Phospholipase C Zeta in Human Spermatozoa: A Systematic Review on Current Development and Clinical Application

During fertilization, the fusion of the spermatozoa with the oocytes causes the release of calcium from the oocyte endoplasmatic reticulum. This, in turn, triggers a series of calcium ion (Ca2+) oscillations, a process known as oocyte activation. The sperm-specific factor responsible for oocyte activation is phospholipase C zeta (PLCζ). Men undergoing intracytoplasmic sperm injection (ICSI) with their spermatozoa lacking PLCζ are incapable of generating Ca2+ oscillation, leading to fertilization failure. The immunofluorescence assay is the most used technique to assess the expression and localization of PLCζ and to diagnose patients with reduced/absent ability to activate the oocytes. In these patients, the use of assisted oocyte activation (AOA) technique can help to yield successful ICSI results and shorten the time of pregnancy. However, the production of a stable PLCζ recombinant protein represents a new powerful therapeutic approach to treating individuals with this condition. We aim to conduct a systematic review focusing on the expression, level, and localization of PLCζ, discussing the novel genetic mutation associated with its impairment. In addition, we highlight the benefits of AOA, looking at new and less invasive methods to diagnose and treat cases with PLCζ dysfunction.

P–263 Life Whisperer™, an AI-based algorithm to select non invasively best quality blastocysts for transfer: A multicenter analysis

Study question

Is the AI-based Life Whisperer™ (LW) tool, suitable to evaluate blastocysts quality and predict clinical pregnancy (CP) in couples undergoing ICSI cycles?

Summary answer

LW blastocyst score is comparable to the scores of other classification methods. This AI model showed high sensitivity and a comparable specificity for CP.

What is known already

The morphology grading is the most widely used method for the selection and classification of the embryos in clinical practice.However,this evaluation entails intervariability and intravariability decision among the embryologists.Recently, research has been focused on new embryo selection systems based on computer-assisted evaluation such as time-lapse with complex algorithms that allow the recognition of objective parameters of the embryo morphology.The implementation of these technologies requires substantial investments that are not available for all clinics.LW is a new embryo selection method based on AI,where specific hardware is not needed,as it is based on single blastocyst images taken with a routine microscope.

Study design, size, duration

Between 2017–2020, a total of 513 Day–5 blastocysts, after ICSI, comming from egg donation treatment were included in this retrospective-multicentre study.Day–5 embryos were evaluated with 3 classification methods:Gardner’s blastocyst grade (GB), the computer derived-output Eeva (EV) and LW AI-supported system. The good quality blastocysts were first evaluated using the GB and EV scores and subsequently compared with the LW scores.The sensitivity and specificity of LW was assessed to validate this system as a clinical pregnancy predictor.

Participants/materials, setting, methods

A total of 513 Day–5 blastocysts, from 134 oocyte donation cycles, were evaluated first by GB score: expansion (1–6), inner cell mass and throphoectoderm (A-C).EV analyses the cell division timing P2 (2cells stage duration) and P3 (3cells stage duration) differentiating three categories:High,Medium and Low(VerMilyea et al.,2014).LW scores ranked 1–10 from a single Day–5 blastocyst HR Image performed on inverted microscope,with a threshold >5 for defining a viable blastocyst.T-test and ROC-curves were used for statistical analysis.

Main results and the role of chance

The average of LW score obtained from GB higher blastocyst expansion score (≥4) was 7.48±0.09, while the average of LW score obtained from GB lower blastocyst expansion score (<4) was 4.69±0.3 (P < 0.001). The average of LW score yielded from GB good morphology of Inner Cell Mass and trophoectoderm (AA,AB,BA) was 7.98±0.1 while the average of LW score obtained from GB lower quality blastocyst score (BB,BC,CB,CA,AC) was 6.36±0.156 (P < 0.001).The average of LW score resulted from EV High blastocysts was 7.42±0.17, while the average of this obtained from EV low score was 6.43±0.3 (P = 0.009).A correlation between EV and LW score could be assesed, except for the blastocyst that are considered Medium score from EV.

Therefore, a strong correlation between GB and LW system, as well GB+EV and LW, was found and an equivalent usability of the LW tool could be confirmed.

The analyse of LW score for transferred embryos (N = 156), using ROC curve, showed a high sensitivity (0,928) but a low specificity (0,154) with a threshold of 5. Regarding our data, ROC curve shows that a threshold of 8,46 could enhance the prediction of CPR because in this point the specifity value is higher than 0.5.

Limitations, reasons for caution

The LW score validation compared to GB and EV methodology was carried out on a small number of embryos.Additionally,not all embryos had been transferred at the time of the analysis.Thus to enhance the accuracy of these data and the specificity of the clinical prediction, a higher sample size is needed.

Wider implications of the findings: Blastocyst selection looks equivalent between all systems,but the LW tool is more objective and faster, saving time and costs significantly, without needing substantial hardware investments.

Additionally,the LW-system shows almost the highest sensibility and may also improve the specificity by self-learning feeding the AI-system, thus tailoring predictions to each laboratory unique environment.

Trial registration number

NA

New permeable cryoprotectant-free vitrification method for native human sperm

STUDY QUESTION

Is permeable cryoprotectant-free vitrification of native sperm samples a good alternative to conventional slow freezing?

SUMMARY ANSWER

The permeable cryoprotectant-free sperm vitrification protocol tested in this study renders considerably better recovery rates of good quality sperm compared to slow freezing.

WHAT IS KNOWN ALREADY

Slow freezing is currently the most commonly used technique for sperm cryopreservation, though this method has been repeatedly shown to have negative effects on both structural and functional sperm features. New alternative methods such as vitrification have been established as a successful alternative in other reproductive cell types, but vitrification of spermatozoa is still a rather unexplored methodology, with limited studies showing its efficacy in male gametes.

STUDY DESIGN SIZE, DURATION

This study included 18 normozoospermic sperm samples from patients seeking ART treatment between 2014 and 2015. The effects of a new vitrification protocol on functional and structural sperm quality parameters in comparison to fresh and slow-frozen samples were assessed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All samples were divided into three aliquots: fresh (F), slow freezing-thawing (S) and vitrification-warming (V). Sperm concentration, motility, morphology, vitality, DNA fragmentation, cytoskeleton integrity and spontaneous acrosome reaction were assessed and compared between the groups.

MAIN RESULTS AND THE ROLE OF CHANCE

Results showed improved preservation of sperm features after vitrification compared to conventional freezing. Permeable cryoprotectant-free vitrification presented a significantly higher percentage of live spermatozoa, than slow freezing, better preservation of acrosomes was achieved in vitrified samples and DNA fragmentation was reduced approximately one-third on average compared to slow freezing. Regarding tubulin assay, three different labelling patterns were observed. The frequency of these labelling patterns was similar in F and V groups but this was not the case of the S group. The multivariate analysis of all sperm quality parameters studied revealed that the V group presented features that are closer to the F group than the S group, indicating that samples are better preserved through vitrification than slow freezing.

LIMITATIONS REASONS FOR CAUTION

This validation has been undertaken only on normozoospermic sperm samples. It would be necessary to compare these results in pathological samples and also to evaluate the influence of the application of this methodology on clinical outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

The sperm vitrification protocol here described warrants better maintenance of sperm quality parameters than traditional freezing methods and may be a good alternative to preserve sperm samples from patients seeking IVF treatment.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by IVF-Spain Foundation. The authors have no conflicts of interest to declare.

Analysis of drug resistance-associated mutations in treatment-naïve individuals infected with different genetic forms of HIV-1 circulating in countries of the former Soviet Union

There are few data on drug resistance-associated mutations in the former Soviet Union since, studies have usually been focused on the env or gag genes for subtype information. This study examines the prevalence and patterns of resistance-associated mutations to reverse transcriptase and protease inhibitors (RTI, PRI) in 278 HIV-1-infected treatment-naïve subjects from countries of Eastern Europe, and defines characteristic polymorphisms of RT and PR sequences in HIV-1 subtype A viruses. Blood samples were collected between 1997 and 2004. Plasma RNA was used for PR-RT amplification by reverse transcription coupled with nested PCR and sequencing. Phylogenetic analysis was done with neighbor-joining trees and bootscanning. Analysis of drug resistance mutations, with Stanford University HIV Drug Resistance Database's algorithm, resulted in an overall prevalence of 12.9% resistance to RTI and 3.9% to PRI. The most frequent substitutions in the RT region were at positions 62 and 236. V77I substitution in PR was found in 47.8% of samples. Polymorphisms in subtype A sequences were identified. This is the first study reporting the prevalence and patterns of both PRI and RTI resistance-associated mutations in naïve HIV-1 infected patients from the former Soviet Union. These data underline the importance of genotypic resistance testing of chronically HIV-1-infected patients before initiating treatment, in order to select the most suitable drug regimen.

Natural resistance-associated mutations to Enfuvirtide (T20) and polymorphisms in the gp41 region of different HIV-1 genetic forms from T20 naive patients

BACKGROUND

The natural occurrence of primary resistance mutations in reverse transcriptase (RT) and protease (PR) genes of HIV-1 isolates from untreated patients has been reported and it may have important implications for the response to drug treatment. It is predictable that the same occurs in the HR1 region of gp41 sequence from patients who have never received T20 therapy, and in this regard it would be important to know not only the mutation frequencies at HR1 region but also the natural polymorphisms at resistance-associated positions present in the absence of this drug.

OBJECTIVES

The objectives of this study are to investigate the existence of natural resistance-associated mutations to T20 in HR1 gp41 region corresponding to different HIV-1 genetic forms from T20 naive patients and to determine their prevalence.

STUDY DESIGN

Two hundred HIV-1 gp41 sequences were included: subtype B: 164 (81.3%); subtype A: 15 (8.2%); subtype G: 10 (4.6%); subtype F: 6 (3.5%); subtype C: 3 (1.8%); subtype K: 1 (0.6%); and subtype D: 1 (0.6%). We analyzed the resistance-associated mutations previously described: Q32H/R, G36D/S, I37V, V38A/M, Q39R/H, Q40H, N42T/D/Q/H, N43D/S/K/Q, L44M, L45M, R46M and V69I.

RESULTS

Natural resistance mutations to T20 were found at a high frequency: 10.5%, corresponding to 9.1% in subtype B and 16.7% in non-B subtype samples. Polymorphisms were more frequent in non-B and recombinant forms than in subtype B (p<0.001). Different substitutions were related to subtypes: N42S in subtypes A, B, G and C, but not in F, Q56R in subtype A from CRF02_AG, and L54M in subtype B from CRF14_BG.

CONCLUSIONS

To our knowledge this is the first study describing natural-resistance to T20 among different HIV-1 subtypes, warranting a study of the biological significance of this mutations and their clinical relevance. The detection of differences between subtypes may have an influence on the rate and patterns of resistance in patients undergoing T20 treatment.

Detection and quantification of multiple drug resistance mutations in HIV-1 reverse transcriptase by an oligonucleotide ligation assay

OBJECTIVES

To develop an assay for the early detection and quantification of minor human immunodeficiency virus-1 populations bearing multiple drug resistance (MDR) mutations.

STUDY DESIGN/METHODS

The oligonucleotide ligation assay (OLA) is based on ligation of probe and detector oligonucleotides annealed to a polymerase chain reaction amplicon strand with detection by an enzyme immunoassay. In OLA-MDR, oligonucleotides were designed to detect MDR mutations. The method was validated with wild-type and MDR mutant clones mixed at different proportions.

RESULTS

K103N mutants were detected as minor populations (5%-30%) by OLA in 6 of 18 samples from patients treated with nonnucleoside reverse transcription inhibitors and classified as wild type by sequencing. In one patient, the kinetics of the increase of MDR mutants could be followed in sequential samples, with K103N being detected earlier by OLA than by sequencing. Q151M mutants were detected as minor populations (13%-24%) by OLA but not by sequencing in 4 samples.

CONCLUSIONS

Oligonucleotide ligation assay MDR exhibits higher sensitivity than sequencing for detection of minor MDR mutant populations.

HIV-1 genetic diversity in Galicia Spain: BG intersubtype recombinant viruses circulating among injecting drug users

BACKGROUND

The HIV-1 epidemics in Western Europe are dominated by B subtype viruses. Non-B subtype is largely restricted to individuals infected outside of Europe and to their direct contacts and is generally acquired by the heterosexual route.

METHODS

Protease and a segment of reverse transcriptase were amplified and sequenced from plasma RNA in 451 individuals from seven cities of Galicia, north-western Spain. Subtype sequence homologies were determined using the BLAST algorithm. Non-B sequences were examined by phylogenetic analysis and intersubtype recombination by bootscanning. The env V3 region was analysed in all non-B and in 38 B subtype viruses.

RESULTS

Ten different non-B genetic forms were identified in 20 (4.4%) individuals. Subtypes were concordant between pol and V3 in five viruses; 14 (70%) infections were with intersubtype recombinant viruses, and one individual had a dual B+G infection. Seven recombinant viruses were phylogenetically related to five reported recombinant forms. Three non-recombinant G and six recombinant BG viruses formed a monophyletic cluster for pol. All but three individuals with non-B infections were native Spanish. Only 6 of 16 individuals referred to sexual contacts with sub-Saharan Africans. Twelve (60%) non-B subtype infections, including all with G and BG viruses, were in injecting drug users (IDU).

CONCLUSIONS

Non-B subtype viruses were identified in 4.4%, with a high diversity of genetic forms, including 70% infections with intersubtype recombinant viruses. The majority of individuals with non-B infections were IDU, most of them without known contacts with non-European sources, and among whom BG recombinant viruses are circulating.

Single- and multidrug resistance mutations to reverse transcriptase and protease inhibitors: human immunodeficiency virus type 1-infected patients from two geographical areas in Spain. Spanish Groups for Antiretroviral Resistance Studies

OBJECTIVES

To describe the prevalence of genotypic resistance mutations, including single and multidrug resistance (MDR) to reverse transcriptase (RT) and protease (PR) inhibitors in treated and untreated patients from two geographical areas in Spain (Madrid and Galicia).

STUDY DESIGN/METHODS

Resistance mutations to RT inhibitors were studied by line probe assay (LiPA) or by automated sequencing in 468 patients (Madrid, 268; Galicia, 200), and resistance mutations to PR inhibitors were studied by automated sequencing in 295 patients (Madrid, 85; Galicia, 210).

RESULTS

The proportion of resistance mutations in treated and untreated patients results were higher by the LiPA method than by sequencing. By sequencing, we detected resistance mutations to nucleoside analogue RT (NRT) inhibitors and NRT inhibitors plus nonnucleoside RT (NNRT) inhibitors in 35.4% and 17.2% of treated patients, respectively. We also detected MDR to zidovudine plus lamivudine in 13.9% of treated patients from Galicia, in 1.7% from Madrid (p < 0.001), and in 1.5% of untreated patients from Galicia. Also, we detected MDR to NRT inhibitors in 3.8% and to NNRT inhibitors in 9.1%. We found resistance mutations to PR inhibitors in 38.1% of treated patients and in 0.9% of untreated patients.

CONCLUSIONS

These findings reinforce the usefulness of testing for resistance mutations in some cases to evaluate their prevalence in a given population and in the follow-up of treated patients.

Evaluation of mixtures of wild-type HIV-1 and HIV-1 with resistance point mutations against reverse transcriptase inhibitors

The presence of resistance-related mutations in 185 serial proviral DNA samples from 108 HIV-infected patients was monitored using the line probe assay (LiPA). The proportions of wild-type and mutant virus in each sample were determined. Subsequent samples from the same patient were analysed. Resistance mutations were detected in 58 of 108 patients studied (53.7%), 53 of 73 (72.6%) treated with antivirals and 5 of 35 (14.2%) untreated. The mutations were against zidovudine (51), lamivudine (1), zidovudine and lamivudine (4), zidovudine and zalcitabine (1) and zidovudine and didanosine (1). Among the 58 patients with resistant virus, 168 related mutations were observed: 161 to zidovudine (90 in codon 70, 25 in codon 41 and 46 in codon 215), 5 to lamivudine (codon 184), 1 to zalcitabine (codon 69) and 1 to didanosine (codon 74). Mixtures of wild-type and resistant mutants were detected in 76 of 90 (84.4%) mutated at codon 70, 28 of 46 (60.8%) mutated at codon 215 and in 21 of 25 (84%) mutated at codon 41. The mutations at codon 184 were mixtures of wild-type and resistant in 4 of 5 samples. The agreement between LiPA and sequencing was 96.5%. LiPA was more sensitive for the detection of mutants that were present at low frequency. The analysis of sequential samples from the same patient allowed evaluation of the dynamics of appearance of the resistant mutants.

Improved conditions for extraction and amplification of human immunodeficiency virus type 1 RNA from plasma samples with low viral load

OBJECTIVES

We attempted to define optimal conditions for amplification of low copy number HIV-1 RNA sequences in plasma samples, applying improved conditions for nucleic acid extraction and amplification.

METHODS

Several methodologic parameters were evaluated, including methods of RNA extraction, volumes of plasma samples, proportion of extracted RNA used as a template for amplification, and reverse transcriptase-DNA polymerase enzyme combination employed in cDNA synthesis and polymerase chain reaction amplification.

RESULTS

With this improved assay, we were able to obtain sufficient amounts of amplified material for direct sequencing in 97% of all plasma samples in our study, including 88% of samples with viral loads <80 copies/mL, 78% of samples with viral loads <50 copies/mL, and even 2 (67%) of 3 samples with <20 copies/mL.

CONCLUSIONS

This procedure could be useful for testing resistance mutations in patients undergoing highly active antiretroviral therapy, in which the viral load is commonly <400 copies/mL, and even if it is <20 RNA copies/mL.

Sequence analysis of the polymerase domain of HIV-1 reverse transcriptase in naive and zidovudine-treated individuals reveals a higher polymorphism in alpha-helices as compared with beta-strands

We report a statistical analysis of genetic heterogeneity of the reverse transcriptase (RT)-coding region of human immunodeficiency virus type 1. Both newly determined sequences and sequences contained in the data banks have been examined. For the calculations, the viral samples and the regions within the RT molecule were divided in two groups. The viral samples were split into those from patients not subjected to antiretroviral therapy and those from patients treated with zidovudine (AZT, 3'-azido-3'-deoxythymidine) alone or in combination with other RT inhibitors. The RT-coding region was divided into segments encoding beta-strands and segments encoding alpha-helices. A significantly lower heterogeneity was observed in beta-strands relative to the alpha-helix coding segments. Application of the D test of Tajima has provided evidence of operation of negative (or purifying) selection in sequences from viruses of patients not subjected to antiretroviral treatment as well as in treated patients. In the group of untreated individuals, regions encoding beta-strands are subjected to stronger negative selection than those encoding alpha-helices. It is likely that the observed differences reflect stronger functional constraints in beta-strands than in alpha-helices of RT.

[Expression of different HIV-1 phenotypic subpopulations through the natural history of the infection]

BACKGROUND

Multiple viral subpopulations coexist in an HIV infected patient with dynamics of selection established between them. In order to get insight on the phenotype of these subpoblations, and its relation with disease progression, we have studied the biological variability of HIV-1 in 113 patients. Variability was related with CD4+ T lymphocyte counts, clinical status, way of viral transmission and antiretroviral treatment.

PATIENTS AND METHODS

113 patients (80 adults and 33 children) were studied for HIV-1 isolation in cocultures of infected and non infected lymphocytes. Viral replication was evaluated as rapid (R)/slow (S) or high (H)/low (L). Syncytia formation was estimated in MT2 cell line (SI/NSI). The tropism toward lymphocytes and monocytes (LM) was studied on H9 and U937 cell lines.

RESULTS

Up to 86.7% of viral isolates were R, 56.6% were H and 49.6% were SI. These percentages increased with disease progression. Eight viral strains were R/H/NSI cocultivated in MT2 cells and SI in cocultured lymphocytes (NSI/SI), which may be considered as a new phenotype. All the SI isolates and all the R/H (SI and NSI) isolates were LM. Three categories were established: R/H/SI/LM, R/H/NSI/LM and S/L/NSI/NLM. The first two categories corresponded to patients with CD4+ T lymphocytes <200 x 10(6)/I (56%, 50%). The third category corresponded to patients with > 500 x 10(6)/I (53.3%).

CONCLUSIONS

Viral replication and SI phenotype, independently, are useful markers for severity of HIV infection. The biological differences among NSI of the 3 viral phenotype categories, including the new subgroup NSI/SI, may indicate the existence of more pathogenic NSI subpopulations.

Structural and thermodynamic properties of DNA uncover different evolutionary histories

We propose an index of DNA homogeneity (IDH) based on a binary distribution model that quantifies structural and thermodynamic aggregates present in DNA primary structures. Extensive analysis of sequence databases with the IDH uncovers significant constraints on DNA sequence other than those derived from codon usage or protein function. This index clearly distinguishes between organisms of different evolutive origins and places them in disjoint domains of DNA sequence space.

Rubisco activase, a possible new member of the molecular chaperone family

The present research addresses the question of whether Rubisco activase (R-A), the enzyme reported to activate Rubisco, is actually a molecular chaperone rather than a conventional enzyme. Several biochemical properties known to be characteristics of molecular chaperones were tested for R-A with positive results. The experiments were performed either in vitro with purified spinach Rubisco and Rubisco activase or in vivo in maize seedling leaves. Our results confirmed that activation of Rubisco by R-A is an ATP hydrolysis-dependent process and further demonstrated that (a) R-A binds preferably to non-native Rubisco protein, than to the native form, and dissociates from this complex after addition of ATP, (b) R-A increases during heat shock treatment in maize seedling leaves, and (c) a large recovery of Rubisco activity is achieved from heat-inactivated Rubisco by addition of R-A and an energy source. We conclude that R-A characteristics strongly suggest that this protein belongs to the molecular chaperone group. The possible role of R-A on maintaining Rubisco activity in vivo is discussed.

Sex identification of humpback whales, Megaptera novaeangliae, on the wintering grounds of the Mexican Pacific Ocean

The sex of 43 humpback whales (Megaptera novaeangliae) from different social groupings in the Mexican Pacific was identified by a molecular analysis of skin biopsy samples. Of the 18 whales sampled from surface-active groups, 17 were males. Three singers were sampled and identified as males. In two cases, whales interrupting and joining a singer without exhibiting agonistic behavior were identified as females. A higher proportion of males was found in the samples collected at the Revillagigedo Islands, reflecting a greater sampling effort on surface-active groups. Preliminary data showed that along the Mexican Pacific coast, the migratory arrival of males corresponds closely to the timing of competitive activity.

A redefinition of the Asp-Asp domain of reverse transcriptases

The rules defining the Asp-Asp domain of RNA-dependent polymerases deduced by Argos (1988) were tested in a set of 53 putative reverse transcriptases (RTs) sequences. Since it was found that some of these rules are not followed by RTs coded by bacteria, group II introns, and non-LTR retrotransposons, we present here a more strict definition of the Asp-Asp domain.

[The evidence of human immunodeficiency virus infection in the seronegative subjects of high-risk groups]

BACKGROUND

Polymerase chain reaction (PCR) is a new diagnostic procedure which has been used to recognise HIV-infected individuals who remain seronegatives.

METHODS

Genomic DNA isolated from the peripheral blood mononuclear cells of 90 high-risk individuals were analyzed by PCR using gag primers SK 38/39. Subjects were classified in four groups: 42 drug abusers, 35 heterosexual partners of HIV-infected individuals, 9 homosexual men, and 4 health care workers accidentally exposed to HIV. Liquid hybridization using radiolabelled probes was done to confirm the results. All samples were also tested for HIV antigen and antibodies (Ab) using EIA and Western blot (WB).

RESULTS

Two out of 11 (18%) drug abusers and 5 out of 34 (14%) couples were PCR positive in absence of HIV antibodies. This silent HIV infections were not recognized in homosexuals and health care workers. All 38 seropositive samples were PCR positive. None of the samples PCR+/Ab- was positive for HIV antigenemia or showed indeterminate results in the WB assay.

CONCLUSIONS

Silent HIV infections were recognized in drug abusers (18%) and couples of HIV-infected individuals (14%). Mechanisms involved in the production of this "occult" HIV infections are reviewed.

Influence of PCR parameters on amplifications of HIV-1 DNA: establishment of limiting sensitivity

We have investigated the optimal reaction conditions and the limiting sensitivity for detection of HIV-1 DNA by PCR. The amplification systems studied were gag (SK38/SK39); pol (P3/P4); and two other systems described here for the first time, LTR (LTR1/LTR2) and nef (Nef1/Nef2), which amplify fragments of 115 bp, 308 bp, 632 bp and 643 bp, respectively. Two PCR profiles were assayed, and the requirements for deoxynucleoside triphosphate and MgCl2 concentrations for each amplification reaction were determined. Optimal reaction conditions were oriented toward selecting maximal amplification of the expected size fragment. Limiting sensitivity was estimated by testing the decreasing copy number of a plasmid containing HIV-1 genome and obtaining a positive amplification signal with at least 5, 5, 10 and 5 copies for LTR, gag, pol and nef, respectively. We conclude that the establishment of the detection sensitivity on a PCR is an important parameter to be considered for the interpretation of results on HIV-1 infection.

High affinity uptake and Ca2+-dependent release of glutamic acid in the developing cerebellum

This study was undertaken in order to evaluate the postulated role of glutamic acid as the neurotransmitter for the parallel fibers of the cerebellar cortex. We studied the Ca2+-dependent release and the high affinity uptake of glutamic acid in the developing cerebellum. The Ca2+-dependent release of glutamic acid from cerebellar molecular layer during development closely follows the time course of parallel fibers synaptogenesis. Little glutamic acid release was observed at 15 days, then it increased to the adult values at the 21st postnatal day. In the rat the bulk of synapses of the parallel fibers appear between the 15th and the 21st postnatal days, the time at which the nerve terminals of the climbing fibers, the other excitatory input to the Purkinje cells, are already developed. An enhanced Na+-dependent, high affinity uptake of glutamic acid was observed in the developing cerebellum relative to the adult rat. That this higher accumulation of glutamic acid is not related to a releasable pool is suggested by the fact that an enhanced glutamic acid, Ca2+-dependent release relative to the adult was not observed. These results support the view that glutamic acid is the transmitter for the cerebellar parallel fibers.

Antimelanoma hybridoma antibodies against partially purified melanoma antigen

We have immunised BALB/c mice with a melanoma antigen obtained after papain solubilisation of the membranes of a metastatic melanoma tumour and fused the immune spleen cells to the mouse myeloma line P3-NS1/1-Ag4.1. The produced hybridoma antibodies (Mel-PV antibodies) recognised the initial melanoma antigen in haemagglutination, but did not react with any of the HLA phenotypes tested by cytotoxicity on a panel of B lymphocytes with known HLA-A and B phenotypes. We rosetted red blood cells coated with protein A with dispersed cells from fresh melanoma tumours, and a high degree of specificity for human malignant melanocytes was observed. Purified Mel-PV antibodies were also tested by indirect immunofluorescence and found to be oriented towards cytoplasmic components of malignant melanoma cells. These results indicate that the use of melanoma antigens for preparing monoclonal antibodies maintained a satisfactory degree of specificity and may be an adequate starting point for defining common and specific antigenic determinants on human melanoma.

Differential staining and segregation of parental chromosomes in mouse-rabbit hybridomas

Hoechst 33258 fluorescent staining can be coupled with G-banding to identify the chromosomal contribution of each parent in mouse-rabbit hybridomas. A fast and essentially complete segregation of rabbit chromosomes is obtained in these cells. The rabbit X chromosome is preferentially maintained in media imposing HGPRT activity for cell growth. Mouse-rabbit hybridomas, some of which secrete rabbit immunoglobulin chains, should be a convenient material for the identification of chromosomes governing rabbit Ig chain synthesis.