Search PubMed⌕ Search

Biomedical subjects

A J Robertson

Publications and source records attributed to A J Robertson.

At least 37 records · Page 2Linked to original sources
PubMed1996

Common features of analogous replacement histone H3 genes in animals and plants.

Phylogenetic analysis of histone H3 protein sequences demonstrates the independent origin of the replacement histone H3 genes in animals and in plants. Multiple introns in the replacement histone H3 genes of animals in a pattern distinct from that in plant replacement H3 genes supports this conclusion. It is suggested that replacement H3 genes arose at the same time that, independently, multicellular forms of animals and of plants evolved. Judged by the degree of invariant and functionally constrained amino acid positions, histones H3 and H4, which form together the tetramer kernel of the nucleosome, have co-evolved with equal rates of sequence divergence. Residues 31 and 87 in histone H3 are the only residues that consistently changed across each gene duplication event that created functional replacement histone H3 variant forms. Once changed, these residues have remained invariant across divergent speciation. This suggests that they are required to allow replacement histone H3 to participate in the assembly of nucleosomes in non-S-phase cells. The abundant occurrence of polypyrimidine sequences in the introns of all replacement H3 genes, and the replacement of an intron by a polypyrimidine motif upstream of the alfalfa replacement H3 gene, suggests a function. It is speculated that they may contribute to the characteristic cell-cycle-independent pattern of replacement histone H3 genes by binding nucleosome-excluding proteins.

Amino Acid Sequence↗
PubMed1996

Observer variability in histopathological reporting of non-small cell lung carcinoma on bronchial biopsy specimens.

AIMS: To evaluate the ability of histopathologists to sub-classify non-small cell lung carcinomas on bronchial biopsy material using the current World Health Organisation (WHO) classification. METHODS: Twelve histopathologists each reviewed 100 randomly selected bronchial biopsy specimens which had originally been reported as showing non-small cell lung carcinoma. For each case, two sections were circulated, one stained by haematoxylin and eosin and the other by a standard method for mucin (alcian blue/periodic acid Schiff). The participants were allowed to indicate their degree of confidence in their classification of each case. A standard proforma was completed and the results were analysed using kappa statistics. RESULTS: Where the participants were confident in their classification, they were actually quite good at sub-classifying the non-small cell carcinoma sections (kappa = 0.71, standard error = 0.058). Overall, however, the results were only fair (kappa = 0.39, standard error = 0.034). CONCLUSIONS: The majority of non-small cell lung carcinomas can be correctly categorised on adequate bronchial biopsy material. Where a confident diagnosis was made, both squamous carcinoma (kappa = 0.73) and adenocarcinoma (kappa = 0.83) were well recognised.

Adenocarcinoma↗
PubMed1996

Identification of three highly expressed replacement histone H3 genes of alfalfa.

One genomic and six cDNA clones for the replacement histone H3.2 protein of alfalfa (Medicago sativa) were isolated and sequenced. By gene organization they represent 3 distinct genes. PCR methods were used to confirm that only three intron-bearing histone H3.2 genes of this type exist per haploid genome. They co-exist with approximately 56 copies of the previously characterized replication-dependent, intronless histone H3.1 variant gene. Comparison of the relative expression of few constitutive H3.2 genes with the high S phase expression of the abundant cell cycle-dependent H3.1 genes by mRNA levels and protein synthesis measurements revealed that the replacement histone H3.2 genes are very highly expressed. Structural analysis of the genomic replacement H3.2 gene revealed a unique feature. A repeated polypyrimidine sequence motif in the 5' untranslated region of this gene replaces the ubiquitous intron present in all known replacement H3 genes. A hypothesis is presented that this motif and other, non-randomly distributed polypyrimidine sequences in the introns of replacement histone H3 genes of alfalfa and Arabidopsis, may affect nucleosome assembly. Chromatin repression of these replacement genes would be avoided, consistent with the high, constitutive expression of replacement H3 histone genes in plants.

Amino Acid Sequence↗
PubMed1995

Histone H3 transcript stability in alfalfa.

The stability of histone H3 transcripts in alfalfa for replication-dependent and -independent gene variants was measured by northern analysis under conditions of inhibition of transcription and/or translation. Replication-dependent histone H3.1 transcripts were about three-fold less stable than the equally polyadenylated mRNA for replacement variant H3.2 histone. In actively growing suspension cultures treated with dactinomycin half-lives of 2 and 7 h were observed for H3.1 and H3.2 mRNAs, respectively. mRNA stabilities were also measured indirectly by histone protein synthesis. The translation inhibitor cycloheximide strongly increased mRNA levels for both histone H3 variants. The dependence of histone mRNA turnover on translation in animals also appears to exist in plants. The combination of inhibition of transcription and translation by dactinomycin and cycloheximide was used in an indirect assessment of H3 mRNA stability throughout the cell cycle in partially synchronized and cycle-arrested cultures. Destabilization of replication-dependent histone H3.1 mRNA was detected in non-S phase cells.

Cell Cycle↗
PubMed1995

Histones of Chlamydomonas reinhardtii. Synthesis, acetylation, and methylation.

Histones of the green alga Chlamydomonas reinhardtii were prepared by a new method and fractionated by reversed-phase high-performance liquid chromatography. Acid-urea-Triton gel analysis and tritiated acetate labeling demonstrated high levels of steady-state acetylation for the single histone H3 protein, in contrast to low levels on histones H4 and H2B. Twenty percent of histone H3 is subject to dynamic acetylation with, on average, three acetylated lysine residues per protein molecule. Histone synthesis in light-dark-synchronized cultures was biphasic with pattern differences between two histone H1 variants, between two H2A variants, and between H2B and ubiquitinated H2B. Automated protein sequence analysis of histone H3 demonstrated a site-specific pattern of steady-state acetylation between 7 and 17% at five of the six amino-terminal lysines and of monomethylation between 5 and 81% at five of the eight amino-terminal lysines in a pattern that may limit dynamic acetylation. An algal histone H3 sequence was confirmed by protein sequencing with a single threonine as residue 28 instead of the serine28-alanine29 sequence, present in all other known plant and animal H3 histones.

Amino Acid Sequence↗
PubMed1995

Women's experiences at cervical screening.

Concerns about attendance for cervical screening has focussed on determining the reasons why some women never attend. Less attention has been paid to whether women continue to attend for further smears, although this is essential for further screening. This study investigated women's experiences of cervical screening and their views on subsequent attendance. Three hundred and thirty nine women aged 20-64 were identified from a computerised register of cervical smears as having had a smear test within the previous three years. They were interviewed at home about their most recent experience of screening. Just over half of the women (53%) recalled being anxious before the test, and about one fifth reported embarrassment (19%) or pain (20%) during it. The frequencies of discomfort were higher amongst those who were anxious about the test, although 24% of those who were embarrassed and 28% who had pain reported being unconcerned beforehand. The frequencies of pain and embarrassment were only slightly higher when the smear taker was male. Many women (22%) reported being concerned about the test result although only 10% of those who were concerned were recalled for further assessment. Although a number of women had unpleasant experiences, almost all (95%) who were under 60 years of age said they were likely to attend for a subsequent smear. Taking cervical smears is often an unpleasant experience for women, although some of the distressing events could easily have been avoided. Attention to technique and to the concerns of individual patients, especially ensuring privacy, could reduce the extent of the problem. The uptake of subsequent smears should be monitored to ensure that women are not being discouraged from attendance.

Adult↗
PubMed1994

Connexin43 and connexin45 form gap junctions with different molecular permeabilities in osteoblastic cells.

We examined the expression and function of gap junctions in two rat osteoblastic cell lines, ROS 17/2.8 and UMR 106-01. The pattern of expression of gap junction proteins in these two cell lines was distinct: ROS cells expressed only connexin43 on their cell surface, while UMR expressed predominantly connexin45. Immunoprecipitation and RNA blot analysis confirmed the relative quantitation of these connexins. Microinjected ROS cells passed Lucifer yellow to many neighboring cells, but UMR cells were poorly coupled by this criterion. Nevertheless, both UMR and ROS cells were electrically coupled, as characterized by the double whole cell patch-clamp technique. These studies suggested that Cx43 in ROS cells mediated cell-cell coupling for both small ions and larger molecules, but Cx45 in UMR cells allowed passage only of small ions. To demonstrate that the expression of different connexins alone accounted for the lack of dye coupling in UMR cells, we assessed dye coupling in UMR cells transfected with either Cx43 or Cx45. The UMR/Cx43 transfectants were highly dye coupled compared with the untransfected UMR cells, but the UMR/Cx45 transfectants demonstrated no increase in dye transfer. These data demonstrate that different gap junction proteins create channels with different molecular permeabilities; they suggest that different connexins permit different types of signalling between cells.

Animals↗
PubMed1994

A simple method to make better probes from short DNA fragments.

A detailed method is presented for the creation of head-to-tail multimers of short blunt restriction fragments, ligated into a plasmid vector in a single-tube reaction. Random priming of the concatemer insert readily yields hybridization probes of high specificity, unattainable from the short monomer fragments.

DNA Ligases↗
PubMed1994

Abscisic acid-induced heat tolerance in Bromus inermis Leyss cell-suspension cultures. Heat-stable, abscisic acid-responsive polypeptides in combination with sucrose confer enhanced thermostability.

Increased heat tolerance is most often associated with the synthesis of heat-shock proteins following pre-exposure to a nonlethal heat treatment. In this study, a bromegrass (Bromus inermis Leyss cv Manchar) cell suspension cultured in a medium containing 75 microM abscisic acid (ABA) without prior heat treatment had a 87% survival rate, as determined by regrowth analysis, following exposure to 42.5 degrees C for 120 min. In contrast, less than 1% of the control cells survived this heat treatment. The heat tolerance provided by treatment with 75 microM ABA was first evidenced after 4 d of culture and reached a maximum tolerance after 11 d of culture. Preincubation with sucrose partially increased the heat tolerance of control cells and rendered ABA-treated cells tolerant to 45 degrees C for 120 min (a completely lethal heat treatment for control cells). Comparative two-dimensional polyacrylamide gel electrophoresis of cellular protein isolated from heat-tolerant cells identified 43 ABA-responsive proteins of which 26 were heat stable (did not coagulate and remained soluble after 30 min at 90 degrees C). Eight heat-stable, ABA-responsive proteins ranging from 23 to 45 kD had similar N-terminal sequences. The ABA-responsive (43-20 kD), but none of the control heat-stable, proteins cross-reacted to varying degrees with a polyclonal antibody directed against a conserved, lysine-rich dehydrin sequence. A group of 20- to 30-kD heat-stable, ABA-responsive proteins cross-reacted with both the anti-dehydrin antibody and an antibody directed against a cold-responsive winter wheat protein (Wcs 120). In ABA-treated cells, there was a positive correlation between heat- and pH-induced coagulation of a cell-free homogenate and the heat tolerance of these cells. At 50 degrees C, control homogenates coagulated after 8 min, whereas cellular fractions from ABA-treated cells showed only marginal coagulation after 15 min. In protection assays, addition of heat-stable, ABA-responsive polypeptides to control fractions reduced the heat-induced coagulation of cell-free homogenates. Sucrose (8%) alone and control, heat-stable fractions enhanced the thermostability of control fractions, but the most protection was conferred by ABA-responsive, heat-stable proteins in combination with sucrose. These data suggest that stress-tolerance mechanisms may develop as a result of cooperative interactions between stress proteins and cell osmolytes, e.g. sucrose. Hypotheses are discussed implicating the role of these proteins and osmolytes in preventing coagulation and denaturation of cellular proteins and membranes.

Abscisic Acid↗
PubMed1994

Observer variability in the histopathological reporting of abnormal rectal biopsy specimens.

AIMS: To study the consistency of reporting of abnormal rectal biopsy specimens, especially in the differentiation of inflammatory bowel disease from other causes of abnormality. METHODS: Sixty rectal biopsy specimens were identified from patients presenting with bloody diarrhoea. These were then circulated to the 11 consultant pathologists in the study who filled in a proforma with a list of 12 diagnostic categories and 22 features. RESULTS: Forty one of the 60 cases were examples of inflammatory bowel disease. In 33 of these cases nine or more pathologists had made the diagnosis. Further categorisation into ulcerative colitis and Crohn's disease showed better recognition of ulcerative colitis. In the 19 cases of non-inflammatory bowel disease recognition of pseudomembranous colitis and solitary rectal ulcer syndrome was good, but the results were poorer in the case of infective colitis. CONCLUSION: The findings suggest that a group of consultant pathologists can differentiate between inflammatory bowel disease and other causes of an abnormal rectal biopsy specimen and can also recognise pseudomembranous colitis and solitary rectal ulcer syndrome satisfactorily.

Biopsy↗
PubMed1994

Observer variability in histopathological reporting of malignant bronchial biopsy specimens.

AIMS: To evaluate the ability of histopathologists to classify lung carcinomas on bronchial biopsy material using the current World Health Organisation (WHO) classification. METHODS: Eleven histopathologists each reviewed 100 randomly selected bronchial biopsy specimens which had originally been reported as showing lung carcinoma. A single haematoxylin and eosin stained section from each case was circulated and a standard proforma completed. These were analysed using kappa statistics. RESULTS: The histopathologists were excellent at distinguishing between small cell and non-small-cell carcinoma kappa = 0.86), but not so good at subclassifying the non-small cell carcinoma group kappa = 0.25). CONCLUSIONS: The clinically important distinction between small cell and non-small cell carcinoma of the lung is reliably made by competent histopathologists even on limited material.

Biopsy↗
PubMed1994

Cervical screening: the optimum visit plan for contacting users and non-users in Scotland.

OBJECTIVE: To investigate the numbers of visits required to obtain interviews with users and non-users of cervical screening, and to determine the workload involved to enable an optimum visit plan to be developed. DESIGN: Case-control study of users and non-users of cervical screening using a flexible visit plan that involved up to eight attempts at contact. Visits were made in mornings, afternoons, and evenings, the visit pattern being determined by information gained from local sources. PATIENTS: Altogether 660 non-users of cervical screening (cases), aged 20-64 and registered with 23 randomly selected general practitioners (GPs), were identified from the Tayside computerised register of cervical smears. These women were selected from the computerised lists of 18 GPs in Dundee and five in Perth. A total of 417 women recorded as having a smear within the previous three years (controls), matched by age and GP, were also identified from the computerised register. RESULTS: Altogether 1834 attempts were made to contact the cases, of whom 339 were interviewed, giving a workload of 18 interviews per 100 attempts. For the controls 1359 attempts were made at contact to yield 339 interviews, a workload of 25 interviews per 100 attempts. Refusals (19%) and incorrect addresses (23%) were the two major reasons for failing to achieve interview. Only for four (0.6%) of the cases and one (0.2%) of the controls was no information gained. The proportion of attempts which led to interview remained constant with increasing numbers of call-backs (up to six for the cases and eight for the controls). CONCLUSIONS: A flexible approach to visit scheduling that takes account of local knowledge can lead to interviews with 66% of non-users of health screening, when incorrect addresses are removed. It is preferable to plan for many (up to six) visits to achieve interview. This will minimise non-response bias without increasing the workload per successful interview.

Adult↗
PubMed1993

Efficient large-scale purification of restriction fragments by solute-displacement ion-exchange HPLC.

Extreme overloading of HPLC columns with sample can create a condition of binding site saturation causing competition and displacement among solutes during column elution. This has been termed solute-displacement chromatography (SD-HPLC). We present an example of this phenomenon for the preparative fractionation and purification of restriction fragments of almost identical size (1337 and 1388 bp) which cannot be resolved by agarose gel electrophoresis. Standard analytical ion-exchange HPLC chromatography failed to separate these fragments from each other and from an unexpectedly early eluting pUC-derived vector fragment of 2.7 kbp. We demonstrate that by intentional overloading of the small (4.6 x 35 mm) non-porous TSK-DEAE HPLC column, hundreds of micrograms of DNA restriction fragments could be resolved and purified in a single HPLC run of less than 30 minutes.

Binding Sites↗
PubMed1993

How fatal is breast cancer? A prospective study of breast carcinoma deaths in Tayside.

A prospective autopsy study of deaths of women who had been diagnosed previously as having cancer of the breast was performed between October 1986 and December 1990. During the study period 28 deaths occurred and nine of these (32%) were attributable directly to breast cancer; a figure similar to that found in our earlier retrospective study. In this study the autopsy findings in both the breast cancer and non-breast cancer deaths were recorded and five cases underwent post-mortem radiological skeletal survey to detect metastases. The findings confirm the role of the post mortem in modern medicine as a method of auditing clinical practice. Of particular importance, is the finding that the clinical presumption of disseminated breast cancer as a cause of 'terminal' illness in some patients may be misleading and dangerous, possibly denying some patients treatment of potentially remedial conditions by the institution of inappropriate terminal care.

Breast Neoplasms↗
PubMed1993

Whipple's procedure: is it justified?

Debate continues as to the appropriateness of the Whipple procedure. This retrospective review confirms that it is a worthwhile operation when done by experienced surgeons on suitable patients. Meticulous intra-operative technique must be followed by judicious postoperative care. In this series of 27 Whipple operations major morbidity occurred in 26% of cases. Leakage from the pancreatic anastomosis was infrequent (11%). Various anastomotic techniques were used, depending on the findings at operation. There were no peri-operative deaths and five-year actuarial survival is 63%.

Adult↗
PubMed1993

Connexin43 mediates direct intercellular communication in human osteoblastic cell networks.

We have examined cell coupling and expression of gap junction proteins in monolayer cultures of cells derived from human bone marrow stromal cells (BMC) and trabecular bone osteoblasts (HOB), and in the human osteogenic sarcoma cell line, SaOS-2. Both HOB and BMC cells were functionally coupled, since microinjection of Lucifer yellow resulted in dye transfer to neighboring cells, with averages of 3.4 +/- 2.8 (n = 131) and 8.1 +/- 9.3 (n = 51) coupled cells per injection, respectively. In contrast, little diffusion of Lucifer yellow was observed in SaOS-2 monolayers (1.4 +/- 1.8 coupled cells per injection, n = 100). Dye diffusion was inhibited by octanol (3.8 mM), an inhibitor of gap junctional communication. All of the osteoblastic cells expressed mRNA for connexin43 and connexin45, but not for connexins 26, 32, 37, 40, or 46. Whereas all of the osteoblastic cells expressed similar quantities of mRNA for connexin43, the poorly coupled SaOS-2 cells produced significantly less Cx43 protein than either HOB or BMC, as assessed by immunofluorescence and immunoprecipitation. Conversely, more Cx45 mRNA was expressed by SaOS-2 cells than by HOB or BMC. Thus, intercellular coupling in normal and transformed human osteoblastic cells correlates with the level of expression of Cx43, which appears to mediate intercellular communication in these cells. Gap junctional communication may serve as a means by which osteoblasts can work in synchrony and propagate locally generated signals throughout the skeletal tissue.

Alkaline Phosphatase↗
PubMed1992

A retrospective study of 932 second trimester terminations using gemeprost (16,16 dimethyl-trans delta 2 PGE1 methyl ester).

A retrospective study of 932 second trimester terminations between 12-27 weeks gestation was carried out to determine the efficacy of gemeprost for second trimester termination. A single course of 5 x 1 mg gemeprost pessaries was administered every three hours. If abortion had not occurred after the first course of pessaries, a further course of 5 x 1 mg pessaries was administered. Intravenous oxytocin was administered after 36 hours if abortion had not occurred. Eighty per cent and ninety five per cent of patients aborted within 24 and 48 hours respectively. Of the remaining 5 per cent of women, 3 per cent aborted with escalating doses of oxytocin. In the remaining 18 (2 per cent) women, the pregnancies were electively terminated with an alternative method. The median induction-abortion interval was 18.0 hours and 15.0 hours in nulliparous and parous women respectively (P less than 0.0001). The number of pessaries required to induce abortion was not influenced by parity. Significantly more parous women bled more than 500 ml. The incidence of pelvic sepsis (0.1 per cent) and cervical tear (0.1 per cent) was low. Twenty six per cent of women had diarrhoea and 23 per cent vomited following administration of prostaglandin. This study confirmed the efficacy of gemeprost for second trimester termination of pregnancy. This method of termination is safe, non-invasive, simple and has a low complication rate.

Abortion, Induced↗