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Biomedical subjects

M Safi

Publications and source records attributed to M Safi.

10 recordsLinked to original sources
PubMed2004

Developmental changes in inhibin alpha and inhibin/activin betaA and betaB mRNA levels in the gonads during post-hatch prepubertal development of male and female chickens.

Dimeric inhibins and activins are barely detectable in the plasma during prepubertal development of male and female chickens. This may be misconstrued to indicate that the proteins are not produced in the gonads and have no functional significance during this period. Very few studies have actually determined the mRNA expression profile of the inhibin and activin subunits in the gonads prior to puberty in order to establish their secretion at the local level and postulate potential roles for the inhibin and activins at this developmental stage. In this study, the expression of the mRNA for the alpha-, betaA-, and betaB-subunits was determined in the ovary and testis of chickens during prepubertal development. Gene expression was determined at 3, 5, 6, 8, 10, 12, 16, and 18 weeks of age by RT-PCR. Messenger RNA level was quantified by competitive RT-PCR at 3, 6, 12, and 18 weeks of age in order to detect any changes with development, suggest potential relationship to the profile of dimeric inhibins and activins reported previously and to suggest potential paracrine and endocrine roles for them. The results show that all the inhibin/activin subunit mRNAs are expressed in the testis of the chicken throughout the period of prepubertal development up to 18 weeks of age. However, in the ovary, only the betaA- and betaB-subunits were detected at all ages whereas the alpha-subunit mRNA could only be detected just before puberty. Quantification of the mRNA levels showed variation of each subunit with age. These temporal changes suggest relationship with paracrine functional role in the ovary or the testis. Quantitative changes in expression levels also suggests that there may be some relationship between mRNA levels and the type and amount of dimeric inhibins and activins produced at any developmental stage. There are major differences between the male and female gonads in the timing of the expression of different subunits. In conclusion, the expression of the mRNA subunits in the testis and ovary suggests that inhibins and activins are being produced but may be principally involved in autocrine/paracrine function within the gonads.

Animals↗
PubMed2003

Regulation of inhibin alpha- and beta(A)-subunit messenger ribonucleic acid levels by gonadotropins and IGF-I in cultured chicken granulosa cells.

A quantitative competitive reverse transcription polymerase chain reaction assay (QC RT-PCR) for quantifying the absolute levels of the expression of inhibin alpha- and beta(A)-subunits in chicken granulosa cells showed that these subunits are expressed in different amounts depending on follicular maturation. The present study determined the regulation of the expression of these subunits. The individual effect of different doses of IGF-I, LH or FSH (1-100 ng/ml) or the combination of IGF-I with either LH or FSH at different concentrations, on the expression of inhibin alpha- and beta(A)-subunit was determined on cultured granulosa cells of F(1) and the combined F(4)+F(5) follicle. Cells were cultured for 48 h in 6-well plates with or without added hormones. Culture medium was discarded, cells were washed and total RNA was extracted from the cells. Five hundred nanograms of total RNA was reverse transcribed using specific primers and coamplified with an internal standard, as described previously, to determine expression level in the cells. IGF-I, LH, and FSH enhanced the inhibin alpha-subunit mRNA levels in a dose dependent manner in both F(1) and the combined F(4)+F(5) whereas inhibin beta(A)-subunit was not affected. The effects of FSH, LH were more expressed in F(1) follicles compared to F(4)+F(5) on the alpha-subunit. The addition of IGF-I and either LH or FSH during the culture period significantly increased the stimulatory effects of both LH and FSH on the expression of inhibin alpha-subunit in F(1) follicles but had no significant effect on the inhibin beta(A)-subunit. The results suggest that the changing expression levels of inhibin alpha-subunit during follicular development are the result of the regulatory effect of the interaction between IGF-I and the gonadotropins and that the regulation of this subunit may be the main factor for the regulation of the protein inhibin levels. Other factors may be also implicated in the changing expression levels of the beta(A)-subunit.

Animals↗
PubMed2001

Developmental expression of activin/inhibin alpha- and beta(A)-subunit genes in the gonads of male and female chick embryos.

The expression of inhibin alpha- and beta(A)-subunits was investigated in gonads of male and female chick embryos during the last week of their 21-day incubation period. Fertilized Hisex brown laying hen eggs were incubated at 37.8 +/- 0.2 degrees and 60% relative humidity in an automatic forced-draft incubator with constant lighting. Embryos were killed after 14, 18, and 21 days of incubation, sexed by macroscopical inspection of the gonadal phenotype, and further dissected to obtain the gonads. Total RNA was isolated using the ultraspec RNA method. The expression of alpha- and beta(A)-subunits was evaluated by competitive RT-PCR. Significant differences were found within and between sexes in the expression of the alpha- and beta(A)-subunits. The level of the alpha-subunit in the testis was about 23-fold higher than that in the ovary at all ages. Testicular content of inhibin alpha mRNA levels was similar at days 14 and 18 but declined significantly at day 21 of incubation, whereas no significant differences were observed between the three age groups in the ovary. Testicular and ovarian inhibin beta(A)-subunit increased significantly from day 14 to day 18 followed by a significant decline before hatch. However, inhibin beta(A) level at day 14 was significantly higher in the ovary than in the testis. At days 18 and 21, there were no differences in the levels of the inhibin beta(A) in the sexes. The expression of inhibin beta(A)-subunit in the ovary was significantly higher than that of the alpha-subunit at all ages. In the testis, however, the expression of the beta(A)-subunit was higher at days 18 and 21 than at day 14. The sex difference in gonadal inhibin subunits expression suggests differential roles of inhibin/activin in the development of the chicken gonads. The changing level of expression during incubation also suggests changing biological roles within sexes.

Activins↗
PubMed1999

Insulin-like growth factors in the regulation of avian ovarian functions.

In the past three decades, overwhelming evidence has accumulated to show that insulin-like growth factor (IGF)-I and -II, their receptors and binding proteins (IGFBP) (the IGF system), have major roles to play in the regulation of ovarian function in mammals. Although studies in birds did not start until 5-6 years ago, the limited information thus far available suggests that the IGFs act as autocrine/paracrine regulators of follicular growth and differentiation, just as observed in mammals. The genes for IGF-I and -II, type-I IGF receptor, IGFBP-2, and IGFBP-5 are expressed in both granulosa and theca cells of the chicken ovary. The mechanisms by which the IGF system controls ovarian function in the avian species are complex and involve interactions with the gonadotrophins (LH and FSH), growth hormone, and even other growth factors. Effects are different between strains and nutritional status.

Animals↗
PubMed1999

Effects of timing and duration of feed restriction during rearing on reproductive characteristics in broiler breeder females.

The objective of this study was to determine whether there exists a critical period during rearing when restricted feeding of broiler breeder hens can be most beneficial on subsequent egg production. Broiler breeder pullets were subjected to combinations of either ad libitum or restricted feeding during three periods before sexual maturity. Body weight gain, feed intake, and egg production were recorded. Ovary and oviduct weights were noted at age of first oviposition. At 15 and 18 wk of age and at age of first oviposition, chicken luteinizing hormone releasing hormone-I (cLHRH-I) in the median eminence and the levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the pituitary and plasma were determined. The results demonstrated that alternation between ad libitum and restricted feeding during rearing changed the growth curves of the birds. Feed restriction from 7 to 15 wk followed by either ad libitum or restricted feeding led to improved reproductive performance, suggesting that long-term feed restriction may not be necessary to attain good reproductive performance. The birds restricted from 7 to 15 wk of age had higher proportional weights of ovary (> or = 1.7%) and oviduct (> or = 1.58%) at age of sexual maturity. The cLHRH-I levels in the median eminence and gonadotrophin contents in the pituitary followed that of growth in response to feeding levels and timing of feeding and could be related to the timing of the onset of lay. At age of first egg, all groups had similar levels of cLHRH-I, LH, and FSH. However, no clear effect of level of feed intake or time period of restriction could be observed for plasma LH or FSH concentrations.

Animal Feed↗
PubMed1998

Quantification of inhibin/activin alpha and betaA subunit messenger ribonucleic acid by competitive reverse transcription-polymerase chain reaction in chicken granulosa cells during follicular development.

The very sensitive quantitative competitive reverse transcription-polymerase chain reaction (RT-PCR) was used to investigate the expression of inhibin/activin subunits in the granulosa cells of developing ovarian follicles of the hen. Two competitors specific to inhibin alpha and betaA subunits were constructed. In one study, the expression of inhibin alpha and betaA genes was determined in the granulosa cells of the five largest yellow follicles (F1, F2, F3, F4/5), the small yellow follicles (SYF), and the large white follicles (LWF) of a layer strain of chickens. Competitive RT-PCR for inhibin alpha subunit revealed 10.35 +/- 2.15 pg/ microg total RNA in the LWF. The expression increased 40-fold in the SYF and remained at that level in the F4/5 but decreased markedly thereafter up to the F1 stage. Inhibin/activin betaA subunit was also detected in the LWF in low amounts and showed no significant increase until the F2 stage. The highest level was found in the F1. The pattern of the mRNA for alpha and betaA subunits in the five largest follicles (F1, F2, F3, F4/5) of a broiler breeder strain of chicken was compared with that in the layer strain. Expression of the alpha subunit was significantly higher in the three largest follicles (F1, F2, F3) of the broiler breeder hens, but only in the F2 for the betaA. The results suggest that inhibin alpha may play an important role in the recruitment and differentiation of follicles and that differences between broiler breeders and layers may have consequences at both the pituitary and ovarian levels.

Activins↗
PubMedDate not supplied

Quantitative evaluation of a comprehensive motion, resolution, and attenuation correction program: initial experience.

BACKGROUND: Tomographic myocardial imaging is widely used in the diagnosis and evaluation of patients with coronary artery disease. However, its specificity remains suboptimal because of attenuation, resolution, and motion artifacts. The purpose of this study was to optimize and assess the value of attenuation, blur, and motion correction of myocardial single photon emission computed tomographic data. METHODS AND RESULTS: Forty-seven studies were selected for analysis to provide 3 patient groups. Group A consisted of 18 patients with a low likelihood of coronary artery disease who were used to construct a quantitative normal database and assess changes in the normal bull's-eye produced by filtering and by attenuation correction. Group B consisted of 13 patients with a high probability of normal results, and group C consisted of 16 patients with coronary artery disease defined on angiography. The effects of attenuation correction, especially in conjunction with RESTORE (a depth-dependent deblurring filter), have been quantitated. Analysis indicates a trend to improved sensitivity and specificity for detecting individual vessel disease in this retrospective study. The motion correction program was successfully applied to 93% of patients but detected significant motion requiring correction in only 11 (24%) patients. CONCLUSION: This preliminary retrospective study indicates a potential for improved myocardial single photon emission computed tomography imaging with the use of attenuation and motion correction together with a restorative deblurring filter. Confirmation by a multicenter study and larger patient numbers remain necessary to assess fully the prospective value of the technique.

Adult↗