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1.
Phys Rev Lett ; 123(24): 247203, 2019 Dec 13.
Article in English | MEDLINE | ID: mdl-31922868

ABSTRACT

In the metallic magnet Nb_{1-y}Fe_{2+y}, the low temperature threshold of ferromagnetism can be investigated by varying the Fe excess y within a narrow homogeneity range. We use elastic neutron scattering to track the evolution of magnetic order from Fe-rich, ferromagnetic Nb_{0.981}Fe_{2.019} to approximately stoichiometric NbFe_{2}, in which we can, for the first time, characterize a long-wavelength spin density wave state burying a ferromagnetic quantum critical point. The associated ordering wave vector q_{SDW}=(0,0,l_{SDW}) is found to depend significantly on y and T, staying finite but decreasing as the ferromagnetic state is approached. The phase diagram follows a two-order-parameter Landau theory, for which all of the coefficients can now be determined. Our findings suggest that the emergence of spin density wave order cannot be attributed to band structure effects alone. They indicate a common microscopic origin of both types of magnetic order and provide strong constraints on related theoretical scenarios based on, e.g., quantum order by disorder.

2.
Phys Rev Lett ; 104(10): 106406, 2010 Mar 12.
Article in English | MEDLINE | ID: mdl-20366444

ABSTRACT

We report for the first time simultaneous microscopic measurements of the lattice constants, the distribution of the lattice constants, and the antiferromagnetic moment in high-purity URu(2)Si(2), combining Larmor and conventional neutron diffraction at low temperatures and pressures up to 18 kbar. Our data demonstrate quantitatively that the small moment in the hidden order (HO) of URu(2)Si(2) is purely parasitic. The excellent experimental conditions we achieve allow us to resolve that the transition line between HO and large-moment antiferromagnetism (LMAF), which stabilizes under pressure, is intrinsically first order and ends in a bicritical point. Therefore, the HO and LMAF must have different symmetry, which supports exotic scenarios of the HO such as orbital currents, helicity order, or multipolar order.

3.
J Phys Condens Matter ; 22(5): 052201, 2010 Feb 10.
Article in English | MEDLINE | ID: mdl-21386332

ABSTRACT

We investigate the evolution of the electrical resistivity of BaFe(2)As(2) single crystals with pressure. The samples used were from the same batch, grown using a self-flux method, and showed properties that were highly reproducible. Samples were pressurized using three different pressure media: pentane-isopentane (in a piston-cylinder cell), Daphne oil (in an alumina anvil cell) and steatite (in a Bridgman cell). Each pressure medium has its own intrinsic level of hydrostaticity, which dramatically affects the phase diagram. An increasing uniaxial pressure component in this system quickly reduces the spin density wave order and favours the appearance of superconductivity, which is similar to what is seen in SrFe(2)As(2).

4.
J Inherit Metab Dis ; 32(4): 570-5, 2009 Aug.
Article in English | MEDLINE | ID: mdl-19504350

ABSTRACT

The content of coenzyme Q(10) (CoQ(10)) was examined in skin fibroblasts of 10 patients with mevalonic aciduria (MVA) and of 22 patients with methylmalonic aciduria (MMA). Patients with these inborn errors of metabolism are thought to be at risk for CoQ(10) depletion either by direct inhibition of the proximal pathway of CoQ(10) synthesis (MVA) or indirectly by inhibition of mitochondrial energy metabolism (MMA). We demonstrated that CoQ(10) concentrations were not significantly different from controls in MVA patients, suggesting that there may be upregulatory effects. On the other hand the CoQ(10) content in fibroblasts of patients with MMA was significantly reduced.


Subject(s)
Fibroblasts/metabolism , Fibroblasts/pathology , Metabolism, Inborn Errors/pathology , Mevalonate Kinase Deficiency/pathology , Ubiquinone/analogs & derivatives , Case-Control Studies , Cells, Cultured , Down-Regulation , Female , Humans , Metabolism, Inborn Errors/metabolism , Methylmalonic Acid/urine , Mevalonate Kinase Deficiency/metabolism , Muscles/metabolism , Muscles/pathology , Ubiquinone/metabolism
5.
Phys Rev Lett ; 102(18): 186602, 2009 May 08.
Article in English | MEDLINE | ID: mdl-19518895

ABSTRACT

Recent small angle neutron scattering suggests that the spin structure in the A phase of MnSi is a so-called triple-Q state, i.e., a superposition of three helices under 120 degrees. Model calculations indicate that this structure in fact is a lattice of so-called Skyrmions, i.e., a lattice of topologically stable knots in the spin structure. We report a distinct additional contribution to the Hall effect in the temperature and magnetic field range of the proposed Skyrmion lattice, where such a contribution is neither seen nor expected for a normal helical state. Our Hall effect measurements constitute a direct observation of a topologically quantized Berry phase that identifies the spin structure seen in neutron scattering as the proposed Skyrmion lattice.

6.
J Phys Condens Matter ; 21(16): 164215, 2009 Apr 22.
Article in English | MEDLINE | ID: mdl-21825395

ABSTRACT

Systems lacking inversion symmetry, such as selected three-dimensional compounds, multilayers and surfaces support Dzyaloshinsky-Moriya (DM) spin-orbit interactions. In recent years DM interactions have attracted great interest, because they may stabilize magnetic structures with a unique chirality and non-trivial topology. The inherent coupling between the various properties provided by DM interactions is potentially relevant for a variety of applications including, for instance, multiferroic and spintronic devices. The, perhaps, most extensively studied material in which DM interactions are important is the cubic B20 compound MnSi. We review the magnetic field and pressure dependence of the magnetic properties of MnSi. At ambient pressure this material displays helical order. Under hydrostatic pressure a non-Fermi liquid state emerges, where a partial magnetic order, reminiscent of liquid crystals, is observed in a small pocket. Recent experiments strongly suggest that the non-Fermi liquid state is not due to quantum criticality. Instead it may be the signature of spin textures and spin excitations with a non-trivial topology.

7.
J Chem Phys ; 120(21): 10225-30, 2004 Jun 01.
Article in English | MEDLINE | ID: mdl-15268046

ABSTRACT

The interaction of oxygen molecules with a fullerene surface has been studied using high resolution electron energy loss spectroscopy and temperature programmed desorption. Vibrational excitation of the adsorbed oxygen is observed at 190 meV, an energy value comparable with that for molecular oxygen in the gas phase. We take this to indicate physisorption of molecular oxygen on the C(60) surface. Thermal desorption results also show that the bonding of oxygen molecules to the C(60) overlayer is comparable to that on a graphite surface. A detailed study of the energy dependence of the vibrational excitation reveals an inelastic electron resonance scattering process. The angular dependence of the resonant vibrational excitation exhibits features distinctively different from those for molecular oxygen physisorbed on the related graphite surface, at a comparable coverage. One possible reason is that the corrugated surface potential, due to the curvature of the C(60) molecules, promotes the preferential ordering of the physisorbed oxygen molecules perpendicular to the surface plane of the C(60) overlayer.

8.
Anal Biochem ; 282(2): 209-17, 2000 Jul 01.
Article in English | MEDLINE | ID: mdl-10873275

ABSTRACT

A HPLC-method was developed for the simultaneous detection of the lipophilic antioxidants ubiquinol-10, ubiquinone-10, alpha-tocopherol, and gamma-tocopherol in plasma macrosamples (100 microl) as well as microsamples (10 microl) using electrochemical detection with internal standardization (gamma-tocotrienol, ubiquinol-9, ubiquinone-9). The use of a mobile phase containing ammonium formate instead of lithium perchlorate as conductivity salt and the use of a PEEK column instead of a steel column improved the reproducibility of the method. The components were separated on a RP C18 column. The detection limits for all components were between 1 and 28 fmol. The within-day precision varied between 3 and 13% for all measured substances. The analytical recovery was between 93 and 109%. The plasma levels from 10 healthy donors were determined in microsamples and macrosamples taken by micropuncture or venous puncture, respectively. A good correlation of the antioxidant levels for both methods strengthened the reliability and the transferability of the results. The present method can be used to assess the role of these antioxidants in diseases associated with oxidative damage in childhood.


Subject(s)
Antioxidants/analysis , Chromatography, High Pressure Liquid/methods , Oxidative Stress , Ubiquinone/analogs & derivatives , Ubiquinone/analysis , Ubiquinone/blood , Vitamin E/analysis , Vitamin E/blood , Benzophenones , Electrochemistry , Formates , Humans , Ketones , Polyethylene Glycols , Polymers , Reference Standards , Sensitivity and Specificity , Temperature
9.
Endocrinology ; 138(10): 4101-8, 1997 Oct.
Article in English | MEDLINE | ID: mdl-9322918

ABSTRACT

When exposed to short-day conditions, hamsters and other long-day breeders undergo gonadal regression. With chronic exposure to short days, however, the animals become photorefractory and gonadal recrudescence occurs. The underlying mechanism for this insensitivity is still unknown. There is growing evidence, however, that specific cells of the pituitary pars tuberalis (PT) mediate these photoperiod/nonphotoperiod-dependent changes as a direct or indirect "Zeitgeber" for the endocrine system. We investigated messenger RNA (mRNA)/protein formation for several hypophyseal hormones (beta-TSH, beta-LH, PRL, common alpha-chain) in the pars distalis (PD) and PT of female Djungarian hamsters in long photoperiod (LP) and after 18, 28, and 38 weeks of short photoperiod (SP). As indicated by gonadal and body weight, the hamsters displayed gonadal regression after 18 and 28 weeks of SP; after 38 weeks of SP, all animals showed recrudescence. At 18 and 28 weeks of SP, only PRL mRNA and protein levels were significantly reduced in the PD and returned to LP values after 38 weeks of SP. The expression of hypothalamic tyrosine hydroxylase in the arcuate nucleus that was determined by immunocytochemistry and by in situ hybridization was also down-regulated in SP18 and SP28 with increasing levels at SP38. Urinary 6-sulfatoxymelatonin levels were elevated in SP with highest levels in the SP18 group. In the PT, beta-TSH mRNA and protein were not detectable in all SP groups compared with the moderate signal intensity in LP. The common alpha-chain mRNA and protein, however, which were also reduced in the animals of the SP18 group, were already elevated after 28 weeks of SP and nearly reached LP-levels after 38 weeks of SP. These results show that, in contrast to LH and TSH, PRL expression in the PD is a sensitive indicator for photoperiod dependent changes of the endocrine system and seems to be tyrosine hydroxylase independent. The increase of common alpha-chain expression in PT-specific cells depending upon duration of SP that precedes the hormonal changes in the PD leads us to speculate that PT-specific cells initiate spontaneous recrudescence via a PT-PD pathway.


Subject(s)
Photoperiod , Pituitary Gland/cytology , Pituitary Gland/metabolism , Pituitary Hormones/biosynthesis , Pituitary Hormones/genetics , Animals , Arcuate Nucleus of Hypothalamus/enzymology , Base Sequence , Cloning, Molecular , Cricetinae , DNA/analysis , DNA/chemistry , DNA/genetics , Dopamine/pharmacology , Female , Gene Expression Regulation , Gene Expression Regulation, Enzymologic , Immunohistochemistry , In Situ Hybridization , Luteinizing Hormone/analysis , Luteinizing Hormone/genetics , Luteinizing Hormone/metabolism , Melatonin/analogs & derivatives , Melatonin/urine , Molecular Sequence Data , Phodopus , Pituitary Gland/physiology , Pituitary Hormones/chemistry , Polymerase Chain Reaction , Prolactin/analysis , Prolactin/genetics , Prolactin/metabolism , RNA, Messenger/analysis , RNA, Messenger/metabolism , Random Allocation , Thyrotropin/analysis , Thyrotropin/genetics , Thyrotropin/metabolism , Tyrosine 3-Monooxygenase/chemistry , Tyrosine 3-Monooxygenase/genetics
10.
J Endocrinol ; 154(3): 475-81, 1997 Sep.
Article in English | MEDLINE | ID: mdl-9379125

ABSTRACT

In hypogonadal male Djungarian hamsters FSH alone can induce normal spermatogenesis. However, for the induction of mating behavior, supplementation with testosterone is necessary. We have here investigated, by in vitro fertilization, whether sperm produced by photoinhibited hamsters treated with FSH alone can fertilize without testosterone. Photoinhibited hypogonadal male Djungarian hamsters were injected daily with human FSH (10 IU; Fertinorm) for 5-7 weeks. The hormone stimulated regrowth of the testes. Neither body weight nor the weights of the androgen-dependent organs-epididymides, prostates, accessory glands-showed significant differences from photoinhibited controls; furthermore FSH treatment did not raise intratesticular or serum testosterone levels. In eleven out of the twelve FSH-treated photoinhibited hamsters, elongated spermatids were found in the testes; in five out of nine epididymides, sperm was found by histological examination. In two out of the twelve FSH-treated hamsters, the amount of sperm in the caudal part of the epididymis was sufficient for in vitro fertilization with oocytes collected from superstimulated females. These spermatozoa fertilized 16-29% of the oocytes. Spermatozoa from photostimulated controls produced similar levels of fertilization.


Subject(s)
Fertilization in Vitro , Follicle Stimulating Hormone/therapeutic use , Hypogonadism/physiopathology , Light , Spermatozoa/physiology , Animals , Cricetinae , Female , Follicle Stimulating Hormone/blood , Hypogonadism/drug therapy , Male , Phodopus , Spermatogenesis/drug effects , Stimulation, Chemical , Testis/drug effects
11.
J Pineal Res ; 21(4): 231-8, 1996 Nov.
Article in English | MEDLINE | ID: mdl-8989722

ABSTRACT

The effects of exogenous melatonin on gonadal function and on the endogenous melatonin profiles of male and female Djungarian hamsters were investigated. Daily afternoon subcutaneous injections of melatonin (50 micrograms) in hamsters kept in long photoperiods (LD 16:8) led to gonadal inhibition in all the treated females (n = 13) but in only 2 of 13 males within the treatment period of 8 weeks (uteri: 244 +/- 11 mg in controls vs. 79 +/- 4 mg in treated hamsters, P < 0.001; ovaries: 13.6 +/- 0.6 mg in controls vs. 7.9 +/- 0.7 mg in treated hamsters, P < 0.001; testes: 1,021 +/- 54 mg in controls vs. 732 +/- 100 mg in treated hamsters, P < 0.05; and accessory glands: 641 +/- 38 mg in controls vs. 548 +/- 70 mg in treated hamsters, P > 0.05). These results indicate that there are some circumstances under which the gonadal responses of the reproductive organs of male and female Djungarian hamsters differ. Interestingly, pineal concentrations of melatonin were found to be significantly higher in males (P < 0.01), possibly indicating a more robust endogenous supply with the hormone, whereas serum melatonin levels were not significantly different between males and females. However, the subcutaneous injection of melatonin (5, 25, and 125 micrograms) exerted no acute effect on the endogenous, circadian melatonin-profile, independent of dosage and sex.


Subject(s)
Melatonin/metabolism , Melatonin/pharmacology , Pineal Gland/metabolism , Reproduction/physiology , Animals , Circadian Rhythm/physiology , Cricetinae , Dose-Response Relationship, Drug , Drug Administration Schedule , Estrus/physiology , Female , Injections, Subcutaneous , Male , Ovary/drug effects , Ovary/metabolism , Phodopus , Photoperiod , Pineal Gland/drug effects , Reproduction/drug effects , Sex Factors , Testis/drug effects , Testis/metabolism , Uterus/drug effects , Uterus/metabolism
12.
Endocrinology ; 137(5): 1804-13, 1996 May.
Article in English | MEDLINE | ID: mdl-8612518

ABSTRACT

Hamster hypophyseal pars tuberalis (PT)-specific cells are characterized by the expression of common alpha-chain and TSH beta. Immunoreactivity for these subunits and the morphology of these cells are known to exhibit remarkable seasonal changes. The high density of melatonin (Mel) receptors on PT-specific cells leads to the supposition that fluctuations in circulating Mel levels induced by photoperiodic signals are a crucial factor for the morphological alterations. To more closely investigate transcriptional and translational activities in PT-specific cells, we cloned and sequenced hamster alpha and TSH beta complementary DNA fragments and assessed messenger RNA/protein formation by in situ hybridization and immunocytochemistry under short and long photoperiod and in pinealectomized animals kept in short photoperiod. Hamster common alpha-chain and TSH beta exhibited high sequence homology with the corresponding rat hormones [94% (alpha-chain) and 90% (TSH beta) on the nucleotide level and 100% (alpha-chain) and 96% (TSH beta) on the amino acid level]. Immunocytochemical staining with antibodies directed against the common alpha-chain and TSH beta revealed a reduced immunoreactivity of PT-specific cells under short photoperiod, but this was not altered in pinealectomized animals exposed to short photoperiod. In situ hybridization against both hormonal subunits paralleled these changes, with a dramatic decrease in hormonal messenger RNA in short photoperiod. This regulatory influence was also blocked in pinealectomy. Taken together, these results demonstrate that transcription and translation of hormonal subunits are regulated by photoperiod in hamster PT-specific cells, whereas expression remained unchanged in short photoperiod if pinealectomy was performed. We, therefore, conclude that in hamsters, the Mel Signal not the light regimen per se, is a direct or indirect Zeitgeber for the transduction of photoperiodic information to the secretory activity in this pituitary cell type.


Subject(s)
Glycoprotein Hormones, alpha Subunit/metabolism , Photoperiod , Pineal Gland/physiology , Pituitary Gland, Anterior/metabolism , Thyrotropin/metabolism , Amino Acid Sequence , Animals , Base Sequence , Blotting, Northern , Cloning, Molecular , Cricetinae , DNA, Complementary/chemistry , Female , Glycoprotein Hormones, alpha Subunit/chemistry , Glycoprotein Hormones, alpha Subunit/genetics , In Situ Hybridization , Microscopy, Electron , Molecular Sequence Data , Phodopus , Pineal Gland/surgery , Rats , Sequence Analysis, DNA , Thyrotropin/chemistry , Thyrotropin/genetics
13.
J Neuroendocrinol ; 7(8): 607-13, 1995 Aug.
Article in English | MEDLINE | ID: mdl-8704734

ABSTRACT

Hypophyseal pars tuberalis (PT)-specific cells are known to exhibit remarkable seasonal changes in morphology especially in photoperiodic animals like the Djungarian hamster Phodopus sungorus. Their high density of melatonin-receptors leads to the supposition that fluctuations in circulating melatonin levels are a crucial factor for the morphological alterations induced by photoperiodic signals. To prove this hypothesis the nocturnal elevation of melatonin in long photoperiods was prolonged by late afternoon administration of melatonin. We investigated whether this treatment induces cytological changes usually observable under short photoperiod. Electron microscopy revealed that in contrast to hamsters maintained in long photoperiods PT-specific cells of hamsters injected with melatonin or those kept in short photoperiods appear inactive, containing a relatively high number of secretory granules, sparse endoplasmatic reticulum, irregularly outlined and invaginated cell nuclei and a high amount of glycogen. Furthermore immunoreactivity for the common alpha-chain of glycoprotein hormones and beta-TSH was significantly weaker in hamsters kept in short photoperiods or daily injected with melatonin than untreated or vehicle injected controls in long photoperiod. These results demonstrate that an exogenous prolongation of the elevated nocturnal melatonin levels causes a similar morphological appearance of PT-specific cells as observed in short photoperiods. It is tempting to speculate that the melatonin signal is a direct 'Zeitgeber' for the transduction of photoperiodic information to the secretory activity in this cell type.


Subject(s)
Melatonin/pharmacology , Photoperiod , Pituitary Gland, Anterior/drug effects , Animals , Body Weight/drug effects , Cricetinae , Female , Glycoproteins/metabolism , Immunohistochemistry , Melatonin/administration & dosage , Melatonin/metabolism , Microscopy, Electron , Organ Size/drug effects , Phodopus , Pituitary Gland, Anterior/cytology , Pituitary Gland, Anterior/ultrastructure , Receptors, Cell Surface/metabolism , Receptors, Melatonin , Thyrotropin/metabolism
14.
Biol Reprod ; 51(4): 714-24, 1994 Oct.
Article in English | MEDLINE | ID: mdl-7819454

ABSTRACT

Male Djungarian hamsters with previous light experience of long photoperiods of 16 h of light per day (16L:8D) or short photoperiods (8L:16D) were transferred either to the opposite photoperiods or to intermediate photoperiods (14L:10D). It was demonstrated that the same intermediate photoperiod could exert inhibitory or stimulatory effects on coat color, body weight, and the reproductive system, dependent on the previous light history. The response was graduated in accordance with the degree of change in day length. Despite opposite responses to the same photoperiod, diurnal patterns of melatonin in the pineal glands were identical. However, the circadian melatonin pattern in serum of photoinhibited hamsters had a more pronounced nighttime elevation than that found in the serum of photostimulated animals. In hamsters nonresponsive to short photoperiods, no proper short-day pattern was found. Melatonin production is a highly dynamic process, causing concentration shifts in the pineal gland and changes in the serum amplitude during prolonged exposure to short photoperiods. The different reactions to identical photoperiods are associated with different serum melatonin patterns, as shown here for the first time.


Subject(s)
Melatonin/blood , Melatonin/metabolism , Photoperiod , Pineal Gland/metabolism , Animals , Circadian Rhythm , Cricetinae , Hair Color , Male , Organ Size , Phodopus , Testis/anatomy & histology
15.
Biol Reprod ; 49(2): 243-50, 1993 Aug.
Article in English | MEDLINE | ID: mdl-8373948

ABSTRACT

This study was designed to analyze morphological changes in the reproductive organs and endocrine changes in the serum and pituitaries of female Djungarian hamsters during regression, the period of involution and early spontaneous recrudescence in response to short photoperiods. In addition, the involvement of the pineal gland on the inhibitory response to short photoperiods was investigated. In the first study, 63 adult female hamsters were divided into five groups, which were either pinealectomized at the time of transfer or 11 wk after transfer into short photoperiods, or exposed to different light regimens. The estrous cycles of these hamsters were recorded by vaginal smears for a period of 34 wk. In a second study, 156 adult female hamsters were divided into 14 groups and maintained under the influence of long or short photoperiods for 0-33 wk. The animals were killed by decapitation at 3-wk intervals and analyzed for changes in body weight and morphology of the vagina, ovary, and uterus. A loss of cyclic activity and complete involution of uterus and vagina were observed between Week 9 and Week 27 after transfer into short photoperiods. During this time period, no corpora lutea were observed in the ovaries. Under the influence of short photoperiods, the numbers of medium and antral follicles declined continuously until Week 15, and afterwards gradually recovered to maximal numbers in Week 27. This biphasic response to short photoperiods was not observed in the number of small follicles. These morphological changes were accompanied by changes in serum and pituitary FSH concentrations. Pinealectomy prevented the loss of estrous cyclicity after transfer into short photoperiods.(ABSTRACT TRUNCATED AT 250 WORDS)


Subject(s)
Estrus/physiology , Ovary/anatomy & histology , Photoperiod , Pineal Gland/physiology , Uterus/anatomy & histology , Vagina/anatomy & histology , Animals , Body Weight , Cricetinae , Female , Follicle Stimulating Hormone/blood , Organ Size , Phodopus , Pineal Gland/surgery
16.
J Pineal Res ; 12(2): 64-70, 1992 Mar.
Article in English | MEDLINE | ID: mdl-1578338

ABSTRACT

In the Djungarian hamster (Phodopus sungorus) there is strong evidence that the nightly decompression or lengthening, respectively, of the pineal melatonin pattern is involved in conveying the inhibitory influence of short photoperiods. Some hamsters, however, are insensitive to photoinhibitory influences; other late-responding hamsters show a delayed reaction of several months. The daily pattern of pineal melatonin proves that the mechanisms determining long- or short-day patterns become effective in the morning and evening hours when melatonin concentrations of photoinhibited hamsters are clearly elevated, while those of long-day hamsters are reduced to negligible low values. At two decisive time points in the morning and evening, male and female early-responding photosensitive hamsters were killed after 5, 10, 15, and 20 weeks in short photoperiods, nonresponding hamsters after 10 and 20 weeks, and late-responding after 20 weeks. In all early-responding hamsters changes in gonadal stage, body weight, and pelage color corresponded to the decompression of the nightly melatonin pattern. During prolonged exposure to short photoperiods a decrease of mean melatonin concentrations in the morning and an increase of evening concentrations was observed in both sexes. The lengthening of nightly elevated melatonin concentrations was missing in photoinsensitive hamsters. In late-responding hamsters this decompression seems to be delayed, as melatonin concentrations of female late responders indicate. In conclusion, the lengthening of the melatonin pattern seems to predict a photoperiodic reaction of the effector system. The lengthened pattern of photosensitive hamsters may not be unchangeable, as it may be subjected to modifications during prolonged exposure to short photoperiods.


Subject(s)
Circadian Rhythm/physiology , Light , Melatonin/metabolism , Pineal Gland/metabolism , Animals , Body Weight , Cricetinae , Dark Adaptation/physiology , Female , Male , Organ Size , Radioimmunoassay , Testis/growth & development , Uterus/growth & development
17.
Andrologia ; 23(2): 99-107, 1991.
Article in English | MEDLINE | ID: mdl-1952128

ABSTRACT

In the Djungarian hamster, Phodopus sungorus, the morphological alterations of Sertoli and Leydig cells were investigated under the influence of gonadotropins (LH and/or FSH) after testicular regression induced either by hypophysectomy or photoinhibition. Stimulation with LH or LH/FSH lead to a redifferentiation of morphological features of Leydig cells such as nuclear structure, smooth endoplasmic reticulum and size of cell and nucleus area within 7 days of hormone treatment. Similarly, stimulation with FSH or LH/FSH caused redifferentiation of Sertoli cell nuclear structure, rough endoplasmic reticulum and nuclear size within 7 days. Incomplete restoration of Leydig and Sertoli cell morphology was observed under FSH and LH treatment respectively. In both Leydig and Sertoli cells combined LH and FSH application resulted in an increased response in respect to morphological redifferentiation, possibly indicating paracrine regulatory mechanisms. In all groups treated an intact blood-testis barrier (BTB) was reestablished after a minimum of 7 days, indicating that the existence of the blood-testis barrier is not dependent on specific gonadotropin supply but on the developmental stage of the seminiferous epithelium. Sham-operated animals showed increased cell and nucleus area of Leydig cells in comparison to photostimulated animals. After testicular involution as well as after LH or FSH treatment there were no significant morphological differences between hypophysectomized and photoinhibited animals in respect to the documented ultrastructural and morphometrical characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)


Subject(s)
Follicle Stimulating Hormone/pharmacology , Hypophysectomy , Leydig Cells/ultrastructure , Luteinizing Hormone/pharmacology , Sertoli Cells/ultrastructure , Testis/physiology , Animals , Blood-Testis Barrier/physiology , Cell Nucleus/ultrastructure , Cricetinae , Endoplasmic Reticulum/ultrastructure , Leydig Cells/drug effects , Light , Male , Microscopy, Electron , Periodicity , Reproduction/physiology , Sertoli Cells/drug effects
18.
Biol Reprod ; 41(5): 871-80, 1989 Nov.
Article in English | MEDLINE | ID: mdl-2516470

ABSTRACT

Effects of pure human follicle-stimulating hormone (hFSH) and ovine luteinizing hormone (oLH) on testicular function were investigated in long-term hypophysectomized or photoinhibited Djungarian hamsters. hFSH (5 IU) or oLH (5 micrograms) or a combination of FSH and LH (5 IU and 5 micrograms, respectively) were injected s.c. twice daily for 7 days to hypophysectomized and photoinhibited hamsters. Other photoinhibited hamsters were treated for 14 and 21 days with FSH and LH (3 IU and 3 micrograms, respectively) in a similar way. LH alone had little, if any, effect on testicular weights; FSH, when injected alone or in combination with LH (FSH/LH), caused a significant increase in testes weights at each time point. On the other hand, LH or FSH/LH, but not FSH alone, caused a significant increase in the accessory organ weights. FSH had no effect on intratesticular testosterone (T) or on 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity but enhanced the in vitro response of interstitial cells to hCG. LH and FSH/LH had pronounced effects on intratesticular T, 3 beta-HSD activity, and in vitro response of interstitial cells to human chorionic gonadotropin. Treatment with FSH or FSH/LH caused regrowth of the testis and restoration of tubular lumen and tubular diameter and restored complete spermatogenesis. However, LH had little effect on spermatogenesis in spite of increased intratesticular and peripheral T levels. These results indicate that although LH can cause a full redifferentiation of Leydig cells in photoinhibited hamsters, it has only minor effects on tubular function. On the other hand, FSH alone induces full restoration of tubular function in these animals and has no direct effect on Leydig cell steroidogenesis, but may enhance the Leydig cell responsiveness to LH.


Subject(s)
Follicle Stimulating Hormone/pharmacology , Hypophysectomy , Leydig Cells/physiology , Light , Luteinizing Hormone/pharmacology , Spermatogenesis/drug effects , 3-Hydroxysteroid Dehydrogenases/metabolism , Animals , Chorionic Gonadotropin/pharmacology , Cricetinae , Genitalia, Male/anatomy & histology , Leydig Cells/drug effects , Male , Organ Size , Spermatogenesis/physiology , Testis/analysis , Testis/anatomy & histology , Testis/metabolism , Testosterone/analysis , Testosterone/metabolism
19.
Biol Reprod ; 39(2): 489-98, 1988 Sep.
Article in English | MEDLINE | ID: mdl-2846085

ABSTRACT

Hypophysectomy of 40-day-old male hamsters kept under long photoperiods resulted in a change in coat color from the brownish summer coat to the whitish winter coat, within 5 wk of the surgery, cessation of growth, and, most frequently, an additional loss in body weight. The testes of the hypophysectomized animals were involuted within 14 days after surgery. Continuous substitution of prolactin by implantation of two anterior pituitaries under the kidney capsule was able to reverse partly or totally the inhibitory effects of hypophysectomy on coat color and body weight, although there was no influence on testicular volume. The same effects could be achieved by daily s.c. injections of prolactin (100 micrograms ovine-PRL/day) into hypophysectomized hamsters, whereas the injection of adrenocorticopropic hormone (5 IU porcine-ACTH/day) or melanocyte-stimulating hormone (35 micrograms synthetic alpha-MSH/day) was ineffective. Additional pinealectomy influenced neither the inhibitory effects of hypophysectomy on coat pigmentation and body weight nor the stimulatory effects of prolactin substitution in hypophysectomized animals. Thus, the study provides evidence that the effects of the pineal gland on annual changes in body weight and coat color are mediated via the pituitary.


Subject(s)
Body Weight , Hair Color , Light , Pineal Gland/physiology , Pituitary Gland/physiology , Testis , Adrenocorticotropic Hormone/pharmacology , Animals , Cricetinae , Hypophysectomy , Immunohistochemistry , Male , Melanocyte-Stimulating Hormones/pharmacology , Periodicity , Prolactin/analysis , Prolactin/pharmacology
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