidence to support the assumption that long term administration of androgens and estrogens results in an estrogenic milieu in rat prostates and in the ensuing development of dysplasia and cancer. Both androgen and estrogen have been reported to stimulate proliferation of cultured prostate cancer cells, primarily through receptor-mediated effects. As for estrogens, the two major receptor types, ERalpha and ERbeta, are expressed in both normal and diseased human prostate, though with a different cellular localization. Since these two receptors are different in terms of ligand binding, heterodimerization, transactivation, and estrogen response element activity, it is likely that an imbalance of their expression may be critical to determine the ultimate estrogen effects on prostate cancer cells. In prostate cancer, ERbeta activation appears to limit cell proliferation directly or through ERalpha inhibition, and loss of ERbeta has been consistently associated with tumor progression. Several splicing variants of both ERalpha and ERbeta exist. Little is known about their expression and function in the human prostate, although reciprocal regulation and interaction with gene promoter both warrant further investigation. In summary, although multiple consistent evidence suggests that estrogens are critical players in human prostate cancer, their role has been only recently reconsidered, being eclipsed for years by an androgen-dominated interest.     

Influences of Sex,Castration, and Androgens on the Eumelanin and Pheomelanin Contents of Different Feathers in Wild Mallards

In mallards the bright nuptial plumage of the drake represents the neutral, sex hormone-independent coloration of the species that both sexes eventually exhibit after castration. We compared the pheo- and eumelanin contents of feathers from the head, breast, flank, and under-tail coverts in five groups of mallards after the post-nuptial molt in summer: intact hens, intact drakes, castrated drakes, castrated drakes injected with testosterone during the spring, and castrated drakes injected with 5α-dihydrotestosterone during the spring. In the head feathers and under-tail coverts, the gonadal hormones of the intact birds and the testosterone injections into castrates significantly reduced the eumelanin content, tended to increase the pheomelanin content, and, thereby, changed the melanin type from eumelanic in the untreated castrates to mixed melanic in the other three groups. The eumelanin contents of the flank feathers did not differ among the groups, but the pheomelanin contents at this site was significantly elevated in the two intact groups and the testosterone-treated compared to the uninjected castrates. Again, the melanin type changed from eumelanic in the castrates to mixed melanic in the other three groups. The high pheomelanin content of the breast feathers in the castrated birds was significantly reduced in the hens, intact drakes, and testosterone-injected castrates with a concomitant tendency for elevated eumelanin contents. At this site, a change occurred from pheomelanic to mixed melanic. 5α-dihydrotestosterone was clearly less effective than testosterone in affecting the melanin contents in castrates and resulted in an intermediate coloration. The differing effects of the two androgens might be a result of differences in their conversion to estrogens.