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Biomedical subjects

L Robertson

Publications and source records attributed to L Robertson.

At least 55 records · Page 3Linked to original sources
PubMed1998

Evaluation of semen from individual male domestic fowl by assessment of sperm: perivitelline interaction in vitro and in vivo.

1. Spermatozoa in semen samples from 8 individual male domestic fowls were shown to have a differential and characteristic ability to hydrolyse holes in the inner perivitelline layer from laid eggs in an in vitro assay. 2. The number of holes produced by samples of spermatozoa per unit area of inner perivitelline layer in vitro was linearly correlated with sperm ATP content (r = 0.85) and motility (r = 0.76). 3. The number of holes formed in the inner perivitelline layer in vitro was also linearly correlated with the numbers of holes formed in the inner perivitelline layer of eggs fertilised in vivo, in inseminated hens (r = 0.90); and was correlated logarithmically with the proportion of fertile eggs laid by these hens.

Animals↗
PubMed1998

Oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells transformed with c-myc and H-ras form high-grade glioma after stereotactic injection into the rat brain.

The oligodendrocyte-type-2 astrocyte lineage (O-2A) comprises a progenitor cell that is able to differentiate into an oligodendrocyte or astrocyte in vitro. The lineage was originally identified in the neonatal rat central nervous system but evidence suggests that the equivalent O-2A lineage also exists in humans. Apart from its putative and widely studied role in glial repair, this cell type could potentially be involved in malignant glioma formation. In this study we demonstrate that a rat O-2A progenitor cell line carrying the bacterial beta-galactosidase reporter gene and transformed with the c-myc and H-ras oncogenes which has lost its differentiation capacity in vitro generates glioma-like growth after stereotactic injection into the adult rat brain. Tumour pathology was similar to human glioblastoma, suggesting that one of the pathways in the generation of human glioblastomas may be the transformation of adult O-2A progenitor cells. Parallel studies demonstrated the presence of a DNA-binding protein complex, termed APprog, in a panel of human glioma cell lines. This protein was initially identified in O-2A progenitor cells and not their differentiated progeny. These data lead us to propose that APprog could be used as an indicator of the lineage origin of gliomas.

Animals↗
PubMed1997

Use of the polymerase chain reaction to sex the bovine fetus using cells recovered by ultrasound-guided fetal fluid aspiration.

The aim of this study was to carry out first trimester fetal sex diagnosis using the polymerase chain reaction (PCR) to amplify DNA from bovine fetal cells recovered by transvaginal ultrasound-guided uterine puncture and fetal fluid aspiration. For sex determination, a nested, allele-specific, PCR amplification of the bovine zfx and zfy gene fragments was utilised. The PCR assay was validated using fetal fluids recovered from uteri post mortem. Cells were harvested from the fetal fluids, genomic DNA extracted and the PCR assay applied. A technique which was developed for transvaginal ultrasound-guided follicle aspiration was modified to recover fetal fluid from live animals. Small volumes of fetal fluid (0.5-5 ml) were recovered between days 61-97 of gestation and the PCR assay applied. The gender determined by PCR of fetal fluid cells was in all cases confirmed by visual inspection (n = 15 abattoir specimens) or ultrasound scanning (n = 7 live animals). Fetal death, attributed to the introduction of intrauterine infection, occurred in 4/4 cows in the first series of aspirations but in only 1/3 heifers in the second series of aspirations.

Abattoirs↗
PubMed1997

Sequence of the bovine HDL-receptor (SR-BI) cDNA and changes in receptor mRNA expression during granulosa cell luteinization in vivo and in vitro.

Steroidogenic activity in the mature corpus luteum of most mammals depends upon provision of cholesterol from the circulating lipoproteins. In cattle, as in many species, high-density lipoprotein (HDL) is the major lipoprotein involved. The recent identification of the scavenger receptor SR-BI as an HDL-receptor allows control of this process to be investigated more closely. In this study, we have sequenced the bovine SR-BI HDL-receptor and examined changes in expression of the receptor mRNA during corpus luteum development in vivo and granulosa cell luteinization in vitro. Sequencing of the bovine HDL-receptor showed that it codes for a protein of 509 amino acids with close identity to hamster, mouse, rat and human sequences. Examination of the tissue distribution of the HDL-receptor mRNA showed high levels in adrenal cortex and corpus luteum and lower levels in spleen and liver. Using a semi-quantitative, reverse transcription-polymerase chain reaction technique levels of HDL-receptor mRNA were measured in corpora lutea from cattle at known stages of the oestrus cycle and in bovine granulosa cells luteinized in culture. Levels of HDL-receptor mRNA were low in isolated bovine granulosa cells, but increased 7-fold during corpus luteum development in vivo and 5-fold during granulosa cell luteinization in culture. Results show that luteinization of granulosa cells is associated with an increase in HDL-receptor RNA levels which, along with changes in steroidogenic enzyme activity, is likely to explain the marked increase in steroidogenic capacity which occurs during corpus luteum formation.

Amino Acid Sequence↗
PubMed1997

Isolation and characterization of secretions from the plant-parasitic nematode Globodera pallida.

Electrophoresis of secretions collected from Globodera pallida revealed a smeared region between 25 and 50 kDa, and a single band of < 20 kDa. The secretions were used to raise an antiserum (LW1). Immunoblotting of parasite homogenates with LW1 differentiated G. pallida from its sibling species G. rostochiensis and revealed differences between different populations of G. pallida and G. rostochiensis. Indirect immunofluorescence studies with LW1 indicated that at least some of the secretions were surface localized and that antibody binding to the nematode surface was periodate sensitive. Periodate sensitivity indicated that these differences could be due to glycosylation differences. Glycosylation differences were also detected by blotting nematode homogenates with the lectin wheat germ agglutinin (WGA), WGA was also able to differentiate between G. rostochiensis which gave 2 bands at 130 kDa and 110 kDa, and G. pallida which produced 2 bands present at 120 kDa and 110 kDa. Further localization studies using immunoelectron microscopy demonstrated that antibody binding could be seen to secretions found in the pump chamber of the metacorpal bulb at the base of the stylet. From further specimens it could be observed that the contents of the subventral glands were heavily labelled, indicating that the material seen in the metacorpal bulb had originated from the subventral glands.

Animals↗
PubMed1997

Regulatory sequences of Arabidopsis drive reporter gene expression in nematode feeding structures.

In the quest for plant regulatory sequences capable of driving nematode-triggered effector gene expression in feeding structures, we show that promoter tagging is a valuable tool. A large collection of transgenic Arabidopsis plants was generated. They were transformed with a beta-glucuronidase gene functioning as a promoter tag. Three T-DNA constructs, pGV1047, p delta gusBin19, and pMOG553, were used. Early responses to nematode invasion were of primary interest. Six lines exhibiting beta-glucuronidase activity in syncytia induced by the beet cyst nematode were studied. Reporter gene activation was also identified in galls induced by root knot and ectoparasitic nematodes. Time-course studies revealed that all six tags were differentially activated during the development of the feeding structure. T-DNA-flanking regions responsible for the observed responses after nematode infection were isolated and characterized for promoter activity.

Animals↗
PubMed1997

Characterization and application of an avian in vitro spermatozoa-egg interaction assay using the inner perivitelline layer from laid chicken eggs.

The inner perivitelline layer, separated from laid chicken eggs, was investigated as readily available material for studying the spermatozoa-egg interaction in vitro. This layer was found to have a similar response to hydrolysis by spermatozoa as the inner perivitelline layer from ovulated and follicular ova, in terms of the numbers of points of hydrolysis made by spermatozoa during a 5 min incubation at 40 degrees C. Initiation of hydrolysis of the inner perivitelline layer was found to occur within 2.5 min, after which the size, but not the number of holes, increased with time. The frequency of the points of hydrolysis per unit area of the inner perivitelline layer was positively correlated with the concentration of spermatozoa in the incubation medium. The perivitelline hydrolysis assay was able to detect more damaged spermatozoa in samples that had been either stored at 5 degrees C or cryopreserved in liquid N2 than did other tests of sperm quality, which are known to overestimate the fertilizing ability of stored avian semen.

Animals↗
PubMed1996

Expression of the calcium-binding protein S100A4 (p9Ka) in MMTV-neu transgenic mice induces metastasis of mammary tumours.

Increased levels of S100A4 (p9Ka) confer metastatic ability on a normally non-metastatic epithelial cell line. To find out whether S100A4 can induce metastasis in vivo, transgenic mice expressing high levels of S100A4, but which show no phenotypic effect, have been mated with MMTV-neu transgenic mice which succumb to stochastic mammary neoplasia related to expression of the MMTV-neu transgene. Resultant bitransgenic, multiparous, female progeny expressing both S100A4 and Neu have a slightly earlier incidence of palpable mammary tumours than the MMTV-neu offspring and specifically exhibit macroscopic metastatic lesions in the lungs. The S100A4 transgene is expressed in primary and secondary lesions of bitransgenic offspring and its expression is particularly associated with regions of invasion of primary lesions and metastases.

Animals↗
PubMed1996

Expression of follicle-stimulating hormone-receptor mRNA alternate transcripts in bovine granulosa cells during luteinization in vivo and in vitro.

In cattle, as in many other species, formation of the corpus luteum is associated with loss of sensitivity to FSH. To determine whether this is associated with changes in FSH-receptor mRNA levels or alternate splicing of the primary transcript, reverse transcription and the polymerase chain reaction (RT-PCR) were used to examine transcripts during granulosa cell luteinization in vivo and in vitro. Using RT-PCR and Southern blotting, three alternate transcripts of the FSH-receptor were found consistently in bovine granulosa cells. The largest transcript encoded the full-length receptor while the other transcripts lacked either exon 9 or exons 4, 5 and 9. One day after luteinization in vivo, full-length FSH-receptor mRNA was detectable at low levels in the newly-formed corpus luteum. By day 3, however, no full-length transcripts were detectable in the corpus luteum. In contrast, when primers were used which amplify only the extracellular domain, FSH-receptor transcripts were detectable in all corpora lutea tested up to mid-cycle. In granulosa cells, luteinized in vitro, there was a similar loss of full-length FSH-receptor transcripts after day 1 but continued expression of transcripts encoding the extracellular domain. Results show that granulosa cell luteinization in cattle is associated with a change in splicing of the FSH-receptor primary transcript such that after luteinization only shortened transcripts coding for the extracellular domain are detectable. This process resembles, in reverse, changes in FSH-receptor transcript splicing during development of the gonads.

Alternative Splicing↗
PubMed1996

Temporal lobe metabolic differences in medication-free outpatients with schizophrenia via the PET-600.

Regional cerebral glucose metabolic rates (rCMRglc) were compared in 18 unmedicated outpatients with schizophrenia and 11 normal controls using high resolution positron emission tomography (PET) and the tracer [F-18]-2-fluoro-2D-deoxyglucose (FDG). From previous work we expected to see abnormal hippocampal rCMRglc in the patients, but no striatal abnormalities. Trial-by-trial Stroop cognitive task, which has been shown to activate the anterior cingulate, was performed within a day of the PET study. As our patients performed abnormally on the Stroop we tested for a correlation between the anterior cingulate rCMRglc and Stroop performance. We found no whole slice cortical average glucose metabolic abnormalities. As, predicted we found abnormally decreased left hippocampal rCMRglc in the patients. No striatal or cingulate rCMRglc abnormalities were noted in patients, but they demonstrated a highly positive correlation between anterior and cingulate rCMRglc and Stroop facilitation. Patients with higher Stroop interference had more prominent hippocampal metabolic decreases. These localized temporal lobe abnormalities could account for some of the patient's positive symptoms and are consistent with recent findings in the literature.

Adult↗
PubMed1996

A detailed study of the effect of videoframe rates of 25, 30 and 60 Hertz on human sperm movement characteristics.

A comparison was made of the movement characteristics of human spermatozoa analysed at three videoframe rates (25, 30 and 60 Hz) using two computerized motility analysers from Hamilton-Thorn Research (the HTM-2030 and the IVOS) operating at 25 and 30 Hz respectively. Analysis at 30 and 60 Hz was performed on the IVOS. The use of uncapacitated, capacitated and pentoxifylline-stimulated spermatozoa ensured a full range of movement characteristics was analysed. The velocity parameters curvilinear velocity and average path velocity were highly frame-rate dependent, and mean values increased with videoframe rate. An interaction of framing rate and time of data collection resulted in an increase in straight-line velocity with framing rate. Mean lateral head displacement and linearity were similar at 25 or 30 Hz but significantly depressed at 60 Hz. Beat-cross frequency increased by 74% when analysed at 60 rather than 30 Hz. The following criteria: curvilinear velocity > 100 microns/s, linearity < 65% and lateral head displacement > 7.5 microns, were used to define hyperactivated spermatozoa. Significantly more hyperactivated cells were identified at 30 Hz than 25 Hz (1-10%) but not at 60 Hz. A different population of cells is likely to have been identified as hyperactivated at 60 Hz due to alterations in component movement parameters from which the definition of hyperactivation was derived. In conclusion, direct comparisons should not be drawn between data analysed at 25 and 30 Hz. Analysis at 60 Hz introduced complex alterations which made simple comparisons with 30 Hz data invalid.

Electronic Data Processing↗
PubMed1996

Evaluation of CI-973, a platinum analogue, in refractory or relapsed acute leukemia.

The purpose of the study was to define the maximally tolerated dose (MTD), major toxicities, and possible antitumor activity of CI-973 a new platinum analogue, in patients with refractory or relapsed acute leukemia. CI-973 was given as a 5-day continuous infusion every 3 to 4 weeks to patients with refractory or relapsed acute leukemia, at doses ranging from 150 mg/m2 to 1350 mg/m2 per course. Thirty-six patients were treated including 18 patients with acute myelogenous leukemia (AML), four with acute lymphocytic leukemia (ALL) and 14 with chronic myelogenous leukemia in blastic phase (CML-BP). Severe gastrointestinal and renal side-effects were the dose-limiting toxicities occurring in four of five patients treated with CI-973 1200 to 1350 mg/m2 per course. At the MTD of 1000 mg/m2 per course, three of 13 patients treated (23%) had moderate to severe nausea and vomiting, three (23%) had moderate diarrhea and one had moderate mucositis. Among 21 patients treated at > or = 1000 mg/m2 (15 AML, 6 CML-BP) no objective complete or partial responses were observed. Twelve of 18 patients (66%) with evaluable marrows on day 14 showed significant suppression of marrow blasts percentage and marrow leukemic infiltrate percentage. Tests for measurement of DNA adduct formation in leukemic cells in vivo after CI-973 therapy, and in vitro following exposure of leukemic cells to CI-973 were developed. This study defined the MTD of CI-973 to be 1000 mg/m2 by continuous infusion over 5 days every 3 to 4 weeks in patients with refractory or relapsed acute leukemia. Gastrointestinal and renal side-effects were dose-limiting. No objective responses were noted in this heavily resistant population. Correlations between CI-973-induced DNA adduct formation and individual patient response to CI-973 will help to define its role in leukemia subsets.

Acute Disease↗