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Cortical phase changes measured using 7-T MRI in subjects with subjective cognitive impairment, and their association with cognitive function
Rooden, Sanneke van; Buijs, Mathijs ; Vliet, Marjolein E. van; Versluis, Maarten J. ; Webb, Andrew G. ; Oleksik, Ania M. ; Wiel, Lotte van de; Middelkoop, Huub A.M. ; Blauw, Gerard Jan ; Weverling-Rynsburger, Annelies W.E. ; Goos, Jeroen D.C. ; Flier, Wiesje M. van der; Koene, Ted ; Scheltens, Philip ; Barkhof, Frederik ; Nieuwerth-van de Rest, Ondine ; Slagboom, P.E. ; Buchem, Mark A. van; Grond, Jeroen van der - \ 2016
NMR in Biomedicine 29 (2016)9. - ISSN 0952-3480 - p. 1289 - 1294.
AD pathology - Alzheimer's disease - brain imaging - cognition - human 7-T MRI - phase - subjective cognitive impairment

Studies have suggested that, in subjects with subjective cognitive impairment (SCI), Alzheimer's disease (AD)-like changes may occur in the brain. Recently, an in vivo study has indicated the potential of ultra-high-field MRI to visualize amyloid-beta (Aβ)-associated changes in the cortex in patients with AD, manifested by a phase shift on T2*-weighted MRI scans. The main aim of this study was to investigate whether cortical phase shifts on T2*-weighted images at 7 T in subjects with SCI can be detected, possibly implicating the deposition of Aβ plaques and associated iron. Cognitive tests and T2*-weighted scans using a 7-T MRI system were performed in 28 patients with AD, 18 subjects with SCI and 27 healthy controls (HCs). Cortical phase shifts were measured. Univariate general linear modeling and linear regression analysis were used to assess the association between diagnosis and cortical phase shift, and between cortical phase shift and the different neuropsychological tests, adjusted for age and gender. The phase shift (mean, 1.19; range, 1.00–1.35) of the entire cortex in AD was higher than in both SCI (mean, 0.85; range, 0.73–0.99; p <0.001) and HC (mean, 0.94; range, 0.79–1.10; p <0.001). No AD-like changes, e.g. increased cortical phase shifts, were found in subjects with SCI compared with HCs. In SCI, a significant association was found between memory function (Wechsler Memory Scale, WMS) and cortical phase shift (β = –0.544, p = 0.007). The major finding of this study is that, in subjects with SCI, an increased cortical phase shift measured at high field is associated with a poorer memory performance, although, as a group, subjects with SCI do not show an increased phase shift compared with HCs. This increased cortical phase shift related to memory performance may contribute to the understanding of SCI as it is still unclear whether SCI is a sign of pre-clinical AD.

The value chain for seed and ware potatoes in Kenya: Opportunities for development
Janssens, S.R.M. ; Wiersema, S.G. ; Goos, H.J.Th. ; wiersma, W. - \ 2013
Den Haag : LEI Wageningen UR (Memorandum / LEI Wageningen UR 13-080) - 57
aardappelen - pootaardappelen - kleine landbouwbedrijven - tropische gewassen - opbrengsten - voedselgewassen - kenya - potatoes - seed potatoes - small farms - tropical crops - yields - food crops
In Kenya potato is an important food crop, second after maize. Potatoes are grown on 128,000 ha per year with average yields of about 8 tonnes per ha. The yield is far below its po-tential and should be improved to enhance food security. Of all potato growers in Kenya, 98% are characterised as small-scale farmers, producing less than 0.4 ha of potatoes per year per farm (total of two planting seasons). They produce 83% of the national production. Lack of good quality seed is a main reason for low yields. The fast-track seed project aims to improve availability of certified seed. Imported seed needs to be multiplied locally once or twice to reduce the cost price and make it affordable for small-scale growers. It is estimated that there is potential for at most 1,000 ha of professional seed production in Kenya to meet the market demand for certified seed. In Kenya about 98% of ware potatoes are sold for 'fresh' consumption. For industrial processing the most favourable opportunities are the production of crisps and fresh - not frozen - French fries. To change the low-input low-output strategy of many small-scale farmers linkages between producers and markets need to be improved. In the short term, improvement of potato growing and crop management should receive higher priority than storage and mechanisation. Storage and mechanisation should be adapted to local conditions and needs. Two cases have been indicated in which investments in professional cooled storage facilities are necessary; - storage of seed potatoes of varieties with a long dormancy period; - storage of ware potatoes for processing industry and some high-end retailers. Long-term seed storage in modern stores required for varieties with long dormancy increases the cost price of seed by 50% compared with short-term storage in diffused light stores. This makes short dor-mancy an important trait for potato varieties in Kenya, where potatoes are planted during two growing seasons. Machinery supplied for potato growing in Kenya should be geared to local needs. Higher yields and more multiplications of imported seed reduce the cost price of seed potatoes produced in Kenya. The cost price of imported seed after two multiplications is competitive with locally produced seed from minitubers after three multiplications. This report describes the current situation of the potato sector in Kenya and opportunities for further de-velopment. The study focuses on possibilities of the Dutch agribusiness to facilitate these developments. Existing information has been collected, although information on potato production was not easily availa-ble. In addition, during a mission to Kenya stakeholders were visited and interviewed. This resulted in cost- price calculations for seed potato production (short and long-term storage, imported seed and minitubers) and market information.
Stress-induced facilitation of the cortisol response in 17a-hydroxylase deficient XX mas -1/mas -1 carp (Cyprinus carpio)
Ruane, N.M. ; Goos, H.J.Th. ; Komen, J. - \ 2007
General and Comparative Endocrinology 150 (2007)3. - ISSN 0016-6480 - p. 473 - 479.
pituitary-interrenal axis - common carp - rainbow-trout - recessive mutation - adrenal axis - food-intake - fish - growth - adrenocorticotropin - hyperplasia
Facilitation of the stress response results from a reduction of the inhibitory effects of circulating corticosteroids, allowing an animal to respond to a novel stressor. In this study, the existence of a facilitated cortisol stress response in normal (STD) and 17¿-hydroxylase deficient XX mas¿1/mas¿1 (E5) carp was investigated. E5 carp had previously been characterized as having a low cortisol response to stress. Fish were subjected to either cortisol feeding or daily-acute stress, from 45 until 140 days post-hatch (dph) and were then subjected to a novel net-confinement stressor at 141 dph. Growth of E5 fish was reduced in both the daily-acute stress and cortisol-fed groups, but STD fish were only affected by daily-acute stress. Cortisol feeding had no effect on the stress response of STD fish but daily-acute stress significantly inhibited the response to a subsequent novel stressor. In contrast, daily-acute stress facilitated the cortisol stress response of E5 fish to a novel stressor, while cortisol feeding inhibited the cortisol response. Facilitation was accompanied by significant enlargement of the head-kidney tissue (which contains the steroidogenic interrenal tissue) in E5 fish. To our knowledge this is the first report of stress-induced facilitation in a lower vertebrate
Hypocorticism and interrenal hyperplasia are not directly related to masculinization in XXmas(-1)/mas(-1) carp, Cyprinus carpio
Ruane, N.M. ; Lambert, J.G.D. ; Goos, H.J.Th. ; Komen, J. - \ 2005
General and Comparative Endocrinology 143 (2005)1. - ISSN 0016-6480 - p. 66 - 74.
congenital adrenal-hyperplasia - common carp - recessive mutation - stress-response - rainbow-trout - cortisol - hormone - fish - differentiation - localization
This study reports on a homozygous XX male strain of common carp (E5), which fail to mount a normal cortisol stress response. Earlier classical genetic analysis had indicated that masculinization of E5 fish was caused by a putative recessive mutation (mas¿1/mas¿1). Hypocorticism in E5 fish was studied to investigate if it was related to masculinization. Head-kidney tissues isolated from E5 fish showed a low cortisol-producing capacity in vitro, and also demonstrated a reduced sensitivity to stimulation with ACTH, when compared with an isogenic XY male carp strain (STD). There was no strain difference in androgen production by head-kidney tissues in vitro. E5 fish exhibited significant hyperplasia of the interrenal tissue (adrenal homologue of teleost fish) located in the head-kidney. Conversion of pregnenolone was significantly lower in E5 head-kidney homogenates, compared to STD homogenates, however, no strain difference was found in the conversion of 17¿-hydroxyprogesterone into cortisol. Gonad homogenates incubated with pregnenolone showed no strain difference in conversion to corticosteroids and androgens. Results indicate that the interrenal hyperplasia and hypocorticism in this strain of carp may be due to a dysfunction of the 17¿-hydroxylase activity of the enzyme P450c17 in the interrenal, but that this defect may not be the primary factor resulting in masculinization of these XX genotypes
Sex steroids and their involvement in the cortisol-induced inhibition of pubertal development in male common carp
Consten, D. ; Keunig, A. ; Bogerd, J. ; Zandbergen, Th. ; Lambert, J. ; Komen, J.G.D. ; Goos, H.J.Th. - \ 2002
Biology of Reproduction 67 (2002). - ISSN 0006-3363 - p. 465 - 472.
Corticosteroids affect the testicular androgen production in male common carp, Cyprinus carpio L.
Consten, D. ; Lambert, J.G.D. ; Komen, J. ; Goos, H.J.Th. - \ 2002
Biology of Reproduction 66 (2002). - ISSN 0006-3363 - p. 106 - 111.
Long term cortison treatment inhibits pubertal development in male common carp, Cyprinus carpio L.
Consten, D. ; Bogerd, J. ; Komen, J. ; Lambert, J.G.D. ; Goos, H.J.Th. - \ 2001
Biology of Reproduction 64 (2001). - ISSN 0006-3363 - p. 1063 - 1071.
The onset and regulation of puberty is determined by functional development of the brain-pituitary-gonad (BPG) axis. Stress has been shown to interfere with reproduction and the functioning of the BPG axis. The response to chronic and severe stress may require much energy and force the organism to make adaptive choices. Energy that is normally available for processes like growth, immune response, or reproduction will be channeled into restoration of the disturbed homeostasis. Cortisol plays a key role in the homeostatic adaptation during or after stress. In the present study, immature common carp were fed with cortisol-containing food pellets covering the pubertal period. We showed that cortisol caused an inhibition of pubertal development, by affecting directly or indirectly all components of the BPG axis. The salmon GnRH content of the brain was decreased. Luteinizing hormone- and FSH-encoding mRNA levels in the pituitary and LH plasma levels were diminished by long-term cortisol treatment, as was the testicular androgen secretion. Testicular development, reflected by gonadosomatic index and the first wave of spermatogenesis, was retarded.
Crosstalk between the neuro-endocrine and immune system in teleosts
Verburg-van Kemenade, B.M.L. ; Engelsma, M.Y. ; Huising, M.O. ; Kwang, J. ; Muiswinkel, W.B. van; Saeij, J.P.J. ; Metz, J.R. - \ 2001
In: Perspective in comparative endocrinology: unity and diversity / Goos, H.J.Th., Rastogi, R.K., Vaudry, H., Pierantoni, R., Monduzzi editore - p. 359 - 367.
Internal and external factors controlling reproduction in the African catfish, Clarias gariepinus.
Goos, H.J.Th. ; Richter, C.J.J. - \ 1996
Aquatic Living Resources 9 (1996)suppl. 1. - ISSN 0990-7440 - p. 45 - 48.
Endocrine control of sex differentiation in XX female, and in XY and XX male common carp (Cyprinus carpio, L.).
Komen, J. ; Lambert, J.G.D. ; Richter, C.J.J. ; Goos, H.J.Th. - \ 1995
In: Proc. Fifth Int. Symp. on Reprod. Physiol. Fish, F. Goetz and P. Thomas (eds.). The University of Texas, Austin, 2-8 July - p. 383 - 383.
Internal and external factors controlling reproduction in the African catfish, Carias gariepinus.
Goos, H.J.Th. ; Richter, C.J.J. - \ 1994
In: Abstracts Basil '94: Int. Workshop Biological bases for aquaculture of Siluriformes, Montpellier, France - p. 96 - 96.
Stimulation of gonadal and germ cell development in larval and juvenile carp (Cyprinus carpio L.) by homologous pituitary extract.
Winkoop, A. van; Timmermans, L.P.M. ; Goos, H.J.Th. - \ 1994
Fish Physiology and Biochemistry 13 (1994). - ISSN 0920-1742 - p. 161 - 171.
Induction of ovarian development in European eel (Anguilla anguilla) with low dosages of carp pituitary suspension.
Eding, E.H. ; Zanten, G.H. van; Bongers, A.B.J. ; Richter, C.J.J. ; Lambert, J.G.D. ; Goos, H.J.Th. - \ 1991
In: Proc. 4th Int. Symp. Reproductive physiology of fish. Univ. East Anglia, Norwich, UK (1991) 321
Pheromones and ovarian growth in the African catfish Clarias gariepinus
Weerd, J.H. van - \ 1990
Agricultural University. Promotor(en): E.A. Huisman; H.J.T. Goos. - S.l. : van Weerd - 155
Siluridae - voortplanting - excretiestelsel - voortplantingsorganen - urogenitaalsysteem - seksueel gedrag - Clarias gariepinus - Siluridae - reproduction - excretory system - reproductive organs - urogenital system - sexual behaviour - Clarias gariepinus

Pheromones are defined as 'substances which are secreted to the outside by an individual and received by a second individual of the same species, in which they release a specific reaction'. In teleost fish, pheromones play a role in a variety of social interactions. Sex pheromones are involved in reproduction of several teleosts species, including the African catfish Clarias gariepinus. They regulate spawning behavior and endocrine events leading to reproduction. Most, if not all reports in literature describing the action of sex pheromones in teleosts pertain to advanced phases of the reproductive cycle. In those phases, sex pheromones influence oocyte maturation and ovulation in females, and spermiation in males. Furthermore, they play a role in mediating attraction of prospective mates and in triggering spawning behavior and release of gametes. To date, all teleost sex pheromones identified are steroids and steroid glucuronides, derivatives of reproductive hormones, with the exception of prostaglandins. In C.gariepinus the presence of males enhances ovarian growth in pubertal females under hatchery conditions and in wild-caught adult females kept in ponds. This phenomenon led to the assumption that sex pheromones are also involved in the early phases of the reproductive cycle of C. gariepinus, i.e. ovarian development and possibly also of the testes and seminal vesicles. Experiments described in the present thesis were carried out to validate this hypothesis, the rationale being that findings might be applied to other fish species which do not or rarely reach the stage of ovarian growth in captivity.

In juvenile C. gariepinus, males stimulate ovarian development of females. Chemical and tactile stimuli are relevant to the process, whereas the other cues investigated are not (visual, auditory, electric). Also in adult female C. gariepinus which had entered the stage of recrudescence, i.e. ovarian development after induced maturation, ovulation and stripping of eggs, is influenced by stimuli from males. Chemical cues in holding water are perceived by the sense of smell, since females deprived of their sense of smell (anosmia) do not respond. Metabolites which are known to negatively influence ovarian growth and which are inevitably present in holding water, do not affect the female response. Hence, the chemical cues are indeed pheromones, and their male origin is strongly suggested by the fact that female holding-water has no effect. Male tactile stimuli do not play a role in ovarian development of adult C. gariepinus. The importance of tactile stimuli, which may actually encompass a combination of signals of different types (gustatory, mechanical) may be different in pubertal and adult C. gariepinus.

In pubertal female C. gariepinus, ovarian growth is parallelled by changes in plasma levels of estradiol-17β(the female sex steroid) and vitellogenin (the femalespecific precursor of yolk proteins) and is reflected in increases in diameter and relative proportion of vitellogenic oocytes within the ovary. The effects were less clear in adult females during recrudescence, presumably as a consequence of their short gonadal cycle. Male stimuli cause changes in levels of estradiol-17β, vitellogenin, and ovarian development, and temporal shifts in the pattern of vitellogenesis. These are most pronounced in pubertal C.gariepinus. It seems likely, that male stimuli trigger these changes through the olfactory-brain-pituitarygonad axis. The effect of stimulation of ovarian development is seen in an increase in both the diameter and the relative proportion of exogenous vitellogenic: oocytes, indicating both an enhanced vitellogenesis and an increased recruitment of oocytes into the stage of vitellogenesis. Monitoring the effect of stimulation on the basis of the parameters mentioned above does not lead to earlier detection of actual stimulation than with the use of gonadosomatic: index or oocyte development. However, it may make sacrifice of fish unnecessary.

An experiment aiming at investigating the interaction between the sexes with respect to emission of stimuli was hampered by the fact that anosmia in males depressed development of testes and seminal vesicles. Nevertheless, the experiment indicated that not only male tactile and olfactory cues stimulate ovarian development, but that also male olfactory cues stimulate gonadal development of other males. Tactile stimuli from females do not influence, or perhaps even tend to curb gonadal development of males, suggesting the existence of a female inhibitory cue. The emission of 'female-directed' olfactory cues by males is not modified by females, but the emission of 'male-directed' olfactory cues is, suggesting two types of male olfactory cues, differentially influenced.

Several of the experiments suggest that the male gonad is involved, directly or indirectly, in the ovarian growth stimulating effect of holding water, since male, but not female holding water is effective. Extirpation of testes, seminal vesicles or both, however, did not abolish the effect of holding water. Still-circulating androgens in operated fish may have been effectively converted to pheromonal steroid glucuronides, leading to holding water concentrations above the detection threshold of females.

Holding water was analyzed by gas chromatography and mass spectrometry and was found to contain several of the steroids and steroid glucuronides known to act as pheromones in later stages of the reproductive cycle of C.gariepinus. This holding water originated from a mixed-sex group of adult male and female C.gariepinus. A provisional calculation learned that the concentration in holding water of the glucuronide of one steroid in particular, 5β-pregnane-3α,17α-diol-20-one, of presumed male origin, approached the detection threshold of the olfactory epithelium.
It is concluded that in C.gariepinus, pheromones of male origin stimulate ovarian development, through the olfactory-brain-pituitary-gonad axis. Emission of pheromones and gonadal development are modulated by interaction between the sexes. The question whether male pheromones are of gonadal origin could not be answered conclusively. Holding water with the capacity to stimulate ovarian development contains steroids and steroid glucuronides. The actual involvement in stimulation of ovarian development of these compounds, however, awaits experimental confirmation.

Eel research in Japan.
Richter, C.J.J. ; Heinsbroek, L.T.N. ; Goos, H.J.Th. - \ 1988
Wageningen : Vakgroep Visteelt en Visserij, Landbouwuniversiteit - 62 p.
The effect of pimozide-LHRAa and 17_-hydroxy-progesterone on plasma steroid levels and ovulation in African catfish, Clarias gariepinus.
Richter, C.J.J. ; Eding, E.H. ; Goos, H.J.Th. ; Leeuw, R. de; Scott, A.P. ; Oordt, P.G.W.J. van - \ 1987
Aquaculture 63 (1987). - ISSN 0044-8486 - p. 157 - 168.
Pituitary gonadotropin content and ultrastructure of the gonadotrops in the African catfish, during the annual reproductive cycle in a natural habitat.
Peute, J. ; Zandbergen, M.A. ; Goos, H.J.Th. ; Leeuw, R. de; Pinkas, R. ; Viveen, W.J.A.R. ; Oordt, P.G.W.J. van - \ 1987
Canadian Journal of Zoology 64 (1987). - ISSN 0008-4301 - p. 1718 - 1726.
Pimozide-LHRHa-induced breeding of the African catfish, Clarias gariepinus (Burchell)
Leeuw, R. de; Goos, H.J.Th. ; Richter, C.J.J. ; Eding, E.H. - \ 1985
Aquaculture 44 (1985). - ISSN 0044-8486 - p. 295 - 302.
Proc. Int. Symposium on Reproductive Physiology of Fish
Richter, C.J.J. ; Goos, H.J.Th. - \ 1982
Wageningen : Unknown Publisher
Monoclonal antibodies in the study of gonadal differentiation in carp (Cyprinus carpio L.)
Parmentier, H.K. ; Timmermans, L.P.M. ; Egberts, E. ; Groningen, J.J.M. van - \ 1982
In: Reproductive Physiology of Fish / Richter, C.J.J., Goos, H.J.Th., Wageningen : Pudoc - p. 80 - 80.
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