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W J Meijer

Publications and source records attributed to W J Meijer.

30 records · Page 2Linked to original sources
PubMed1995

Effects of the generation of single-stranded DNA on the maintenance of plasmid pMV158 and derivatives in different Bacillus subtilis strains.

The effects of the single-strand origins (SSOs) of plasmid pMV158 on (i) the conversion of its single-stranded (ss) replication intermediates to double-stranded (ds) plasmid DNA and (ii) its maintenance were analyzed. The rolling-circle plasmid pMV158, which replicates via ssDNA intermediates, contains two single-strand origins (SSOs) of replication, palA and palU. In this paper the results obtained with Bacillus subtilis are described; complementary studies with Lactococcus lactis are presented in the accompanying paper (Meijer et al., 1995). While in L. lactis both SSOs are functional as ssDNA conversion signal, only palU appeared to be active B. subtilis. Similar to the situation in L. lactis, the accumulation of large amounts of ssDNA resulted in a severe decrease in plasmid maintenance in B. subtilis. In the latter bacterium large amounts of ssDNA were only accumulated, however, when plasmids lacking a functional SSO were propagated in RecA mutant strains. In wild-type RecA strains these plasmids accumulated only modest amounts of ssDNA and they were maintained at fairly stable levels. The results suggest that in B. subtilis a RecA-mediated alternative pathway exists for the conversion of ssDNA which can improve plasmid maintenance. In addition to ssDNA accumulation and the antagonizing role of RecA therein, two other plasmid regions were shown to affect pMV158 maintenance in B. subtilis. One was the mob gene region, which had a negative effect on plasmid maintenance, and the other the palA type SSO. Although palA was not functional as an ssDNA conversion signal in B. subtilis, its presence had a positive effect on pMV158 maintenance.

Bacillus subtilis↗
PubMed1995

Effects of the generation of single-stranded DNA on the maintenance of plasmid pMV158 and derivatives in Lactococcus lactis.

The effects of the single-strand origins (SSOs) of the broad-host-range streptococcal plasmid pMV158 on (i) the conversion of its single-stranded (ss) DNA replication intermediates to double-stranded (ds) plasmid DNA and (ii) its maintenance were analyzed. pMV158 is distinguished from most other plasmids that replicate by the rolling-circle mechanism by the presence of two single-strand origins of replication, palA and palU. In this paper the results obtained with Lactococcus lactis are presented; complementary studies with Bacillus subtilis are presented in the accompanying paper (Meijer et al., 1995). In the presence of both SSOs, no ss plasmid DNA was observed in L. lactis. The removal of either palA or palU resulted in the appearance of low amounts of ssDNA. High amounts of ssDNA were detected, however, when both SSOs were deleted. The results indicated that both SSOs were active, albeit that palU was the most effective of the two. In the presence of both SSOs, the plasmid was stably maintained in L. lactis under nonselective growth conditions. Also, the derivatives containing only one of the two SSOs were maintained rather stably. In contrast, the derivative devoid of both SSOs was poorly maintained. It was concluded that, in the absence of a functional SSO, the generation of large amounts of ssDNA drastically reduces the maintenance of pMV158 in L. lactis. The results also showed that the presence of the plasmid-located mob gene, required for conjugative mobilization, was involved neither in the accumulation of ssDNA nor in the maintenance of pMV158.

Bacterial Proteins↗
PubMed1995

The endogenous Bacillus subtilis (natto) plasmids pTA1015 and pTA1040 contain signal peptidase-encoding genes: identification of a new structural module on cryptic plasmids.

Various strains of Bacillus subtilis (natto) contain small cryptic plasmids that replicate via the rolling-circle mechanism. Like plasmids from other Gram-positive bacteria, these plasmids are composed of several distinct structural modules. A new structural module was identified on the B. subtilis plasmids pTA1015 and pTA1040. It is composed of two genes: one specifies an unidentified protein with a putative signal peptide; and the other (sipP) specifies a functional type 1 signal peptidase (SPase). The homologous, but non-identical, sipP genes of the two plasmids are the first identified plasmid-specific SPase-encoding genes. With respect to structure and activity, the corresponding enzymes (denoted SipP) are highly similar to the chromosomally encoded SPase, SipP, of B. subtillis and several newly identified SPases of other bacilli. Our findings suggest that plasmid-encoded SPases have evolved because, of under certain conditions, SPase can be a limiting factor for protein secretion in B. subtilis.

Amino Acid Sequence↗
PubMed1992

Prophylactic oophorectomy.

The risks and benefits of prophylactic bilateral oophorectomy (BO) accompanying hysterectomy are reviewed. The potential reduction in the risk of subsequent ovarian cancer is quantified using literature data and a mathematical model. The risks of subsequent breast cancer from low-dose ERT are estimated using a comprehensive mathematical model. It is hypothesized that BO may have a substantial protective effect on breast cancer risk despite subsequent low-dose or non-low-dose ERT, when BO is performed at an early age. In women with a family history of ovarian cancer or breast cancer, the individual risks must be assessed on the basis of a pedigree analysis. In conclusion, a decision on BO must be based on weighing the potential benefits of reduced ovarian and breast cancer risks against the psychological importance of retaining the ovaries and the risk of osteoporosis and cardiovascular disease when compliance with ERT is less than perfect. The provided quantitative data may help in making the right decision.

Adult↗
PubMed1992

Transient hypothyroxinaemia associated with developmental delay in very preterm infants.

In 563 surviving very preterm (less than 32 weeks gestational age) and/or very low birthweight (less than 1500 g) infants the relationship between neonatal thyroxine concentration and psychomotor development at 2 years of age (corrected for preterm birth) was studied. A significant association was found between low neonatal thyroxine concentration and a negative score on the three milestones of development. These findings do not support the view that transient hypothyroxinaemia in preterm infants is harmless.

Child, Preschool↗
PubMed1991

Trends in the incidence of non-melanoma skin cancer in the SE Netherlands 1975-1988: a registry-based study.

The trends in the incidence and the sites of primary basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) of the skin were examined in a defined population of 650,000 persons in the SE Netherlands during the period 1975-88. The data was obtained from the Cancer Registry in Eindhoven and was from the dermatological and surgical clinics of 12 community hospitals. The incidence rates for BCC during this period rose from 42 to 53/100,000 person years for males and 24 to 38/100,000 person years for females. The rate of incidence for SCC varied with an increase mainly among males. In about 80% of the cases BCC and SCC occurred on the head and neck. Allowing for some detection bias a rise in the true incidence of BCC and SCC was observed, with an increase in SCC only since 1982. There was a marked decline in the incidence of SCC on the lips of males. These rates and trends fit into a pattern observed in other parts of Europe.

Adolescent↗
PubMed1985

[Screening for congenital hypothyroidism].

In the Netherlands nation-wide screening for CH began in January 1981. The aim of the combined T4-TSH screening method is to detect all forms of CH, primary as well as secondary and tertiary. More than 99% of the newborns are screened. The rate of false-positives in premature infants was reduced in June 1982 by a change of the indications for follow-up. Further study is performed on T4 values of premature infants. The information, given to the parents in case of recall, is not optimal yet. Although there is still delay in screening and follow-up, the initiation of treatment is considerably advanced. The effect of earlier treatment on development will be assessed by Prof. Dr. A. F. Kalverboer. Very likely, the early treatment will lead to a considerable reduction of damage to the central nervous system.

Child Development↗
PubMed1975

Midwifery in Holland.

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Maternal Health Services↗