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Biomedical subjects

H Chu

Publications and source records attributed to H Chu.

87 records · Page 5Linked to original sources
PubMed1982

Tubular complexes of endoplasmic reticulum in lymphoblastic lymphoma: case report.

Distinctive intracytoplasmic tubular complexes have been identified occasionally by electron microscopy in a wide variety of hematologic and nonhematologic disorders. The mechanism of induction and significance of these tubular complexes are unknown. Tubular complexes were identified in the majority of bone marrow lymphoma-leukemia cells in a patient with documented lymphoblastic lymphoma in lymph node. These complexes varied in size but in general ranged from 800--1500 nm, and consisted of masses of nonparallel, twisted, smooth, 40-nm tubules. Continuity with adjacent endoplasmic reticulum was evident in some of the complexes. Cytochemical characteristics of the malignant cells included strong, focal, paranuclear acid phosphatase reactivity and strong, stippled nuclear terminal deoxynucleotidyl transferase positivity. Flow cytometric analysis showed a DNA-RNA content pattern consistent with acute lymphoblastic leukemia and typical of T-cell lymphoma. This represents the first report of such tubular complexes in a presumed T-cell malignancy.

Acid Phosphatase↗
PubMed1979

Isolation and characterization of dnaX and dnaY temperature-sensitive mutants of Escherichia coli.

Escherichia coli mutants with temperature-sensitive (ts) mutations in dnaX and dnaY genes have been isolated. Based on transduction by phage P1, dnaX and Y have been mapped at minutes 10.4--10.5 and 12.1, respectively, in the sequence dnaX purE dnaY. Both dna Xts36 and Yts10 are recessive to wild-type alleles present on episomes. F13 carries both dnaX+ and Y+; the shorter F210 carries dnaY+, but not X+. Lambda tranducing phages that carry dnaX+ or Y+ have been isolated, and hybrid plasmids of Col E1 and E. coli DNA from the Clarke and Carbon (1976) collection also carry portions of the dnaX purE dnaY region. Results obtained with the lambda transducing phages and the hybrid plasmids suggest that dnaX is a different gene from the previously characterized dnaZ gene, which is also near minute 10.5--The dnaXts36 mutant, after a shift to 42 degrees, stopped DNA synthesis gradually, and the total amount of DNA increased two-fold. When this mutant was shifted to 44 degrees, the rate of DNA synthesis dropped immediately and the final increment of DNA was only 10% of the initial amount. Replicative DNA synthesis in toluene-treated cells was completely inhibited at 42 degrees and was partially inhibited even at 30 degrees.--When the dnaYts10 mutant was shifted to 42 degrees, DNA synthesis gradually stopped, and the amount of DNA increased 3.6-fold. At 44 degrees, residual DNA synthesis amounted to a two-fold increase. Replicative DNA synthesis in vitro in toluene-treated cells was inactivated after 20 minutes at 42 degrees or by "preincubation" of cells at 42 degrees before toluene treatment.--The dnaX and dnaY products probably function in polymerization of DNA, although participation also in initiation cannot be excluded.

Base Sequence↗
PubMed1978

Effects of furosemide and spironolactone on the behavior of morphine-tolerant rats.

In morphine-tolerant rats, a reappearance of morphine catalepsy and a disappearance of the turning behavior characteristic of brain-lesioned tolerant animals were observed under the influence of furosemide and spironolactone. The administration of spironolactone together with daily morphine treatment resulted first in an intensification of the morphine symptoms as measured by catalepsy and a retarded appearance of tolerance, typically characterized by a shift from catalepsy to turning movements in animals with single-sided brain lesions. Nontoxic doses of spironolactone raised the sensitivity of morphine-tolerant rats so that previously tolarated morphine doses become lethal.

Animals↗
PubMed1978

Bacteriophage lambda mutants (lambdatp) that overproduce repressor.

Lambda tp mutants, selected for their ability to form turbid plaques on lon hosts, overproduce repressor. The tp1 and tp2 mutations have been located within (or adjacent to) the cIII gene. The tp1 mutation reduced late gene expression, as measured by endolysin synthesis (in the absence of functional cI repressor) and progeny phage yield. The tp4 mutation was mapped in the cY-cII region, and complementation tests indicated that tp4 affects the diffusible product of the cII gene. The tp4 mutation also reduced progeny production, but did not markedly affect endolysin synthesis.

Coliphages↗
PubMed1977

Physiological effects of growth of an Escherichia coli temperature-sensitive dnaZ mutant at nonpermissive temperatures.

The physiological effects of incubation at nonpermissive temperatures of Escherichia coli mutants that carry a temperature-sensitive dnaZ allele [dnaZ(Ts)2016] were examined. The temperature at which the dnaZ(Ts) protein becomes inactivated in vivo was investigated by measurements of deoxyribonucleic acid (DNA) synthesis at temperatures intermediate between permissive and nonpermissive. DNA synthesis inhibition was reversible by reducing the temperature of cultures from 42 to 30 degrees C; DNA synthesis resumed immediately after temperature reduction and occurred even in the presence of chloramphenicol. Inasmuch as DNA synthesis could be resumed in the absence of protein synthesis, we concluded that the protein product of the dnaZ allele (Ts)2016 is renaturable. Cell division, also inhibited by 42 degrees C incubation, resumed after temperature reduction, but the length of time required for resumption depended on the duration of the period at 42 degrees C. Replicative synthesis of cellular DNA, examined in vitro in toluene-permeabilized cells, was temperature sensitive. Excision repair of ultraviolet light-induced DNA lesions was partially inhibited in dnaZ(Ts) cells at 42 degrees C. The dnaZ(+) product participated in the synthesis of both Okazaki piece (8-12S) and high-molecular-weight DNA. During incubation of dnaZ(Ts)(lambda) lysogens at 42 degrees C, prophage induction occurred, and progeny phage were produced during subsequent incubation at 30 degrees C. The temperature sensitivity of both DNA synthesis and cell division in the dnaZ(Ts)2016 mutant was suppressed by high concentrations of sucrose, lactose, or NaCl. Incubation at 42 degrees C was neither mutagenic nor antimutagenic for the dnaZ(Ts) mutant.

Alleles↗
PubMed1975

Ultrastructure of the compound eye of the diploid female beetle, Xyleborus ferrugineus.

The compound eye of female (diploid) Xyleborus ferrugineus beetles was examined with scanning and transmission electron microscopy. The eye is emarginate, and externally consists of roughly 70-100 facets. Each ommatidium is composed of a thickly biconvex lenslet with about 50 electron dense and rare layers. The lens facet overlies a crystalline cone of the acone type which is roughly hourglass-shaped. Pigment cells envelop the entire ommatidium, and pigment granules also are abundant throughout the cytoplasm of the 8 retinular cells. The rhabdomeres of 2 centrally situated photoreceptor cells effectively fuse into a rhabdom that extends from the base of the crystalline cone deeply into the ommatidium. Six distal peripheral retinular cells encircle the 2 central cells, and their rhabdomeres join laterally to form a rhabdomeric ring around the central rhabdom. The rhabdom and rhabdomeric ring are effectively separated by the cytoplasm of the two central retinular cells which contains the usual organelles and an abundance of shielding pigment granules. Eight axons per ommatidium gather in a tracheae-less fascicle before exiting the eye through the fenestrate basement membrane. No tracheation was observed among the retinular cells. Each Semper cell of each observed crystalline cone contained an abundance of virus-like particles near the cell nucleus. The insect is laboratory reared, and the visual system seems very amenable to photoreceptor investigations.

Animals↗
PubMed1968

Fatty Acid composition in tobacco I. Green tobacco plants.

The major fatty acids (16 and 18 carbons) in leaves, flowers, and seeds of Nicotiana tabacum L. cv. Catterton have been analyzed at various intervals during the growth period. From the pattern of their accumulation and relative distribution, it was found that A) the amount of fatty acids in upper young leaves attained a maximum about 75 days after transplanting which is the time of early flowering, while in older leaves the fatty acids continuously declined; B) the relative amount of linolenic acid (18:3) increased progressively with leaf development, from 30% at an early stage to 60% at maturity, while other fatty acids (18:2, 18:1, 18:0, and 16:0) decreased during the same period, indicating a progressive desaturation; and C) a rapid increase of fatty acids was found as flowers developed into seedpods, particularly of linoleic acid (18:2), which comprises 75% of tobacco seed oil.Air-curing resulted in a loss of fatty acids, especially the unsaturated ones.

Journal Article↗