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Biomedical subjects

J Grinsted

Publications and source records attributed to J Grinsted.

At least 37 records · Page 2Linked to original sources
PubMed1988

Gas-chromatographic measurement of carboxyhemoglobin in blood from mothers and newborns.

HbCO in blood sampled from 20 mothers and newborns immediately after birth was measured with a new, simple gas-chromatographic method for CO. The mean ratio of HbCO to total hemoglobin for 13 non-smoking mothers did not differ significantly from that for their infants (mean 0.38%, SD 0.26% vs 0.38%, SD 0.13%), but the HbCO ratio varied more in the mothers than in the infants (P less than 0.05). The infants of seven cigarette-smoking mothers, tobacco-abstinent for 7 h during labor, had higher HbCO ratios than their mothers (mean 1.88% vs 1.28%, P less than 0.05). The results are in harmony with the concept of equal affinities of fetal and adult hemoglobin for CO and a long time for passage of CO across the placenta.

Carboxyhemoglobin↗
PubMed1987

The nucleotide sequence of the tnpA gene of Tn21.

The nucleotide sequence of the tnpA gene of Tn21 is presented. The transposase encoded by this gene is exactly the same length (988 amino acids) as the Tn501 transposase (4), and shows 72% homology overall with this protein, with greater homology towards the C-terminus. The sequence of the transposase is discussed in the context of the evolution of Class II transposable elements and of the characteristics of the enzyme's action.

Amino Acid Sequence↗
PubMed1987

Tn2501, a component of the lactose transposon Tn951, is an example of a new category of class II transposable elements.

Tn2501 is a cryptic class II transposon found as part of the lactose transposon Tn951. Insertional inactivation and nucleotide sequence analysis of Tn2501 allowed us (i) to localize the transposase (tnpA) and the resolvase (tnpR) genes as well as the resolution site (res) of Tn2501 and (ii) to compare Tn2501 with other well-known elements of the two subgroups of class II transposons (Tn3, gamma delta, Tn951, IS101; and Tn21, Tn501, Tn1721). The genetic organization of Tn2501 is similar to that of Tn3 with divergent transcription of the tnpA and tnpR genes away from the intervening res site. The tnpR gene of Tn2501 shows weak homology with that of Tn3 and even less with those of Tn21 and Tn501. However, the tnpA gene and the inverted repeat sequences of Tn2501 present more homology with those of Tn21 and Tn501 than with those of Tn3. Complementation studies showed that TnpA- mutants of Tn2501 can be complemented, at a low frequency, by the Tn21 transposase. None of the tested transposons complemented TnpR- mutants of Tn2501.

Amino Acid Sequence↗
PubMed1987

Effects of induced abortion on the third stage of labor in subsequent pregnancy.

The aim of the study was to investigate whether the expulsion of the placenta was delayed among women who had previously undergone induced abortion by suction curettage. We studied the duration of the third stage of labor retrospectively by comparing the third stage of labor, recorded in minutes, between 76 second gravida women with previously induced abortions and 95 second para women with previously uncomplicated pregnancies. The duration of the third stage of labor was also compared among a group of primigravidas and a group of second gravidas with previously induced abortions. We excluded women with previous gynecological disorders (e.g. resulting in curettage of the uterine cavity). All patients included presented normal pregnancies and deliveries resulting in full term (greater than 37 weeks), liveborn infants. By the statistical analysis (analysis of variance and Duncan's test), it could be shown that the 3rd stage of labor lasted significantly longer among women with previously induced abortions (mean: 12 minutes), than among the other groups included in the study (mean: 9 minutes). This discrete difference in length of the third stage of labor need not indicate an altered routine for women, who give birth subsequent to an induced abortion.

Abortion, Induced↗
PubMed1986

Ultrastructure of germ cells and adjacent somatic cells correlated to initiation of meiosis in the fetal pig.

The ultrastructure of female and male germ cells and associated somatic cells were studied in morphologically sex differentiated fetal pig gonads from day 27 to day 95 post insemination. Before meiosis starts in the ovary, the organelles of germ cells and somatic cells of both sexes are poorly developed. In oocytes in leptotene stage, the endoplasmic reticulum attains close proximity to the plasma membrane forming characteristic contact areas which in addition are only seen in male germ cells of the same age. As meiosis progresses, the organelles of the oocyte increase in number and degree of differentiation. In particular the ER is prominent in the diplotene stage. At midgestation the male germ cells become polarized, the organelles gathering at one side of the nucleus. In the granulosa cells the number and extension of organelles increase concomitantly with the oocytes proceeding through meiosis. The Sertoli cells grow progressively complex in shape, with numerous mitochondria and a prominent ER, whereas the Golgi complex remains poorly developed. Small dense bodies are present both in germ cells and somatic cells. They are electron dense, membrane bounded, rounded or elongated granules often connected with endoplasmic reticulum. No activity of peroxidase, catalase or acid phosphatase could be traced in the granules, making them improbable candidates as peroxisomes or lysosomes. Their number is high in all germ cells and somatic cells on day 27 post insemination and in germ cells in leptotene stage.

Animals↗
PubMed1986

Evolution of transposable elements.

Transposable elements are at an advantage compared with other DNA sequences. This has led to the generation of transposable systems from a variety of different sources. Once fabricated, these elements can very simply acquire accessory genes, such as those that encode resistance to antibiotics. This can lead to further evolutionary advantages and to their shorter-term importance. It is likely that many new transposable systems will be discovered, owing to the advantages conferred on sequences by transposition, and it is certain that many new transposons that encode varying drug resistance patterns will arise.

Biological Evolution↗
PubMed1985

Junction sequences generated by 'one-ended transposition'.

In the presence of the cognate transposase, plasmids containing a single inverted repeat (IR) sequence of Tn21 or of Tn1721 can fuse efficiently with other plasmids ('one-ended transposition'). The junctions across the sequences of donor and recipient DNA in recombinants generated by this process have been determined. These show that the segment of donor DNA starts precisely at the IR sequence (it is variable at the other end), and is flanked by a direct repeat of host DNA (usually 5bp) that was present only once in the original host sequence. These are characteristics of recombinants generated by transposition of Tn21 and Tn1721 themselves, suggesting that the mechanism of one-ended transposition is very similar to that of the corresponding entire elements.

Base Sequence↗
PubMed1985

Is low temperature of the follicular fluid prior to ovulation necessary for normal oocyte development?

Because low temperature in the testis is essential to normal spermatogenesis, we speculated whether a low follicular temperature could also be of importance for the oocytes as they resume meiosis at ovulation. We measured the temperature of the follicular fluid and of the ovarian stroma in 26 follicles in 14 women. In 25 follicles (13 women) the follicular fluid was colder than the ovarian stroma. This temperature difference increases toward ovulation (maximum, 2.3 degrees C). In one case, the measurements of the follicular/stromal temperature difference showed an inverse pattern, the follicular fluid being 0.2 degree C warmer than the stroma. This woman was infertile, and oocyte evaluation for in vitro fertilization had five times shown the oocytes unable to divide in culture. The present study supports the idea that low temperature of the follicular fluid prior to ovulation may be essential for normal oocyte development.

Adult↗
PubMed1984

Mesonephric excretory function related to its influence on differentiation of fetal gonads.

The mammalian intermediate fetal kidney, the mesonephros, is known in different species to excrete body waste products during a limited period of fetal life. Recently, the mesonephros and its derivatives have been shown to influence gonadal functions in several ways. Thus, the mesonephric cells are responsible for regulating the onset of meiosis in different mammals by the secretion of two substances, a meiosis-inducing substance (MIS) and a meiosis-preventing substance (MPS). In this paper, the relation between mesonephric kidney function and its influence on the gonads is reviewed through literature studies. It seems that cessation of mesonephric excretion precedes onset of meiosis in the ovary in different species. It is suggested that the mesonephric renal function interferes with synthesis and/or secretion of MIS or that the excreted products may interfere with the responsiveness to MIS of the germ cells.

Animals↗
PubMed1984

A Tn21 terminal sequence within Tn501: complementation of tnpA gene function and transposon evolution.

The prokaryotic mercury-resistance transposon Tn501 contains a sequence, 80 nucleotides from one end, which is identical with an inverted terminal repeat (IR) of Tn21. This Tn21 IR sequence is used when Tn21 complements a TnpA- derivative of Tn501, but not when Tn501 is used for the complementation. Complementation by Tn1721 shows a preference for the normal Tn501 IRs. The element (Tn820) transposed when Tn21 is used to complement a Hg- TnpR- TnpA- Res- deletion mutant of Tn501 contains the Tn21 IR sequence at one terminus and a Tn501 IR at the other. Transposition of Tn820 can be complemented by Tn501 and Tn1721, but at a much lower frequency than transposition of the parental element (Tn819) which has two Tn501 IRs. The relationship between the transposition functions of Tn501, Tn21 and Tn1721, and available nucleotide sequence data suggest that Tn501 evolved by the transposition of a Tn21-like element into another transposable element (similar to that found within Tn1721) followed by deletion of the Tn21-like transposition functions.

Base Sequence↗
PubMed1984

Plasmids containing one inverted repeat of Tn21 can fuse with other plasmids in the presence of Tn21 transposase.

In the presence of the Tn21 transposase, plasmids that contain a single Tn21 inverted repeat sequence fuse efficiently with other plasmids. This reaction occurs in recA strains, is independent of the transposon-encoded resolution system, and results in insertions into different sites in the recipient plasmid. All fusion products studied contained at least one complete copy of the donor plasmid; most also contained some duplication of it as well. The data are consistent with processive models of transposition.

Base Sequence↗
PubMed1984

Is resumption of meiosis in the human preovulatory oocyte triggered by a meiosis-inducing substance (MIS) in the follicular fluid?

Aspirates from 31 ovarian follicles and 2 corpora lutea of 26 women at different stages of the menstrual cycle were investigated for activity of meiosis-inducing substance (MIS) and meiosis-preventing substance (MPS). The aspirated follicles were classified as dominant (i.e., preovulatory), healthy, or atretic according to their size, steroid hormone content, and stage of the menstrual cycle. To test for MIS and MPS activity, gonads of sexually undifferentiated fetal mice were cultured in media containing either 15% follicular fluid aspirate (test gonads) or 15% human blood serum (control gonads). MIS activity is present in follicular fluid if the test testes contain more meiotic germ cells than the control testes. MPS activity is present if the test ovaries have less meiotic germ cells than their controls. MIS activity was present only in healthy follicles of the late follicular phase (12 of 15 follicles). No MIS activity was seen in healthy or atretic follicles from other phases of the menstrual cycle. The MIS activity is apparently unrelated to the composition of steroids in the follicular fluid. MPS activity was not found in any of the follicles. It is proposed that the preovulatory resumption of meiosis may be triggered by a MIS in the follicular fluid.

Adolescent↗
PubMed1984

Advanced grandmaternal age on the mother's side--a risk of giving rise to trisomy 21.

The age distribution of maternal grandmothers of children with Down syndrome was compared with paternal grandparents of the same group and with grandparents of healthy children (controls). The significant advanced maternal grandmaternal age was found in cases of Down syndrome caused by first meiotic error in the maternal oogenesis. The advanced maternal grandmaternal age was found independent of maternal age. No differences were found between the ages of grandfathers of Down syndrome and of controls.

Adult↗
PubMed1983

The tetracycline resistance determinants of RP1 and Tn1721: nucleotide sequence analysis.

Nucleotide sequences of the homologous tetracycline resistance (tet) determinants of plasmid RP1 and transposon Tn1721 have been determined. Two open reading frames of divergent polarity have been assigned to a regulatory gene (tetR) and a gene encoding a resistance protein (tetA). The intercistronic region contains appropriate regulatory and transcription signals. The tetR gene can code for a protein of 216 amino acids (deduced mol.wt. 23,288) and the tetA gene for a protein of 399 amino acids (deduced mol. wt. 42,205). Based on the deduced amino acid sequence, the tetA proteins of RP1/Tn1721 are 78% homologous with that of pBR322 and 45% homologous with that of Tn10. We conclude that a single tetA gene mediates resistance in each of these tet determinants.

Bacterial Proteins↗
PubMed1983

DNA sequences of and complementation by the tnpR genes of Tn21, Tn501 and Tn1721.

DNA sequences that encode the tnpR genes and internal resolution (res) sites of transposons Tn21 and Tn501, and the res site and the start of the tnpR gene of Tn1721 have been determined. There is considerable homology between all three sequences. The homology between Tn21 and Tn501 extends further than that between Tn1721 and Tn501 (or Tn21), but in the homologous regions, Tn1721 is 93% homologous with Tn501, while Tn21 is only 72-73% homologous. The tnpR genes of Tn21 and Tn501 encode proteins of 186 amino acids which show homology with the tnpR gene product of Tn3 and with other enzymes that carry out site-specific recombination. However, in all three transposons, and in contrast to Tn3, the tnpR gene is transcribed towards tnpA gene, and the res site is upstream of both. The res site of Tn3 shows no obvious homology with the res regions of these three transposons. Just upstream of the tnpR gene and within the region that displays common homology between the three elements, there is a 50 bp deletion in Tn21, compared to the other two elements. A TnpR- derivative of Tn21 was complemented by Tn21, Tn501 and Tn1721, but not by Tn3.

Base Sequence↗
PubMed1983

Abnormal growth of ovarian antral follicles in breast cancer patients.

Ovarian antral follicles from patients with breast cancer were compared with follicles from healthy women. Steroid levels in the follicular fluid and the health status of the follicles were evaluated. Follicles were judged to be healthy or atretic by flow cytometric determinations of the deoxyribonucleic acid content of aspirated granulosa cell nuclei. Fifteen of the 25 follicles (60%) from the cancer patients contained unmeasurable or abnormally low steriod levels (i.e., less than 100 ng/ml) which were significantly (P less than 0.001) lower than in follicles of the same health status from healthy women (500 to 1000 ng/ml). It is speculated whether substances other than the usual follicular steriods are produced by the cancer patients, which stimulate mitotic activity of the granulosa cells.

Adult↗