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Biomedical subjects

A Chu

Publications and source records attributed to A Chu.

At least 127 records · Page 7Linked to original sources
PubMed1984

Stages in development of mink cell focus-inducing (MCF) virus-accelerated leukemia in AKR mice.

Flow cytometric techniques involving correlated dual parameter analysis of fluorescence and light scatter and transplantation bioassays were used to describe a series of cellular changes in thymus of young (1-4 mo old) AKR mice during development of mink cell focus-inducing (MCF) virus-accelerated leukemia. Three stages of leukemogenesis were defined before appearance of frankly leukemic mice. Stage 1, apparent 28-40 d after injection of MCF 69L1 virus, represented steady-state infection of thymocytes by MCF virus without apparent change in light scatter properties of the cells or in expression of alloantigens Thy-1, Lyt-1, Lyt-2, L3T4a, B2A2, or H-2K on the major thymocyte subpopulations. Expression of MCF virus was highest in the population of small cortical thymocytes. Stage II was observed at highest frequency 50-60 d postinjection and represented the emergence of a clonal population of cells with transformed properties which could be resolved from normal thymocytes by light scatter and expression of B2A2, H-2K, and gp70 antigens. Stage III was observed at highest frequency at 70 d postinjection, when considerable enlargement of thymus had occurred, and appeared to represent the outgrowth of fully transformed cells that replaced the normal thymocyte subpopulations. The alloantigen phenotype of blast cells from frankly leukemic mice did not differ qualitatively from that of stage II or stage III cells but displayed considerable heterogeneity with respect to quantitative expression of alloantigens and gp70. At least two populations of leukemic blasts could be resolved in the majority of primary thymomas analyzed. It is unclear whether these populations represent the outgrowth of independent clones of transformed cells or if they are related in some way. Our data are consistent with MCF virus-induced transformation of cells in the lineage to small peanut agglutinin-positive, cortisone-sensitive thymocytes, a subpopulation that predominates in the thymus and which is thought to be destined for cell death in situ.

Animals↗
PubMed1984

Cerebral energy metabolism studied with phosphorus NMR spectroscopy in normal and birth-asphyxiated infants.

Phosphorus (31P) nuclear magnetic resonance spectroscopy was used to study intracellular metabolism in the brains of 6 normal newborn infants and 10 infants who had been asphyxiated during delivery. In the normal infants spectral peaks mainly attributable to adenosine triphosphate, phosphocreatine (PCr), phosphodiesters plus phospholipids, and inorganic orthophosphate (Pi) were always detected, together with an additional large peak in the phosphomonoester region indicating the presence of a metabolite or metabolites (probably largely phosphoethanolamine) which may be involved in rapid growth of the brain. In the asphyxiated infants, data obtained on the first day of life showed no differences from those in normal infants, but by the second to ninth days inverse changes in the concentrations of PCr and Pi had caused a significant reduction in PCr/Pi. This latency suggest the possibility of effective early treatment before irreversible metabolic damage sets in. Mean intracellular pH when PCr/Pi was minimal was 7.17 +/- 0.10. Values for PCr/Pi below 0.80 were associated with a very bad prognosis for survival and early neuro-developmental outcome.

Adenosine Diphosphate↗
PubMed1984

The effect of phenothiazines on Ca2+ fluxes in skeletal muscle sarcoplasmic reticulum.

The effect of phenothiazines (trifluoperazine, chlorpromazine, methochlorpromazine, and imipramine) on Ca2+ fluxes in light and heavy sarcoplasmic reticulum (SR) isolated from rabbit fast-twitch skeletal muscle was investigated. These drugs inhibited Ca2+ loading and (Ca2+,Mg2+)-ATPase activity, but had no effect on unidirectional Ca2+ efflux from vesicles loaded either actively or passively with Ca2+. Chlorpromazine, which is membrane permeable, and its quaternary analog, methochlorpromazine, which is membrane impermeable, gave identical results. It is concluded that (a) the enhancement of net Ca2+ release by phenothiazines is due to inhibition of Ca2+ influx mediated by the Ca2+ pump rather than to the opening of a Ca2+ channel; and (b) phenothiazines act at the outer (myoplasmic) face of the SR membrane.

Animals↗
PubMed1984

Motor deficits in patients with large-fiber sensory neuropathy.

The issue of whether brain signals in the absence of peripheral feedback are sufficient to specify accurate movement was evaluated by studying motor performance in patients with loss of somesthetic afferent input as a result of acquired large-fiber sensory neuropathy. With visual guidance, movements and postures were impaired relatively little, but when visual guidance was unavailable, the patients exhibited postural drift and gross inaccuracy of movement. Impairments were more apparent for smaller (3 degrees) than for larger (15 degrees) movements. Previous studies that have failed to show major motor impairments in deafferented subjects examined movements involving rather large joint displacements, and this may have been a factor in the failure of these studies to reveal severe deficits. The present results demonstrate a critical role for somesthetic feedback in regulating centrally generated levels of motor output and show that central motor programs deprived of such feedback are unable to subserve accurate motor control.

Afferent Pathways↗
PubMed1984

Preparation and morphology of sarcoplasmic reticulum terminal cisternae from rabbit skeletal muscle.

We have developed a procedure to isolate, from skeletal muscle, enriched terminal cisternae of sarcoplasmic reticulum (SR), which retain morphologically intact junctional "feet" structures similar to those observed in situ. The fraction is largely devoid of transverse tubule, plasma membrane, mitochondria, triads (transverse tubules junctionally associated with terminal cisternae), and longitudinal cisternae, as shown by thin-section electron microscopy of representative samples. The terminal cisternae vesicles have distinctive morphological characteristics that differ from the isolated longitudinal cisternae (light SR) obtained from the same gradient. The terminal cisternae consist of two distinct types of membranes, i.e., the junctional face membrane and the Ca2+ pump protein-containing membrane, whereas the longitudinal cisternae contain only the Ca2+ pump protein-containing membrane. The junctional face membrane of the terminal cisternae contains feet structures that extend approximately 12 nm from the membrane surface and can be clearly visualized in thin section through using tannic acid enhancement, by negative staining and by freeze-fracture electron microscopy. Sections of the terminal cisternae, cut tangential to and intersecting the plane of the junctional face, reveal a checkerboardlike lattice of alternating, square-shaped feet structures and spaces each 20 nm square. Structures characteristic of the Ca2+ pump protein are not observed between the feet at the junctional face membrane, either in thin section or by negative staining, even though the Ca2+ pump protein is observed in the nonjunctional membrane on the remainder of the same vesicle. Likewise, freeze-fracture replicas reveal regions of the P face containing ropelike strands instead of the high density of the 7-8-nm particles referable to the Ca2+ pump protein. The intravesicular content of the terminal cisternae, mostly Ca2+-binding protein (calsequestrin), is organized in the form of strands, sometimes appearing paracrystalline, and attached to the inner face of the membrane in the vicinity of the junctional feet. The terminal cisternae preparation is distinct from previously described heavy SR fractions in that it contains the highest percentage of junctional face membrane with morphologically well-preserved junctional feet structures.

Animals↗
PubMed1984

Rapid confirmatory identification of Neisseria gonorrhoeae with lectins and chromogenic substrates.

A group of five tests utilizing wheat germ and soybean lectins and chromogenic substrates (orthonitrophenyl-beta-D-galactopyranoside, gamma-glutamyl-beta-naphthylamide, and prolyl-beta-naphthylamide derivatives) was used as a rapid (30-min) method for the identification of Neisseria gonorrhoeae. The rapid method agreed with Minitek test results for all 126 N. gonorrhoeae isolates and all 39 nongonococcal isolates tested. Soybean lectin was useful for the identification of rare strains (4 of 126) of N. gonorrhoeae which are not agglutinated by wheat germ lectin. The chromogenic substrates differentiate N. gonorrhoeae from Neisseria meningitidis, Neisseria lactamica, and other Neisseria species which may grow on Thayer-Martin or other selective media.

Agglutination Tests↗
PubMed1983

Anion effects on in vitro sarcoplasmic reticulum function. Co-transport of anions with calcium.

In isolated sarcoplasmic reticulum vesicles, calcium-chelating but non-calcium-precipitating dicarboxylates, such as maleate and succinate, stimulated ATP-dependent Ca2+ accumulation and its ensuring spontaneous Ca2+ accumulation and its ensuring spontaneous Ca2+ release, and Ca2+-dependent ATPase activity (Chu, A., Tate, C. A., Bick, R. J., Van Winkle, W. B., and Entman, M. L. (1983) J. Biol. Chem. 258, 1656-1664). We further examined the effect of dicarboxylates on enzyme turnover. The anionic buffer maleate enhanced the rate of rapid acyl phosphoenzyme hydrolysis compared to that in the zwitterionic buffer piperazine-N,N'-bis(2-ethanesulfonic acid) but had no effect on the phosphoenzyme formation. The presence of a calcium-precipitating anion, oxalate, or a Ca2+ ionophore, A23187, eliminated the differences observed in the phosphoenzyme decay between the two buffers, but accelerated the rate of decay. Furthermore, the catalytic activity of the purified Ca2+-dependent ATPase was not affected by maleate, whether oxalate was present or not. [14C]Succinate was transported into the sarcoplasmic reticulum in a manner which was dependent on Ca2+ transport, and occurred over a similar time course as Ca2+ accumulation/release. The net succinate uptake was equivalent to the amount of succinate-stimulated Ca2+ accumulation. Rapid efflux of both [14C]succinate and 45Ca2+ was induced by A23187, whereas the efflux induced by ethylene glycol bis(beta-aminoethylether)-N,N,N',N'-tetraacetic acid was slower and less compared to A23187. Succinate accumulation exhibited saturation kinetics with positive cooperativity (Km congruent to 20 mM; Hill coefficient = 1.70). When maleate and succinate were both present, they were equipotent, and had an additive stimulatory effect on peak 45Ca2+ accumulation at low concentrations. Maleate was a competitive inhibitor of succinate accumulation (Ki approximately equal to 17 mM; Hill coefficient = 1.75). KCl in the presence or absence of valinomycin did not influence succinate accumulation or release. The data suggest that succinate accumulation is Ca2+-dependent, but occurs at a saturable, divalent, anion-specific site. While this carrier or channel requires Ca2+ transport, it may be controlled by additional factors as well.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1983

Anion effects on in vitro sarcoplasmic reticulum function. The relationship between anions and calcium flux.

Isolated sarcoplasmic reticulum vesicles exhibited different functional characteristics in the presence of zwitterionic as compared to anionic buffers. In the absence of oxalate, dicarboxylic anions (e.g. maleate, succinate) in a dose-dependent manner enhanced ATP-supported Ca2+ accumulation, the ensuing spontaneous Ca2+ release, and Ca2+-dependent ATPase activity compared to zwitterionic buffers (e.g. piperazine-N,N'-bis(2-ethanesulfonic acid) (Pipes) and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) (Hepes). This was not attributed to ionic strength and osmotic effects. The additional anion-dependent Ca2+ accumulation was linked to augmented Ca2+-dependent ATPase activity, and both could be induced by the addition of anion at any time during Ca2+ accumulation as long as ATP was present. Since the initial Ca2+ accumulation rates and acyl phosphoenzyme formation were the same between the two buffer classes, and the presence of either oxalate (a Ca2+-precipitating anion) or A23187 (a Ca2+ ionophore) abolished differences in Ca2+-dependent ATPase activity between the two buffer classes, it is likely that conditions favoring high intravesicular Ca2+ concentration allow the expression of the observed effect of the anions. Initial spontaneous Ca2+ release in the presence of maleate was not caused by ATP depletion, and it was virtually absent in Pipes buffer. The rate of spontaneous release was also stimulated in a dose-dependent manner by the dicarboxylic anions, with the time of release being related to the time of anion addition and not ATP addition. A later, more rapid release phase in either maleate or Pipes buffer corresponded to ATP depletion, and could be duplicated at any time in the Ca2+ accumulation/release cycle by the addition of an ATP trap. With an ATP-regenerating system present or with very high ATP concentrations, the maximal peak Ca2+ accumulation in Pipes buffer could approach that in maleate buffer. The data suggest that dicarboxylic anions stimulate the filling of a Ca2+ compartment from which spontaneous Ca2+ release occurs.

Animals↗
PubMed1983

The diagnostic use of monoclonal antibodies in a variety of dermatologic conditions.

Monoclonal antibodies have been used to characterize subpopulations of lymphocytes in a variety of dermatologic conditions by immunofluorescence and immunoperoxidase staining. Various clinical presentations of cutaneous T-cell lymphoma have been shown to be neoplastic expansions of helper T-lymphocytes. Immunoperoxidase studies using subset-specific monoclonal antibodies have allowed the differentiation of patients with cutaneous T-cell lymphoma from lymphocytoma cutis and B-cell lymphomas secondarily involving the epidermis. Increased numbers of OKT-6 positive Langerhans' cells in the dermal infiltrates of patients with cutaneous T-cell lymphoma may be another immunocytological marker of this disease. Studies done on circulating lymphocytes of patients with psoriasis and pemphigus vulgaris have shown normal ratios of T-cell subsets in patients with psoriasis and an expansion of the helper T-cell subset in an untreated patient with pemphigus. Immunofluorescence and immunoperoxidase techniques used in conjunction with highly specific monoclonal antibodies have been shown to be valuable for histopathologic study of dermatologic diseases.

Antibodies, Monoclonal↗
PubMed1982

Relation between regional distribution of thallium-201 and myocardial blood flow in normal, acutely ischemic, and infarcted myocardium.

Myocardial localization of thallium-201 was compared with direct measurements of myocardial perfusion in normal, acutely ischemic, and recently infarcted myocardium. Studies were performed in 6 chronically instrumented dogs that were subjected to myocardial infarction by occlusion of the proximal left circumflex coronary artery. Four days after myocardial infarction, thallium-201 and 9 +/- 1 micrometer niobium-95-labelled microspheres were injected simultaneously after acute left anterior descending coronary arterial occlusion; the animals were killed 5 minutes later and the entire left ventricle was sectioned into 1 to 2 g samples. Regression analyses between thallium-201 activity and regional myocardial blood flow using all myocardial samples demonstrated a very close linear relation in each dog; r values were 0.98 or greater, indicating that the initial localization of thallium-201 in acutely ischemic and recently infarcted myocardium as a function of regional blood flow was essentially identical. Consequently, in each dog the regional distribution of thallium-201 closely approximated myocardial perfusion over a wide range of blood flow and potentially different local metabolic conditions that may be encountered in the clinical use of the isotope.

Animals↗
PubMed1982

In situ identification of Langerhans cells in the dermal infiltrate of cutaneous T cell lymphoma.

A population of cells showing the surface phenotype of Langerhans cells (LCs) was identified in the dermal infiltrates of cutaneous T cell lymphoma (CTCL). Peroxidase-conjugated OKT6, a monoclonal antibody reactive with epidermal LCs, was used to directly label frozen tissue sections of diseased skin from twenty-three patients with CTCL, two patients with secondary cutaneous involvement by a B cell lymphoma, and three patients with lymphocytoma cutis. OKT6-reactive cells represented a significant although minor population in the dermal infiltrate of twenty-two of the twenty-three CTCL biopsies, accounting for up to 5% of the cells. Double-labeling studies revealed that the OKT6-positive cells also exhibited Ia but not T cell antigens. Since OKT6-reactive cells were not found in either the B cell lymphomas or lymphocytoma cutis, their presence in a malignant infiltrate is suggestive of a T cell neoplasm.

Fluorescent Antibody Technique↗
PubMed1982

Immunoelectron microscopic identification of Langerhans cells using a new antigenic marker.

The specificity of a monoclonal antibody (OKT6) for epidermal Langerhans cells was examined by immunoelectron microscopy. Peroxidase-labeled OKT6 bound to 1-5% of suspended human epidermal cells, as determined by light microscopy. Electron microscopic examination of peroxidase-labeled cells revealed that all Birbeck granule-containing Langerhans cells bound OKT6. In addition, a small population of indeterminate cells, lacking the Birbeck granule, was also labeled with OKT6. The ultrastructural studies confirm the specificity of OKT6 for Langerhans cells and suggest that the indeterminate cell represents a related cell population.

Antibodies, Monoclonal↗
PubMed1982

Diagnosis of cutaneous T cell lymphoma by use of monoclonal antibodies reactive with tumor-associated antigens.

Two murine monoclonal antibodies (BE1 and BE2), produced by using leukemic helper T cells from a patient with cutaneous T-cell lymphoma (CTCL) as immunogens, reacted selectively with CTCL lymphocytes and some transformed cultured lymphocytes, as determined by radioimmunoassay (RIA) and indirect immunofluorescence (IIF). BE1 reacted significantly (P less than or equal to 0.001) with leukemic CTCL lymphocytes and with CTCL cells from infiltrated lymph nodes (RIA, mean +/- SD = 776 +/- 275 cpm), as compared with background counts (263 +/- 68). BE1 binding to normal blood mononuclear cells (RIA, mean +/- SD = 283 +/- 58 cpm) was indistinguishable from background. BE1 also reacted with Epstein-Barr virus (EBV)-transformed B-cell lines (RIA, mean +/- SD = 794 +/- 230) and some long-term T-cell lines. BE1 did not react with the majority of lymphoid cell lines or tumor cell lines tested. BE1 also did not react with any normal tissues screened by IIF. BE1 precipitated a molecule from CTCL cells that, under reducing conditions, has two components with molecular mass of 27,200 and 25,800 D. BE2 also reacted significantly (P less than or equal to 0.001) with CTCL cells from two of four patients (RIA, mean +/- SD = 519 +/- 113 cpm). The binding of BE2 to normal mononuclear cells was indistinguishable from background (309 +/- 38 cpm). BE2 also reacted with an antigen present on EBV-B-cell lines (RIA, mean +/- SD = 654 +/- 194) and MOLT 3 and HUT 78 T-cell lines. BE2 reacted with an antigen expressed on a subpopulation of lymphocytes from five of eight patients with B-cell CLL studied by IIF (mean +/- SD = 18 +/- 6). Other long-term T-cell lines and tumor cell lines studied by IIF were unreactive with BE2. BE2 did not react with any of the normal tissues studied. BE2 precipitated a molecule (78,000 D) from CTCL cells and EBV-B cells with a single component under reducing conditions. Immunoperoxidase-labeled BE1 and BE2 reacted with CTCL cells in frozen sections of infiltrated lymph nodes and skin. In addition, BE1 and BE2 reacted with blood lymphocytes from 16 of 21 patients whose CTCL had otherwise been considered localized to skin. These two monoclonal antibodies react with tumor antigens associated with CTCL and appear to be useful in the diagnosis of this disorder.

Antibodies, Monoclonal↗