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W E Thomas

Publications and source records attributed to W E Thomas.

At least 55 records · Page 3Linked to original sources
PubMed1990

Method for the identification of brain macrophages/phagocytic cells in vitro.

The use of labelled latex beads, with acute incubation conditions, for the identification of active macrophages in mixed cell cultures based on their phagocytic activity is described. Fluorescent beads provided the best results and selectively labelled active macrophage cells in cultures of blood monocytes. When this technique was applied to primary cultures of rat cerebral cortex, a specific cell type was significantly labelled. This was a small round cell, previously uncharacterized, which in addition to phagocytic activity indicated by the ingestion of beads also possessed macrophage biochemical markers. Thus, the procedure appears useful for phagocytic macrophage identification in vitro, and should be generally applicable to any tissue culture system. Additionally, this procedure can be rendered compatible with cell viability and, therefore, be utilized for long-term monitoring of macrophages.

Animals↗
PubMed1990

Characterization of the dynamic nature of microglial cells.

Dynamic properties of ramified microglia were investigated in tissue cultures of rat brain cells. Microglia were identified in viable cultures based on previously determined aspects of their morphology and location, and this identification was confirmed through immunohistochemical staining for type-three complement receptors. When living microglial cells were monitored using time-lapse video recording, an extremely dynamic nature was revealed. These cells exhibited morphological alteration, surface and cytoplasmic activity, and migration. All of these properties were both constant and rapid, with individual cells being capable of assuming a completely different overall morphology within a period as short as 5-10 min. These dynamic properties were consistently observed in microglia and appeared specific to this cell type. Thus, ramified microglia appear to possess a unique and highly dynamic nature, and this feature is proposed as a potential marker for these cells. Additionally, the significance of microglial cellular dynamics in the functional role of this cell population in vivo is considered.

Animals↗
PubMed1990

Morphological diversity of ependymal cells in tissue culture.

Ependymal cells were visualized in primary cultures of cerebral cortex from rat using an immunohistochemical staining technique. Five different morphological subtypes of cuboidal ependyma were recognized: 1) round, 2) triangular, 3) columnar, 4) cone- and spindle-shaped, and 5) large pleomorphic cells. These cells varied in size and almost all possessed cilia. Two distinct forms of tanycyte ependyma were detected based on the presence of cilia. These features reflect a significant level of development of the ependymal cells in culture and may correspond to functional diversity within this group.

Animals↗
PubMed1990

Squamous cell carcinoma of the stomach following gastric surgery.

The development of adenocarcinoma in the gastric remnant following surgery for peptic ulceration is well recognised. However, squamous cell carcinoma of the stomach is rare, with only 80 cases being reported in the literature and none reported following gastric surgery. We report a case in which a squamous cell carcinoma with only minute areas of adenocarcinoma developed 22 years after surgery for a duodenal ulcer.

Adenocarcinoma↗
PubMed1990

Gastrointestinal malignancies as a complication of chronic myeloid leukaemia.

A 70-year-old patient is presented who, after chemotherapy for chronic myeloid leukaemia, developed two separate gastrointestinal malignancies. His family history indicated a strong family tendency towards neoplasia, and it is speculated that this predisposition may have been potentiated by the chemotherapy or the leukaemic process itself. It is stressed that, in such cases of multiple malignancy, each condition should be treated on its own merits.

Adenocarcinoma↗
PubMed1989

Further studies on the identification of microglia in mixed brain cell cultures.

The investigation of brain microglia in primary cultures of dissociated cerebral cortical cells has been continued here utilizing a histochemical procedure for thiamine pyrophosphatase, which selectively stains microglia in whole tissue. This procedure also selectively stained a subpopulation of cells in the cortical cultures. The stained cells were small and exhibited quite variable morphology; from these features, a corresponding cell population could be identified in viable cultures. The stained cells, which were distinct from previously identified macrophage forms, were also distinguished from similar appearing cell types--small neurons and oligodendrocytes. Based on their staining properties, morphology, and distinction from other cell types, the identified cells are proposed as equivalents of ramified microglia.

Animals↗
PubMed1988

Ontogeny of dopaminergic function in the rat midbrain tegmentum, corpus striatum and frontal cortex.

Ontogenic development of the dopaminergic system in rat brain was investigated. This was accomplished by monitoring changes in postsynaptic dopamine receptor formation and presynaptic dopamine content in the midbrain tegmentum, frontal cortex and corpus striatum from the 18th day of gestation through adulthood. The dopamine antagonist spiperone was used as the binding ligand to quantitate receptor number while dopamine content was measured chromatographically. [3H]Spiperone binding kinetics in adult animals revealed that the maximum number of receptor sites (Bmax) was 160, 900 and 597 fmol/mg protein in midbrain tegmentum, frontal cortex and corpus striatum, respectively, while the corresponding equilibrium constant (Kd) values were 0.15, 0.52 and 0.15 nM. During the course of development, the affinity for spiperone binding in corpus striatum and frontal cortex did not change significantly, while in midbrain tegmentum the binding affinity in younger animals was significantly lower. Results from competitive inhibition experiments using various serotonergic and dopaminergic antagonists suggested that at all ages dopamine D2-receptors were responsible for spiperone binding in corpus striatum and midbrain tegmentum. In frontal cortex, binding properties consistent with D2-receptors were observed in non-adult animals; by the time adulthood was reached, however, spiperone binding characteristics were altered and appeared to correspond to serotonin sites. The developmental patterns of the dopaminergic markers were different in all 3 tissues. Adult receptor levels were achieved very early in midbrain tegmentum, while increases in receptor number continued in corpus striatum and frontal cortex, at different rates, throughout the postnatal period. A marked increase in dopamine in corpus striatum occurred during the second and third postnatal weeks and the transmitter content remained relatively constant after this time. Transient fluctuations in endogenous dopamine during the postnatal period were observed in midbrain tegmentum and frontal cortex. A general feature of the ontogenic pattern in all tissues appeared to be increases in dopamine receptor preceding increases in dopamine synthesis. A hypothesis on the developmental regulation of dopamine neurons was derived.

Aging↗
PubMed1988

Acquired dysfibrinogenaemia masquerading as disseminated intravascular coagulation in acute pancreatitis.

Acquired dysfibrinogenaemia as the cause of coagulation abnormalities occurred in a case of acute pancreatitis. Initial coagulation studies showed a prolonged thrombin time and increased concentrations of serum fibrinogen/fibrin degradation products and plasma D-dimer. Further studies on purified fibrinogen showed evidence of degradation of the C-terminal ends of the A-alpha chains, which, it is suggested, resulted from the action of circulating pancreatic proteases. Fibrin polymerisation was thus shown to be impaired, which explains the prolongation of the thrombin time. There was a temporal relation between increased amylase activities and the prolonged thrombin time, both of which returned to normal three weeks after admission. Acquired dysfibrinogenaemia may be an underrecognized phenomenon in acute pancreatitis and may lead to misinterpretation of coagulation test abnormalities.

Acute Disease↗
PubMed1987

Evidence for ADP-ribosylation in the mechanism of rapid thyroid hormone control of mitochondria.

Triiodothyronine in vitro at concentrations between 10(-13) and 10(-11) M very rapidly activates oxidative phosphorylation in hypothyroid rat liver mitochondria. Comparing the concentrations of hormone with estimates of the amounts of respiratory chain components present suggests that this activation may involve an amplification mechanism. Here we present evidence that while no changes in phosphorylation were detected following hormone administration, nicotinamide, an inhibitor of mono ADP-ribosylation reported to occur rapidly and reversibly in mitochondria, prevented activation by hormone. Moreover incubation with nicotinamide of euthyroid mitochondria and derived intact inner membrane vesicles revealed lowered ADP/O ratios under the same conditions as shown by hypothyroid preparations. While this lesion could be reversed simply by washing the intact mitochondria, the membrane vesicles required triiodothyronine addition.

Adenosine Diphosphate Ribose↗
PubMed1987

The influence of nanomolar calcium ions and physiological levels of thyroid hormone on oxidative phosphorylation in rat liver mitochondria. A possible signal amplification control mechanism.

Using different conditions mitochondria from hypothyroid rats can show both unchanged ADP/O ratios and lowered ADP/O ratios without evidence of uncoupling when compared with euthyroid controls. Raising the free Ca2+ concentration to around 25 nM progressively lowered the ADP/O ratio in hypothyroid but not in euthyroid mitochondria. Ruthenium Red did not alter this behaviour and further increasing the Ca2+ concentration to levels below those which stimulate State 3 respiration had no additional effect. Measurements of the free Ca2+ concentration in the mitochondrial suspending medium using a Quin 2 fluorescence assay showed that the mitochondria did not buffer the free Ca2+ at these low concentrations. At 25 nM-free Ca2+, addition of 10-13) M-T3 to hypothyroid mitochondria produced an immediate and significant increase in the ADP/O ratio without altering the free Ca2+ concentration. The hormone effect was maximal by 10(-11) M. The concentration of ATP synthetase can be estimated to lie at about 10 nM in these experiments. Hence it appears possible that a substantial amplification of the hormone signal may have taken place. Comparison with binding studies suggests that T3 may have been maximally stimulating when somewhat less than half its receptor sites had been filled. The possible mechanisms by which this receptor mediated alteration of the ADP/O ratio might be achieved are discussed.

Adenosine Diphosphate↗
PubMed1987

Identification of somatostatin-containing neurons in primary cultures of rat cerebral cortex.

The expression of somatostatin-like immunoreactivity was investigated in primary cultures of dissociated cerebral cortical tissue from the rat. A subpopulation of neurons in the cortical cultures exhibited intense staining for somatostatin. These somatostatin-immunoreactive neurons corresponded to 1.25% of the total neuronal population. Stained neurons were typically small with a soma size of 10-20 micron. The majority of somatostatin-containing cells had stellate and bipolar morphology, with the bipolar class predominating.

Animals↗
PubMed1987

Ultrastructure of ependymal cells in primary cultures of cerebral cortex.

Ultrastructural features of ependymal cells growing in primary cultures of dissociated cerebral cortical tissue were investigated using electron microscopy. The ependyma exhibited a specific orientation in tissue culture such that the cell surface corresponding to the apical surface in situ was directed toward the culture medium. The membrane on the apical surface of cultured ependyma was characterized by the presence of cilia and microvilli. The lateral margins were marked by a variety of junctions: zonula occludens, zonula adherens, and membrane interdigitations. The cell cytoplasm contained pleomorphic mitochondria, Golgi profiles, clusters of ribosomes, rough endoplasmic reticulum, and particularly profuse scattered microfilaments and microtubules. These features support the identity of the cells as ependymal in the cultures and establish them as a relatively accurate reflection of ependyma in situ.

Animals↗
PubMed1987

Presence and development of ependymal cells in primary tissue cultures derived from embryonic rat cerebral cortex.

Using indirect immunohistochemistry, a secondary antibody was detected in a commercial preparation of antiserum against vasoactive intestinal polypeptide. The secondary antibody selectively stained ependymal cells during the first 3 weeks in vitro in cultures of dissociated cerebral cortical tissue from rat. This staining provided a convenient mechanism for investigating the development and properties of these cells in cultures. The overall level of immunofluorescent staining during the initial 3-week time period appeared to directly reflect the proliferation and development of ependymal cells. Fluorescent staining was initially detected in cells which appeared to correspond to matrix cells or progenitor cells from the ependyma. These cells underwent rapid cell division, as evidenced by distinct morphological stages, to yield daughter cells which were the precursors of mature ependymal cells. Three different morphological classes of mature ependymal cells were observed in the cortical cultures. These classes corresponded to the cuboidal, tanycyte and secretory ependymal cell types described in vivo. Direct counting of stained cells showed that these morphological classes were represented in the cultures in roughly the same proportions seen in vivo (cuboidal 75%, tanycyte 19% and secretory 6%). The temporal aspects of ependyma development permitted the staining of developmental stages corresponding to the various morphological classes or types. The morphological sequence of development of the cuboidal cell and tanycyte from the precursor cell or matrix cell--daughter cell was determined. These two cell types displayed marked differences in their developmental sequence. The developmental sequence of the secretory cell could not be resolved; however, what appeared to be multiple morphological subtypes of this cell class were encountered.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

The status of the study of invertebrate neurons in tissue culture--phylum Arthropoda.

1. Neurobiological studies employing tissue culture are discussed for all invertebrate organisms in phylum Arthropoda and above. Only arthropod species have been investigated in these studies. 2. The members of phylum Arthropoda utilized were Periplaneta, Locusta, Drosophila, and Schistocerca. 3. Some of the initial studies of nerve cells in tissue culture were performed with Periplaneta and Drosophila; these studies were primarily concerned with differentiation, growth and development. 4. Cultured neurons from cockroach and locust have been used in pharmacological investigations of neurotransmitter receptors. 5. Embryos of the grasshopper Schistocerca were cultured in series of developmental studies related to axon guidance and peripheral nerve formation. 6. Recent studies with Drosophila neurons in vitro have applied a genetic approach to the investigation of molecular properties and function of the axonal sodium channel. 7. An overall view of neuronal tissue culture of invertebrates and analysis of the various areas of research is presented.

Animals↗
PubMed1987

On the status of the study of invertebrate neurons in tissue culture--phyla Mollusca and Annelida.

The utilization of tissue culture in neurobiological studies is discussed for all phyla phylogenetically preceding Phylum Arthropoda. Only two phyla, Mollusca and Annelida, are represented in such studies. The members of Phylum Mollusca which have been so investigated are Aplysia, Helisoma and Lymnaea. The mollusc Aplysia has been used to investigate several processes, including neurosecretion, synaptic transmission and synaptogenesis. Helisoma was employed to study factors regulating neurite growth and the specificity of synapse formation; mechanisms of neurite growth were investigated in the snail Lymnaea. The only member of Phylum Annelida involved in appropriate studies has been the leech Hirudo. This organism was used to investigate axonal regeneration and synaptic mechanisms.

Animals↗
PubMed1987

Identification of microglia in primary cultures of mixed cerebral cortical cells.

Microglia were investigated in tissue cultures of dissociated cerebral cortex from embryonic rat. Three different forms of microglia were identified in relatively mature cultures on the basis of morphological criteria, esterase histochemistry, and immunohistochemical staining for Fc receptors. Two of these forms corresponded to the amoeboid and ramified microglia; the amoeboid form stained intensely for esterase activity and ramified cells possessed Fc receptors. The third microglial cell form was distinguished by its morphological properties and was characterized by the presence of numerous filopodial processes. This morphological form occasionally possessed esterase staining and was the predominate type of microglia observed in the cultures. The identification of these cell types supports the potential use of this culture system to investigate functional aspects of microglia and their interaction with other brain cells.

Animals↗
PubMed1987

Cooling prevents ischaemic testicular damage after spermatic cord clamping in rats.

A controlled trial was conducted on four groups of seven rats to evaluate any beneficial effect of cooling to 15 degrees C on testicular ischaemia induced by clamping of the spermatic cord for 2, 4, 6 or 8 h. At operation the microscopic appearance of the testes on unclamping was a poor guide to ultimate viability, whereas by the third day macroscopic and microscopic appearances concurred. When killed on the third day, testicular histology demonstrated that increasing periods of clamping led to gross ischaemia and infarction when testes were maintained at 37 degrees C, and this was reduced greatly by testicular cooling. For each period of clamping, maintenance of spermatogenesis, expressed in terms of Johnsen's histological scores, was significant (P less than 0.01), being 2 (37 degrees C) vs 5.3 (15 degrees C) for 8-h clamping. It is proposed that testicular cooling should be used during autotransplantation of testes in humans.

Animals↗