Analysis of pir gene expression across the Plasmodium life cycle

Background

Plasmodium interspersed repeat (pir) is the largest multigene family in the genomes of most Plasmodium species. A variety of functions for the PIR proteins which they encode have been proposed, including antigenic variation, immune evasion, sequestration and rosetting. However, direct evidence for these is lacking. The repetitive nature of the family has made it difficult to determine function experimentally. However, there has been some success in using gene expression studies to suggest roles for some members in virulence and chronic infection.

Methods

Here pir gene expression was examined across the life cycle of Plasmodium berghei using publicly available RNAseq data-sets, and at high resolution in the intraerythrocytic development cycle using new data from Plasmodium chabaudi.

Results

Expression of pir genes is greatest in stages of the parasite which invade and reside in red blood cells. The marked exception is that liver merozoites and male gametocytes produce a very large number of pir gene transcripts, notably compared to female gametocytes, which produce relatively few. Within the asexual blood stages different subfamilies peak at different times, suggesting further functional distinctions. Representing a subfamily of its own, the highly conserved ancestral pir gene warrants further investigation due to its potential tractability for functional investigation. It is highly transcribed in multiple life cycle stages and across most studied Plasmodium species and thus is likely to play an important role in parasite biology.

Conclusions

The identification of distinct expression patterns for different pir genes and subfamilies is likely to provide a basis for the design of future experiments to uncover their function.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03979-6.

Assessment of condoms as probe covers for transvaginal sonography

PURPOSE

This prospective study assessed the incidence of transvaginal probe contamination and breakage of condoms used to cover those probes during transvaginal sonography.

METHODS

Over a 9-month period, 214 women underwent transvaginal sonography with probes that had been coated with gel and then covered with a latex condom. Condom defects were detected after the scans by inspection, by adding hydrogen peroxide, and by filling the condoms with 500 ml of water. After the condoms were removed, the probe was either wiped with a dry tissue (during the first 18 weeks of the study) or wiped first with a dry tissue and then with a 70% isopropyl alcohol wipe. Probe head contamination was assessed by periodic swab sampling and culturing for bacteria and herpes simplex virus. Samples of the sonographic gel also were tested for bacterial contamination at approximately weekly intervals.

RESULTS

A total of 217 condoms were used, 3 of which broke and were discarded while being applied to the probe. Two of the 214 condoms used (0.9%) were found upon visual inspection to have perforations. None of the other 212 condoms leaked upon being filled with water; none of the 204 condoms tested with hydrogen peroxide showed bubbles. Only 1 of the 46 probe swab samples was positive for bacteria (Acinetobacter species); none of the 26 probe swab samples cultured for viruses or the 25 gel samples cultured for bacteria were positive.

CONCLUSIONS

Condoms used to cover transvaginal probes showed a low rate of perforation. Disinfection of the probe with isopropyl alcohol wipes further reduced the risk of contamination.

The prognostic value of fetal ultrasonography before induction of labour

OBJECTIVE

To investigate whether ultrasound examination of the fetus and amniotic fluid before induction of labour can provide useful prognostic information about the course of labour and mode of delivery.

DESIGN

A prospective observational study.

SETTING

The delivery suite of St Mary's Hospital, London.

SUBJECTS

101 women undergoing induction of labour. MEASURED VARIABLES: Biparietal diameter, head circumference, abdominal circumference, occipital position, amniotic fluid volume and umbilical artery Doppler velocimetry waveforms.

MAIN OUTCOME MEASURES

The outcome of labour was assessed in terms of the induction delivery interval, the mode of delivery and the incidence of abnormal cardiotocograms in labour.

RESULTS

Seven women were delivered by emergency caesarean section early in the first stage of labour because of a significant abnormality of the fetal heart trace and these pregnancies were characterized by small fetal abdominal circumference measurements. Marked oligohydramnios was also noted in five of these seven subjects. Small or average size babies who were surrounded by an adequate volume of amniotic fluid tended to be born spontaneously, whereas the majority of operative deliveries for failure to progress in labour were associated with fetal abdominal circumference measurements > or = 340 mm. The mean Bishop score of women before labour who delivered spontaneously was not significantly different from the scores of women who had a forceps delivery or caesarean section. Abnormal cord Doppler waveforms were observed in only one instance.

CONCLUSIONS

In women undergoing induction of labour, the measurement by ultrasonography of two variables (fetal abdominal circumference and amniotic fluid volume) may allow the prospective identification of pregnancies at increased risk of fetal distress or dystocia. If these findings can be replicated in early spontaneous labour than more rational utilization of resources may be possible in hospital based obstetric practice.