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Biomedical subjects

B Avery

Publications and source records attributed to B Avery.

At least 37 records · Page 2Linked to original sources
PubMed1996

A sporadic case of delayed implantation after in-vitro fertilization in the human?

A possible case of delayed implantation after in-vitro fertilization (IVF) is described. The patient was sterilized in 1981, and made fertile again by tubal anastomosis in 1988. In 1990 and 1992 the patient had two right-sided tubal pregnancies, the first was treated with prostaglandin instillation, the second with salpingectomy. In connection with the salpingectomy in 1992, the left tube was observed to be constricted in the middle part and with phimosis of the ostium. In 1994 three IVF embryos were transferred, but 15 days after the transfer, serum human chorionic gonadotrophin (HCG) was negative (< 10 IU/ml). Seven weeks after the embryo transfer, menstruation was still missing, and the serum HCG was now positive (329 IU/ml). Subsequent ultrasound scans were compatible with an intrauterine pregnancy, progressing normally, but 5 weeks delayed compared with the oocyte aspiration. The pregnancy was successfully carried to term. Such a long delay in detection of HCG, in association with a normal pregnancy, has not been described in the literature before.

Adult↗
PubMed1996

A comparison of two murine monoclonal antibodies humanized by CDR-grafting and variable domain resurfacing.

The variable domain resurfacing and CDR-grafting approaches to antibody humanization were compared directly on the two murine monoclonal antibodies N901 (anti-CD56) and anti-B4 (anti-CD19). Resurfacing replaces the set of surface residues of a rodent variable region with a human set of surface residues. The method of CDR-grafting conceptually consists of transferring the CDRs from a rodent antibody onto the Fv framework of a human antibody. Computer-aided molecular modeling was used to design the initial CDR-grafted and resurfaced versions of these two antibodies. The initial versions of resurfaced N901 and resurfaced anti-B4 maintained the full binding affinity of the original murine parent antibodies and further refinements to these versions described herein generated five new resurfaced antibodies that contain fewer murine residues at surface positions, four of which also have the full parental binding affinity. A mutational study of three surface positions within 5 A of the CDRs of resurfaced anti-B4 revealed a remarkable ability of the resurfaced antibodies to maintain binding affinity despite dramatic changes of charges near their antigen recognition surfaces, suggesting that the resurfacing approach can be used with a high degree of confidence to design humanized antibodies that maintain the full parental binding affinity. By comparison CDR-grafted anti-B4 antibodies with parental affinity were produced only after seventeen versions were attempted using two different strategies for selecting the human acceptor frameworks. For both the CDR-grafted anti-B4 and N901 antibodies, full restoration of antigen binding affinity was achieved when the most identical human acceptor frameworks were selected. The CDR-grafted anti-B4 antibodies that maintained high affinity binding for CD19 had more murine residues at surface positions than any of the three versions of the resurfaced anti-B4 antibody. This observation suggests that the resurfacing approach can be used to produce humanized antibodies with reduced antigenic potential relative to their corresponding CDR-grafted versions.

Amino Acid Sequence↗
PubMed1996

Transcription and cell cycle-dependent development of intranuclear bodies and granules in two-cell bovine embryos.

Bovine two-cell embryos were produced by maturation and fertilization in vitro and isolated at 27, 30 or 33 h after insemination. Embryos were incubated with [3H]uridine for 10 h. Other embryos were incubated with [3H]uridine for 1 h starting at 0-3 h, 3-6 h, 6-9 h or 9-12 h after cleavage (hpc) to the two-cell stage. Subsequently, all embryos were washed, fixed, dehydrated, embedded in Epon and sectioned for light microscope autoradiography and transmission electron microscopy. Thus, at the time of fixation the embryos incubated in [3H]uridine for 1 h represented the periods 1-4, 4-7, 7-10 and 10-13 hpc. Among embryos subjected to [3H]-uridine incubation for 10 h, a majority of those in interphase displayed auto-radiographic labelling over the nuclei, whereas none of the embryos incubated for 1 h did so. At 1-4 hpc, two-cell embryos presented electron-dense nucleolus precursor bodies and large clusters of electron-dense granules of various sizes in their nuclei. At 4-7 hpc, ring-shaped or horseshoe-shaped bodies of the same electron density as the nucleolus precursor bodies were found in the periphery of the granule clusters. At 7-10 hpc, several incomplete ring-like bodies of the same electron density as the nucleus precursor bodies were found deeply embedded in the granule clusters. The interior of these bodies contained granules lining a central vacuole. At 10-13 hpc, all two-cell embryos were in mitosis. It is concluded that bovine embryos produced in vitro display a certain rate of transcription during the second cell cycle without the presence of a well-defined transcriptional peak, and that this activity is paralleled by cell cycle-dependent interaction of intranuclear bodies and granules.

Animals↗
PubMed1995

Impact of Percoll on bovine spermatozoa used for in vitro insemination.

Percoll treatment of bovine frozen/thawed spermatozoa was identified as the cause of low cleavage and blastocyst rates in our in vitro embryo production system. Percoll treatment of spermatozoa yielded very high, stable and repeatable results for many months of cleavage and blastocyst rates of 83 +/- 5% (+/-SD) and 33 +/- 10%, respectively. This was followed by a period with significantly lower cleavage and blastocyst rates of 60 +/- 9% and 14 +/- 5%, respectively. In the last period, the results became even lower, with cleavage and blastocyst rates of 32 +/- 5% and 5 +/- 3%, respectively. These results were significantly different from those of the 2 previous periods. We were able to correlate precisely these changes in outcomes to the introduction of new Percoll batches. When compared with washed spermatazoa and under otherwise identical circumstances, the cleavage and blastocyst rates from spermatozoa treated with Percoll increased significantly from 33 to 73% and from 4 to 26%, respectively. We suggest that this adverse effect of Percoll is not due to Percoll particles per se, but may be ascribed to the effect of unbound polyvinylpyrrolidone (PVP) in the Percoll.

Journal Article↗
PubMed1995

Development of in vitro matured and fertilized bovine embryos, cultured from days 1-5 post insemination in either Menezo-B2 medium or in HECM-6 medium.

Bovine embryos were produced by in vitro maturation and fertilization of abattoir oocytes. The embryos were randomly allocated either to coculture with bovine oviduct cells in Menezo-B2 medium (control group), or to culture in the defined HECM-6 medium. At Day 5 after insemination the HECM-6 embryos were transferred to Menezo-B2 medium with (HECM-B2/BOEC) or without (HECM-B2) oviduct cells for further culture. The proportion of cleaved embryos and blastocysts, the morphology and the speed of development were compared for the control and HECM groups. Significantly more HECM-6 embryos than control embryos cleaved (88 +/- 3% vs 76 +/- 5% (+/- SD)). Significantly fewer blastocysts developed in the HECM-B2 than in the control group (28 +/- 2% vs 35 +/- 3%), in addition the speed of development was delayed and the morphology was impaired. In the HECM-B2/BOEC group no differences in neither morphology, blastocyst rates (31 +/- 8%) nor speed of development could be demonstrated, when compared with the control group. A portion of the control and HECM-B2 embryos were vitrified at Days 7-8, but no differences were noted in survival or morphology at 48 and 72 h post thawing. It can be concluded, that the defined medium HECM-6 can support bovine embryonic development through the 8-16 cell in vitro block stage without the use of coculture in a reliable way. In our system it was however necessary to transfer the embryos at Day 5 to coculture in Menezo-B2 medium to ensure optimal continuation of development.

Journal Article↗
PubMed1995

Differences in expression of angiotensin II receptors and renin in porcine and bovine ovaries.

The expression of angiotensin (Ang) II receptors, active renin and prorenin in porcine and bovine ovarian follicles and corpora lutea was investigated and compared. In the wall tissue of porcine follicles, the Ang II receptor density was 47 (range 19-97; n = 13) fmol/mg membrane protein. The active renin concentration was 1.32 (0.40-3.43; n = 23) GU/kg wet tissue. These values were about 35-fold and 15-fold lower, respectively, than previously found in bovine follicles. No prorenin could be detected in the porcine follicular wall tissue. Ang II receptors of subtype 2 (AT2 receptors) with a dissociation constant (Kd) of 1.01 (0.64-1.79; n = 8) nmol/l for [Sar1-Ile5-Ile8]-Ang II were demonstrated in the bovine corpus luteum. The receptor density was 22.7 (1.9-93; n = 26) fmol/mg membrane protein, which was about 10-fold higher than in porcine corpora lutea. The active renin concentration was 20.7 (2.2-60.0; n = 26) GU/kg tissue in bovine and 0.40 (0.16-1.09; n = 17) GU/kg tissue in porcine corpora lutea. No prorenin could be detected in corpora lutea from both species. The variation between species in expression of the ovarian renin-angiotensin system indicates the existence of species differences in the physiological role.

Animals↗
PubMed1994

In vitro incubation of bovine ovarian follicles: indications for an active and regulated renin-angiotensin system.

1. The ovarian follicular renin-angiotensin system was investigated by using an in vitro incubation method, based on tissue incubation of individual bovine follicles. 2. Very high and varying concentrations of active renin (median 18.0 GU/kg, range 2.1-107 GU/kg; n = 101) and prorenin (11.7 GU/kg, range < 2.6-142 GU/kg; n = 101) existed in unincubated ovarian follicular tissue. 3. Active renin and prorenin increased 35 and 959%, respectively, in follicular wall tissue and incubation medium during 72 h of in vitro incubation. The protein synthesis inhibitor cyclohexamide inhibited active renin and prorenin formation. No activation of prorenin occurred in incubation medium or follicular fluid in vitro. Active renin was degraded during incubation. 4. Primarily prorenin but also active renin were secreted into the incubation medium. Secretion was directed both to the internal and external surface of the follicular wall. 5. Follicle-stimulating hormone (FSH) slightly stimulated the synthesis and secretion of prorenin in vitro. 6. The synthesis and secretion rates of active renin and prorenin varied markedly between individual follicles. 7. The finding of very high and varying concentrations of active renin in follicular wall tissues together with the formation and secretion of active renin during in vitro incubation provide further evidence for an active and regulated renin-angiotensin system in ovarian follicles.

Animals↗
PubMed1992

Morphological development and sex of bovine in vitro-fertilized embryos.

Bovine in vitro-fertilized embryos at the blastocyst stage were collected at days 7, 8, and 10 postinsemination and sex was determined via the polymerase chain reaction (PCR) to compare the embryonic development with the sex of the embryos. The percentages of males (sex ratio) after division of the embryos into three developmental groups were 68%, 48%, and 35% in the fast, intermediate, and slow groups, respectively (P = 0.014). The percentages of males on days 7, 8, and 10 were 60%, 40% and 33%, respectively (P = 0.043). The average sex ratio for the whole material was 50%. It is thus concluded that male bovine preimplantation embryos develop faster than female embryos.

Animals↗
PubMed1992

The freezability of biopsied bovine embryos.

A biopsy of 1-5 blastomeres was taken from 86 bovine compacted morulae, using a technique, that did minimal damage to the zona pellucida. As soon as possible after the micromanipulation the embryos were frozen, without sealing the penetrated zona pellucida. In order to evaluate the viability of the biopsied frozen-thawed embryos, half of them were transferred to synchronized recipients while the remaining half were co-cultured to evaluate the developmental capacity. A control group of 43 intact embryos was subjected to the same procedures. This study revealed a slight, but not significant, decrease in the pregnancy rate of the biopsied embryos after freezing and thawing, although the embryos by co-culture with bovine oviduct epithelial cells revealed normal morphology and developmental rate. It is concluded that the described biopsy technique did not compromise the freezability of 7-day-old bovine embryos.

Journal Article↗
PubMed1992

Measurement and identification of prorenin and renin in ovarian follicular fluid from cattle and pig.

1. In previous studies we have demonstrated and solved several methodological problems in relation to the measurement of prorenin by trypsin activation in rat, bovine, hog and horse plasma. 2. The aim of the present study was to develop a method for the measurement of prorenin in bovine and porcine ovarian follicular fluid. 3. Trypsin activation of follicular fluid generated angiotensin I immunoreactive material (AI IM) in both species. 4. The AI IM interfered with the renin assay, but could be completely removed by a cation exchange resin in a batch-wise technique. 5. The enzymatic activity of trypsin-activated prorenin and pre-existing active renin was completely inhibited by a specific inhibitor of renin. 6. The reactions were optimized and an accurate measurement of prorenin in ovarian follicular fluid was developed. 7. The existence of prorenin and renin in bovine ovarian follicular fluid was established. Prorenin and renin in porcine ovarian follicular fluid was demonstrated for the first time. 8. The ratio between ovarian follicular fluid and plasma was 43 for prorenin and 19 for active renin in cattle. The same ratios in pigs were 1.3 and 0.4, respectively. These findings indicate a species difference with respect to the amount of prorenin or active renin present in ovarian follicular fluid.

Angiotensin II↗
PubMed1992

Coculture of bovine demiembryos prior to freezing.

Pregnancy rates after transfer of frozen/thawed bisected embryos, demiembryos, have until now been very low. In the present study it was attempted to improve the freezability rate of demiembryos by culturing them on a monolayer of bovine oviduct epithelial cells (BOEC) prior to freezing. The cultured frozen/thawed demiembryos showed a lower developmental rate than intact embryos. The pregnancy rate (23%) following transfer was not different from the pregnancy rate after transfer of unfrozen demiembryos (26%). The calving rate (4%), however, was significantly lower than the calving rate after transfer of fresh demiembryos (23%). Although the overall pregnancy rate achieved in this study was low, it can be concluded that a co-culture period upon BOEC prior to freezing does not improve the viability of frozen demiembryos.

Animals↗
PubMed1992

Impact of incubator type on the yield of in vitro produced bovine blastocysts.

Because of suboptimal in vitro production of bovine blastocysts a new incubator model (Mini) was tested against the traditional (Heraeus). The difference between their properties seemed only to be the volume of the incubator space. No difference was noted between the CO2 or the temperature, but the data clearly showed a highly significant increase of the blastocyst rates, 6% versus 51% in the Heraeus and the Mini incubator, respectively, calculated as blastocysts per cleaved embryos. It was concluded that the incubator type or model may be a very important part of the in vitro production of bovine embryos, although we were not able to pin point specific causes for this difference.

Animals↗
PubMed1992

Blastomere content of cultured/frozen bovine demiembryos.

The purpose of the study was to evaluate whether a period of co-culture with bovine oviduct epithelial cells (BOEC) could improve the tolerance of bisected bovine embryos to freezing and thawing. Day 6 embryos were bisected and the resulting demiembryos were stained with Hoechst 33342 and cell counts were made by counting intact blastomere nuclei. Of these, 11 were stained as freshly manufactured demiembryos, 25 after co-culture for 24 h with BOEC and 37 stained after 24 h co-culture and freezing and thawing. The staining revealed, that there was no significant difference in cell count of demiembryos that were stained immediately after bisection, compared to those, that were co-cultured for a 24 h period. Also, the co-cultured/frozen/thawed demiembryos had a significant decrease in cell numbers compared to the non-frozen demiembryos. We conclude, that a 24 h period of co-culture with BOEC does not result in appreciable cellular proliferation in demiembryos and therefore instead of improving the survival of frozen/thawed demiembryos by giving them opportunity to multiply their cell number and thus make them more resistant to cell damage, rather compromised the viability of cryopreserved demiembryos.

Animals↗
PubMed1991

Sex and development in bovine in-vitro fertilized embryos.

In vitro fertilized bovine embryos were karyotyped at Day 7 and Day 8 post insemination. The results showed that the percentage of males (sex ratio) was dependent on the developmental stage. Among expanded blastocysts (the most advanced embryos), the sex ratio was 100%, followed by 89% for expanding blastocysts, 75% for blastocysts, and 40% for young blastocysts, all analyzed at Day 7. For embryos karyotyped at Day 8, the sex ratio was 20%. The average mitotic index for all in vitro fertilized embryos was 3.5%. These results suggest that the apparent relationship between sex and developmental rate could be used as a method for noninvasive sexing of in vitro fertilized embryos.

Journal Article↗
PubMed1991

The effect of endotoxin-contaminated medium on in vitro fertilization and development of bovine oocytes matured in vitro.

The purpose of this study was to determine whether the presence of bacterial endotoxin in the bovine serum albumin (BSA) used to supplement media utilized for sperm preparation and co-culture of bovine sperm and oocytes affects in vitro penetration and embryonic development of oocytes matured in vitro. The chromogenic limulus amoebocyte lysate (LAL) test was used for quantification of the content of endotoxin. The proportion of penetrated ova was significantly greater (P greater than 0.0005) for the endotoxin-contaminated group (89%) versus the non-contaminated group (61%), but this was probably not due to endotoxin contamination. The presence of endotoxin resulted in a high rate of polyspermy (27% versus 4%, respectively; P greater than 0.0005), while the occurrence of parthenogenetic activation was the same for each group (8%). The proportion of total embryos put into culture that developed to the blastocyst stage by day 8 was similar (30% and 26%) for the contaminated and non-contaminated group, respectively. Fifty-three and 69%, respectively, hatched on day 10. These results suggest that endotoxin induces polyspermy, but has no adverse effect on embryonic development.

Animals↗
PubMed1989

Differential cleavage rates and sex determination in bovine embryos.

The purpose of this study was to determine whether a correlation between embryonic cleavage rates and sex ratios in dairy cattle could be substantiated. Embryos were collected at Day 7 after estrus following superovulation and artificial insemination. Embryos from flushings where at least two different developmental stages within the same flushing could be identified were examined. A total of 476 such embryos was transferred to recipients and 110 calves were born. The sex effect was only demonstrable in flushings yielding embryos of at least three different developmental stages. The sex ratios from this group were 32%, 58% and 62% in the slow, intermediate and fast developing groups of embryos, respectively. The deviations were not significant (P = 0.084). Only 23% of the flushings provided embryos that fell into this cathegory, which limits the use of differential cleavage rates as a sexing method, unless additional embryo culture is introduced to the technique.

Journal Article↗
PubMed1989

Impact of asynchronous ovulations on the expression of sex-dependent growth rate in bovine preimplantation embryos.

In cattle, male embryos have a faster growth rate than female embryos, and this results in alteration of the normal 1:1 sex ratio in embryos divided into three developmental groups. The fastest developed one-third are predominantly males, the slowest one-third predominantly females, and in the intermediate one-third no alteration of the sex ratio is seen, However, the deviations of the sex ratios are only 15-20% from random. These findings are compatible with the assumption that, in superovulated cows, ovulations follow a normal distribution and that, at the time of sampling at Day 7, male and female embryos differ with regard to development by 1 or 2 h. Because of this it is unlikely that larger changes in the sex ratios can be expected.

Animals↗