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H D Niall

Publications and source records attributed to H D Niall.

At least 19 recordsLinked to original sources
PubMed1990

Differential expression of inhibin alpha and beta A subunit genes in rat and mouse ovarian follicles during pregnancy.

Relative levels of rat ovarian alpha inhibin (alpha I) and beta A inhibin (beta AI) mRNAs were measured during pregnancy by dot-blot hybridization of ovarian poly(A+) RNA. Follicular patterns of alpha I and beta AI expression in contralateral ovaries from the same rats were also studied by hybridization histochemistry. Oligodeoxynucleotide probes specific for porcine alpha I and beta AI were synthesized, 32P end-labelled and used as hybridization probes on dot-blots of ovarian RNA and frozen sections of ovarian tissue from pregnant rats. During pregnancy, levels of alpha I and beta AI mRNAs remained fairly constant from day 7 after mating until parturition and then fell within 16 h post partum. In all ovaries observed, expression of inhibin genes was located in granulosa cells of healthy antral follicles. In general, the strongest signals for alpha I and beta AI mRNAs were obtained in large follicles, with weaker signals in smaller follicles. Follicular patterns of alpha I and beta AI expression during pregnancy were often dissimilar when alpha I and beta AI were compared over a range of follicles. Considerable alpha I mRNA was detectable in some follicles in which beta AI was reduced or undetectable, despite strong signals for both alpha I and beta AI in an adjacent follicle. Essentially, alpha I mRNA levels were relatively consistent between groups of follicles, whereas beta AI levels varied considerably. beta AI mRNA was never observed in a follicle in the absence of alpha I mRNA, indicating that activin production in any follicle occurs in the presence of alpha I mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Antenatal serum levels of relaxin in patients having preterm labour.

This study is the first report of antenatal levels of relaxin measured by homologous radioimmunoassay in peripheral serum from patients who subsequently had a preterm delivery. Serial blood samples were collected antenatally from a group of subjects known to be at increased risk of preterm labour because of a past history of shortened pregnancy. Serum relaxin was measured using an homologous radioimmunoassay based on a synthetic bioactive analogue of the native hormone. In women whose pregnancies ended preterm most measurements were within the range of values previously established in normal antenatal patients although some measurements early in pregnancy were above the normal range. These findings suggest that low serum levels of relaxin are not causatively related to the onset of labour before term.

Female↗
PubMed1987

Relaxin in human pregnancy serum measured with an homologous radioimmunoassay.

This study reports serum levels of relaxin in normal and special-interest pregnancies using an homologous radioimmunoassay for human relaxin. The mean levels in uncomplicated antenatal patients were lower than those reported in studies using heterologous assays, but the trend in serum levels was similar. Serum levels peaked at ten weeks' gestation and decreased progressively to term. Relaxin was detectable in all pregnant subjects assessed at the time of the first missed menses. The mean relaxin levels in patients having in vitro fertilization and embryo transfer who subsequently delivered a single infant were significantly higher than those in normal antenatal patients at an equivalent gestational age. Patients with twin pregnancies after in vitro fertilization and embryo transfer generally had higher levels than patients with single pregnancies. Some pregnant patients who aborted after in vitro fertilization and embryo transfer had declining levels of relaxin before 40 days postlaparoscopy.

Embryo Transfer↗
PubMed1986

Radioimmunoassay of relaxin in pregnancy with an analogue of human relaxin.

A radioimmunoassay for relaxin was developed in which a synthetic analogue of human relaxin was used as standard, tracer, and immunogen. Relaxin could not be measured in sera from men or non-pregnant women, but was measurable in pregnant women from the tenth week of gestation until term. Concentrations ranged from 0.19-1.18 ng/ml, with highest levels measured in the first trimester.

Animals↗
PubMed1986

Structure of two human ovarian inhibins.

The complete amino acid sequences of two forms of human ovarian inhibin have been determined through cloning and nucleotide sequencing of cDNAs encoding their individual subunit precursors. The alpha subunit common to both forms of human inhibin is homologous (84 percent conserved) to its equivalent porcine alpha subunit; the subunits which are different in both inhibins (beta A and beta B) are identical to their porcine equivalents in all but one of 232 sequence positions.

Amino Acid Sequence↗
PubMed1986

Purification and characterization of ovine angiotensinogen.

The two major forms of ovine angiotensinogen (renin substrate) have been purified to homogeneity from plasma and a third form has been partially purified. The purification procedure involved ammonium sulphate fractionation, gel filtration, ion-exchange chromatography and chromatofocusing. The pure proteins have apparent relative molecular masses of 56 000 as determined by sodium dodecyl sulphate gel electrophoresis. The amino acid compositions of the two major forms appear to be the same; however, they do have different carbohydrate compositions. Antibodies raised against the a form showed complete cross-reactivity with the b and c forms. Both major forms have the same amino-terminal sequence, which includes that of ovine angiotensin I: Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu. Thus ovine angiotensin is the Ile5 form and not the Val5 form as had previously been suggested.

Amino Acid Sequence↗
PubMed1986

The nucleotide sequences of baboon chorionic gonadotropin beta-subunit genes have diverged from the human.

The placental glycopeptide hormone chorionic gonadotropin (CG) is involved in establishing and maintaining pregnancy. The hormone consists of two different non-covalently associated subunits termed alpha and beta. In man there are seven closely linked genes coding for beta CG-like peptides, but only three of these appear capable of expression in the placenta. The organization of beta CG-like genes in man and baboon appears to be similar. We demonstrate here that the baboon genome contains multiple copies (at least five) of beta CG-related genes, and that these genes are closely linked in the genome. Nucleotide sequence data from several beta CG cDNA clones indicates that at least two of these beta CG-related genes are expressed in the baboon placenta. Analysis of beta CG sequences from baboons and human subjects demonstrates that these genes have diverged markedly between species. In contrast, these sequences are remarkably homogeneous within their respective genomes. Gene conversion events may be responsible for retaining the high degree of identity among the various beta CG gene family members. Knowledge of beta CG sequences from baboon may lead to development of a long-term antipregnancy vaccine. The ability of CG antibodies to interfere with the maintenance of pregnancy can now be investigated within a homologous system.

Animals↗
PubMed1985

Hybridization histochemistry.

In this review we have used our own recent work as a flagship to illustrate the recent renaissance of interest in hybridization histochemistry. A trickle of papers followed the initial key excursion into the in situ labeling of tissue sections (48-50). Our own entry into this field started in 1978 and since then a confluence of important questions and technical advances has served to make hybridization histochemistry much more attractive as a research tool. Hybridization histochemistry is able to solve some problems for which there is no other suitable technique at this time. Hybridization histochemistry provides the location of anatomical sites of gene expression, and viral replication, with uniquely high specificity. We have taken 32P-labeled probes to what appears to be their limit of resolution, which is single cells in thin sections. While 32P has clear disadvantages, exposure time is relatively short and the use of fast-X-ray film to preview the results and estimate exposure time for emulsion has been turned to advantage. Our introduction (27) of the use of whole-mouse sections in hybridization histochemistry has great potential in hormonal, enzymatic, and growth factor gene expression and will no doubt prove of great use in developmental studies and examination of viral infection. The use of synthetic DNA (synthetic oligonucleotides) unshackles the technique from the need for an associated molecular biology laboratory and at once widens the horizon of application of the technique. Although hybridization histochemistry is a valuable research tool which will soon find a niche in many fields, in a short time it should become a key diagnostic aid. It may well become the method of preference for detection of the expression of oncogenes and other cancer-related genes and for viruses which for other reasons are difficult to detect.

Animals↗
PubMed1985

The isolation and characterization of lysozyme from human foetal membranes: a comparison with the enzyme from other sources.

Lysozyme (muramidase) was isolated from an acidic extract of human foetal membranes by adsorption and elution from octadecyl silica. It was further purified by gel-filtration and ion-exchange. The final product was homogeneous by high performance liquid chromatography (h.p.l.c.) and electrophoresis. It was indistinguishable from human milk lysozyme by all criteria investigated, including amino acid composition, electrophoretic mobility, retention time on h.p.l.c. and sequence of the first nine residues. Human uterine decidual tissue was shown to contain a similar concentration of lysozyme to foetal membranes. The enzyme was also present at lower concentrations in amnion, placenta and amniotic fluid.

Amino Acids↗
PubMed1985

Variability in the apparent molecular weight of inhibin.

An in vitro bioassay based on suppression of GnRH-stimulated FSH secretion by pituitary cells in culture was used to monitor inhibin activity after dialysis, gel filtration or polyacrylamide gel electrophoresis of protein preparations from a variety of gonadal secretions and extracts under native and dissociating conditions. The suggestion that inhibin is a peptide of molecular weight less than 5000 was not confirmed. Although some fractions of low molecular weight suppressed FSH secretion, the amount of activity was low and the dose response curves were not parallel with a standard preparation of inhibin. Under most conditions, inhibin eluted with an apparent molecular weight of about 90 000. However, gel filtration of rete testis fluid protein in 1 M acetic acid resulted in elution of inhibin activity with a lower apparent molecular weight and with polyacrylamide gel electrophoresis in 0.1% (w/v) sodium dodecylsulfate, the apparent molecular weight was 30 000. It is concluded that inhibin is a protein which tends to aggregate and coelute with larger molecules.

Animals↗
PubMed1985

Renin gene expression in vessels of the ovine renal cortex.

Using hybridization histochemistry, a technique which localizes specific mRNA populations in tissue sections with a 700 base pair recombinant DNA probe which codes for ovine renin, we have localized renin gene expression in the afferent arteriole of the juxtaglomerular apparatus (JGA) in the sheep renal cortex. Specific labelling representing renin gene expression was also found at a distance from the glomerular tuft in the walls of the afferent arteriole and also in cells in the medial layer of larger vessels of the renal cortex, specifically the interlobular arteries. These observations provide morphological evidence of renin gene expression at these sites and, combined with ultrastructural and immunocytochemical evidence suggest that renin is synthesized and stored in the afferent arteriole either within the JGA or at a distance from the glomerulus, and in the smooth muscle coat of the interlobular arteries in the sheep kidney.

Animals↗
PubMed1984

Two human relaxin genes are on chromosome 9.

We have recently cloned two different human relaxin gene sequences. One of these (H1) was isolated from a human genomic clone bank and the other (H2) from a cDNA library prepared from human pregnant ovarian tissue. Southern gel analysis of the relaxin genes within the genomes of several unrelated individuals showed that all genomes contained both relaxin genes. Hence it is unlikely (p less than 0.001) that the two relaxin gene sequences are alleles. Rather, it is probable that there are two relaxin genes within the human genome. It is likely that relaxin and insulin genes have evolved from a common ancestral gene by gene duplication, since structural similarities between insulin and relaxin are evident at both the peptide and gene level. To investigate the evolutionary relationship between the two human relaxin genes and the insulin gene, we have determined the chromosomal position of the relaxin genes using mouse/human cell hybrids. We found that the human insulin and relaxin genes are on different chromosomes. Both human relaxin genes are located on the short arm region of chromosome 9.

Alleles↗
PubMed1984

Relaxin.

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Animals↗
PubMed1984

Gene expression in the brain and the control of blood pressure.

Identification of genes involved in initiation or maintenance of hypertension is complicated by the possibility that blood pressure may not be directly regulated. However, a promising avenue of investigation would be to look for biochemical abnormalities associated with hypertension in a genetically defined strain of rats, and to analyze the structural and functional features of the genes which subserve the relevant biochemical pathways. Recent major advances in recombinant DNA and gene transfer technology should facilitate such studies. Within 10 years the important genetic markers of hypertension in man should be defined at a molecular level.

Animals↗
PubMed1984

Hybridization histochemistry: use of recombinant DNA for tissue localizations of specific mRNA populations.

A procedure of in situ hybridization, termed hybridization histochemistry has been developed to locate in specially prepared whole sections of tissue those areas which contain specific mRNA populations, the presence of which would indicate that a certain gene is "switched on" and production of a specific protein or peptide is highly probable. In the main 32P-labelled recombinant DNA probes were used. These probes were complementary to several peptide hormones or enzymes. 32P-labelled DNA probes were favoured initially because the short time needed for exposure enabled the development of the procedure to proceed quickly. The results indicate that the mRNA's of the species being examined are present in whole sections of tissue in a physical state which leaves them accessible to cDNA probes. The results are highly reproducible and specific. Because the method allows a clear distinction to be made between those cells which manufacture a peptide or protein and those which have imported the material it will have a special use in resolving many controversies over specific sites of origin of peptides and proteins, especially in tissues e.g. CNS and gut which are functionally complex and morphologically heterogeneous.

Animals↗