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Biomedical subjects

J Jiang

Publications and source records attributed to J Jiang.

467 records · Page 26Linked to original sources
PubMedDate not supplied

Production of neutrons from interactions of GCR-like particles.

In order to help assess the risk to astronauts due to the long-term exposure to the natural radiation environment in space, an understanding of how the primary radiation field is changed when passing through shielding and tissue materials must be obtained. One important aspect of the change in the primary radiation field after passing through shielding materials is the production of secondary particles from the breakup of the primary. Neutrons are an important component of the secondary particle field due to their relatively high biological weighting factors, and due to their relative abundance, especially behind thick shielding scenarios. Because of the complexity of the problem, the estimation of the risk from exposure to the secondary neutron field must be handled using calculational techniques. However, those calculations will need an extensive set of neutron cross section and thicktarget neutron yield data in order to make an accurate assessment of the risk. In this paper we briefly survey the existing neutron-production data sets that are applicable to the space radiation transport problem, and we point out how neutron production from protons is different than neutron production from heavy ions. We also make comparisons of one the heavy-ion data sets with Boltzmann-Uehling-Uhlenbeck (BUU) calculations.

Aerospace Medicine↗
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Multivalent melanotropic peptide and fluorescent macromolecular conjugates: new reagents for characterization of melanotropin receptors.

Radioreceptor binding studies have documented the presence of melanotropin receptors on some but not all of the various human melanoma cell lines that have been studied. Using a newly developed class of multivalent fluorescent melanotropin-macromolecular conjugates, we have demonstrated for the first time the presence of specific melanotropin receptors on all of the melanoma cell lines, both mouse and human, melanotic as well as amelanotic, that were investigated. The conjugates developed by us consisted of multiple copies of both a potent melanotropin analogue and a fluorophore, both arranged in a pendent fashion on a biologically inert macromolecule. While the multivalency of these conjugates may have established stronger binding with the melanotropin receptors on the cell surface (perhaps by establishing simultaneous multiple interactions), the presence of multiple copies of the fluorophore also greatly increased the level of detection in fluorescence labeling experiments. Membrane receptor-hormone-associated phenomena, such as capping and internalization of the receptor-ligand complex, also were observed. The details of these methods are described using B-16 mouse melanoma cells as a model system. The demonstration of MSH receptors as a common marker for melanoma suggests that this methodology might be employed for early clinical detection and anatomical localization of melanoma. These results also offer the possibility that substitution of the fluorophore in these conjugates by a chemical agent of (chemo-)therapeutic relevance may provide a powerful tool for site specific (tumor) targeting and cytotoxicity.

Amino Acid Sequence↗
PubMedDate not supplied

Cyanide self-addition, controlled adsorption, and other processes at layered double hydroxides.

Layered double hydroxides (LDH) are anion-exchanging materials of the type M(III)-M(II)x(OH)(2x + 2)Y that occur abundantly in nature, and can concentrate, protect, and activate simple organic anionic species of possible relevance to the earliest organisms. We now wish to report progress in the following areas: 1) Internal vs. external uptake of anions. Ferrocyanide does not displace carbonate from synthetic hydrotalcite (Mg:Al LDH carbonate) but is nevertheless taken up on the outside of the particles. In other cases, anion uptake is controlled by specific hydrogen bonding requirements rather than by charge density alone, a feature that can be used to control whether uptake will be both internal and external, or external only. These two findings taken together have important implications for specific catalysis by LDH, since specific hydrogen bonding will affect the individual and relative conformations of substrate anions, and anions occupying space in the interlayer will be under tighter constraints than those adsorbed externally. 2) Specific reactions catalyzed by LDH. We have found that the LDH Mg2Al(OH)6Cl catalyzes the self-addition of cyanide, to give in a one-pot reaction at low concentrations an increased yield of diaminomaleonitrile and in addition, at higher (> or = 0.05 M) concentrations, a purple-pink material that adheres to the LDH. We are investigating whether this reaction also occurs with hydrotalcite itself, what is the minimum effective concentration of cyanide, and what can be learned about the products and how they compare with those reported at high HCN concentrations in the absence of catalyst.

Adsorption↗
PubMedDate not supplied

Maternal blood lead level during pregnancy in South Central Los Angeles.

Twenty-five years of public health efforts produced a striking reduction in lead exposure; the blood lead average in the United States has decreased to less than 20% of levels measured in the 1970s. However, poor minority groups that live in large urban centers are still at high risk for elevated lead levels. In this study, our data showed that pregnant immigrants (n = 1,428) who live in South Central Los Angeles--one of the most economically depressed regions of California--have significantly higher (p < .0001) blood lead levels (geometric mean = 2.3 microg/dl [0.11 micromol/l]) than 504 pregnant nonimmigrants (geometric mean = 1.9 microg/dl [0.09 micromol/l]). The most important factors associated with lower blood lead levels in both groups were younger age; more-recent date of blood sampling (i.e., decreasing secular trend); and blood sampling in mid-autumn, instead of mid-spring (i.e., seasonal trend). Blood lead levels of immigrants were strongly dependent on time elapsed since immigration to the United States; each natural log increase in years of residence was associated with an approximately 19% decrease in blood lead levels. Although blood lead means for both groups were almost the same as the estimated national average, 25 of the 30 cases of elevated blood lead (i.e., > or = 10 microg/dl [0.48 micromol/l) occurred in the immigrant group. The odds ratio (95% confidence intervals within parentheses) for having elevated blood lead levels (a) was 9.3 (1.9, 45.8) if the immigrant engaged in pica; (b) was 3.8 (1.4, 10.5) if the immigrant had low dietary calcium intake during pregnancy; and (c) was .65 (.43, .98) for every natural log unit increase of years of residence in the United States. The control of pica and dietary calcium intake may offer a means of reducing lead exposure in immigrants.

Adolescent↗
PubMedDate not supplied

Blood lead level and blood pressure during pregnancy in South Central Los Angeles.

In many studies in which the relationship between blood pressure and blood lead level has been examined, investigators have found significant--but small--associations. There was only one previous report of a significant association of blood lead with blood pressure in pregnant women. We measured blood lead level and sitting blood pressure of 1,627 women in their third trimester of pregnancy. We eliminated subjects with known causes of hypertension. Most women (98.4%) were normotensive. We controlled for body mass index, age, and stress--among other factors--and constructed multiple-regression models of lead association with diastolic and systolic blood pressures. Immigrants (73% of total) had significantly higher blood lead levels and different blood pressures than nonimmigrants, suggesting that analysis be stratified by "immigrant, nonimmigrant" status. Positive relationships between blood lead level and blood pressure were found only for immigrants (p < or = .001). From the 5th to 95th blood-lead percentiles (0.9-6.2 microg/dl) in immigrants, systolic blood pressure increased 2.8 mm Hg, and diastolic blood pressure increased 2.4 mm Hg. Higher prior lead exposure of immigrants (97.7% from Latin countries) than nonimmigrants might explain the differential effect of these low levels of blood lead on blood pressure in nonimmigrants. Perhaps some immigrants are at higher risk than nonimmigrants for lead-associated elevated blood pressure during pregnancy, despite blood lead levels within the currently considered acceptable range.

Adult↗
PubMedDate not supplied

In vitro studies on sterically stabilized liposomes (SL) as enzyme carriers in organophosphorus (OP) antagonism.

This study describes a new approach for organophosphorous (OP) antidotal treatment by encapsulating an OP hydrolyzing enzyme, OPA anhydrolase (OPAA), within sterically stabilized liposomes. The recombinant OPAA enzyme was derived from Alteromonas strain JD6. It has broad substrate specificity to a wide range of OP compounds: DFP and the nerve agents, soman and sarin. Liposomes encapsulating OPAA (SL)* were made by mechanical dispersion method. Hydrolysis of DFP by (SL)* was measured by following an increase of fluoride ion concentration using a fluoride ion selective electrode. OPAA entrapped in the carrier liposomes rapidly hydrolyze DFP, with the rate of DFP hydrolysis directly proportional to the amount of (SL)* added to the solution. Liposomal carriers containing no enzyme did not hydrolyze DFP. The reaction was linear and the rate of hydrolysis was first order in the substrate. This enzyme carrier system serves as a biodegradable protective environment for the recombinant OP-metabolizing enzyme, OPAA, resulting in prolongation of enzymatic concentration in the body. These studies suggest that the protection of OP intoxication can be strikingly enhanced by adding OPAA encapsulated within (SL)* to pralidoxime and atropine.

Animals↗
PubMedDate not supplied

Arsenic trioxide induces apoptosis in cisplatin-sensitive and -resistant ovarian cancer cell lines.

Arsenic trioxide (As(2)O(3)), has been used for centuries in traditional Chinese medicine; it has considerable efficacy in the treatment of relapsed acute promyelocytic leukemia, inducing partial differentiation and promoting apoptosis of malignant promyelocytes. Although a number of studies have demonstrated that As(2)O(3) has potent activity against cell growth in a series of leukemia cell lines, little information is available regarding this compound's effect on cell growth in solid tumor cell lines. In this study, we investigated the effects of As(2)O(3)in vitro on ovarian cancer cell lines sensitive (3AO) and resistant (3AO/CDDP) to cisplatin. The 3-(4,5-dimethy-thiazoyl-2-yl)-2,5-diphenyl-tetrazolium bromide assay was used to evaluate cytotoxicity. Flow cytometric analysis was used to determine the apoptosis, cell cycle distribution. We clearly demonstrated that As(2)O(3) induced cell apoptosis and inhibition of cell growth in both the cell lines. Furthermore, we identified that As(2)O(3)-induced apoptosis involved Fas pathway. As(2)O(3) is an active agent against ovarian cancer cells and could be effective in the clinical treatment of ovarian cancer.

Apoptosis↗
PubMedDate not supplied

Phacofragmentation without perfluorocarbon liquid for dislocated crystalline lenses or lens fragments after phacoemulsification.

PURPOSE: To evaluate the clinical outcome of vitrectomy with phacofragmentation without perfluorocarbon liquid (PFCL) in the management of dislocation of the crystalline lens, caused by trauma, hereditary disorders, or hypermature cataracts, and lens fragments due to phacoemulsification. METHODS: A prospective study was conducted to evaluate 30 eyes of 29 patients who had undergone standard pars plana vitrectomy with phacofragmentation without PFCL in the vitreous cavity, for the removal of dislocated crystalline lenses or lens fragments, from January 1998 to July 2000. All cases were followed for more than six months. RESULTS: Final best corrected visual acuity of 0.5 or better increased from 0% preoperatively to 36.7% postoperatively, and 0.2 or better rose to 76.7%. The mean IOP was significant reduced, from 26.35 mmHg to 12.75 mmHg. No intraoperative complications occurred. Although two eyes (6.7%) developed retinal detachment, one (3.3%) had cystoid macular edema (CME) and one (3.3%) had a transient intraocular pressure increase (to 25 mmHg) postoperatively, all others had a favorable outcome. CONCLUSIONS: Standard pars plana vitrectomy with phacofragmentation without PFCL in the vitreous cavity is a safe, simple, and effective method for removing a dislocated crystalline lens or lens fragments, with good visual outcome.

Aphakia, Postcataract↗
PubMedDate not supplied

Techniques for covering soft tissue defects resulting from plantar ulcers in leprosy: Part I--General considerations and summary of results.

Recurrent plantar ulceration is a common and serious complication occurring consequent to impairment of the tibial nerve in leprosy patients. In spite of many therapies and long therapeutic course, it is extremely difficult to abolish this complication in many cases because of extensive skin and soft tissue cushion loss due to repeated infection. Since the early 70's we have been using microscopic surgical techniques to reconstruct the ulcerated area using eight types of the flaps. In this series of papers we review our experience (76 patients). Post-operatively, the flaps survived in all cases, the long-term results have proved satisfactory, and recurrent ulceration occurred in only three patients.

Adult↗
PubMedDate not supplied

Techniques for covering soft tissue defects resulting from plantar ulcers in leprosy: Part II--First toe web and dorsal foot flaps.

The first toe web flap consists of the skin and subcutaneous tissues of the contiguous sides between the great and second toes. It is based on the first dorsal metatarsal artery or the common plantar digital artery. This flap was used as artery pedicled island graft to reconstruct losses of skin and soft tissue cushion in the ball of the foot in the first and second metatarsal head region in 16 cases. Follow-up examination revealed that ulceration had recurred in one case due to dehiscence of the flap margin 12 months post-operatively. The other 15 patients have done well without recurrence at 48 to 124 months follow-up examination. The dorsal flap of the foot based on the dorsalis pedis artery, the corresponding veins and the deep peroneal nerve was designed in 1974 to resurface skin and soft tissue defects in the sole of the foot. This flap was used in 30 cases of leprosy with excellent results. During follow-up 36 to 120 months after surgery the plantar ulcer had recurred in only one case. All the others have done well. The long-term curative effect has thus proved satisfactory.

Foot Ulcer↗
PubMedDate not supplied

Techniques for covering soft tissue defects resulting from plantar ulcers in leprosy: Part IV. Use of medial leg flap and medial knee flap.

The medial leg flap, based on the cutaneous branches of the posterior tibial artery is raised from the middle and lower regions of the medial aspect of the leg. It has a long pedicle, and it can be used as a free flap to reconstruct the distant soft tissue defects and also as an island flap. We have used this retrograde island flap for surfacing ulcerated areas in six leprosy patients. The flap survived in all cases. At 24 to 60 months follow-up examination, ulceration had not recurred in any of them. The medial knee flap consisting of the skin and subcutaneous tissue of the lower part of the medial side of the thigh and the upper part of the leg, is suitable for covering soft tissue cushion defects of the extremities because of the constant vessels, long pedicle, wide diameter, well-recognizable sensory nerves and less subcutaneous fat. We have used the medial knee flap for the resurfacing sizeable raw areas due to ulceration in three leprosy patients. The flap survived in all cases and there was no recurrence of ulceration during the 70-148 months follow-up period.

Foot Ulcer↗
PubMedDate not supplied

Techniques for covering soft tissue defects resulting from plantar ulcers in leprosy: Part V. Use of the flap in the inguinal region and latissimus dorsi musculocutaneous flap.

The area of distribution of the superficial circumflex iliac, superficial epigastric and superficial external pudental arteries is large and flaps based on them can meet the requirement of different recipient sites. We have transplanted free flaps based on the superficial epigastric artery for repairing plantar soft tissue defects in six leprosy patients. During the follow-up examination 58 to 118 months later there has been no recurrence of ulceration in any of these cases. The latissimus dorsi muscle, is mainly nourished by the thoracadorsal artery and the latissimus dorsi musculocutaneous flap is a large sized, composite structure with abundant blood provision and strong anti-infectious property. The latissimus dorsi flap can be used as an artery-pedicled island flap or as a free flap besides its use as a muscle graft, because of its constant vascular position, wide outer-diameter of the vessels and long pedicle. It can therefore be utilized for repairing soft tissue defect or replacement of paralyzed muscle. We have used the latissimus dorsi musculocutaneous free flap for repairing large skin and soft tissue defects resulting from plantar ulceration in three leprosy patients. During the follow-up period, one patient who had complete drop-foot and had refused corrective surgery had recurrence of the ulcer in the 12th post-operative month. No ulcers had recurred in the other two cases during the follow-up at 48 and 114 months.

Foot Ulcer↗
PubMedDate not supplied

The effects of gossypol on the invasiveness of MAT-LyLu cells and MAT-LyLu cells from the metastasized lungs of MAT-LyLu-bearing Copenhagen rats.

Recently, we isolated a novel subline of the MAT-LyLu cell line from the metastasized lungs of MAT-LyLu-bearing Copenhagen rats (MLL cells). In this study, we compared the MLL cells to the parental MAT-LyLu cells with respect to invasive ability, mRNA expression level for the nm23 metastasis suppressor gene, and response to gossypol (GP), a natural compound with documented antiproliferative and antimetastatic activity, in an in vitro invasion assay. ML cells were isolated from mechanically dissociated metastasized lungs from MAT-LuLu-bearing Copenhagen rats. Comparisons of the invasive ability and steady-state levels of nm23 mRNA between MLL and MAT-LuLu cells were determined by in vitro invasion assay and RT-PCR, respectively. The results show that MLL cells display a higher penetration percentage than MAT-LyLu cells in the in vitro invasion assay. Furthermore, RT-PCR revealed that MLL cells possess lower steady state levels of nm23 mRNA than MAT-LyLu cells, suggesting a molecular basis for the observed differences in in vitro invasive ability. Finally, both MLL and MAT-LyLu cells were susceptible to gossypol, which induced dose-dependent inhibition of invasive activity. These results report the isolation of a novel, more highly invasive subline of the MAT-LyLu cell line that is as susceptible to the inhibitory effects of gossypol as the parental MAT-LyLu cells. The MLL cells, in combination with the parental MAT-LyLu cells, can be valuable tools for investigating the biology and behavior of metastatic cells and their response to chemotherapeutic/preventive agents.

Animals↗
PubMedDate not supplied

Transplantation of fibula with vascular pedicle for fusion of ankle in leprotic drop-foot.

Devascularized bone grafts are pieces of dead bone and they simply serve as scaffolds for new bone to grow and fill the gap, taking a long time when they succeed in doing so. In contrast, vascularized grafts being living tissues have short healing time, great vitality and strong infection-resisting capacity. We report here the successful use of vascularized grafts of the lower end of fibula for fusing the ankle in five leprosy patients.

Adult↗
PubMedDate not supplied

Phrenic and intercostal repetitive nerve stimulation: a useful electroneurophysiological method to detect the respiratory status of myasthenia gravis patients.

OBJECTIVE: To get a comprehensive recognition about the profile of phrenic repetitive nerve stimulation (PRNS) and intercostal repetitive nerve stimulation (IRNS) in healthy people, to investigate the electrophysiological features about respiratory function of myasthenia gravis (MG) patients, and to detect the predictive value of IRNS and PRNS on the respiratory deterioration of MG patients during the pulse treatment with large dosage of adrenal corticosteroid. SUBJECTS AND METHODS: Bilateral PRNS and IRNS with stimulation frequency of 3 and 5 Hz were tested in 28 healthy people and 113 MG patients; limb and cranial repetitive nerve stimulation (RNS), clinical score and forced vital capacity (FVC) were also recorded from those MG patients. Further more, PRNS and IRNS of 36 MG patients were tested 3 days before the beginning of their adrenal corticosteroid pulse treatment, FVC, clinical score and respiratory changes of the MG patients were simultaneously observed. RESULTS: For healthy people, there were no significant differences in the results of PRNS or IRNS in different age, sex and testing sides. After combining the left result with the right one, the amplitude decrement percentage in PRNS and IRNS was less than 7%. PRNS had more technical difficulty than IRNS. For 113 MG patients, FVC was dependent on the values of PRNS, IRNS and facial RNS. A subclinical respiratory dysfunction was found in patients with type I and II MG. The abnormal rate of PRNS in type IIb MG was similar to that in type III and IV MG, even though a difference in the percentage of amplitude decrement between them was observed. Meanwhile, both the abnormal rate and the percentage of amplitude decrement of IRNS had no difference between type IIb MG and type III and IV MG. The general incidence of abnormal PRNS and abnormal IRNS were higher than those of decreased FVC and clinical dyspnea, and the sensitivity of PRNS in type IIa MG patients was higher than that of IRNS. Among 36 MG patients under the adrenal corticosteroid pulse treatment, 14 showed the newly clinical dyspnea or worsened original one 2 to 13 days after the beginning of the therapy. There were significant difference of the above parameters between the patients with and without respiratory deterioration during the treatment. Logistic regression analysis showed that when the mean value of the bilateral IRNS amplitude decrement was larger than 30%, the odds ratio of the occurrence of the respiratory deterioration was 19.523, for both 3 and 5 Hz stimulation. CONCLUSIONS: It is recommended that PRNS and IRNS will be defined as abnormal when their amplitude reduces more than 15%. PRNS and IRNS are neurophysiological indices reflecting the damage of respiratory muscles in MG, they are helpful in evaluating the clinical condition correctly and making the classification of MG properly. It is necessary to test the PRNS and IRNS in type II MG patients regularly. Although the respiratory damage during the adrenal corticosteroid treatment was correlated with PRNS, IRNS, FVC, MG clinical score and type, only IRNS had predictive value on the respiratory deterioration during the treatment.

Adrenal Cortex Hormones↗
PubMedDate not supplied

Low frequency electron paramagnetic resonance investigation on metabolism of chromium (VI) by whole live mice.

Detection of Cr(V) in the reduction of Cr(VI) by whole live mice and its characterization were carried out by low frequency electron paramagnetic resonance (EPR). Intravenous injection of Cr(VI) to mice generated Cr(V). The Cr(V) was found predominantly in the liver with a small amount in the blood. Liver homogenates from Cr(VI) treated mice generated essentially the same Cr(V) spectrum as that obtained from the whole live mice. This Cr(V) species was identified to be a Cr(V)-nicotinamide adenine dinucleotide (NAD) (P)H complex with an oxygen bond to Cr(V). Pretreatment of the mice with ascorbic acid and glutathione reduced the Cr(V) formation, while pretreatment with reduced nicotinamide adenine dinucleotide (NADH) enhanced it. Metal chelators, ethylenediaminetetraacetic acid (EDTA), 1,10-phenanthroline, and diethylenetriaminepentaacetic acid (DTPA) inhibited the intensity of the Cr(V) signal. The results suggest that Cr(V) generated in the whole body of a live animal is a Cr(V)-NAD(P)H complex and NAD(P)H/flavoenzymes and not glutathione or ascorbate as the major one-electron Cr(VI) reductant responsible for observed formation of Cr(V)-NAD(P)H complex in vivo.

Animals↗