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Biomedical subjects

Z Jiang

Publications and source records attributed to Z Jiang.

At least 217 records · Page 12Linked to original sources
PubMed1997

Laser-based microfocused x-ray source for mammography: feasibility study.

A laser-produced plasma (LPP) x-ray source with possible application in mammography was created by focusing a laser beam on a Mo target. A Table-Top-Terawatt (TTT) laser operating at 1 J energy per pulse was employed. A dual pulse technique was used. Maximum energy transfer (approximately 10%) from laser light to hot electrons was reached at a 150 ps delay between pulses and the conversion efficiency (hard x-ray yield/laser energy input) was approximately 2 x 10(-4). The created LPP x-ray source is characterized by a very small focal spot size (tens of microns), Gaussian brightness distribution, and a very short pulse duration (a few ps). The spectral distribution of the generated x rays was measured. Images of the focal spot, using a pinhole camera, and images of a resolution pattern and a mammographic phantom were obtained. The LPP focal spot modulation transfer function for different magnification factors was calculated. We have shown that the LPP source in conjunction with a spherically bent, high throughput, crystal monochromator in a fixed-exit Rowland circle configuration can be used to created a narrow band tunable mammography system. Tunability to a specific patient breast tissue thickness and density would allow one to significantly improve contrast and resolution (exceeding 20 lp/mm) while lowering the exposure up to 50% for thicker breasts. The prospects for the LPP x-ray source for mammographic application are discussed.

Biophysical Phenomena↗
PubMed1997

[Changes in external secretion of the pancreas in morphine-dependent rat].

The present study was done both in vivo by cannulating pancreatic duct of morphine-dependent rats and in vitro using perfused pancreatic slices from morphine-dependent rats. The results were as follows: (1) In morphine-dependent rat the pancreatic amylase secretion induced by CCK-8 was significantly declined; (2) Amylase content of pancreatic tissue in morphine-dependent rats was lower than that of normal rats. It is suggested that the synthesis of amylase in morphine-dependent rat pancreas may be inhibited.

Amylases↗
PubMed1997

[Effect of recombinant growth hormone on amino acids metabolism in blood and urine after major operation].

To determine the effects of recombinant human growth hormone (GH) on postoperative amino acids metabolism, we performed a placebo-controlled randomized double-blind trial in 18 patients after elective gastrectomy or colectomy. The same amount of calories and amino acids were administered. Research group was daily injected growth hormone 0.15 IU/(kg.day) and control group was given placebo during the first postoperative week. All urine were analyzed for nitrogen balance and excretion of 3-methylhistidine. On the seventh postoperative day while the parenteral nutrients were being infused, amino acid exchange across the forearm was measured. On the seventh postoperative day all patients' amino acids in plasma were slightly increased by comparing with preoperative day but was not statistical significance. Forearm arterial-venous difference (A-V) measured on POD + 7 was markedly different between groups. There was continued release of amino acids from the forearm in the control subjects, while there was marked amino acid uptake in the GH patients (total amino acid nitrogen exchange was -398 +/- 158 mumol/L vs +165 +/- 61 mumol/L, P < 0.01). Excretion of urinary 3-methylhistidine in control group loss more than in GH group (7.3 +/- 1.0 mumol/(kg.24 h) vs 4.4 +/- 0.3 mumol/(kg.24 h), P < 0.05). The results demonstrated that GH can increase the uptake of amino acid from forearm and decrease the excreation of 3-methylhistidine in urine after operation, but did not disturb the balance of amino acids in plasma.

Amino Acids, Branched-Chain↗
PubMed1997

[Circadian rhythm of PGE2 level in plasma and condylar cartilage of young growing rats].

This paper reports the circadian rhythm of PEG2 level in plasma and condylar cartilage of young frowing rats. The samples were measured at 0:00, 4:00, 8:00, 12:00, 16:00, and 20:00 respectively. The count of PGE2 were determined by RIA and analysed with simple Cosinor and coordination. The results revealed: (1) The levels of PGE2 in plasma and condylar cartilage of young growing rats fluctuated in strong circadian rhythm; (2) The rhythm of PGE2 in plasma between 16:00 and 24:00 was significantly different from that between 4:00 and 12:00, so for analysing PGE2 level in plasma, one should proper sampling time or adjust it to circadian rhythm; (3) The circadian rhythm of PGE2 in condylar cartilage could provide important reference for reatments in dentistry and orthopaedics.

Animals↗
PubMed1997

[Chemical constituentes of Teucrium bidentatum Hemsl].

Two diterpenes were isolated from the herb Teucrium bidentatum and identified as teucvin and teupernin A on the basis of chemical properties and spectral data. They were obtained from T. bidentatum for the first time.

Diterpenes↗
PubMed1997

[Paclitaxel (Tesu) as a single agent in the treatment of breast cancer].

OBJECTIVE: To evaluate the efficacy and the side effects of paclitaxel (Tesu) in breast cancer patients. METHODS: Tesu was administered at 175 mg/m2(170.9-210.8 mg/m2) to 22 patients with advanced breast cancer from March to July 1995. Tesu was given once in 21 days as one cycle, and the patients recieved 1-4 cycles (median: 3 cycles) of treatment. RESULTS: Tesu induced 3 complete responses and 11 partial responses. The duration of remission was 2-7 months (median 3.5 months). The most frequent toxicities associated with Tesu administration were leukopenia, alopecia and myalgias. CONCLUSION: Tesu as a single agent is effective in the treatment of breast cancer and the side effects are tolerable.

Adult↗
PubMed1997

Analysis of social factors and human behavior attributed to family distribution of schistosomiasis japonica cases.

An investigation of family distribution patterns of schistosomiasis japonica was carried out in four pilot villages in Yunnan Province. Family clustering of the disease was present in Bihuayuan Village before and after economic reform (site A); however, such clustering did not occur in Tuanshan and Liantie Villages (sites B and C) in the same periods. Being contrary to the stage prior to economic reform family clustering existed in Zhonghe Village (site D) after the reform. The results obtained from single- and multifactor analysis showed that the main human behavior related to family distribution of schistosomiasis in mountainous regions of Yunnan Province included the frequency of laborer migration, contact with cercariae-infested water in public places or family microenvironments with a high transmission potential, promiscuous defecation and status of cattle grazing. The frequency of laborer migration and human contact with cercariae-infested water in public places in sites B and C without family clustering was higher than that in sites A and D with family clustering. Place for promiscuous defecation and cattle grazing in site A converged compared with that in sites B and C.

Animals↗
PubMed1997

Influence of livestock husbandry on schistosomiasis transmission in mountainous regions of Yunnan Province.

An investigation was conducted in the highly endemic areas of schistosomiasis japonica in Weishan and Eryuan counties, Yunnan Province. The results are summarized as follows: 1) the number of domestic animals was increasing annually; 2) the proportion of animal husbandry gains in the total agriculture income had a yearly escalating tendency; 3) the infection rate of inhabitants was upgrading as a result of the development of and the prevalence in domestic animals in the recent decades. Owing to frequent migration of domestic animals, serious spread of infection sources and high prevalence of schistosomiasis japonica occurred. It is suggested that more attention should be paid to the control of schistosomiasis japonica in mountainous endemic regions during the course of economic development, especially in the development of domestic animals.

Agricultural Workers' Diseases↗
PubMed1996

pRb controls proliferation, differentiation, and death of skeletal muscle cells and other lineages during embryogenesis.

Mice deficient for the RB gene (RB-/-), prior to death at embryonic day 14.5, show increased cell death in all tissues that normally express RB1: the nervous system, liver, lens, and skeletal muscle precursor cells. We have generated transgenic mice (RBlox) that express low levels of pRb, driven by an RB1 minigene. RBlox/RB-/- mutant fetuses die at birth with specific skeletal muscle defects, including increased cell death prior to myoblast fusion, shorter myotubes with fewer myofibrils, reduced muscle fibers, accumulation of elongated nuclei that actively synthesized DNA within the myotubes, and reduction in expression of the late muscle-specific genes MCK and MRF4. Thus, insufficient pRb results in failure of myogenesis in vivo, manifest in two ways. First, the massive apoptosis of myoblasts implicates a role of pRb in cell survival. Second, surviving myotubes failed to develop normally and accumulated large polyploid nuclei, implicating pRb in permanent withdrawal from the cell cycle. These results demonstrate a role for pRb during terminal differentiation of skeletal muscles in vivo and place pRb at a nodal point that controls cell proliferation, differentiation, and death.

Animals↗
PubMed1996

Dual mechanisms of repression of E2F1 activity by the retinoblastoma gene product.

The retinoblastoma gene product, pRb, negatively regulates cell proliferation by modulating the activity of the transcription factor E2F1 that controls expression of S-phase genes. To dissect transcriptional regulation of E2F1 by pRb, we developed a means to control the subcellular localization of pRb by exchanging its constitutive nuclear localization signal (NLS) with an inducible nuclear targeting domain from the glucocorticoid receptor (GR). In co-transfection experiments in hormone-free media, pRb delta NLS-GR sequestered E2F1 in the cytoplasm; addition of steroid hormones induced co-translocation of pRb delta NLS-GR and E2F1 to the nucleus. A pRb allele lacking a NLS, pRb delta NLS, also sequestered E2F1 in the cytoplasm. Both nuclear and cytoplasmic pRb delta NLS-GR repressed transcription from a simple, E2F1-activated, promoter equally well. pRb delta NLS-GR exerted differential effects on complex promoters containing an activator and E2F sites that acted as either positive or negative elements. We propose a dual mechanism of transcriptional repression by pRb which allows tight control of E2F1-responsive genes: a pRb-E2F1 repressor unit is assembled off DNA to pre-empt transcriptional activation by E2F1; recruitment of this repressor unit to cognate binding sites on promoters allows silencing of adjacent promoter elements.

3T3 Cells↗
PubMed1996

A calcium switch for the functional coupling between alpha (hslo) and beta subunits (KV,Ca beta) of maxi K channels.

KV,Ca beta subunit dramatically increases the apparent calcium sensitivity of the alpha subunit of MaxiK channels when probed in the micromolar [Ca2+]i range. Analysis in a wide range of [Ca2+]i revealed that this functional coupling is exquisitely modulated by [Ca2+]i. Ca2+ ions switch MaxiK alpha+beta complex into a functionally coupled state at concentrations beyond resting [Ca2+]i. At [Ca2+] < or = 100 nM, MaxiK activity becomes independent of Ca2+, is purely voltage-activated, and its functional coupling with its beta subunit is released. The functional switch develops at [Ca2+]i that occur during cellular excitation, providing the molecular basis of how MaxiK channels regulate smooth muscle excitability and neurotransmitter release.

Amino Acid Sequence↗
PubMed1996

Effect of different chemically modified oligodeoxynucleotides on immune stimulation.

Based on previous studies that certain oligonucleotides can stimulate cell proliferation and immunoglobulin production, this study was carried out to establish the relationship between the stimulatory effect and the chemical modification of the oligonucleotide. First, the effects of oligonucleotide and analogs on immune stimulation were studied in vitro using murine splenic lymphocytes. Our results show that cell proliferation and immunoglobulin production (IgG and IgM) depend on the sequence and the chemical modification of the oligonucleotide. Phosphorothioate oligodeoxynucleotides displayed a greater stimulatory effect than partially modified phosphorothioate oligonucleotides. Second, we studied the effects of these chemically modified oligonucleotides after injection in mice. Massive splenomegaly and stimulation of cell proliferation were observed with some phosphorothioate oligonucleotides. These effects were minimized markedly by chimeric and hybrid oligonucleotides. We also demonstrate that in vitro the effects of oligonucleotides on murine lymphocytes were unaffected by T cell depletion, suggesting that oligonucleotides exert their effects mainly on the B cells.

Adjuvants, Immunologic↗