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Biomedical subjects

D R Turner

Publications and source records attributed to D R Turner.

At least 55 records · Page 3Linked to original sources
PubMed1991

Persistent karyomegaly caused by Penicillium nephrotoxins in the rat.

Continuous or intermittent consumption by rats of food moulded by Penicillium aurantiogriseum induced prominent and extensive histopathological changes within several weeks seen specifically at the renal cortico-medullary junction. Many cells of the P3 segment of proximal tubules contained either giant nuclei or multiple enlarged nuclei, described in this text as karyomegaly, but also included within a cytomegalic change. The changes contrasted with the tubular cell necrosis and concomitant mitosis elicited after only four days consumption of nephrotoxic mould. Unilateral nephrectomy enabled persistence of histopathological changes to be assessed directly after detailed histology at an earlier stage. After ten days consumption of food with a 100-fold excess of fungal extract containing the amphoteric nephrotoxins, the typical acute histopathology evolved, over a period of three weeks on normal diet, into the bizarre karyomegalic histopathology, implying a latent effect. Karyomegaly persisted for at least twelve months after nephrotoxin dosage ceased. P. aurantiogriseum karyomegaly was much more striking than that induced by a relatively high chronic dose of another Penicillium nephrotoxin, ochratoxin A. Although the study does not attempt to measure relative potencies, qualitatively similar ultrastructural changes (enlarged nuclei, proliferation of smooth endoplasmic reticulum and thickening of proximal tubule basement membranes) were induced by the two types of nephrotoxin. The broadly toxic ochratoxin A is the popular putative aetiological agent in the mysterious and insidious Balkan endemic nephropathy and associated urinary tract tumours. As the renal carcinogenicity of ochratoxin A in rats follows karyomegaly, the striking karyomegaly induced by P. aurantiogriseum in the proximal tubules of the kidney must be considered as a potential factor in human chronic renal disease.

Animal Feed↗
PubMed1991

Distribution of collagenase and tissue inhibitor of metalloproteinases (TIMP) in colorectal tumours.

Increased collagenase activity in colorectal carcinomas has recently been shown to be associated with increased malignant potential. To determine the tissue distribution of collagenase and its specific inhibitor, tissue inhibitor of metalloproteinases (TIMP), we carried out an immunohistochemical study on colorectal carcinomas (n = 20), adenomas (n = 7) and normal mucosa (n = 6). We found increased staining for collagenase in the connective tissue stroma of carcinomas, as compared with adenomas and normal mucosa. Little evidence of epithelial cell staining for collagenase was seen in any tissue. In carcinomas, both stromal fibroblasts and collagen fibres stained strongly and stromal staining was strongest close to neoplastic glands. Vascular staining was more prominent in neoplastic than normal tissues, perhaps reflecting the increased proteolytic activity during tumour angiogenesis. The pattern of TIMP immunostaining was similar to that of collagenase, although basement membrane staining for TIMP was generally more intense. Another difference was that, unlike TIMP, staining for collagenase was often increased at the invasive edge of carcinomas, perhaps reflecting increased collagenase activity at this location.

Adenoma↗
PubMed1991

Relationships between epithelial basement membrane staining patterns in primary colorectal carcinomas and the extent of tumour spread.

In colorectal cancer an association has been found between lack of epithelial basement membrane (EMB) immunostaining in the tumour centre and more extensive malignant spread. Interestingly, ultrastructural investigations suggest that EBM loss at the tumour periphery may be part of an invasive mechanism. To further assess the significance of EBM deficiencies in different tumour areas, we carried out a detailed study of the basement membrane laminin immunostaining patterns in 130 cases of colorectal carcinoma. We find that discontinuous EBM staining in the tumour centre is associated with poor tumour differentiation (p less than 0.005), presence of lymph-node metastases (p less than 0.02), and more advanced Dukes stage (p less than 0.02). The latter association is strengthened by excluding cases in which numerous polymorphonuclear leukocytes (PMNs) are present adjacent to EBM breaks, suggesting that these inflammatory cells are a confounding factor. Discontinuous EBM staining is more frequently observed in tumour deep to muscularis propria than in submucosal tumour (p less than 0.02), indicating intra-tumoral variation. At the tumour periphery, extensive EBM discontinuity shows no association with lymph-node involvement, but is linked with deeper local invasion (p less than 0.05). While EBM staining patterns around central and peripheral tumour glands are related (p less than 0.001), staining around peripheral glands is almost invariably more discontinuous. However, EBM lack at the tumour periphery is not as absolute as previously suggested, since in 18% of tumours fewer than 25% of peripheral tumour glands show EBM breaks. This appears consistent with the hypothesis that invasive changes at the tumour periphery are temporary and reversible.

Basement Membrane↗
PubMed1991

Effect of chronic verapamil treatment on ventricular function and growth in chick embryos.

Adjustment of myocardial mass to work load is a fundamental characteristic of the heart. We studied the effect of verapamil, a calcium channel blocker, on growth and function of chick embryonic ventricle. We treated stage 18 chick embryos with verapamil delivered to the extraembryonic vascular bed by a miniosmotic pump and compared them with saline-treated control and untreated embryos. At stages 24, 27, and 29, we measured ventricular pressure and dP/dt by a servo-null system, dorsal aortic stroke volume and dV/dt by pulsed-Doppler, and ventricular and embryo wet weights. Mean myocyte profile area was measured by digital planimetry technique, and cell growth response by DNA and protein assay. Verapamil treatment decreased ventricular pressure in experimental (P less than 0.05) compared with saline control and normal embryos; at stage 27, 1.59 +/- 0.21 vs. 2.17 +/- 0.05 and 2.35 +/- 0.08 (SE) mmHg, respectively. Mean dorsal aortic blood flow decreased in experimental (P less than 0.05) vs. control and normal embryos; at stage 27, 0.98 +/- 0.07 vs. 1.54 +/- 0.10 and 1.56 +/- 0.07 mm3/s, respectively. Stroke volume remained the same in all experimental, normal, and control embryos except at stage 29. Ventricular weight decreased in experimental (P less than 0.05) vs. control and normal embryos; at stage 27, 1.09 +/- 0.07 vs. 1.51 +/- 0.08 and 1.54 +/- 0.11 mg, respectively. Embryo weights, myocyte size, and cytoplasmic fractional volume were similar in all groups. Morphology of ventricles was normal. DNA was lower in experimental (P less than 0.05) compared with control and normal embryos.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Penicillium aurantiogriseum-induced, persistent renal histopathological changes in rats; an experimental model for Balkan endemic nephropathy competitive with ochratoxin A.

Renal histopathological changes in rats, caused by food partially moulded by a common fungus isolated from an area of nephropathy in Yugoslavia, were differentiated into acute and chronic responses. The acute response to a few days on the diet specifically involved necrosis and concomitant mitosis in proximal tubule cells. More protracted, continuous or intermittent administration of nephrotoxic mould led to a marked karyomegaly in the same corticomedullary region. The phenomenon is more prominent than that induced by treatment with ochratoxin A over a similar period, raising the question of the putative role of such mycotoxins in the etiology of chronic human renal disease.

Acute Disease↗
PubMed1990

Molecular nature of in vivo mutations in human cells at the autosomal HLA-A locus.

The mutations present in vivo in normal human cells were studied at the HLA-A locus by isolating mutant lymphocytes using antibody-complement immunoselection and cloning at limiting dilution. The molecular basis for mutation in 127 mutant lymphocytes from 10 individuals was determined by studying a variety of polymorphic gene loci on both arms of chromosome 6. No change was detected in 78 mutants (61.4%), gene deletion was detected in 11 (8.7%), and mitotic recombination was detected in 38 (29.9%). Neither gene conversion nor chromosome loss was detected. These observations document the mechanisms responsible for gene loss in normal human cells in vivo, emphasize the importance of mitotic recombination, and indicate the similarity between mutational mechanisms in normal cells and in cancer cells.

Cells, Cultured↗
PubMed1990

Isolation of fetal trophoblast cells from peripheral blood of pregnant women.

Fetal trophoblast cells were isolated from maternal peripheral blood by means of murine monoclonal antibodies of high specificity and affinity for human syncytiotrophoblast and nonvillous cytotrophoblast cells. The cells were isolated in sufficient numbers to allow polymerase chain reaction (PCR) amplification of the Y-chromosome-specific DNA sequence from the peripheral blood of thirteen pregnant women. The fetal sex predicted by PCR analysis of the isolated trophoblast cells accorded with that ascertained by karyotyping of chorionic villus samples in eleven of twelve women studied in early pregnancy and with the sex of the baby on delivery in one woman studied at 34 weeks' gestation. Isolation of these fetal cells could allow noninvasive diagnosis of a wide range of inherited disorders.

Antibodies, Monoclonal↗
PubMed1990

Dose-dependent effect of metoclopramide on cholinesterases and suxamethonium metabolism.

In obstetric patients undergoing postpartum tubal ligation, we found that metoclopramide produced dose-dependent prolongation of suxamethonium-induced neuromuscular block. Mean block times after suxamethonium 1 mg kg-1 were 8.0 min, 9.83 min and 12.45 min for control and metoclopramide 10 mg and metoclopramide 20 mg groups, respectively. A laboratory study was therefore conducted on the inhibition of human plasma cholinesterase (PCHE) and erythrocyte acetylcholinesterase (ACHE) activity by varying concentrations of metoclopramide using acetylthiocholine as substrate. PCHE showed a greater sensitivity to inhibition by metoclopramide; the concentration of metoclopramide producing 50% inhibition of activity (I50) was 3.16 x 10(-7) mol litre-1, which is within the therapeutic range. ACHE was less sensitive to inhibition by metoclopramide (I50 2.24 x 10(-5) mol litre-1). Analysis of enzyme kinetics at varying substrate concentrations revealed that metoclopramide produced a potent non-competitive, dose-dependent inhibition of both ACHE and PCHE. The inhibition constant, Ki, was 1.88 x 10(-7) mol litre-1 for PCHE and 9.5 x 10(-8) mol litre-1 for ACHE. As metoclopramide is a potent inhibitor of PCHE, interactions might be expected to occur between metoclopramide and drugs that require PCHE for biotransformation, such as suxamethonium and ester local anaesthetics.

Cholinesterase Inhibitors↗
PubMed1989

Assembly of hybrid RNAs with tobacco mosaic virus coat protein. Evidence for incorporation of disks in 5'-elongation along the major RNA tail.

We have shown that during the reassembly of tobacco mosaic virus (TMV) RNA, with the coat protein supplied as a "disk preparation", the lengths of RNA protected from nuclease are "quantized" with steps which correspond to incorporation of the subunits from either a single or, more commonly, both rings of a disk. This interpretation has been challenged and it was suggested that the pattern was due to special, though unspecified features of the sequence of TMV RNA. To test whether the specific sequence of TMV RNA is important during the elongation, rather than just during nucleation, we have now followed growth of particles containing hybrid RNAs, with the TMV RNA origin of assembly but otherwise non-TMV sequences. We have prepared in vitro RNA transcripts containing heterologous RNA 5' to the origin of assembly sequence from TMV RNA, i.e. with a heterologous RNA tail in place of the natural major 5'-tail and no minor tail, and used these for assembly experiments. In each case we observe a banding pattern very similar to that which we had found with native TMV RNA and with a dominant quantum step of just over 100 bases, and sometimes also a step of 50 bases, strongly suggesting that this is not due to any feature of the TMV RNA. This same repeat is also visible even with a heterologous RNA chosen because it had a sequence repeat of 135 or 136 bases, confirming that the quantization is due to a feature of the elongation reaction and in no way to the RNA sequence being encapsidated. We have also followed elongation with the origin of assembly located 5' to the heterologous RNA. This leads to a slower elongation along this 3'-tail, after the initial rapid encapsidation of the origin RNA, which lacks any quantization of length protected. These results are fully compatible with the hypothesis we had advanced earlier, that the major growth along the 5'-tail is from performed aggregates ("disks") while the minor growth along the 3'-tail is from subunits in the "A-protein" adding singly or a few at a time.

Base Sequence↗
PubMed1989

Differential expression of the Lewis Y antigen defined by monoclonal antibody C14/1/46/10 in colonic polyps.

The expression of Le(y) (Lewis(y) Hapten), a difucosylated type 2 blood group-related antigen, in colorectal lesions was studied by using the monoclonal antibody C14. In normal colonic mucosa, strong staining has been observed in the terminal ileum, cecum, and ascending colon with minimal staining in the rest of the colon and rectum. Eighty-three percent of adenomas expressed Le(y), with 70% showing an increased expression of Le(y) compared with normal tissue. Only 25% of metaplastic (nonneoplastic) polyps showed an increased expression of Le(y). The expression of Le(y) in adenomas was correlated with both size and degree of epithelial dysplasia of the adenomas and also showed an association with histologic type. No correlation was found with the location and morphology of the adenomas. The most strongly related parameter was the degree of dysplasia. All adenomas with severe dysplasia showed increased expression of Le(y), with 83% showing marked expression. This finding was irrespective of their size or type. Adenomas which did not exhibit severe dysplasia showed increased expression in 66% of cases, but only 18% showed marked expression. These findings show that the expression of Le(y) in colorectal lesions is associated with features related to malignant potential. Le(y) expression may provide useful prognostic information in the assessment of colorectal polyps.

Adenoma↗
PubMed1989

A morphological study of experimental proteinuria using a novel form of surface fixation.

Careful ultrastructural studies of the rat model of nephrotic syndrome induced by puromycin aminonucleoside have demonstrated morphological features which are only seen in proteinuric glomeruli fixed without interruption of the blood pressure. These consist of balloon-like swellings bounded by attenuated epithelial cell cytoplasm, with an area of bare basement membrane at the base. A theory of the mechanism of proteinuria was proposed on the basis of these findings. To test the proposed wide validity of that theory, we improved the method of surface fixation and performed similar studies in sequential manner, using chronic serum sickness glomerulonephritis in the rat as a model of proteinuria. Glomeruli were studied by light microscopy, transmission and scanning electron microscopy. The findings were correlated with the level of proteinuria in the 24 h preceding death and with the duration of serum sickness. Epithelial cell 'balloons' are also demonstrated in this model, correlating with the presence of proteinuria, but with slightly different configurations from those seen in puromycin nephrosis. Surface fixation revealed similar balloons in two other models of proteinuria: a graft versus host induced model of systemic lupus erythematosus in the mouse, and chronic streptozotocin-induced diabetes in the rat. A lengthy search failed to find bare basement membranes in any of these models of proteinuria. We conclude, therefore, that the mechanism of proteinuria proposed in puromycin nephrosis does not apply in these models, and we suggest an alternative mechanism by which the 'balloons' may develop, as a further manifestation of the epithelial cell dysfunction which causes foot process effacement.

Animals↗
PubMed1989

Human lymphocytes aged in vivo have reduced levels of methylation in transcriptionally active and inactive DNA.

The amount of 5-methylated cytosine (5 mC) in the sequence CmCGG has been measured in DNA extracted from uncultured peripheral blood human lymphocytes obtained from 24 young (mean age 25) and 22 old (mean age 75) individuals. When compared with the young group the old group had significantly reduced levels of 5 mC in total genomic DNA, in transcriptionally active DNA, and in genomic DNA from which transcriptionally active sequences had been removed. In both the young and old groups transcriptionally active DNA contained 10% less 5 mC than the residual 'inactive' DNA. These results indicate that loss of genomic DNA methylation may be involved in aging in vivo and underscore the association of gene regulation with the distribution of methylation in DNA.

5-Methylcytosine↗
PubMed1989

Neuromuscular block by suxamethonium following treatment with histamine type 2 antagonists or metoclopramide.

We have examined the effect of preoperative i.v. administration of three different histamine type 2 (H2) antagonists (cimetidine 400 mg, ranitidine 80 mg and famotidine 20 mg) or metoclopramide 10 mg i.v. on the duration of neuromuscular block produced by an intubating dose (1 mg kg-1) of suxamethonium. The study was conducted blindly in 70 post partum patients, weighing between 45 and 120 kg, scheduled for tubal ligation. The duration of neuromuscular block following suxamethonium was measured from a chart recording of train-of-four (TOF) electromyographic responses. The time from onset of 95% block to 25% recovery ("block time") was not significantly different between the groups receiving cimetidine (A), ranitidine (B), famotidine (C), and control (E). However, there was prolongation of neuromuscular block in patients receiving suxamethonium and metoclopramide (D).

Clinical Trials as Topic↗
PubMed1989

Prolongation of succinylcholine block by metoclopramide.

Laboratory and clinical evidence of the inhibition of plasma cholinesterase by metoclopramide was demonstrated. When succinylcholine is used as the substrate and the product choline assayed by choline oxidase-peroxidase-quinone dye colorimetry, the rate of the choline production as optical density change was reduced to 50% by 19.5 X 10(-6) M metoclopramide at 20 degrees C. Prolongation of neuromuscular blockade produced by concurrent administration of succinylcholine and metoclopramide was studied in 22 patients aged between 18 and 40 years undergoing elective gynecological surgery. EMG activity in the adductor pollicis muscle was recorded in response to a train-of-four (TOF) stimulus delivered every 10 s. Patients were randomly divided into two groups: A and B. In both groups, anesthesia was induced with thiopental and maintained with sufentanil and nitrous oxide. Tracheal intubation followed intravenous succinylcholine. Intraoperatively, after returning of neuromuscular function, patients in both groups received 20 mg succinylcholine for the determination of duration of neuromuscular blockade. Time from 95% suppression of baseline twitch following a 20 mg increment of succinylcholine until recovery to 25% of control activity was determined. Thereafter, in group A, patients receive metoclopramide (10 mg iv) followed by succinylcholine 20 mg iv, and patients in group B received succinylcholine 20 mg iv alone. Recovery times were again measured and found to be prolonged in patients receiving metoclopramide compared with those not receiving metoclopramide (P less than 0.05). Metoclopramide has no intrinsic neuromuscular blocking activity, but its ability to inhibit plasma cholinesterase probably is the mechanism by which it prolongs succinylcholine block. Reducing the dose of succinylcholine may be appropriate when metoclopramide is given concurrently.

Adult↗
PubMed1989

Histopathological assessment of bleeding from polyps of the colon and rectum.

One hundred and twenty seven colorectal polyps were examined to assess histopathological evidence of recent and old haemorrhage to test the usefulness of faecal occult blood tests in detecting colorectal neoplasia, in particular premalignant adenomas. Evidence of haemorrhage was consistently found in adenomas but was rare in non-neoplastic polyps. Haemorrhage within adenomas was predominantly stromal and associated with dilated, congested vessels. Factors associated with more severe haemorrhage were size, pedunculation, and villous growth; the degree of epithelial dysplasia and the age and sex of the patient were not associated factors. Proximal polyps showed more old haemorrhage than rectal polyps, but there was no such difference for recent haemorrhage.

Aged↗