Comparative trial between an ultra-short and long protocol of luteinizing hormone-releasing hormone agonist for ovarian stimulation in in-vitro fertilization.

A total of 312 patients with tubal infertility participated in a prospective randomized study comparing two regimens of ovarian stimulation with a luteinizing hormone-releasing hormone agonist (buserelin) and human menopausal gonadotrophin (HMG). Half of the patients were given an ultra-short treatment protocol when the agonist was administered on days 2, 3 and 4 of the stimulated cycles; the other half were given a long protocol when the agonist was administered from the mid-luteal phase of the cycle preceding the treatment cycle. The mean number of HMG ampoules used per patient was significantly higher in the long protocol. No significant differences were found between the two groups in the incidence of cancelled cycles, failed oocyte recovery, mean number of oocytes recovered per patient, complete failure of fertilization and the fertilization and embryo cleavage rate. More patients undergoing the long protocol had supernumerary embryos cryopreserved and successful deliveries.

Seminal plasma anti-sperm antibodies and IVF: the effect of semen sample collection into 50% serum.

A retrospective analysis was carried out which studied IVF results for couples in whom the male partner had anti-sperm antibodies in seminal plasma, as judged by a positive MAR test. Of the 59 couples studied over a total of 113 cycles, 30 had IVF semen samples collected into sterile, dry pots. Thirty-eight of the couples had samples collected into medium containing 50% serum, and nine couples underwent separate treatment cycles with samples collected both dry and into 50% serum. The results demonstrate that the addition of serum to sample collection pots significantly improves the oocyte fertilization rate and is followed by a greater chance of conception for these couples.

Short-term luteinizing hormone-releasing hormone agonist treatment: prospective trial of a novel ovarian stimulation regimen for in vitro fertilization.

Over a period of 4 months, 262 infertile couples participated in a prospective pseudorandom trial of a novel short-term luteinizing hormone-releasing hormone/human menopausal gonadotropin (LH-RH/hMG) treatment; the short-Buserelin-gonadotropin (Hoechst, Hounslow, United Kingdom) regimen. Patients treated with the short-Buserelin-gonadotropin regimen had a significantly higher likelihood of achieving pregnancy than patients treated with the standard clomiphene citrate (CC)/hMG regimen (respectively, 35.5% and 18% per treatment cycle). A significantly higher number of eggs were collected after short-Buserelin-gonadotropin treatment than CC/hMG, but the proportion of patients having a given number of embryos replaced was similar in the two groups. The short-Buserelin-gonadotropin-treated patients were distinguished from the CC/hMG-treated group by significantly lower levels of LH in the late follicular phase and a lower plasma level of estradiol. A detrimental relationship between elevated endogenous LH secretion and failure of implantation has been established. The nature of the short-Buserelin-gonadotropin regimen provokes high levels of endogenous gonadotropin secretion in the early follicular phase and induces a suppression of gonadotropin secretion in the late follicular phase. This may be the physiologic basis of the greater implantation rate after short-Buserelin-gonadotropin treatment than is seen with conventional CC/hMG treatment.

Selection of methionine tRNAs by avian oncornaviruses.

The free 4S RNA of avian RNA tumor viruses is greatly enriched in one of the four methionine tRNAs of the host cells, tRNA4Met. On the assumption that viral tRNAMet forms are identical to the corresponding tRNAs of mouse or chick cells, the following conclusions were drawn concerning the tRNAMet content of oncornaviruses: (1) tRNAMet species may be compartmentalised within the host cells, and the viral tRNA pool could reflect the cellular compartment in which viral maturation takes place since tRNAMet forms distribute unevenly between different fractions of a cell homogenate. (2) tRNA4Met appears to have no special role in the modulation of protein synthesis in as much as no functional difference between tRNA2Met and tRNA3Met, tRNA4Met could be demonstrated in in vitro protein synthesising systems. (3) tRNA4Met differs in nucleotide sequence from all other host cell tRNAMet forms except possibly tRNA2Met. The nucleotide sequences of two tRNAMet species, tRNA1Met and tRNA4Met, have already been determined and the sequence of another host cell tRNAMet, tRNA3Met, was derived from the analogy of its sequence to that of tRNA4Met since the two molecules differ in only 6 nucleotides out of 76. (4) Avian myeloblastosis virus reverse transcriptase has been shown to bind specifically tRNA4Met and tRNATrp in whole cell tRNA and therefore the free tRNA4Met in the virion particle may exist substantially bound to virion-associated transcriptase.

Methionine transfer ribonucleic acids of avian myeloblastosis virus.

Chick-embryo cells contain four isoaccepting species of methionine transfer RNA (I-IV). One species (I) is the initiator, tRNA(f) (Met), and the others (II, III, and IV) are the donors of internal methionyl residues (tRNA(m) (Met)). Over 85% of the tRNA(Met) in purified avian myeloblastosis virus consists of one tRNA(m) (Met) species, which resembles host-cell tRNA(Met) IV with respect to chromatographic properties on RPC-5, electrophoretic mobility of the terminal methionyl-oligonucleotide, and activity in cell-free protein synthesis in response to synthetic and natural messenger RNAs. Thus, tRNA(Met) IV of avian myeloblastosis virus is structurally indistinguishable from the corresponding host-cell species, and, although not involved in initiation of viral protein synthesis, is able to function in peptide-chain elongation.