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Biomedical subjects

M Hill

Publications and source records attributed to M Hill.

At least 19 recordsLinked to original sources
PubMed1992

Expression of TTK, a novel human protein kinase, is associated with cell proliferation.

We have isolated the full-length sequence for a unique human kinase, designated TTK. TTK was initially identified by screening of a T cell expression library with anti-phosphotyrosine antibodies. The kinases most closely related to TTK are the SPK1 serine, threonine and tyrosine kinase, the Pim1, PBS2, and CDC2 serine/threonine kinases, and the TIK kinase which was also identified through screening of an expression library with anti-phosphotyrosine antibodies. However, the relationships are distant with less than 25% identity. Nevertheless, TTK is highly conserved throughout phylogeny with hybridizing sequences being detected in mammals, fish, and yeast. TTK mRNA is present at relatively high levels in testis and thymus, tissues which contain a large number of proliferating cells, but is not detected in most other benign tissues. Freshly isolated cells from most malignant tumors assessed expressed TTK mRNA. As well, all rapidly proliferating cell lines tested expressed TTK mRNA. Escherichia coli expressing the complete kinase domain of TTK contain markedly elevated levels of phosphoserine and phosphothreonine as well as slightly increased levels of phosphotyrosine. Taken together, these findings suggest that expression of TTK, a previously unidentified member of the family of kinases which can phosphorylate serine, threonine, and tyrosine hydroxyamino acids, is associated with cell proliferation.

Amino Acid Sequence↗
PubMed1992

Major histocompatibility complex independent clonal T cell anergy by direct interaction of Staphylococcus aureus enterotoxin B with the T cell antigen receptor.

The Staphylococcal enterotoxin superantigens stimulate vigorous responses in T cells bearing certain T cell antigen receptor (TCR) V beta regions. In addition to activation, these superantigens also impart negative signals to T cells resulting in a profound state of unresponsiveness or anergy. The Staphylococcus aureus enterotoxins (SE) B and C2 bind to a closely related site on major histocompatibility complex (MHC) human leukocyte antigen (HLA)-DR1 molecules. Only SEB, however, interacts with the TCR V beta 3 region of HA1.7, a human HLA-DR1 restricted T cell clone specific for influenza haemagglutinin. In competition experiments, we demonstrated that the induction of anergy in HA1.7 by SEB is unaffected by the presence of SEC2. These results suggest that SEB-induced anergy is MHC independent and involves a direct interaction between the TCR and SEB. To resolve definitively whether SEB binds directly to T cells in the absence of MHC class II molecules, the cDNAs encoding the HA1.7 TCR were transfected into an MHC class II-negative human T cell line. The addition of SEB to these transfectants resulted in the downregulation of cell surface TCR expression, an increase in the concentration of intracellular calcium ions, the production of lymphokines, and reduced responsiveness to a subsequent challenge with SEB. We conclude that SEB interacts directly with the TCR in the absence of cointeraction with MHC class II molecules, and that this interaction may induce anergy in HA1.7.

Amino Acid Sequence↗
PubMed1992

Hypertension during reduction of long-term steroid therapy in young subjects with asthma.

Corticosteroids can induce hypertension, which reportedly remits as the drug is withdrawn. We studied nine patients with steroid-requiring asthma, aged 9 to 16 years, who had elevated blood pressures during corticosteroid treatment. Unlike in previous studies, all nine patients developed hypertension during corticosteroid reduction. Diastolic blood pressures were 50 to 84 mm Hg during maximum corticosteroid therapy (1 to 4 mg/kg/day); these values were in the normal range for seven of the nine patients and in the high normal range for the other two patients. Maximum diastolic pressures were 100 to 120 mm Hg, 1 to 8 weeks after corticosteroid reduction was started. Hypertension occurred at 0% to 70% of their maximum corticosteroid dose. Corticosteroid reduction was the only medication change. Renal causes of hypertension were excluded. Six patients had levels of renin and aldosterone measured before onset of treatment. All six patients had elevated levels of renin, and five patients had elevated levels of aldosterone. Blood pressure elevations were resistant to diuretic therapy but responded rapidly to angiotensin-converting enzyme inhibitors. Caretakers of subjects with asthma need to be aware that hypertension may occur both during maximum corticosteroid use and during corticosteroid reduction.

Adolescent↗
PubMed1992

Asthma pathogenesis and the implications for therapy in children.

Gaining greater insight into the pathogenesis of asthma has redefined the approach to treatment of children with asthma. Clearly, the Expert Panel of the National Heart, Lung, and Blood Institute National Education Program has played a major role in taking the message to a wide audience of health care providers. Although only early trends are evident at this point in time, within several years therapeutic trends underway currently will be more commonplace, and we may observe how asthma continues to impact society and our health care system. The approach to therapy will continue to evolve and most likely be controversial for years to come.

Asthma↗
PubMed1992

Improved detection of antibodies to hepatitis C virus in dialysis patients using a second-generation enzyme immunoassay.

We tested serum samples from 99 patients undergoing maintenance hemodialysis for hepatitis C virus (HCV) antibodies using a first-generation, licensed anti-HCV enzyme immunoassay (EIA) and a second-generation anti-HCV EIA that detect three gene products c100-3, NS3, and core. Specimens that were repeatedly reactive by either or both screening assays were further evaluated by testing with supplemental EIAs and a dot blot immunoassay. There was 87.9% agreement between the licensed HCV EIA and the HCV EIA second generation. HCV EIA Second Generation detected 10 more positive specimens than HCV EIA, for an increase in detection from 33.3% (33/99) to 43.4% (43/99). We conclude that HCV EIA Second Generation improves detection of HCV infection in hemodialysis patients.

Adult↗
PubMed1992

T-lymphocyte proliferation: tyrosine kinases in interleukin 2 signal transduction.

Interleukin 2 (IL-2)-induced tyrosine phosphorylation appears to play a major role in IL-2-induced cellular proliferation. Several intracellular substrates including the beta chain of the IL-2 receptor complex (IL-2R beta), raf, MAP2 kinase, the regulatory 83 kDa subunit of phosphatidylinositol-3 kinase and S6 kinases are substrates for the IL-2 receptor activated kinase(s). However, none of the identified members of the IL-2 receptor complex exhibits intrinsic tyrosine kinase activity. Therefore, the IL-2R complex must activate intracellular tyrosine kinases. We have demonstrated that specific tyrosine and serine/threonine kinases are coprecipitated with IL-2 receptor constructs that mediate IL-2-induced cell proliferation but not with those that do not. The IL-2-activated tyrosine kinase appears to be associated with a serine and proline rich intracellular domain which is highly conserved between IL-2R beta and the erythropoietin receptor. Although the responsible kinase has not been identified, lck, fyn, fgr, ltk, hck and lyn can be ruled out as obligatory mediators. Using methods to clone tyrosine kinases from T cells, we have identified potential candidate kinases, including several which had not been known to be expressed by T lymphocytes as well as several unique kinases which had not been previously identified in any cell type.

Amino Acid Sequence↗
PubMed1992

Neither the LCK nor the FYN kinases are obligatory for IL-2-mediated signal transduction in HTLV-I-infected human T cells.

IL-2 is one of the principal growth factors regulating the proliferation of T lymphocytes. Although two independent IL-2-binding molecules have been molecularly cloned and shown to participate in the formation of a high affinity receptor complex, their primary structures do not suggest a specific mechanism for IL-2 growth signal transduction across the cell membrane. Neither IL-2 receptor subunit contains an intrinsic kinase domain; nevertheless, tyrosine phosphorylation of various intracellular substrates is one of the first biochemical changes observed following activation of the IL-2 receptor (IL-2R). Both serine/threonine and tyrosine kinases can be co-precipitated as part of the IL-2R complex suggesting that the IL-2 signalling may involve the activation of non-covalently associated intracellular kinases. However, controversy exists as to which kinases are involved in IL-2 signal transduction; in particular, which kinase(s) mediates the first or proximal event(s) in the signalling process. Activation of the IL-2R leads to serine and threonine phosphorylation of the SRC tyrosine kinase family member, LCK, and an increase in LCK tyrosine kinase activity. Furthermore, LCK can be co-immunoprecipitated with the beta chain of the IL-2R indicating its association with the receptor complex. IL-2 has also been reported to increase FYN kinase activity and to alter its association with the 85 kDa subunit of phosphatidylinositol-3 kinase thus suggesting a role for FYN in IL-2 signal transduction. However, in this report, we now demonstrate that neither LCK nor FYN are obligatory for IL-2-induced growth of HTLV-I-infected human T cells. Lack of expression of LCK or FYN in the HTLV-I-infected T cell lines was demonstrated by a combination of Northern blotting, polymerase chain reaction, Western blotting, and in vitro kinase activity. Despite the absence of LCK or FYN, IL-2 induced similar patterns of rapid tyrosine phosphorylation. Similar results were observed in cell lines lacking expression of the LYN, FGR, HCK, and LTK tyrosine kinases. Thus, none of these tyrosine kinases alone appears to be required for growth signalling through the IL-2R in the HTLV-I-infected T cell lines analyzed. The findings raise the possibility that an, as yet, unidentified tyrosine kinase is involved. Alternatively, this biological signalling system may exhibit remarkable redundancy whereby several different tyrosine kinases may be capable of associating with the IL-2R complex and mediating intracellular signalling.

Cell Division↗
PubMed1992

Developmental regulation of sialoadhesin (sheep erythrocyte receptor), a macrophage-cell interaction molecule expressed in lymphohemopoietic tissues.

Stromal macrophages in lymphohemopoietic tissues express novel macrophage-restricted plasma membrane receptors involved in nonphagocytic interactions with other hemopoietic cells. One such receptor with lectinlike specificity for sialylated glycoconjugates on sheep erythrocytes and murine hemopoietic cells has been characterized immunochemically and termed sialoadhesin. We have examined sialoadhesin expression during mouse development to learn more about its regulation and function. Immunocytochemical, rosetting, and Western blot studies show that sialoadhesin is first detected on fetal liver macrophages on day 18 of development, 7 days after numerous F4/80+ macrophages are found within erythroblastic islands. In spleen and bone marrow, sialoadhesin appears between day 18 and birth, in parallel with myeloid development. Strongly labeled macrophages in the marginal zone of spleen, characteristic of adult lymphoid tissues, appeared gradually between 1-4 weeks after birth, as the white pulp became enlarged. Isolation of fetal liver macrophages at day 14 confirmed that sialoadhesin was not involved in the binding of erythroblasts, which is mediated by a distinct cation-dependent receptor (Morris et al., 1988, p. 649). Sialoadhesin could be expressed by isolated fetal liver macrophages after cultivation in adult mouse serum, a known source of inducer activity, but was not dependent on the presence of this inducer, unlike adult-derived macrophages. Fetal plasma contained inducing activity on day 13, but adult levels were not reached until 2 weeks postnatally. These studies show that sialoadhesin is differentially regulated compared with the erythroblast receptor and F4/80 antigen, that it is not required for fetal erythropoiesis, and that its induction on stromal macrophages is delayed until the onset of myeloid and lymphoid development. Sialoadhesin provides a marker to study maturation and functions of macrophages during ontogeny of the lymphohemopoietic system.

Animals↗
PubMed1992

The suppression of the synthesis of a nuclear protein in cells blocked in G2 phase: identification of NP-170 as topoisomerase II.

Previous studies of a nuclear protein of molecular weight 170 kDa (NP-170) have shown it to have two interesting properties. First, NP-170 synthesis began in mid- to late S phase and became maximal in G2 phase. Second, the synthesis of NP-170 was suppressed in cells blocked in G2 phase following irradiation with 6.8 Gy (J. M. Holland et al., Radiat. Res. 122, 197-208, 1990). The molecular weight of NP-170 is the same as that of Topoisomerase II (Topo II), an enzyme involved in the alteration of DNA supercoiling status with a double-strand passing function. This study was undertaken to determine whether NP-170 could be Topo II. The results from the present study show that both the proteins have identical cell cycle synthesis patterns. The synthesis of both these proteins is suppressed following irradiation. NP-170 was found to be recognized by a Topo II antibody in both Western blots and immunoprecipitation. This study characterizes NP-170 as Topo II.

Autoradiography↗
PubMed1992

Rearrangement of the human tre oncogene by homologous recombination between Alu repeats of nucleotide sequences from two different chromosomes.

The rearranged region of the tre oncogene originating from chromosomes 5q23q31 and 18q12 was cloned from tumor genomic DNA, sequenced and aligned with wild-type sequences cloned from a normal human genomic library. In the breakpoint region each wild-type sequence contained two Alu repeats. The recombination occurred between the 3'-most Alu from chromosome 5 and the 5'-most Alu from chromosome 18 and, consequently, resulted in a hybrid Alu flanked with one Alu on either side. The recombinant joint was located to a 20-bp homology region in left arms of the Alu repeats involved in recombination. The same homology region was identified in the hybrid Alu of the rearranged tre. At its 5' extremity the homology region overlaps the B box of Alu-borne RNA polymerase III promoter. The 100% identity score in the region of homology suggests that the recombination process was conservative and not error prone.

Base Sequence↗
PubMed1992

A novel transcriptional unit of the tre oncogene widely expressed in human cancer cells.

Tre is a recombinant gene isolated from NIH3T3 cells transfected with human Ewing's sarcoma DNA. It is composed of three major genetic elements derived, 5' to 3', from human chromosomes 5, 18 and 17. We report here on transcripts from the 3' domain of tre. The transcripts were cloned from a cDNA library of cytoplasmic poly(A)+ RNA from tre-transfected NIH3T3 tumor cells. The complete cDNA sequence, 8201 nucleotides, possessed an unusually long non-coding region and a translatable region with two open reading frames. In one cDNA clone, the presence of two insertions suggested the possibility of alternative splicing. The sequence mapped to the centromere-proximal region of 17q. Transfection-tumorigenicity assays with the open reading frames subcloned into expression vectors were positive for the reading frame adjacent to the 5' non-coding region and negative for the second, downstream, reading frame and the possible alternatively spliced versions of both reading frames. Analysis of the 786 amino acid sequence deduced from the 5' reading frame predicted a highly hydrophilic protein with two charge clusters suggesting nucleic acid-binding properties. When used as probe, the cloned sequence detected RNA transcripts in a wide variety of human cancer cells regardless of their lineage of origin from different tissues, but not in human cells from normal tissue.

3T3 Cells↗
PubMed1991

Body temperature modulates the effect of platelet-activating factor (PAF) on airways responsiveness in the rabbit.

Platelet-activating factor (PAF) is a potent mediator known to cause bronchoconstriction and increase airways responsiveness. In vitro studies have shown that the effects of PAF on cell function can be very temperature-dependent. The aim of the current study was to investigate the effect of elevated body temperature on numbers of circulating cells and pulmonary function in anesthetized rabbits in response to PAF. PAF was given intravenously, at a dose of 1.2 micrograms/kg hour, whereas the control experiments were performed after the animals received a saline infusion. Alteration of airways function was assessed by measuring specific pulmonary conductance (SGL) and dose-response relationships to inhaled histamine, where airways responsiveness was expressed as the effective concentration causing 50% of maximal change in specific airways conductance (EC50SGL). The rabbits were studied at two body temperatures: a normal temperature (rectal temperature of 39.8 C), and a higher temperature (rectal temperature 41.2 degrees C). Changes in circulating inflammatory cells, plasma corticosterone concentrations and in hematocrit were also monitored, to examine some potential mechanisms which might explain why body temperature altered airways responsiveness. At the normal body temperature infusion of PAF caused a significant increase in airways responsiveness (p less than 0.025), while at the high body temperature, there was a significant decrease in responsiveness (p less than 0.025). However, at both body temperatures, a profound but similar thrombocytopenia and neutropenia was observed. While plasma corticosterone levels and hematocrit showed increases coincident with the infusion of PAF, this response was unchanged by altering body temperature. We conclude that increased body temperature reduces the effect of PAF on airways responsiveness apparently through a mechanism independent of PAF effects on hemoconcentration, plasma corticosterone or circulating inflammatory cells.

Aerosols↗
PubMed1991

Interferon-induced chronic active hepatitis?

A 54-year-old man with chronic B hepatitis was treated with interferon alfa. Despite resolution of the hepatitis B viral infection, he experienced severe jaundice, ascites, and encephalopathy. Further work-up showed hyperglobulinemia, chiefly immunoglobulin G, and positive smooth muscle and anti-nuclear antibodies. Because of these "autoimmune" features, the patient was treated with prednisone. One month later, a significant clinical and biochemical improvement was observed. A possible autoimmune mechanism induced by interferon alfa is proposed as the cause for the perpetuation of the necroinflammatory activity.

Autoimmune Diseases↗
PubMed1991

Indefinite growth of mammalian cell autotrophs on amino acids, vitamins, and glucose.

Established mammalian cells segregate variants, named autotrophs, able to proliferate in the absence of hormones and proteins of any kind. We provided complete formulas for autotrophic media composed of amino acids, vitamins, glucose, and inorganic salts only and showed that such media are sufficient to sustain continuous propagation of Chinese hamster fibroblasts and human keratinocytes. The cells grew on bare polystyrene and divided every 32 to 44 hours reaching approximately 8 x 10(5) cells/cm2. The results showed that the autotrophs may replace conventional cultures in most experimental and industrial cell production systems.

Amino Acids↗
PubMed1991

The effects of rate, sequencing, and memory on auditory processing in the elderly.

Auditory sequencing, rate, and memory were evaluated in three age groups with a series of subtests that require the identification of tones (Repetition Test; Tallal & Piercy, 1973). The older elderly group (M age = 80), but not the younger elderly group (M age = 70), performed significantly (p less than .05) poorer than the young adult group (M age = 25) when auditory memory of 4 and 5 tones was required and when the interstimulus interval was decreased. Performance was not related to hearing sensitivity, thus suggesting that changes in the auditory mechanism that occur with age may encompass more than a loss of hearing sensitivity. Moreover, performance on the Repetition Test did correlate with memory for digits, which indicates a relationship between auditory processing and higher cortical functions.

Acoustic Stimulation↗