Nanoscale multistate resistive switching in WO3 through scanning probe induced proton evolution

Multistate resistive switching device emerges as a promising electronic unit for energy-efficient neuromorphic computing. Electric-field induced topotactic phase transition with ionic evolution represents an important pathway for this purpose, which, however, faces significant challenges in device scaling. This work demonstrates a convenient scanning-probe-induced proton evolution within WO₃, driving a reversible insulator-to-metal transition (IMT) at nanoscale. Specifically, the Pt-coated scanning probe serves as an efficient hydrogen catalysis probe, leading to a hydrogen spillover across the nano junction between the probe and sample surface. A positively biased voltage drives protons into the sample, while a negative voltage extracts protons out, giving rise to a reversible manipulation on hydrogenation-induced electron doping, accompanied by a dramatic resistive switching. The precise control of the scanning probe offers the opportunity to manipulate the local conductivity at nanoscale, which is further visualized through a printed portrait encoded by local conductivity. Notably, multistate resistive switching is successfully demonstrated via successive set and reset processes. Our work highlights the probe-induced hydrogen evolution as a new direction to engineer memristor at nanoscale.

Analog memristive synapse based on topotactic phase transition for high-performance neuromorphic computing and neural network pruning

Inspired by the human brain, nonvolatile memories (NVMs)-based neuromorphic computing emerges as a promising paradigm to build power-efficient computing hardware for artificial intelligence. However, existing NVMs still suffer from physically imperfect device characteristics. In this work, a topotactic phase transition random-access memory (TPT-RAM) with a unique diffusive nonvolatile dual mode based on SrCoO _x is demonstrated. The reversible phase transition of SrCoO _x is well controlled by oxygen ion migrations along the highly ordered oxygen vacancy channels, enabling reproducible analog switching characteristics with reduced variability. Combining density functional theory and kinetic Monte Carlo simulations, the orientation-dependent switching mechanism of TPT-RAM is investigated synergistically. Furthermore, the dual-mode TPT-RAM is used to mimic the selective stabilization of developing synapses and implement neural network pruning, reducing ~84.2% of redundant synapses while improving the image classification accuracy to 99%. Our work points out a new direction to design bioplausible memristive synapses for neuromorphic computing.

Molecular cloning, mRNA expression and alternative splicing of a ryanodine receptor gene from the citrus whitefly, Dialeurodes citri (Ashmead)

Insect ryanodine receptors are the main targets of diamide insecticides that have highly selective insecticidal activity but are less toxic to mammals. Therefore, these insecticides are ideal for pest control. Ryanodine receptors (RyRs) play a critical role in Ca²⁺ signaling in muscle and non-muscle cells. In this study, we cloned the complete cDNA (DcRyR) of the RyR from the citrus whitefly, Dialeurodes citri, a serious pest of citrus orchards in China. The open reading frame of RyR is 15,378bp long and encodes a protein with 5126 amino acids with a computed molecular weight of 579.523kDa. DcRyR shows a high amino acid sequence identity to RyRs from other insects (76%-95%) and low identity to those from nematodes and mammals (44%-52%). DcRyR shares many features of insect and vertebrate RyRs, including a MIR domain, two RIH domains, three SPRY domains, four copies of RyR repeat domain, RIH-associated domain at the N-terminus, two consensus calcium-binding EF-hands and six transmembrane domains at the C-terminus. The expression of DcRyR mRNA was the highest in the nymphs and lowest in eggs; DcRyR mRNA was 1.85-fold higher in the nymphs than in the eggs. Among the tissues, DcRyR mRNA expression was 4.18- and 4.02-fold higher in the adult head and thorax than in the abdomen. DcRyR had three alternative splice sites and the splice variants showed body part-specific expression and were developmentally regulated. These results may help investigate target-based resistance to diamide insecticides in D. citri.

Tissue-specific effects of estrogen on glycerol channel aquaporin 7 expression in an ovariectomized mouse model of menopause

OBJECTIVE

Elevated fat mass and redistribution of body fat are commonly observed in postmenopausal women. Aquaporin 7 (AQP7), a unique glycerol permeable integral membrane protein, has been associated with the onset of obesity. We hypothesized that estrogen supplementation could counteract this fat accumulation and redistribution through tissue-specific modulation of AQP7.

METHODS

We measured fat depot weight, adipocyte size, and the expression of AQP7 and glycerol kinase (GK) in visceral and subcutaneous fat tissues of ovariectomized mice supplemented with or without 17β-estradiol.

RESULTS

Removal of the ovaries resulted in a significant decrease in AQP7 expression and an increase in GK expression in visceral adipocyte tissue; expression of AQP7 and GK in subcutaneous adipose tissue remained unaltered. Supplementation with estrogen significantly restored the visceral, but not subcutaneous, fat depot mass and adipocyte size to those of sham-operated mice. A marked increase in the expression of AQP7 and a reduction of GK were observed selectively in the visceral fat depots in estrogen-treated mice.

CONCLUSIONS

Our results suggest that estrogen has tissue-specific effects on AQP7 expression, and modulation of AQP7 by estrogen alters the balance of adipocyte metabolism between adipose tissue depots.

Functional characterization of two acetylcholinesterase genes in the brown citrus aphid, Aphis (Toxoptera) citricidus (Kirkaldy), using heterologous expression and RNA interference

Acetylcholinesterase (AChE) is the primary target of organophosphate- and carbamate-based insecticides. We sequenced the full-length cDNAs of two AChE genes from the brown citrus aphid Aphis (Toxoptera) citricidus (Kirkaldy). These two genes, Tcace1 and Tcace2, which encode TcAChE1 and TcAChE2, respectively, had a shared amino acid identity of 29% and were highly similar to other insect ace1 and ace2 genes, respectively, having specific functional motifs. Potential differences in enzymatic function were characterized by the heterologous expression of the two genes using a baculovirus system in Sf9 insect cells. Both of the recombinant AChEs had high specific activities for three typical substrates, acetylthiocholine iodide, butyrylthiocholine iodide, and propinylthiocholine iodide. TcAChE1 had a lower Michaelis-Menten constant value and a higher maximal reaction velocity than recombinant TcAChE2, indicating a higher affinity for substrates and greater catalytic efficiency, respectively. Bioassays showed a greater sensitivity of recombinant TcAChE1 to the 10 tested insecticides. Silencing of Tcace1 and Tcace2 by RNA interference significantly increased the susceptibility of A. citricidus to malathion and carbaryl; however, silencing Tcace1 resulted in a higher mortality rate than silencing Tcace2. Additionally, the specific enzyme activity decreased more after silencing Tcace1 than after silencing Tcace2. Thus, TcAChE1 plays a major role in postsynaptic neurotransmission in A. citricidus.

New species, hyper-diversity and potential importance of Calonectria spp. from Eucalyptus in South China

Plantation forestry is expanding rapidly in China to meet an increasing demand for wood and pulp products globally. Fungal pathogens including species of Calonectria represent a serious threat to the growth and sustainability of this industry. Surveys were conducted in the Guangdong, Guangxi and Hainan Provinces of South China, where Eucalyptus trees in plantations or cuttings in nurseries displayed symptoms of leaf blight. Isolations from symptomatic leaves and soils collected close to infected trees resulted in a large collection of Calonectria isolates. These isolates were identified using the Consolidated Species Concept, employing morphological characters and DNA sequence comparisons for the β-tubulin, calmodulin, histone H3 and translation elongation factor 1-alpha gene regions. Twenty-one Calonectria species were identified of which 18 represented novel taxa. Of these, 12 novel taxa belonged to Sphaero-Naviculate Group and the remaining six to the Prolate Group. Southeast Asia appears to represent a centre of biodiversity for the Sphaero-Naviculate Group and this fact could be one of the important constraints to Eucalyptus forestry in China. The remarkable diversity of Calonectria species in a relatively small area of China and associated with a single tree species is surprising.

Low prevalence of human papillomavirus (HPV) in Chinese patients with breast cancer

This retrospective study investigated the presence of human papillomavirus (HPV) in Chinese women with breast cancer, and the correlation between HPV infection and carcinogenesis. Tumour and non-cancerous breast tissue samples were obtained from 62 female patients with breast cancer; normal breast tissue samples were obtained from 46 women without breast cancer. HPV DNA was detected by nested polymerase chain reaction using consensus primers; HPV subtypes were determined by reverse dot blot and pyrosequencing analyses. HPV was found in tumour tissue samples from four of the 62 patients (6.5%), while no HPV DNA was detected in either the non-cancerous samples from patients with breast cancer or from the normal breast tissue controls. Of the four HPV-positive cases, three were HPV 16 positive (75%) and one was HPV 18 positive (25%). The low frequency of HPV detected in this study suggests that this infection is not a major risk factor in breast cancer development.

Prevalence of human papillomavirus in Chinese patients with colorectal cancer

AIM

The prevalence of human papillomavirus (HPV) was determined in Chinese patients with colorectal cancer (CRC). The study also aimed to determine whether the HPV DNA peripheral blood (PB) assay can be used to diagnose HPV-related CRC.

METHOD

Tumour tissue, noncancerous colorectal tissue and whole-blood samples were obtained from 96 patients with CRC. In addition, 32 colorectal tissue samples were harvested from patients without CRC, and 48 whole-blood samples were collected from healthy blood donors. HPV DNA was detected by means of a nested polymerase chain reaction (PCR) using consensus primers, and HPV genotypes were determined by reverse Southern blot and pyrosequencing.

RESULTS

HPV DNA was detected in 32 of the 96 patients with CRC, and colorectal tissues from the 32 control patients without CRC were negative for HPV DNA (P < 0.001). Among 48 healthy donors, three had detectable levels of HPV DNA in their PB. Patients with CRC did not have significantly higher levels of HPV DNA than controls. The HPV prevalence in tumour tissues was higher than that in noncancerous colorectal tissues (P < 0.001) or that in PB samples (P < 0.001). No correlation between the presence of HPV and demographic or medical characteristics was observed. HPV 16 was the viral type most frequently detected and was found in 33 (94%) of 35 HPV-positive patients.

CONCLUSION

HPV infection may be a risk factor for CRC. However, detection of HPV DNA in PB does not appear to reflect the HPV status of CRC.

[The extracting of left ventricular contour based on adaptive directional filter]

This paper proposes the adaptive directional filter, which is exploited for the extracting of left ventricular(LV) contour. This algorithm could produce the exact ridge point by applying directional filter with smoothing operator in the angiography images damaged by noise the Edge Directional Vector as the result of this filter is efficient for predicting the edge ahead, while the filter parameters is adaptive. This proposed method provides the more precise and more automatic--extracting LV contour only with fewer interactions. The experimental results show that this proposed algorithm could improve the accuracy and reproducibility, and reduce the computational consumption remarkably.

Congenital choledochal cyst with pancreatitis

OBJECTIVE

To understand the relationship among congenital choledochal cyst, anomalous junction of pancreaticobiliary duct (AJPBD) and pancreatitis.

METHODS

25 children with choledochal cyst treated in our hospital were included in this study. Their ages ranged from 2 months to 14 years. Intraoperative cholangiography was performed in 24 children. Pancreatic samples obtained from the head and body of the pancreas at operation were observed under light and electron microscope. Serum amylase was analyzed one week before and after operation respectively. Bile amylase in the cyst and gallbladder was measured at operation.

RESULTS

The incidence of AJPBD was 70%. Inflammatory cell infiltration and fibrous hyperplasia were seen in the pancreatic specimens of 5 children, of whom 4 had AJPBD. No ultrastructural changes were found in 2 children without AJPBD, while different changes were seen in 6 with AJPBD, including those showing no pathological changes under light microscope. All the changes became more severe as the age of the patient increased. The bile and serum amylase levels were higher in children with AJPBD than those without AJPBD (P < 0.05).

CONCLUSION

Congenital choledochal cyst has a close relationship with AJPBD and pancreatitis. Pancreatic pathological changes have a long and chronic course from ultrastructural changes to macroscopic changes for the developing of pancreatitis.

Haptotactic and growth stimulatory effects of fibrin(ogen) and thrombin on cultured fibroblasts

We tested the ability of purified, ultraviolet C virally inactivated components of human fibrin sealant (FS) to modulate the chemotaxis, adherence, and proliferation of cultured cells. A fibrin clot formed on a near-confluent layer of human fibroblasts (HFs) recruited cells from the surrounding area. Thrombin (Thr) enhanced HF proliferation by a factor of 1.5 to 1.8, whereas fibrinogen (Fib) exerted only a minimal proliferative effect. We developed a new cell haptotactic/attachment assay by using Thr and Fib covalently bound to Sepharose beads (SBs). The kinetics of cell binding were approximately equivalent for beads coated with either protein. Uncoated SBs or fibrinogen-bound SBs (Fib-SB) pretreated with plasmin did not attract HFs. AlphaThr-SB induced a positive migratory response that was not affected by blocking its proteolytic site, whereas gammaThr-SB elicited no response. X irradiation of HFs at a dose of 6 Gy showed that the migratory response of HF is independent of proliferation, as confirmed by a bromodeoxyuridine uptake assay. Several types of cultured cells (murine fibroblasts, smooth muscle cells, aortic endothelial cells, and murine mammary carcinoma cells) also attached to Fib-SB. By contrast, human keratinocytes, human ovarian carcinoma cells, murine macrophage-like cells, leukemic cells, and murine mast cells did not attach. Our results provide some mechanistic insights into the haptotactic and proliferative effects of Fib and Thr on different cells.

Combination of cisplatin and radiation in cell culture: effect of duration of exposure to drug and timing of irradiation

Responses to the combination of cisplatin (CDDP) and radiation in experimental and clinical studies have been reported to vary from high radiosensitization to clear sub-additivity. We examined the combined effect of CDDP with ionizing radiation in both murine mammary adenocarcinoma (EMT-6) and human ovarian carcinoma (OV-1063) cells with special reference to the duration of CDDP exposure and timing of irradiation. Cell survival was measured with a colorimetric assay of cell density. The nature of interaction of cisplatin and radiation was evaluated using isobolograms and a combination index (CI). Exposure of both cell lines to CDDP for 24 hr before irradiation yielded an additive or slightly sub-additive response only if the exposure was extended for a few more hours after irradiation. In EMT-6 cells, the combination of radiation with subsequent continuous as well as short-term (4 to 6 hr) CDDP treatment was found to have a clear sub-additive effect; dose escalation of each modality reduced the additional effect of the other. The sub-additive effect may be explained by a radiation-induced arrest of cells in late S phase, which was dose- and time-dependent. Post-radiation exposure to CDDP further increased the S-phase arrest. In contrast, a 2 hr post-radiation drug exposure resulted in a supra-additive combined effect. Our results stress the crucial role of the timing and the doses of both modalities as well as the duration of post-radiation drug exposure on their combined effect.

[Effects of low concentration carbon monoxide on human physiological function]

Human volunteers were exposed to various low concentrations of carbon monoxide (CO) in a closed cabin. The results showed that 35 mg/m3 of CO caused slight subjective symptoms and reduction in contrast vision, operating efficiency and T-wave of ECG. At 80 mg/m3 and 115 mg/m3 the above changes were more severe and a rise in hearing threshold level was observed. It demonstrated that an inhibitory effect on the CNS and heart were caused by low concentrations of CO. According to the absorption curves for human exposed to CO, it is suggested that the sense effect level and vision effect level for CO are 7% COHb, and the hearing effect level is 9% COHb.

Virucidal treatment of blood protein products with UVC radiation

The virus safety of blood derivatives continues to be of concern, especially with respect to nonenveloped and/or heat-stable viruses. Previously, we demonstrated that treatment of whole plasma, AHF concentrate or fibrinogen with short wavelength ultraviolet light (UVC) results in the inactivation of > or = 10(6) infectious doses (ID) of encephalomyocarditis virus (EMCV), hepatitis A virus (HAV) and porcine parvovirus (PPV), each of which is nonenveloped. Protein recovery was enhanced greatly by inclusion of the flavonoid, rutin, added prior to UVC exposure to quench reactive oxygen species. We now report on the treatment of albumin and intravenous immune globulin (IVIG) isolated by a previously described, integrated chromatographic method. Albumin was treated with either 0.1 or 0.2 J/cm2 UVC in the presence of 0.8 or 1.6 mM rutin; IVIG was treated with either 0.05 or 0.1 J/cm2 UVC in the presence of 0.5 or 1.0 mM rutin. Our results show that > or = 10(6.9) ID of EMCV and PPV were inactivated under each of the conditions studied except the treatment of albumin with 0.1 J/cm2 UVC in the presence of 1.6 mM rutin where 10(4.3) ID of EMCV and > or = 10(6.9) ID of PPV were killed. It appears that the sensitivity of PPV to UVC exceeds that of EMCV and that virus kill with UVC is higher in IVIG than in albumin. In the absence of rutin, UVC increased the extent of aggregation of both albumin and IVIG by two- to three-fold. With rutin present, the increase in albumin aggregation was reduced, and it was virtually eliminated by subsequent processing on Sephacryl S-200, a step in the existing procedure designed to remove aggregates. The increase in aggregation of IVIG appeared to be eliminated on inclusion of either 0.5 mM or 1 mM rutin. We conclude that both albumin and IVIG can be treated with UVC to inactivate > or = 10(6) ID of nonenveloped viruses. The inclusion of rutin during treatment helps protect against protein aggregation.

Protecting fibrinogen with rutin during UVC irradiation for viral inactivation

Fibrinogen solutions were irradiated with UVC (254 nm) to inactivate contaminating viruses. In order to protect fibrinogen during UVC irradiation, 0.5 mM rutin was added prior to UVC exposure and subsequently removed during processing. Viral kill by 0.1 J/cm2 UVC resulted in the following inactivation values (log 10): non-lipid-enveloped viruses: Parvo > or = 5.5; encephalomyocarditis virus > or = 6.5; hepatitis A virus > or = 6.5: lipid-enveloped viruses: human immunodeficiency virus > or = 5.7; vesicular stomatitis virus > or = 5.7. Fibrinogen irradiated with 0.5 mM rutin did not significantly differ from unirradiated material in terms of clot time and breaking strength. In the absence of rutin, UVC irradiation of fibrinogen at similar fluence led to loss of solubility, increased clot time and the cleavage of fibrino-peptides that reacted with dinitrophenyl hydrazine as a test for ketonic carbonyl groups. High-performance liquid chromatography and mass spectrometry data showed that rutin exposed to UVC formed numerous breakdown, oxidation and combinational products. Experiments with 3H-rutin showed that after UVC irradiation, subsequent processing by a C18 resin and alcohol precipitation removed > 99% rutin, representing < 10 ppm rutin in the final fibrinogen preparations. Residual 3H-rutin was not covalently bonded to the fibrinogen. Immunochemical studies with rabbit antisera to UVC irradiated (with rutin) fibrinogen showed the absence of neoimmungens. By all measures, rutin prevents fibrinogen degradation during virucidal UVC irradiation.

Reduction of the systemic toxicity of cisplatin by intra-arterial hepatic route administration for liver malignancies

Cisplatin (CDDP) administration by the intra-arterial hepatic route (i.a.h.) in patients with primary or metastatic liver malignancies could enhance the anti-tumor activity of the drug and reduce its systemic toxicity. The aim of the present study was to compare Pt pharmacokinetics and the toxicity of the circulating drug after i.a.h. versus intravenous (i.v.) administration. CDDP pharmacokinetics was followed-up in 11 i.a.h. courses given to 7 patients with liver malignancies and compared with 19 i.v. courses in 15 patients with cancer of different origins. The Pt level in blood was monitored by sensitive atomic absorption spectrometry. The dose given was in the range of 25-80 mg/m2/treatment. For analysis and for comparison purposes, the data from both CDDP treatments were normalized to a standard dose of 35 mg/m2. The mean peak Pt level for i.a.h. treatment was found to be about half of the mean peak value for i.v. administration with a similar dose-independent bi-exponential rate of elimination i.a.h. CDDP treatment was relatively well tolerated with no symptoms of either nephro- or neurotoxicity. For in vitro evaluation of peripheral CDDP toxicity, a sensitive ovarian carcinoma cell line, OV-1063, was used. A cytotoxic effect was recorded only within 2 hr following high-dose i.v. CDDP treatment. A substantial fraction of the drug given by the i.a.h. route was found to be extracted by the liver in the first passage, with reduced drug level in the peripheral blood plasma relative to the dose given. This may explain the apparent diminution of side-effects following i.a.h. CDDP treatment.

Sub-additive effect of the combination of radiation and cisplatin in cultured murine and human cell lines

The use of cisplatin (CDDP) as a potential radiosensitizer in tumors is controversial. Reports about CDDP interaction with radiation range from high radiosensitization to a clear sub-additive effect. We examined the effect of the combination of different concentrations of CDDP with radiation in murine mammary adenocarcinoma (EMT-6) and human ovarian carcinoma (OV-1063) cell lines. CDDP was given in the dose range of 0.01-3.0 micrograms/ml and radiation in the dose range of 1-6 Gy. A methylene blue assay of cell density was used for the evaluation of cell survival and rate of proliferation in 96-microwell plates. The validity of this assay for evaluation of cell survival was verified by colony-forming assay and radiolabeled thymidine uptake. The dose response to CDDP for both OV-1063 and EMT-6 cells lines was examined; the ID50 was 0.06 and 0.9 micrograms/ml respectively. A sub-additive effect of the combination of radiation with CDDP was clearly observed in the two cell lines tested; the increase in dose of each modality resulted in a decrease of the relative contribution on the effect of the other. These findings question the rationale of combining CDDP with radiation for the enhancement of tumor response, since with the increase in the dose of either modality the additional effect of the other decreases.

Packaging zinc, fibrinogen, and factor XIII in platelet alpha-granules

Zinc(II) accumulated by platelets has profound effects on platelet activity. This study is focused on the distribution of Zn(II) between human platelet subcellular compartments. After incubation with 86Rb+ and platelet lysis, the organelles were separated by sucrose density gradient centrifugation. Fibrinogen served as a marker for alpha-granules. 86Rb+ and factor XIII served as markers for the cytoplasmic fractions. Zn(II) was found to be distributed between the cytoplasm and the alpha-granules, with variations between different individual units. The total platelet Zn concentration and its relative subcellular distribution were dependent on its extracellular level. Incubation of platelets with 100 microM Zn(II) resulted in a twofold increase of its level in the cytoplasm and by one order of magnitude in the alpha-granules. In addition to the anticipated factor XIII activity in the cytoplasmic pool fraction, we found thrombin-inducible factor XIII activity within the alpha-granules. Immunoblotting confirmed the presence of both the a and b subunits of plasma factor XIII (a2b2 form) in the alpha-granules. As fibrinogen is not synthesized in the platelet, we propose that by virtue of their mutual binding, fibrinogen, Zn(II) and plasma factor XIII-a2b2 are simultaneously taken up into the alpha-granules by endocytosis, presumably through the vehicle of the GPIIb/IIIa fibrinogen receptor. A rationale for co-packaging these components within the alpha-granules is that Zn(II) inhibits factor XIII activity and thereby prevents the premature cross-linking of the concentrated fibrinogen prior to platelet activation and secretion. By contrast, cytoplasmic Zn(II) may increase platelet responsiveness to agonists due to its interaction with cytoplasmic modulators of platelet activity.

Noninvasive follow-up of platinum pharmacokinetics in the skin of patients on cisplatin chemotherapy

BACKGROUND

Treatment with high-dose cisdiammine-dichloroplatinum (II) (cisplatin, cDDP) often is associated with late complications, predominated by peripheral neuropathy. Pt deposition in different tissues may play a key role in the induction of many of these effects. Main topics of interest include the relationship between cDDP doses given during treatment and the long-term pharmacokinetics of the drug complexes in normal tissues and blood. Noninvasive examination of Pt in tissues during and after cDDP treatment are needed to clarify these points.

METHODS

A novel, high-sensitivity diagnostic x-ray spectrometry (DXS) method was used for the fast, noninvasive analysis of Pt in external tissues of patients with cancer treated with courses of cDDP. The Pt in a small skin area was excited by a monochromatic soft x-ray beam (14.6 KeV) and the spectral L lines emitted from the tissue were detected. A limit of detection below 1 microgram/g wet weight was reached. The pharmacokinetics of Pt in blood was investigated in parallel with the use of high-sensitivity, flameless atomic absorption spectrometry (AAS).

RESULTS

Follow-up of Pt concentrations in the skin of patients with cancer by DXS before cDDP treatment, during treatment, and up to 4 months after its completion, showed prolonged Pt deposition that corresponded to the net cumulative doses of the drug. Pt clearance from the skin fitted a monoexponential curve with a half-life of about 30 days. In comparison, the pharmacokinetics of total Pt in plasma showed a much faster, biexponential clearance with half-lives of 41 minutes and 5.2 days, respectively.

CONCLUSIONS

The amount of nonspecific Pt deposition in the tissues was found to depend on the total doses administered, the time interval between the courses, and the slow rate of clearance. Noninvasive measurements of tissue Pt levels may serve as a major tool in the evaluation of the induction of late cDDP complications.

A sensitive noninvasive analysis of Pt in external tissues. Followup of Pt deposition following cisplatin treatment

Noninvasive analysis of heavy elements in external tissues by diagnostic-x-ray spectrometry (DXS) is presented. Pt can be detected accurately with sensitivity below 1 microgram/g wet weight of tissue. In the present paper the possibility to monitor Pt accumulation and clearance in the external tissues of cancer patients treated with cisplatin [Cis-diamminedichloroplatinum (II)-cDDP] chemotherapy is reported. The DXS method is based on x-ray fluorescence analysis. Heavy elements in the small skin area of interest are analyzed by their excitation with a monochromatic soft x-ray beam of 14.6 KeV. Spectral L lines of heavy metals such as Pt are detected with minimum interference by other elements in the tissues. Skin Pt levels up to about 6 micrograms/g were observed following several courses of cDDP treatment. The Pt seemed to be homogeneously distributed in different skin areas with similar levels in the dermis and epidermis. The rate of clearance of Pt from the skin (50% in about 30 days) was slower by three orders of magnitude than its clearance from plasma. Further studies may use DXS to establish the accurate kinetics of Pt deposition and clearance in tissues of cDDP treated patients, as well as the exact relation between tissue Pt levels and the development of the drug related late complications.

Platelet multielemental composition, lability, and subcellular localization

Diagnostic X-ray spectrometry (DXS), based on X-ray fluorescence, was used to quantitate directly the multiple elemental composition of washed, intact human platelets (n = 16), with the following results: K = 3.08 +/- 1.00 mg/g, Ca = 1.18 +/- 0.29 mg/g, Zn = 35 +/- 9 micrograms/g. These values show that washed platelets contain significant pools of K, Ca, and Zn, the latter some 30-60-fold higher than plasma levels. Dialysis of whole platelets against cation exchange resin (Chelex-100) did not extract Ca(II) and Zn(II) sequestered within whole cells. To identify the subcellular locale of the elements, platelet lysate was subjected to 30-70% sucrose gradient ultracentrifugation and subcellular enriched fractions were obtained. Fractions were analyzed by DXS (for elements), electron microscopy (for dense granules), and subcellular markers fibrinogen and von Willebrand factor. In contrast to Ca and K, which accumulate in the dense granules and the cytoplasm, respectively, Zn appears to be distributed in the alpha-granules (40%) and the cytoplasm (60%). The subcellular distribution of Zn(II) is discussed within the context of the sensitivity of platelet response to the availability of Zn(II) and the platelet release reactions following stimulation.