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Biomedical subjects

Y Heyman

Publications and source records attributed to Y Heyman.

50 records · Page 3Linked to original sources
PubMed1985

Secretion of anti-Müllerian hormone by immature bovine Sertoli cells in primary culture, studied by a competition-type radioimmunoassay: lack of modulation by either FSH or testosterone.

Secretion of anti-Müllerian hormone (AMH) by immature bovine Sertoli cells in primary culture was studied through a competition-type RIA employing a polyclonal antibody and 125I-labelled purified AMH. This RIA is approximately 10 times more sensitive than the solid-phase two-site monoclonal antibody-based RIA described previously. Biosynthesis and secretion of AMH by cultured Sertoli cells require approximately 48 h, are not influenced by FSH or testosterone and steadily decrease over a one-week period of culture. Cyclic AMP response to FSH stimulation is normal in cultured cells. Whether the factors responsible for the extinction of AMH production in vitro are in any way related to those operating during normal maturation, which lead to repression of AMH biosynthesis in adult Sertoli cells, is not known at the present time and deserves further study.

Age Factors↗
PubMed1984

Direct freezing of cattle embryos after partial dehydration at room temperature.

A new and simple method for freezing of bovine morulae and blastocysts was developed. Embryos were predehydrated at room temperature, frozen at -30 degrees C (cooling rate = 12 degrees C/min), and plunged into liquid nitrogen. This method was compared in vitro and in vivo to the slow freezing method (0.3 degrees C/min to -30 degrees C). Predehydration of the embryos in 1.5M glycerol was achieved by sucrose solution that makes the cells osmotically shrink. After the predehydrated morulae and blastocysts were frozen and thawed, 6 .4% (33 52 ) were developed in vitro for 48h and 44.2% (23 52 ) were hatched. Development obtained with slowly frozen embryos were 70.8% (17 24 ) and 58.3% (14 24 ) respectively. After transfer to recipient heifers, 33.3% (7 21 ) of the embryos frozen according this new method developed normally into viable foetuses or calves. This was the case for 48.5% (16 33 ) of the slowly frozen embryos.

Journal Article↗
PubMed1984

Maintenance of the corpus luteum after uterine transfer of trophoblastic vesicles to cyclic cows and ewes.

One or two trophoblastic vesicles (0.4-2 mm diam.) from cow (Day 14) or ewe (Day 11-13) embryos without their disc were transferred, after culture for 24 h, into recipients. Each vesicle was transferred into the uterine horn ipsilateral to the CL by the cervical route in heifers and surgically in ewes on Day 12 of the oestrous cycle. In cows, daily measurements of plasma progesterone concentrations and checks for return to oestrus showed that the CL was maintained in 8 out of 12 recipients. These 8 cows had 25- to 37-day cycles while 4 recipient heifers returned to oestrus normally. Three recipients with an extended cycle were slaughtered. The dissected uterus showed that trophoblastic vesicles had developed in the uterine horns. In ewes, the serum progesterone curve, determined in each recipient, showed that the CL was maintained in 7 out of 12 recipients. These 7 ewes had 20- to 54-day cycles and the other 5 ewes had a normal cycle of 15-19 days comparable to that of 17.0 +/- 0.5 days for the 6 control ewes. Whenever the CL was maintained, high blood progesterone levels were followed by rapid luteolysis. In cattle and sheep, therefore, a trophoblastic vesicle transferred into the uterus can develop in vivo, secreting the embryonic signals when there is no embryonic disc control and transforming the cyclic CL into a CL of pregnancy in about 60% of the cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Cleavage beyond the block stage and survival after transfer of early bovine embryos cultured with trophoblastic vesicles.

Early bovine embryos (1- to 8-cell stages) were recovered from superovulated heifers at slaughter on Days 2 or 3. Embryos were cultured for 3-4 days in Medium B2 supplemented with 15% (v/v) fetal calf serum in the absence (B2SS, 106 embryos) or presence of trophoblastic vesicles (B2SS + TV, 190 embryos). At the end of culture, there were more (P less than 0.001) morulae (greater than or equal to 16 cells) in B2SS X TV (46%) than in B2SS alone (18%) irrespective of the initial cell stage. More 8-cell embryos reached the 16-cell stage than did embryos with less than 8 cells (30% vs 15% in B2SS, P greater than 0.05; 70% vs 41% in B2SS + TV, P less than 0.005). After culture, 102 morulae were transferred non-surgically to temporary recipient heifers (84 embryos cultured in B2SS + TV and 18 in B2SS). After 2 or 3 days, 14 out of 58 embryos from the B2SS + TV group and 3 out of 10 embryos from the B2SS group were recovered as blastocysts. Most blastocysts were deep-frozen and stored for several weeks. After thawing, 10 apparently normal embryos from the B2SS + TV group were transferred non-surgically into 10 recipient heifers. Four pregnancies were induced, but only one embryo survived to term (birth of a normal male calf). It is concluded that trophoblastic vesicles release one or several unknown compound(s) normally present in vivo, promoting the cleavage of early bovine embryos.

Animals↗
PubMed1983

Use of monoclonal antibody techniques to study the ontogeny of bovine anti-Müllerian hormone.

Monoclonal antibodies against bovine anti-Müllerian hormone (AMH) were used to study the hormone in cattle. Anti-Müllerian activity of testicular tissue, immunoreactive testicular AMH, serum AMH concentration and AMH production by incubated testicular tissue were detectable from 42 days, i.e. at the time of seminiferous tubule differentiation, and peaked between 50 and 80 days, when the Müllerian ducts regress in the male fetus. All the values stabilized at a lower level until 30 days after birth and then slowly decreased. At 18 months, only traces of AMH immunoreactivity were detectable in testicular tissue and serum concentration and AMH production by incubated testicular tissue were negligible; the main source of AMH in the adult animal was the rete testis fluid. Study of the disappearance rate of AMH from the serum of castrated calves gave a half-life of approximately 2 days for bovine AMH.

Aging↗
PubMed1982

Production of monozygotic twins by micromanipulation and cervical transfer in the cow.

To develop the practical production of monozygotic twins in cattle, the ability of day 6 to 7 cow embryos to survive after they were split into two halves was tested. Day 6 to 7 embryos were recovered by the cervical method from superovulated Charolais heifers. Only normal embryos were selected at the advanced compaction stage when the cavity appears. Each embryo was cut into two halves and each half was replaced in an empty zona pellucida. After micromanipulation, the half embryos were directly transferred to recipient heifers via the cervix. From 16 normal embryos manipulated, 14 monozygotic half embryo pairs were obtained which were all transferred to 14 recipients (pregnancy rate 64.2 per cent); six recipients carried twins (twinning rate 66.6 per cent). Thus 15 fetuses were recorded from the 14 monozygotic half embryo pairs transferred.

Animals↗
PubMed1981

Cervical transfer of deep frozen cattle embryos.

Cattle blastocysts were collected from 29 donors 7-8 days after estrus and frozen and stored in liquid nitrogen up to several months. Two procedures were used for freezing and thawing: -- procedure A: slow cooling to -60 degrees C (0.3 degrees C/min to -60 degrees C) and slow thawing (12 degrees C/min); -- procedure B: slow cooling to -30 degrees C (0.3 degrees C/min to -30 degrees C) and rapid thawing in a water bath at 37 degrees C. After thawing, the embryos were cultured from 8 to 12 hours before transfer; 36% of the embryos continued normal development during culture; both procedures resulted in a high pregnancy rate (procedure A: 10/15; procedure B: 11/15) after single cervical transfer of the frozen thawed embryos which developed normally in vitro. However the overall survival rate was low (25%) and varied between donors, indicating that progress must be made before the technique of freezing can be extended to applied conditions.

Journal Article↗
PubMed1980

Importance of gestation losses after non-surgical transfer of cultured and non-cultured bovine blastocysts.

Several techniques, including progesterone assay at days 21, 28 and 35, heat detection twice daily, rectal palpation at day 60 or planned slaughter, were combined to determine the importance of gestation losses after a single cervical transfer of 128, 10 to 12-day-old bovine embryos. Using non-cultured embryos (n = 83) transferred within six hours after recovery, 29.3 per cent of the initiated gestations were lost before day 60. Few abortions occurred after that stage. More than 50 per cent of the losses concerned preimplantation embryos from day 21 to day 35. When embryos cultured for 24 hours at 37 degrees C were used, there was a marked increase in the gestation loss (46.3 per cent) occurring mainly at the time of implantation. This suggests that the culture had a detrimental effect on the embryonic disc cells.

Animals↗
PubMed1979

An instrument for transcervical recovery of embryos from heifers.

A non-surgical system of embryo recovery is described. It consists of a rigid probe of small diameter (4 mm) for recovering the embryos from young heifers (10 to 12 days after estrus). An average of 6.35 eggs were recovered per donor from 64 heifers 15 to 22 month-old having more than two palpable corpora lutea after superovulation. Forty donors were slaughtered after recovery to determine the number of ovulations, the state of the uterus and to do a post-mortem perfusion. The average recovery rate of embryos was 56.4 % ; an additional 9 % were recovered after slaughter. We compared two recovery methods differing in mode of liquid return ; no significant differences were found. Twenty-four animals not slaughtered after recovery returned to heat a mean 23.8 days after induced estrus (control cycle).

Journal Article↗
PubMedDate not supplied

Cloning in cattle: from embryo splitting to somatic nuclear transfer.

The ability to obtain genetically identical offspring in cattle (clones) is useful for research and for potential applications to breeding schemes. Experimental possibilities for generating such animals have evolved considerably in the last two decades. Embryo splitting has become a relatively simple technique but is limited to twinning. Embryonic nuclear transfer has improved and is associated with sexing to generate sets of clones despite a great variability of results between parent embryos. The factors of progress are reviewed here. Recently, somatic cells used as a source of nuclei in bovine nuclear transfer has been demonstrated. Here we present the results of the developmental potential of nuclei from skin and muscle cells.

Animals↗