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Biomedical subjects

J Hu

Publications and source records attributed to J Hu.

At least 595 records · Page 33Linked to original sources
PubMed1991

Calcium and phosphorus fluxes during hemodialysis with low calcium dialysate.

We evaluated the acute effects of varying dialysate calcium concentration on plasma concentrations and dialyzer fluxes of calcium and phosphorus in adult hemodialysis patients. Seven individuals with stable end-stage renal failure were dialyzed 4 hours, three times weekly. The effects of dialysates containing 1.75, 1.25, or 0.75 mmol/L (70.1, 50.1, or 30.1 mg/L) of calcium were compared. Each patient was studied once at each bath calcium concentration. Compared with the predialysis mean value of 2.27 mmol/L (9.1 mg/dL), plasma total calcium concentration increased, remained constant, or decreased with the 1.75-, 1.25-, or 0.75-mmol/L calcium dialysates, respectively. The 0.75-mmol/L calcium dialysate did not cause signs or symptoms of hypocalcemia (and the plasma calcium concentration did not fall below 1.80 mmol/L [7.2 mg/dL]). Plasma phosphorus concentrations decreased equally from a predialysis mean value of 2.16 mmol/L (6.7 mg/dL), regardless of the dialysate calcium concentration. After 4 hours of treatment with the three different dialysates, the cumulative calcium fluxes were significantly different. With 1.75 mmol/L calcium, mean bodily calcium accumulation was 21.9 mmol (879 mg). With 1.25 mmol/L, there was no net calcium flux. With 0.75 mmol/L, mean patient calcium loss was 5.8 mmol (231 mg). Mean phosphorus removal after 4 hours was 32.5 mmol (1,006 mg) and was unaffected by dialysate calcium concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Conformation of DNA-DNA polymerase I complex observed by scanning tunneling microscopy.

The conformation of a complex of a 41 mer/31 mer DNA fragment and the Klenow fragment of DNA polymerase I of Escherichia coli was studied by scanning tunnelling microscopy (STM). The results shows that near two turns of double helix of this DNA fragment was outside of enzyme while another part containing more than one turn of helix and 10 nucleotides single strand was combined with enzyme. The dimension and shape of DNA polymerase I (KF) in complex were different from that of free enzyme. The conformation of DNA-DNA polymerase I (KF) complex and the application of STM in studying structure of complex of DNA polymerase with DNA were discussed.

Base Sequence↗
PubMed1991

[Differentiation of Magnolia denudata Desr. flower buds].

The article gives the results of an observation on the differentiation of Magnolia denudata buds. In Huaining County, Anhui Province, differentiation of the buds starts at the beginning of May. By the end of June the differentiation of various parts of the flower is completed. The process takes about 50 days. The differentiation of buds goes on at a fairly fast speed and in a fairly uniform way. Based on the results of the observation, the authors advise that application of fertilizer, especially the top application should not be late. The beginning of March is a very important time for the development of buds in length and size, and for the final harvest as well. The proper time to pick the flower buds comes when they are fully developed before the perianth appears.

Fertilizers↗
PubMed1991

Effects of agonist efficacy on desensitization of phosphoinositide hydrolysis mediated by m1 and m3 muscarinic receptors expressed in Chinese hamster ovary cells.

Muscarinic receptor agonist-induced desensitization of phosphoinositide (PI) hydrolysis and loss of receptors were studied in Chinese hamster ovary (CHO) cells transfected with the m1 and m3 muscarinic receptor genes. Long-term exposure to the full agonist carbamylcholine (CBC) resulted in a time-dependent attenuation of the maximal PI response and a decrease in agonist potency. This desensitization was accompanied by a parallel loss of maximal ligand binding without an alteration of the binding affinity. The time course of both receptor desensitization and down-regulation was similar in m1 and m3 CHO cells. The PI response to the partial agonist McN-A-343 (McN) in m1 cells was more sensitive to desensitization by CBC than the response to the latter agonist, and this desensitization was faster than receptor down-regulation. Desensitization of the PI response to McN was reflected as a decrease in the maximal response without a marked change in potency. McN induced slow desensitization of the PI response to CBC but a much faster desensitization of its own response. Our data provide evidence that although muscarinic agonist-induced desensitization of PI hydrolysis in CHO cells is due mainly to loss of receptors, there are other important factors which play a role in this process, e.g., receptor-effector uncoupling. The relative contribution of these different mechanisms depends on the efficacy of the agonists used for the receptor desensitization and activation steps.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗
PubMed1991

Characterization of the renal and intestinal adaptations to dietary calcium deprivation in growing female rabbits.

To characterize the time courses and efficiencies of the renal and intestinal adaptations to dietary Ca deprivation, growing female albino rabbits were fed a low-Ca diet for up to 44 days while they were housed in metabolism cages. Urinary Ca excretion decreased markedly within 8 h of Ca restriction and became essentially undetectable after 14 days. This persisted as long as dietary Ca was low. The intestinal Ca absorption observed during the predeprivation control period was initially changed to net secretion with dietary Ca restriction. However, after 21 days of the low-Ca diet, intestinal Ca absorption was observed. Fecal Ca contents decreased appropriately with Ca deprivation, but never became undetectable. Hyperphosphaturia, which occurred within 8 h of Ca deprivation and persisted as long as dietary Ca was restricted, diminished positive P balance, despite increased intestinal P absorption. Intestinal hyperabsorption and renal conservation of Ca were observed after dietary Ca repletion, suggesting the presence of driving forces for the restitution of Ca deficits incurred by Ca deprivation during growth. We conclude that there are appropriate intestinal and renal homeostatic adaptations to dietary Ca deprivation in the growing female rabbit and that the latter are more rapidly induced and ultimately more efficient than the former.

Adaptation, Physiological↗
PubMed1991

[Screening studies on anti-inflammatory function of traditional Chinese herb Gardenia jasminoides Ellis and its possibility in treating soft tissue injuries in animals].

This paper reports the study of six fractions and one chemical constituent isolated from the traditional Chinese herb Gardenia jasminoides. The results showed that two fractions (G5.G6,), alcohol extract (G1) and genipoiside(A) had obvious anti-inflammatory effects and were comparatively effective in treating soft tissue injuries in animals.

Animals↗
PubMed1991

[Suppressive effects of safflower yellow on immune functions].

Safflower yellow (SY) extracted from Carthamus tinctorius L contained chalconoid compounds, 75% of which was safflomin A. SY ip 50-450 mg.kg-1.d-1 x 6-8 d in mice decreased serum lysozyme concentration and phagocytosing functions of both peritoneal macrophages and peripheral leukocytes; diminished the production of plaque forming cells, specific rosette forming cells, and antibody; inhibited delayed type hypersensitivity reaction and the activation of T suppressor cells elicited by supraoptimal immunization. Experiments in vitro showed inhibitory effects on [3H]TdR incorporation during human peripheral T- and B-lymphocyte proliferation by SY 0.03-3.0, 0.1-2.0 mg.ml-1 respectively, murine mixed lymphocyte culture response and the production of interleukin-2 by SY 0.1-2.5 mg.ml-1. In conclusion, SY produced declines in both nonspecific and specific immune functions.

Animals↗
PubMed1991

[Studies of 5-fluorouracil nanocapsules].

In this study, a new dosage form for antitumor agents--nanocapsules was prepared from biodegradable butylcyanoacrylate (BCA). Using 5-fluorouracil (5-Fu) as the model drug, scanning electron microscope pictures show that the maximum diameter of nanocapsules particles is about 338 nm. A new gel chromatography method is established for the determination of encapsulation efficiency in nanocapsules. The encapsulation efficiency of 5-Fu is 40.9%. LD50 of BCA is 267.7 mg/kg for intravenous injection in mice. The antitumor activities of 5-Fu nanocapsules on S180, HepS and EAC were found to be higher than that of free 5-Fu.

Animals↗
PubMed1990

Maize chloroplast RNA polymerase: the 180-, 120-, and 38-kilodalton polypeptides are encoded in chloroplast genes.

Prominent polypeptides with apparent molecular masses of 180, 120, 85, and 38 kDa are found in an extensively purified preparation of maize chloroplast DNA-dependent RNA polymerase that retains the capacity to initiate transcription of the cloned chloroplast gene rbcL correctly and the requirement for a supercoiled DNA template for specific and active transcription. Amino-terminal amino acid sequences of the 180-, 120-, and 38-kDa polypeptides have been determined and found to correspond precisely to the sequences deduced from the 5' ends of the maize chloroplast rpoC2, rpoB, and rpoA genes, respectively. These experiments show that these chloroplast rpo genes encode the prominent polypeptides in the highly enriched maize chloroplast RNA polymerase preparation and support the conclusion that these polypeptides are functional components of the enzyme. The rpoB, rpoC1, and rpoC2 genes have been mapped on the maize chloroplast chromosome.

Amino Acid Sequence↗
PubMed1990

Assessment of cellular viability in cardiovascular tissue as studied with 3Hproline and 3Hinulin.

STUDY OBJECTIVE: The aim of the study was to develop a quantifiable assay for the assessment of cellular viability in cardiovascular tissue. DESIGN: Radiolabelled proline and inulin were used to assess metabolic viability of the cellular component of cuspal tissue from porcine heart valves. EXPERIMENTAL MATERIALS: Pig hearts were removed within 20 min of death and transported on ice in tissue culture medium. Cuspal tissues were dissected rapidly and held on ice in physiological medium until assayed. MAIN RESULTS: Radiolabelled inulin was shown to be a useful marker for determining the amount of radiolabelled proline present in the extracellular tissue volume, permitting calculation of the amount of radiolabelled proline accumulated by the cellular component. Proline accumulation by the cellular component was affected by concentration of proline, time allowed for proline accumulation, in vitro cold ischaemia, and metabolic poisons. Based on mg tissue protein, proline and inulin accumulations were equivalent for aortic, pulmonary, mitral, and tricuspid valve tissues, suggesting that these valve tissues may be used interchangeably in assessment of metabolic viability of cellular components of cardiovascular tissue. CONCLUSION: Radiolabelled proline and inulin transport assays allow a quantitative estimate of total cellular viability.

Animals↗
PubMed1990

Effects of moderate dietary phosphorus restriction on intestinal absorption and external balances of phosphorus and calcium in growing female rabbits.

The effects of moderate dietary P restriction on intestinal net fluxes and external balances of P and Ca were studied in growing female albino rabbits that were fed a P-deficient diet for 10 consecutive days while they were housed in metabolism cages. Intestinal P secretion occurred during the first 24 h of P restriction and thereafter changed to absorption. During recovery, when the rabbits were consuming a normal diet, P absorption was significantly greater than either prerestriction control values or than in a separate group of time control rabbits. Phosphorus balance was negative during the 1st day of P restriction but thereafter became positive. This pattern occurred because intestinal P secretion changed to absorption and because urinary losses of P were negligible. Intestinal Ca absorption increased within 24 h of P restriction, reached maximal values by 4 days, and remained elevated for each of the remaining 6 days that dietary P was low. It also was elevated compared to P-sufficient time controls for 8 days after replenishment of dietary P. Despite increased intestinal absorption, Ca balance was significantly reduced during P restriction because of substantial hypercalciuria. Thus, selective dietary P restriction reduced the positive balances of both P and Ca that are characteristic of growth. We conclude that in growing rabbits moderate dietary P restriction induces both intestinal and renal adaptations that conserve this mineral; concomitantly, positive Ca balance is reduced. With dietary P replenishment, adaptations persist to restore the positive mineral balances that were lost because of dietary P restriction during growth.

Animals↗
PubMed1990

Prognostic significance of general immune competence in acute leukemia.

The prognostic significance of lymphocyte transformation rate, E-RFC%, 29 degrees C E-RFC%, serum IgG, IgA, IgM and C3 levels were studied in 286 patients with acute leukemia. In acute lymphoblastic leukemia (ALL), the pretreatment immunological parameters were not related to whether the patients could achieve complete remission (CR), but the patients with E-RFC% greater than 30% before treatment or E-RFC% restored to normal after treatment had a significantly longer survival time. In acute nonlymphocytic leukemia (ANLL), pretreatment LTR and E-RFC% were significantly higher in patients who could achieve CR subsequently, the patients with higher pretreatment levels of LTR, E-RFC% or 29 degrees C E-RFC% survived significantly longer than patients with lower levels of these parameters, and the patients whose LTR could return to normal after treatment had a significantly higher CR rate and longer survival times. Except that the pretreatment IgM level was related to the survival of ANLL patients, serum levels of immunoglobulins and C3 had no prognostic value for both ALL and ANLL. In both ALL and ANLL, the immunological parameters changed significantly when relapse occurred.

Adolescent↗