Biomedical subjects

H B Jones

Publications and source records attributed to H B Jones.

At least 37 records · Page 2Linked to original sources

PubMed1996

A genome screen in multiple sclerosis reveals susceptibility loci on chromosome 6p21 and 17q22.

The population prevalence of multiple sclerosis is 0.1%; however, the risk of the disease in the siblings of affected individuals is very much higher at 3-5%. The importance of genetic factors in accounting for this increased risk is confirmed by the results of twin and adoption studies. Despite the evidence for a strong genetic effect, a weak major histocompatibility complex (MHC) association is the only consistently observed feature in the genetics of multiple sclerosis. Other candidates have been proposed, including genes encoding the immunoglobulin heavy chain, T cell receptor beta chain and APOC2, but none has yet been confirmed. Evidence for linkage and association to the myelin basic protein gene has been reported in a genetically isolated Finnish population, but it has not been possible to reproduce these results in other populations. We used a two-stage approach to search the human genome for the genes causing susceptibility to multiple sclerosis. Two principal regions of linkage are identified, chromosomes 17q22 and 6p21 (MHC). Our results are compatible with genetic models involving epistatic interaction between these and several additional genes.

Chromosome Mapping↗

PubMed1996

Hybrid selection as a method of increasing mapping power for radiation hybrids.

Radiation hybrids have become a widely used tool for physical mapping. A drawback of the technique is that large numbers of hybrids are required to construct robust, high-resolution maps. The information contained within a panel of radiation hybrids is limited by the frequency of retention of chromosomal fragments from the donor cell line. In almost all experiments to date, the retention frequency has been below the optimal level; therefore, many hybrids are needed to produce high-quality maps. Because of the labor-intensive nature of large-scale mapping projects, it is important to make panels as small as possible. One method that has been adopted is to produce initially a large number of hybrids that are all typed with a few loci. Those hybrids showing satisfactorily high retention are admitted to the final panel and the rest are discarded. In this way, a panel of radiation hybrids with higher than expected retention can be created. Methods for conducting such a selection regime are discussed. To investigate the potential advantages of selecting hybrids based on their retention frequency, simulations were run under a variety of conditions. As expected panels with high retention (40%) provided better mapping resources than panels with lower (20%) retention. Beginning with an initial panel of 200 hybrids, comparisons of a random sample of 100 hybrids and the set of those 100 hybrids showing the highest marker retention demonstrated that selection may not be always the best strategy despite the increase in mean retention it yields. The selection of hybrids containing large numbers of fragments leads to an overestimation of the frequency of radiation-induced breaks. When breaks occur with high frequency (for example, when high radiation doses are used), the selection of hybrids leads to a loss of linkage and hence an inability to order the markers. As such, the merits of screening hybrids depends on both the radiation dose and the desired map resolution.

Chromosome Mapping↗

PubMed1996

Pairwise analysis of radiation hybrid mapping data.

Two point lod scores are widely used in pedigree analysis as they provide a fast and efficient method of establishing linkage. Groups of markers that lie in close proximity to one another can be formed by admitting any locus that is linked to at least one existing member of the group with lod score greater than some predetermined value. It seems natural to extend this technique to Radiation Hybrid Mapping both for constructing groups of tightly linked loci that may then be analysed using more powerful statistics and as a method of ordering in its own right. A general extension of two point analysis is derived and the problems associated with radiation hybrid data are discussed. In particular, the additional parameters representing the probabilities of different fragments being retained (which have no parallel in classical linkage analysis) lead to a range of estimators of the breakage probability, O, which have equal and maximal likelihood. Ways of circumventing this problem are discussed along with the potential errors they introduce. Importantly the ambiguity in estimation of theta is not carried through to the lod score as this depends only on the maximum value of the likelihood and not on the particular value of theta at which it occurs. Thus even though two point analysis fails to provide robust estimates of either breakage probabilities or the distance between loci, it represents a simple and effective method of constructing linkage groups that may be analysed with more powerful statistical methods. This is particularly important given the large number of microsatellites, ESTs and candidate genes currently being typed on radiation hybrids.

Chromosome Mapping↗

PubMed1996

A high-resolution radiation hybrid map of the region surrounding the Gorlin syndrome gene.

We have constructed a set of hybrid cell lines by irradiation of GM 64063 (human chromosome 9q only on hamster background) and fusion to hamster A23 Tk-, 109 independent lines were tested by PCR with 24 markers from chromosome 9q. The marker density is highest in the 9q22.3-q31 region containing the gene for Gorlin syndrome, a familial predisposition to basal cell carcinoma. The resolution of our map in this region is significantly higher than other published maps and will enable accurate placing of new markers and genes within the 9q22.3-q3.1 region. This is important since yeast artificial chromosomes from the region are likely to contain deletions.

Animals↗

PubMed1996

Neuropathological changes in rat brain following oral administration of 2-chloropropionic acid.

The agrochemical intermediate, L-2-Chloropropionic acid (L-2-CPA) and D-2-chloropropionic acid (D-CPA), when administered separately by oral gavage to rats, produced extensive cerebellar granule cell necrosis (> 80%) characterised by varying degrees of nuclear condensation and nuclear karyorrhexis. In contrast a few necrotic Purkinje cells (< 5%) were observed. Purkinje cell damage consisted of cytoplasmic and nuclear shrinkage and hyperchromasia. Karyorrhexis was not seen in Purkinje cells. Extensive vacuolation (edema) was present both in the cerebellar granular layer and Purkinje cell layer. Astrogliosis (hypertrophy and hyperplasia) was seen at lesion sites and activity was recognised by positive glial fibrillary acidic protein (GFAP) staining. Proliferative activity of astrocytes at lesion sites was confirmed by positive proliferating cell nuclear antigen (PCNA) immunostaining. Astrogliosis was focused exclusively in the necrotic granule cell layer. A single oral dose of 750 mg/kg of either stereoisomer or three consecutive daily doses of 250mg/kg L-2-CPA. produced the lesion. Cerebellar water content increased with time in parallel with the edematous response noted by neuropathological examination. The earliest onset of the lesion was observed at 36 hours appearing more extensive at 48 and 72 hours post-dosing. No other major neuropathological changes were detected in the brain, spinal cord, spinal ganglia, Gasserian ganglia, peripheral nerves and voluntary muscle following L-2-CPA administration. In conclusion, both stereoisomers of CPA were found to be selective neurotoxicants of the rat central nervous system.

Administration, Oral↗

PubMed1995

The topography, structure and incidence of mineralized bodies in the basal ganglia of the brain of cynomolgus monkeys (Macaca fascicularis).

Whole coronal slices from 6 levels of the brain of 16 cynomolgus monkeys (8 control and 8 treated by daily gavage with a novel pharmaceutical agent for one year) were examined histologically. Mineralized bodies were identified only in coronal sections passing through the optic chiasma and mammillary bodies. Identical mineralized structures were present in the basal ganglia of both control and treated animals. The majority were seen in the globus pallidus, occasionally in the putamen and once in the nearby caudate nucleus. These structures were partially ferruginated and also partially calcified. They appeared to arise in relation to small vessels. They are part of the naturally occurring background pathology of several species of non-human primates and the incidence in this study (3/8 control and 5/8 treated) was approximately what might be expected from reports in the literature. Mineralized bodies of the basal ganglia of primates represent a spontaneous lesion with a characteristic distribution. They may cause confusion in interpretation of toxicological studies if their natural occurrence is not appreciated.

Animals↗

PubMed1994

Pathological and morphometric assessment of testicular parameters in patients with metastatic prostate cancer following treatment with either the antiandrogen Casodex (ZM176,334) or bilateral orchidectomy.

Casodex is an orally active non-steroidal antiandrogen that is highly selective for androgen receptors in animals and man. It is indicated for the non-surgical treatment of advanced prostate cancer in man. The present open controlled study in 13 Casodex-treated and 21 orchidectomy-alone (control) patients addressed the hypothesis that chronic administration of antiandrogens will result in Leydig cell hyperplasia as a result of feedback inhibition of the pituitary resulting in increased luteinising hormone (LH) stimulation of Leydig cells. Although Casodex has been shown to produce a moderate rise in circulating plasma testosterone concentration on chronic treatment in prostate cancer patients, a controlled histopathological and morphometric assessment of the testis following orchidectomy in relapsed Casodex patients showed no effect on Leydig cell populations compared with an orchidectomy alone (control) group. No evidence for induction of Leydig cell hypertrophy or hyperplasia as a result of chronic oral administration of 50 mg Casodex daily was obtained in this study.

Androgen Antagonists↗

PubMed1994

Assessment of the labelling index of cohorts of the pancreatic islet cell population in phenobarbitone-treated male rats using a double immunohistochemical technique for 5-bromo-2'-deoxyuridine and pancreatic hormones.

A previous study demonstrated that administration of phenobarbitone to male AP Wistar rats for up to 7 days caused alterations in labelling indices (LIs) in several different tissues (including a reduction of the endocrine pancreas population LI) as determined by immunohistochemical visualisation of 5-bromo-2'-deoxyuridine (BrdU) incorporation into S-phase nuclei. The primary objective of this study was to determine whether treatment with phenorbarbitone influenced the replicative states of specific cohorts of the islet (of Langerhans) cell population or generated a uniform depression of LI. Quantitation of the LIs of individual islet cell cohorts was achieved by utilisation of a dual immunohistochemical staining method for BrdU and islet hormones (insulin, glucagon and somatostatin) using a sequential peroxidase anti-peroxidase (PAP)/alkaline phosphatase anti-alkaline phosphatase (APAAP) method employing diaminobenzidine and New Fuchsin chromogens, respectively. We observed reductions, increases and no change in LIs of insulin-, glucagon- and somatostatin-positive cells, respectively. We conclude that the decreased LI of the insulin-positive cohort was not countered entirely by the LI increase in the glucagon-positive cohort due to the larger size of the former. Furthermore, the effects of phenobarbitone treatment are not manifested generally in the islet cell population but in the insulin- and glucagon-positive cohorts only. The causation of these effects is unknown but is likely to be due to enhanced carbohydrate and hormone metabolism. We believe that the visualisation and quantitation of replicating cells in specific hormone-positive cohorts of the islet cell population provide opportunities for understanding the influence of xenobiotics and disease processes on pancreatic function.

Alkaline Phosphatase↗

PubMed1994

Mechanisms of non-genotoxic carcinogenesis.

Until recently, the mechanism of carcinogenesis has been regarded as a two-stage phenomenon involving damage to the genetic material, which initiates the process, followed by a cell-division stimulus, which promotes the development of the tumour. However, exposure to some chemicals has been shown to result in carcinogenesis without involvement of the initiation step. The mechanism of non-genotoxic carcinogenesis is not fully understood, but is believed to involve stimulation of cell division with a consequent increased probability of a mutation occurring spontaneously. In this article, Ian Shaw and Huw Jones review the theories of non-genotoxic carcinogenesis with reference to specific examples of known non-genotoxic carcinogens.

Animals↗

PubMed1994

Comparative effects of anti-platelet agents as adjuncts to tissue plasminogen activator in a dog model of occlusive coronary thrombosis.

1. This study compares a cyclo-oxygenase inhibitor (aspirin), a 5-HT2 antagonist (ZM170809) and a combined thromboxane synthase inhibitor/receptor antagonist (ZD1542) as adjuncts to tissue plasminogen activator (rt-PA). 2. Application of an anodal current (332 +/- 4.1 microA) to the stenosed left circumflex coronary artery of 20 anaesthetized dogs produced a stable platelet-rich occlusive thrombus. 3. After initial i.v. administration of recombinant human tissue type plasminogen activator (rt-PA, 3 mg bolus +2 mg kg-1 h-1 for 30 min) thrombolysis occurred in 15 out of 20 dogs. All 15 dogs reoccluded. 4. The second i.v. administration of rt-PA in the presence of either aspirin, ZM170809, ZD1542 or saline resulted in thrombolysis in all 20 dogs. 5. Both the combined thromboxane synthase inhibitor/receptor antagonist (ZD1542) and 5-HT2 antagonist (ZM170809) significantly (P < 0.05) reduced the time taken to lyse the thrombus compared with the saline group. The times were 14.4 +/- 2.7 min, 18.0 +/- 3.9 min and 36.8 +/- 6.2 min for ZD1542, ZM170809 and saline respectively. 6. Aspirin did not offer any additional benefit to using rt-PA alone. The times to thrombolysis were 36.8 +/- 8.4 min for aspirin and 36.8 +/- 6.2 min for the saline group. 7. The number of dogs in which the circumflex coronary artery reoccluded within 60 min of terminating the second infusion of rt-PA were five for saline, four for aspirin, two for ZD1542 and two for ZM170809. 8. These results indicate that both ZD1542 and ZM170809 are more effective adjuncts than aspirin in thrombolysis and may provide an improvement in current clinical practice.

Animals↗

PubMed1994

Assessment of the labeling index of cohorts of the anterior pituitary cell population in phenobarbital-treated male rats by a double immunohistochemical technique for bromodeoxyuridine and pituitary hormones.

A previous study demonstrated that administration of phenobarbital for up to 7 days to male AP Wistar rats caused alterations in labeling indices (LIs) of several different tissues as determined by immunohistochemical visualization of bromodeoxyuridine (BrdU) incorporation into S-phase nuclei. The pivotal role of the pituitary gland in the function of the endocrine system and changes in circulating hormone levels that result from administration of xenobiotics prompted our consideration of the possible changes in LIs of individual cohorts of the anterior pituitary cell population that may occur as a specific functional adaptation during phenobarbital administration. We evaluated the LIs of individual anterior pituitary cell cohorts by modifying a double immunohistochemical staining method for bromodeoxyuridine and pituitary hormones using a sequential peroxidase-anti-peroxidase (PAP)/alkaline phosphatase-anti-alkaline phosphatase (APAAP) method employing diaminobenzidine and New Fuchsin chromogens, respectively. The method was robust and reproducible. Differences were noted in individual anterior pituitary cohort LIs between control and phenobarbital-treated groups, although no statistically significant difference was evident. We conclude that no detectable effects on individual cohort LIs were induced by treatment with phenobarbital for up to 7 days and that any functional adaptation to treatment was associated with increased hormone release. We believe that the visualization, identification, and quantitation of replicating cells in specific hormone-positive cohorts of the anterior pituitary cell population provide opportunities for understanding the influence of xenobiotics and disease processes on pituitary function.

Animals↗

PubMed1993

The influence of phthalate esters on Leydig cell structure and function in vitro and in vivo.

Phthalate esters are widely used in the manufacture of plastics and have been shown to cause testicular toxicity, purportedly, by targeting the Sertoli cell alone. Recent evidence, however, indicates that a paracrine control exists between Sertoli and Leydig cells and the breakdown of one component of this relationship is therefore detrimental to normal function. However, no data that explore the influence of testicular toxins on Leydig cell structure and function have been published hitherto. The preliminary studies reported here were initiated to test the hypothesis that phthalate intoxication may adversely alter Leydig cell structural and functional integrity. Four phthalate esters, namely, di(2-ethylhexyl) phthalate (DEHP, di-n-pentyl phthalate (DPP)., di-n-octyl phthalate (DOP), and diethyl phthalate (DEP) were investigated in vivo and their monoesters (MEHP, MPP, MOP, and MEP, respectively) in vitro for indications of Leydig cell toxicity in the rat. Rats were dosed by oral gavage with 2 g phthalate diester/kg/day in corn oil vehicle for 2 days, while Leydig cell primary cultures were incubated with 1,000 microM monoester for 2 hr. Light and electron microscopy were undertaken to determine the type and degree of any changes. Phthalate esters exerted a direct effect on Leydig cell structure and function (as determined by testosterone output) with correlation of the in vitro and in vivo effects of MEHP (DEHP) and MOP (DOP). No effects on Leydig cell structure or function were seen with MPP (DPP), although Sertoli cell cytoplasmic rarefaction and vacuolation were observed in vivo. DEP produced Leydig cell ultrastructural alterations in vivo. We conclude that individual phthalate esters may exert effects on both Sertoli and Leydig cells or one cell type alone.

Animals↗

PubMed1993

Morphological assessment of ethyl choline mustard aziridinium-induced neurotoxicity in rat brain reaggregate cultures.

Foetal rat brain reaggregate cultures have been employed to investigate the morphological changes associated with the neurotoxic action of ethylcholine mustard aziridinium (ECMA). In a companion study we provided evidence for apparent selective cholinergic neurotoxicity. Exposure of 9-day-old cultures to 12.5 microM ECMA for 3 days produced dilatation of selected axon preterminals and terminals in the outer core tissue layer. Axoplasm in these dilated terminals was electron lucent and contained a flocculent, plasma-like material with remnants of the smooth endoplasmic reticulum. Their synaptic vesicle content was much reduced or, absent. Microglial cells were engaged in phagocytosis of these effete structures and a few necrotic neurons were enveloped by glial processes. Exposure to 50 microM ECMA produced widespread necrosis with some surviving neurons, surrounded by the still-persisting capsular layer. Treatment with 100 microM ECMA generated a greater extent of tissue necrosis, with only a few surviving neurons and glial cells being contained within the necrotic tissue mass. Reaggregates frequently disintegrated following capsule loss. Our results indicate that the initial morphological manifestation of ECMA-induced toxicity is dilatation of axon terminals, that are probably of cholinergic origin and are targeted due to their possession of the high-affinity choline transport system which is unique to these neurons.

Animals↗

PubMed1993

Assessment of the influence of subacute phenobarbitone administration on multi-tissue cell proliferation in the rat using bromodeoxyuridine immunocytochemistry.

The effects of daily administration of phenobarbitone on the mitotic rates of several tissues were investigated by bromodeoxyuridine (BrdU) immunocytochemistry. Phenobarbitone (80 mg/kg per day) was dosed to AP Wistar male rats for up to 7 days and BrdU (10 mg/ml) was given by infusion at a rate of 10 microliters/h via subcutaneously implanted osmotic minipumps for 2 days prior to necropsy on days 1, 2, 3, 5 and 7. BrdU-labelled nuclei were visualised by peroxidase-antiperoxidase immunocytochemistry and counts of the numbers of labelled cells (labelling index, LI%) made from at least 1000 cells per tissue section(s). The LIs of several tissues (testis, adrenal cortex and medulla, kidney distal convoluted tubule and exocrine pancreas) showed no statistical difference by comparison with controls. Several tissues exhibited characteristic responses to phenobarbitone administration. Pituitary and endocrine pancreas LIs were decreased while those of thyroid, liver and kidney proximal convoluted tubule were increased. The pattern of LI increase was unique to each tissue with liver (median and lateral lobes) increased two-fold on day 3 and returning to control levels thereafter while kidney proximal tubule LI rose gradually with time and remained elevated on day 7. Thyroid LI on day 1 was almost double that of day 0 control and increased steadily thereafter. These data illustrate the varied responses of different tissues to phenobarbitone exposure, namely, depression and stimulation of mitosis. The causation of these functional changes is discussed in relation to direct and indirect effects on functional parameters, especially enzyme induction, alterations in hormonal and growth factor status and receptor regulation.

Adrenal Glands↗

PubMed1993

Phenobarbital-induced hepatocellular proliferation: anti-bromodeoxyuridine and anti-proliferating cell nuclear antigen immunocytochemistry.

We report modifications to immunocytochemical detection procedures for proliferating cell nuclear antigen (PCNA) which permit its identification in liver samples previously fixed for BrdU immunocytochemistry. Both methods have been used for the assessment of phenobarbital-induced cell proliferation in rat liver. The difficulties associated with the hitherto unsuccessful application of PCNA immunocytochemical methods to tissues fixed in formalin for BrdU visualization were overcome by epitope unmasking with acid hydrolysis, extension of primary antiserum (PC10) incubation, and employment of streptavidin-ABC-HRP. BrdU delivery via osmotic minipumps for 48 hr before euthanasia, followed by fixation in cold formalin for 14 days, yielded reliable and reproducible hepatocellular labeling and a peak of cell proliferation in all lobes on Day 3 (i.e., labeling during Days 1-3) of dosing with 80 mg/kg/day phenobarbital. Labeling indices (LI) of both control and phenobarbital-treated liver were lower in the left and right median lobes as compared with the lateral lobes. In sections of the left lateral lobe from the same liver, PCNA immunocytochemistry revealed a peak of proliferative activity (about one third of the maximum LI generated by BrdU incorporation) on Day 1. These findings, together with the advantages and disadvantages of both techniques, are discussed in the context of their applications to different investigative requirements.

Animals↗

PubMed1992

Multinucleated giant cells in primary cultures derived from canine bone marrow--evidence for formation of putative osteoclasts.

Mononucleated cells derived from canine bone marrow were maintained in vitro for up to 6 weeks. The culture characteristics and development of these cells were evaluated by histological, ultrastructural and histochemical methods. Within 1 week the cells had fused together to form flattened, multinucleated cells. Further fusing with one another and other mononucleated cells produced large (diameters more than 300 microns), multinucleated cells which frequently contained more than 50 nuclei per cell and exhibited ultrastructural and histochemical features that were strikingly similar to those displayed by osteoclasts. The confluent monolayer of mono- and multinucleated cells present at 4 weeks had, by the sixth week, become altered such that fibroblast overgrowth obliterated all other cells. During the development of the culture adipocytes became differentiated from mononuclear cells and frequently were located within spherical multicellular aggregates (spheroids). Functional assessments were employed to investigate whether the multinucleated cells generated in this way, represented osteoclast-like cells, or alternatively, were related to macrophage polykarya as found in foreign body granulomata in vivo. Neither resorption pits on sperm whale dentine slivers (diagnostic of osteoclasts), nor formation of granulomata in vitro, were observed. We believe that the present results indicate that the multinucleated cells generated from canine bone marrow mononuclear precursors in vitro, merit designation as osteoclast-like cells. Definitive characterisation however, must await further functional assessments of hormone responsiveness.

Animals↗

PubMed1989

Dithiobiuret neurotoxicity: an ultrastructural investigation of the lesion in preterminal axons and motor endplates in the rat lumbrical muscle.

2,4-Dithiobiuret was given i.p. to rats for 4 days at a daily dosage of 1 mg/kg and the development of the lesion associated with neuromuscular dysfunction studied in hindlimb lumbrical muscles. The first morphological indication of neurointoxication was the appearance in some motor endplates of masses of branching tubular smooth endoplasmic reticulum (SER) on day 2 which correlated with the initial functional disturbances. By the 3rd day, most motor endplates were distended by accumulations of dense-cored, lucent and synaptic vesicles, abnormally swollen mitochondria, intermediate filaments and branching, tubular SER. Evidence of collateral axonal sprouting was seen first at this time. On days 4 and 5, many motor endplates were markedly enlarged and showed axoplasmic organelle congestion. A significant increase in synaptic vesicle size was noted at these times in some terminals. Interposition of Schwann cell processes between the pre- and postsynaptic membranes and terminal retraction was now evident. Some intramuscular nerves showed hydropic Schwann cell cytoplasm with separation of the outermost myelin lamellae, mitochondrial swelling and adaxonal vacuoles as early as the 1st day. Proliferation and segregation of SER around central cores of neurofilaments was seen in myelinated nerve fibres and preterminals on the 3rd day. At this and later times accumulations of SER and swollen mitochondria were found at sites of axonal varicosities and at the paranodal constrictions at nodes of Ranvier. These ultrastructural data are discussed with regard to reduced terminal Ca2+ content (demonstrated by oxalate-pyroantimonate cytochemistry) and compared with the sequelae of botulinum intoxication.

Animals↗

PubMed1988

The role of ultrastructural investigations in neurotoxicology.

The ways in which ultrastructural approaches have been applied to the investigation of xenobiotic-induced toxicity of the nervous system have been briefly reviewed. These approaches have been grouped in 3 broad areas, viz. morphology, function and composition. Firstly, morphological approaches permit the visualisation of changes in intercellular relationships, the identification of the subcellular target(s) of a xenobiotic substance and the discrimination between what may appear ostensibly to be identical cellular responses to one or more chemically distinct toxins. Secondly, functional approaches using, e.g. cytochemistry, ion precipitation, immunocytochemistry and autoradiography provide indications of metabolic state, the identity or the intra- or extracellular location of the "reactive species". Thirdly, those approaches, viz. electronprobe X-ray microanalysis and electron energy loss spectroscopy which provide information of the elemental composition of cells and tissues permit an assessment of the subcellular distribution and compartmentalisation of endogenous substances and toxic or therapeutic xenobiotics. In concert, ultrastructural approaches possess the ability to contribute unique information on the effects of exposure of cells of the nervous system to toxic substances and so direct further investigation towards an understanding of the mechanism of action.

Animals↗