SYNTHESIS OF ANDROGENS IN VITRO BY TESTES OF RATS ACCLIMATIZED TO A HOT ENVIRONMENT

1971 ◽  
Vol 51 (3) ◽  
pp. 489-498 ◽  
Author(s):  
E. BEDRAK ◽  
V. SAMOILOFF ◽  
U. A. SOD-MORIAH ◽  
S. GOLDBERG
Keyword(s):  
Growth Rate ◽  
Relative Humidity ◽  
Oxygen Uptake ◽  
Leydig Cells ◽  
Environmental Temperature ◽  
High Ambient Temperature ◽  
Male Rats ◽  
Similar Degree ◽  
Hot Environment

SUMMARY The relative activities of enzymes participating in the biosynthesis of testosterone via the 4-ene pathway were determined in testicular homogenates of rats acclimatized to a hot environment (33–35 °C, 25–40% relative humidity). Acclimatized animals showed an increase in activity of 17α-hydroxylase, 17,20-lyase and 20α-hydroxysteroid oxidoreductase, whereas the activity of 17β-hydroxysteroid oxidoreductase was markedly decreased. Histological examination of the testes disclosed that neither the germinal epithelium nor the Leydig cells were adversely affected by the increased environmental temperature. The results are discussed in relation to the synthesis and release of the gonadotrophins. A similar degree of acclimatization, as determined by the comparable decrease in oxygen uptake, was achieved by either of two methods: daily 4 h exposure to a high ambient temperature for 4 weeks or continuous maintenance at 35 °C. The former procedure, however, appeared to be the preferred method for acclimatization of male rats since it did not inhibit growth rate and was free of mortality.

Predictive Model for the Effect of Environmental Conditions on the Postharvest Development of Colletotrichum gloeosporioides Strains Isolated from Papaya (Carica papaya L.)

2020 ◽  
Vol 83 (9) ◽  
pp. 1495-1504
Author(s):  
TERESA SANDOVAL-CONTRERAS ◽  
MARICARMEN IÑIGUEZ-MORENO ◽  
LUIS GARRIDO-SÁNCHEZ ◽  
JUAN ARTURO RAGAZZO-SÁNCHEZ ◽  
JOSÉ ALBERTO NARVÁEZ-ZAPATA ◽  
...  
Keyword(s):  
Growth Rate ◽  
Supply Chain ◽  
Relative Humidity ◽  
Colletotrichum Gloeosporioides ◽  
Growth Models ◽  
External Validation ◽  
Food Microbiology ◽  
Effect Of Temperature ◽  
Primary Model

ABSTRACT Colletotrichum species are the most important postharvest spoilage fungi of papaya fruit. The objective of this research was to evaluate the effect of temperature and relative humidity on growth rate and time for growth to become visible of five strains of Colletotrichum gloeosporioides isolated from papaya fruit in a complex medium. As a primary model, the radial growth rates were estimated using the Baranyi and Roberts model in papaya agar. The Solver MS Excel function was used to obtain the time to visible mycelium (tv). Secondary models obtained with the Rosso et al. cardinal model of inflection were applied to describe the effect of temperature on the growth rate (μ). The Arrhenius-Davey model was used to model tv. The obtained models seem to be satisfactory for describing both μ and tv. The relative humidity had an effect on μ and tv for all tested C. gloeosporioides isolates, but no model accurately described the behavior of the fungus. External validation of models was performed with papaya fruit. Growth models were developed with the same models used in vitro. The bias and the accuracy factors as indices for performance evaluation of predictive models in food microbiology as a function of temperature and RH were 1.22 and 1.33, respectively, for μ and 1.18 and 1.62, respectively, for tv, indicating accurate predictions. The supply chain of papaya is complex and requires constant conditions, and poor conditions can result in damage to the fruit. Knowledge of the behavior of C. gloeosporioides on papaya fruit and application of the developed models in the supply chain will help to establish transport control strategies to combat these fungi. This research has contributed to development of the first models of growth for C. gloeosporioides in Mexico. HIGHLIGHTS

Mechanisms of altered LH secretion in neonatally oestrogenized male rats

1995 ◽  
Vol 147 (1) ◽  
pp. 43-50 ◽  
Author(s):  
L Pinilla ◽  
M Tena-Sempere ◽  
D Gonzalez ◽  
E Aguilar
Keyword(s):  
Leydig Cells ◽  
Postnatal Period ◽  
Male Rats ◽  
Control Groups ◽  
Gonadotrophin Secretion ◽  
Selective Elimination ◽  
Lhrh Release ◽  
Lh Secretion

Abstract It is well known that the control of LH secretion depends on the steroid milieu during the postnatal period. In this study LH secretion was analysed in adult male rats injected neonatally with 500 μg oestradiol benzoate (1) after orchidectomy, (2) after selective elimination of androgens by destruction of Leydig cells with ethylene dimethane sulphonate (EDS), and (3) after removal in orchidectomized animals of Silastic capsules containing testosterone. In addition, (4) in vivo and in vitro LH secretion in response to LHRH agonist and antagonists, (5) the hypothalamic LHRH content, (6) the basal and stimulated in vitro LHRH release, and (7) the LH responses after administration of naloxone (2 mg/kg), α-methyl-p-tyrosine (α-MPT; 250 mg/kg), N-methyl-d-aspartic acid (NMDA, 15 mg/kg) or kainic acid (KA; 15 mg/kg) were also examined. Our data indicated that (1) the LH response after orchidectomy, after EDS administration and after removal of Silastic capsules containing testosterone was diminished in oestrogenized male rats, (2) the pituitaries from oestrogenized males retained responsiveness to LHRH, (3) hypothalamic LHRH content was reduced in oestrogenized males, but the hypothalamus from oestrogenized males released more LHRH than those of control groups both under basal conditions or after depolarization, (4) α-MPT decreased LH secretion only in oestrogenized males, and (5) NMDA and KA stimulated LH only in oestrogenized males. We conclude that in oestrogenized male rats the loss of sensitivity to the negative feedback action of testosterone on LH secretion was not due to decreased pituitary responsiveness to LHRH stimulation or to the inherent damage of LHRH neurones. In contrast, changes in the mechanisms governing LHRH release seem to be involved. A lack of activation of the excitatory noradrenergic and aminoacidergic systems seems to be part of the neurochemical basis of altered gonadotrophin secretion in neonatally oestrogenized male rats. Journal of Endocrinology (1995) 147, 43–50

Activity of LH receptor, LH-stimulated cyclic AMP and testosterone production in the Leydig cell of heat-acclimatized rats

1984 ◽  
Vol 102 (2) ◽  
pp. 167-173 ◽  
Author(s):  
E. Bedrak ◽  
Z. Chap
Keyword(s):  
Relative Humidity ◽  
Cyclic Amp ◽  
Leydig Cell ◽  
Male Rats ◽  
Heat Acclimatization ◽  
Lh Receptor ◽  
Hot Environment ◽  
C 30 ◽  
Lower Capacity ◽  
Trophic Hormone

ABSTRACT Key reactions associated with the capacity of the isolated Leydig cell to synthesize testosterone were studied in male rats acclimatized to a hot environment (33–35 °C, 25–40% relative humidity) and controls (20–22 °C, 30–50% relative humidity). The results demonstrate that acclimatization to heat coincides with: (1) a lower number of human chorionic gonadotrophin (hCG) receptors (P<0·01) in the Leydig cell, (2) higher affinity of the Leydig cell for hCG (P < 0·05), (3) lower hCG-stimulated cyclic AMP production (P<0·05) by the Leydig cell and (4) lower capacity of the Leydig cell to synthesize testosterone (P<0·01) after hCG challenge. It is suggested that the major cellular alteration responsible for the decreased testosterone secretion by the Leydig cell lies distal to the step involving the binding of the trophic hormone to its receptor and that heat-acclimatization induces changes in the integrity of the various cellular membranes leading to the impeded function of adenylate cyclase and 17β-hydroxysteroid oxidoreductase. J. Endocr. (1984) 102, 167–173

scholarly journals Numerical Analysis on the Cooling Performance of a Hybrid Personal Cooling System (HPCS) under Different Hot Environments

2018 ◽  
Author(s):  
Zhanxiao Kang ◽  
Xianfu Wan ◽  
Faming Wang ◽  
Uday Raj ◽  
Bin Yang
Keyword(s):  
Relative Humidity ◽  
Thermal Performance ◽  
Environmental Temperature ◽  
Cooling System ◽  
Cooling Performance ◽  
Hot Environment ◽  
Four Levels ◽  
Hot Environments ◽  
The Impact ◽  
Personal Cooling

The hybrid personal cooling system (HPCS) consisted of ventilation fans and phase change materials (PCMs) covered with insulation pads is a promising wearable cooling system to mitigate heat strain and heat-related illnesses of occupational workers with heavy labor in hot environments. Effects of clothing characteristics (e.g., thermal resistance of insulation pads, latent heat and melting temperature of PCMs) on the thermal performance of the HPCS have been investigated in detail in our previous study. Apart from the aforementioned factors, environmental conditions, i.e., environmental temperature and relative humidity, also significantly affect the thermal performance of the HPCS. In this paper, a numerical parametric study was performed to investigate the effects of the environmental temperature and relative humidity (RH) on the thermal management of the HPCS. Five levels of air temperature under environmental RH=50% were chosen (i.e., 32, 34, 36, 38 and 40 ºC) to study the impact of environmental temperature on the HPCS’s cooling performance. In addition, four levels of environmental RH at ambient temperatures of 36 and 40 ºC were selected (i.e., 30, 50, 70 and 90%) to examine the effect of RH on cooling performance of the HPCS. Results show that high environmental temperatures could accelerate the PCM melting process and thereby weaken the cooling performance of HPCS. In the moderately hot environment (36 °C), the HPCS presented good cooling performance with the maximum core temperature at around 37.5 °C during excise when the ambient RH≤70%, whereas good cooling performance could be only seen under RH≤50% in the extremely hot environment (40 °C). Thus, it may be concluded that the maximum environmental RH for the HPCS exhibiting good cooling performance decreases with the increase in the environmental temperature.

OXYGEN UPTAKE OF RAT MAMMARY TISSUE SLICES

1950 ◽  
Vol 28e (5) ◽  
pp. 217-221 ◽  
Author(s):  
Jules Tuba ◽  
Herbert E. Rawlinson ◽  
Lorna Glen Shaw
Keyword(s):  
Mammary Gland ◽  
Oxygen Uptake ◽  
In Vitro Study ◽  
Female Rats ◽  
Male Rats ◽  
Mammary Tissue ◽  
Oxygen Utilization ◽  
Tissue Slices ◽  
Mammary Gland Tissue

An in vitro study has been made of the oxygen uptake of mammary gland tissue of female rats in various experimental states. Because of the very high proportion of fat in mammary tissue the values of [Formula: see text] are determined on a fat-free as well as a water-free basis, thus providing a more accurate measure of the oxygen consumption of this tissue. The oxygen utilization by mammary gland of pregnant animals is increased approximately three times over the activity in the normal, or resting, gland. This increase is maintained during lactation and a return toward normal levels occurs during postlactational involution. The response to p-phenylenediamine indicated that during lactation the increased energy requirements decreased the reserves of the cytochrome system in mammary tissue. There is a well developed mammary gland in adult male rats; but the average fat content and response to p-phenylenediamine of the tissue are almost identical with values for adult female rats. The use of p-phenylenediamine as a histological stain for the cytochrome system in mammary tissue is described.

Effects of hypoxia on testosterone release in rat Leydig cells

2009 ◽  
Vol 297 (5) ◽  
pp. E1039-E1045 ◽  
Author(s):  
Guey-Shyang Hwang ◽  
Szu-Tah Chen ◽  
Te-Jung Chen ◽  
Shyi-Wu Wang
Keyword(s):  
Calcium Channel ◽  
Adenylyl Cyclase ◽  
Intermittent Hypoxia ◽  
Leydig Cells ◽  
Channel Blocker ◽  
Male Rats ◽  
Plasma Testosterone ◽  
Testosterone Production

The aim of this study was to explore the effect and action mechanisms of intermittent hypoxia on the production of testosterone both in vivo and in vitro. Male rats were housed in a hypoxic chamber (12% O2 + 88% N2, 1.5 l/ml) 8 h/day for 4 days. Normoxic rats were used as control. In an in vivo experiment, hypoxic and normoxic rats were euthanized and the blood samples collected. In the in vitro experiment, the enzymatically dispersed rat Leydig cells were prepared and challenged with forskolin (an adenylyl cyclase activator, 10−4 M), 8-Br-cAMP (a membrane-permeable analog of cAMP, 10−4 M), hCG (0.05 IU), the precursors of the biosynthesis testosterone, including 25-OH-C (10−5 M), pregnenolone (10−7 M), progesterone (10−7 M), 17-OH-progesterone (10−7 M), and androstendione (10−7-10−5 M), nifedipine (L-type Ca2+ channel blocker, 10−6-10−4 M), nimodipine (L-type Ca2+ channel blocker, 10−5 M), tetrandrine (L-type Ca2+ channel blocker, 10−5 M), and NAADP (calcium-signaling messenger causing release of calcium from intracellular stores, 10−6-10−4 M). The concentrations of testosterone in plasma and medium were measured by radioimmunoassay. The level of plasma testosterone in hypoxic rats was higher than that in normoxic rats. Enhanced testosterone production was observed in rat Leydig cells treated with hCG, 8-Br-cAMP, or forskolin in both normoxic and hypoxic conditions. Intermittent hypoxia resulted in a further increase of testosterone production in response to the testosterone precursors. The activity of 17β-hydroxysteroid dehydrogenase was stimulated by the treatment of intermittent hypoxia in vitro. The intermittent hypoxia-induced higher production of testosterone was accompanied with the influx of calcium via L-type calcium channel and the increase of intracellular calcium via the mechanism of calcium mobilization. These results suggested that the intermittent hypoxia stimulated the secretion of testosterone at least in part via stimulatory actions on the activities of adenylyl cyclase, cAMP, L-type calcium channel, and steroidogenic enzymes.

The effect of germ cell complement on the presence of oxytocin in the interstitial and seminiferous tubule fluid of the rat testis

1994 ◽  
Vol 143 (3) ◽  
pp. 471-478 ◽  
Author(s):  
H D Nicholson ◽  
H M Greenfield ◽  
J Frayne
Keyword(s):  
Heat Treatment ◽  
Germ Cell ◽  
Germ Cells ◽  
Seminiferous Tubule ◽  
Leydig Cells ◽  
Male Rats ◽  
Rat Testis ◽  
Pachytene Spermatocytes ◽  
Tubule Fluid

Abstract In the rat testis oxytocin has been localized to the Leydig cells, and these cells have been shown to produce oxytocin in vitro. The present study was performed to determine whether oxytocin is present in the interstitial fluid (IF) and seminiferous tubule fluid (TF) of the rat and whether concentrations of the peptide vary within the two compartments following germ cell destruction. In order to destroy germ cells adult male rats were anaesthetized and their scrotal regions placed in a water bath at 43 °C for 20 min. Control animals were subjected to anaesthesia alone. Groups of 6 animals were killed 3, 7 and 21 days after heat treatment and their testes removed for histological examination or fluid extraction. IF and TF were separated and the oxytocin content of the fluids measured by radioimmunoassay. Immunoreactive oxytocin was detected in both the IF (100 ±11 pg/ml) and TF (27± 4 pg/ml) of control rats and this immunoreactivity co-eluted with the authentic peptide following HPLC. Three days after heat treatment IF levels of oxytocin were significantly reduced but TF levels of the peptide were significantly increased. These changes were associated with a lack of pachytene spermatocytes in the histological sections. Seven and 21 days after heat treatment the levels of oxytocin in the IF and TF were not significantly different from control levels. Similar changes in IF and TF oxytocin levels were seen in a second experiment when pachytene spermatocytes were removed using the testicular toxicant methoxyacetic acid. To investigate whether oxytocin passes from the IF into the TF, 3H-oxytocin was infused into the testicular arteries of both control and heat-treated rats and the rats killed at regular intervals over the next 24 h. In both groups of animals <5% of the 3H-oxytocin passed from the IF into the TF. These data suggest that the seminiferous tubule as well as the Leydig cells may secrete oxytocin and that this secretion may be influenced by the presence of germ cells, particularly pachytene spermatocytes. Journal of Endocrinology (1994) 143, 471–478

Influence of neonatal hemicastration on in-vitro secretion of inhibin, gonadotrophins and testicular steroids in male rats

1985 ◽  
Vol 106 (2) ◽  
pp. 259-265 ◽  
Author(s):  
A. M. Ultee-van Gessel ◽  
F. G. Leemborg ◽  
F. H. de Jong ◽  
H. J. van der Molen
Keyword(s):  
Sertoli Cells ◽  
Leydig Cells ◽  
Feedback Regulation ◽  
Male Rats ◽  
Steroid Production ◽  
Pituitary Secretion ◽  
Lh Releasing Hormone ◽  
Testicular Steroids

ABSTRACT Pituitary secretion of FSH in male animals is regulated, at least partly, by a protein hormone, inhibin, which is produced by Sertoli cells in the testes. To establish at which age the role of testicular inhibin in the regulation of FSH secretion becomes apparent, groups of male rats were hemicastrated or sham-operated on day 1 of life and pituitary and testicular function were investigated in vitro at 21, 42 or 63 days of age. Testis weights were increased in hemicastrated rats at all ages studied. Peripheral concentrations of gonadotrophins generally showed a good correlation with the concentrations of FSH and LH measured in the medium of hemipituitary glands which were incubated in vitro at 37 °C in the absence or presence of LH-releasing hormone. Peripheral testosterone concentrations in hemicastrated animals were not significantly different from those in sham-operated rats at all ages studied. Steroid production by Leydig cells in vitro was not significantly influenced by hemicastration. The secretion of inhibin by Sertoli cells from 21-day-old hemicastrated rats was decreased while Sertoli cells from 42- and 63-day-old hemicastrated animals secreted slightly but not significantly more inhibin than Sertoli cells from sham-operated rats. It is concluded that although compensatory increases of testosterone and inhibin production at later ages make it difficult to draw conclusions about the relative importance of inhibin in the feedback regulation of FSH secretion at different ages, it is likely that inhibin plays a role in the feedback of FSH in immature, rather than in mature male rats. J. Endocr. (1985) 106, 259–265

scholarly journals Effects of Whole-Body 50-Hz Magnetic Field Exposure on Mouse Leydig Cells

2004 ◽  
Vol 4 ◽  
pp. 83-90 ◽  
Author(s):  
Zsolt Forgács ◽  
Zoltán Somosy ◽  
Györgyi Kubinyi ◽  
Hanna Sinay ◽  
Jozsef Bakos ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Luteinizing Hormone ◽  
Leydig Cells ◽  
Culture Media ◽  
Whole Body ◽  
Field Exposure ◽  
Pituitary Glands ◽  
Animal Growth

The main goal of this study was to evaluate the possible effect of whole-body magnetic field (MF) exposure on the steroidogenic capacity of Leydig cellsin vitro. In four separate experiments, male CFLP mice were exposed to sinusoidal 50-Hz, 100-μT MF. The duration of exposure was 23.5 h/day over a period of 14 days. At the end of the exposure, interstitial (Leydig) cells were isolated from the testicles of the sham-exposed and exposed animals. The cells were cultured for 48 h in the presence or absence of 1, 10, or 100 mIU/ml human chorionic gonadotropin (hCG). The luteinizing hormone (LH) analog hCG was used to check the testosterone (T) response of the sham-exposed controls and to evaluate the possible effect of the whole-body MF exposure on the steroidogenic capacity of Leydig cellsin vitro. Testosterone content of the culture media and blood sera was measured by radioimmunoassay (RIA). In the cultures obtained from MF-exposed animals, the hCG-stimulated T response was significanly higher (p < 0.01) compared with the sham-exposed controls, while the basal T production of cells and the level of serum T remained unaltered. No MF exposure–related histopathological alterations were found in testicles, epididymes, adrenals, prostates, and pituitary glands. The MF exposure did not affect the animal growth rate and the observed hematologic and serum chemical variables. Our results indicate a presumably direct effect of whole-body MF exposure on the hCG-stimulated steroidogenic response of mouse Leydig cells.

IN VITRO UPTAKE OF TRITIATED SEX STEROIDS BY THE HYPOTHALAMUS OF ADULT MALE RATS TREATED NEONATALLY WITH AN ANTIANDROGEN (CYPROTERONE)

1972 ◽  
Vol 71 (1) ◽  
pp. 45-54 ◽  
Author(s):  
Pentti Tuohimaa ◽  
Mikko Niemi
Keyword(s):  
Cerebral Cortex ◽  
Median Eminence ◽  
Sex Steroids ◽  
Leydig Cells ◽  
Interstitial Cell ◽  
Anterior Hypothalamus ◽  
Male Rats ◽  
Corpora Lutea ◽  
In Vitro Uptake

ABSTRACT Male rats were injected subcutaneously with 2 mg of cyproterone daily from birth to the 14th postnatal day. At the age of 40 days the animals were polycystic and corpora lutea were absent. There was an increased 37% of the ovarian implants showed distinct corpora lutea indicating cyclic secretion of gonadotrophins; the implants in the control animals were polycystic and corpora lutea were absent. There was an increased interstitial cell stimulating hormone output from the pituitary gland as indicated by the increased amount of 3β-hydroxysteroid dehydrogenase active Leydig cells in the testes of the feminized animals. The in vitro uptake of tritiated testosterone and oestradiol of various tissues was tested on rats, age 4.5 months. The anterior hypothalamus, the rostral middle hypothalamus, the median eminence and the anterior pituitary of the feminized males retained significantly more oestradiol than the cerebral cortex. The oestradiol uptake in these areas also exceeded that of the control animals. Only the median eminence of the cyproterone treated rats concentrated more testosterone than the cerebral cortex. The anterior hypothalamus and cerebral cortex of the feminized male rats were less able to transform tritiated testosterone to dihydrotestosterone or tritiated oestradiol to oestrone, as compared to adult castrated male or female animals, respectively.

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