Use of the organic crystal DAST for terahertz beam applications

We report the use of the organic crystal DAST as a freely propagating electromagnetic-wave sensor at terahertz (THz) frequency. We also report the result of using a DAST crystal as a mid-IR THz emitter. Compared with the optical rectification from our best ZnTe emitter, that obtained by use of DAST demonstrates a sixfold enhancement of radiation at 7-20 THz.

Time-domain transillumination of biological tissues with terahertz pulses

We present time-domain transmission imaging of an opaque structure in pork-fat tissue obtained with a terahertz (THz) field sampling technique. Compared with imaging with near-infrared pulses, the terahertz sampling technique shows significantly enhanced contrast, as a result of low scattering. For enhanced spatial resolution, we show mid-infrared THz imaging of onion cells. Water absorption of THz pulse in muscle tissues is discussed.

Molecular mechanisms of plasminogen activation: bacterial cofactors provide clues

Plasminogen activation is a key event in the fibrinolytic system that results in the dissolution of blood clots, and also promotes cell migration and tissue remodelling. The recent structure determinations of microplasmin in complex with the bacterial plasminogen activators staphylokinase and streptokinase have provided novel insights into the molecular mechanisms of plasminogen activation and cofactor function. These bacterial proteins are cofactor molecules that contribute to exosite formation and enhance the substrate presentation to the enzyme. At the same time, they modulate the specificity of plasmin towards substrates and inhibitors, making a 'specificity switch' possible.

Human plasminogen catalytic domain undergoes an unusual conformational change upon activation

Activation of the serine protease plasmin from its zymogen, plasminogen, is the key step in fibrinolysis leading to blood clot dissolution. It also plays critical roles in cell migration, such as in tumor metastasis. Here, we report the crystal structure of an inactive S741A mutant of human plasminogen catalytic domain at 2.0 A resolution. This structure permits a direct comparison with that of the plasmin catalytic unit. Unique conformational differences are present between these two structures that are not seen in other zymogen-enzyme pairs of the trypsin family. The functional significance of these differences and the structural basis of plasminogen activation is discussed in the light of this new structure.

2D measurement and spatio-temporal coupling of few-cycle THz pulses

The propagation of few-cycle THz pulses are measured by the improved CCD based 2D THz imaging system. There exists strong spatio-temporal shaping effect, leading to dramatically time dependent beam diameter and wave front. Theoretical simulation is given.

Crystal structure of streptokinase beta-domain

Streptokinase, a 47 kDa secreted protein of hemolytic strains of streptococci, is a human plasminogen activator and contains three structural domains linked by flexible loops. We describe here the crystal structure of the isolated streptokinase middle (SKbeta) domain determined at 2.4 A resolution. Among the functionally important structural features is a putative binding site for a kringle domain of plasminogen located at the tip of a fully exposed hairpin loop. The distribution of genetically conserved residues of SKbeta is strongly correlated with their functions. The extensive interface of the SKbeta dimer suggests that such dimers may also exist in solution for free SKbeta.

Terahertz pulse measurement with an optical streak camera

Incorporating an electro-optic modulator with a conventional optical streak camera extends the spectral range of the streak camera from the optical region (UV, visible, and near-IR) to the terahertz region (far-IR and millimeter-wave) with a minimum modification. We demonstrate the temporal measurement of freely propagating terahertz pulses with single-shot capability.

[Genetics and expression stability of exogenous gene construct in transgenic mice]

Transgenic mice were produced by introduced exogene construct lambda 106, an expression construct of HBsAg gene directed by bovine alpha-S1 casein gene, with microinjection. Gene integration test with PCR-Southern hybridization, shows that the construct integration rate is 56% (17/30) and expressed rate, by ELISA, of target gene product HBsAg is 100% (8/8) in the first generation. Generation trailing test suggests that the gene construct can be stably inherited across generation after generation, and expressed more or less than parents among offspring. However positive rate of offspring does not follow genetic ratio that exogenous gene can be integrated randomly into a single site on chromosomes. There may be a machinery of multi-sites for exo-gene integration. Changes of the target gene expression in the offsprings may be related to position effect, changing of gene copy number and changing of chromatin imprinting pattern when parent's genome information was delivered to their progeny.

Crystal structure of the catalytic domain of human plasmin complexed with streptokinase

Streptokinase is a plasminogen activator widely used in treating blood-clotting disorders. Complexes of streptokinase with human plasminogen can hydrolytically activate other plasminogen molecules to plasmin, which then dissolves blood clots. A similar binding activation mechanism also occurs in some key steps of blood coagulation. The crystal structure of streptokinase complexed with the catalytic unit of human plasmin was solved at 2.9 angstroms. The amino-terminal domain of streptokinase in the complex is hypothesized to enhance the substrate recognition. The carboxyl-terminal domain of streptokinase, which binds near the activation loop of plasminogen, is likely responsible for the contact activation of plasminogen in the complex.

Single-shot spatiotemporal terahertz field imaging

Using an optically chirped pulse in an electro-optic detection system, we image the spatiotemporal distribution of a terahertz (THz) pulse. We demonstrate single-shot THz field imaging of photoconductive emitters.

The crystal structure of bovine bile salt activated lipase: insights into the bile salt activation mechanism

BACKGROUND

The intestinally located pancreatic enzyme, bile salt activated lipase (BAL), possesses unique activities for digesting different kinds of lipids. It also differs from other lipases in a requirement of bile salts for activity. A structure-based explanation for these unique properties has not been reached so far due to the absence of a three-dimensional structure.

RESULTS

The crystal structures of bovine BAL and its complex with taurocholate have been determined at 2.8 A resolution. The overall structure of BAL belongs to the alpha/beta hydrolase fold family. Two bile salt binding sites were found in each BAL molecule within the BAL-taurocholate complex structure. One of these sites is located close to a hairpin loop near the active site. Upon the binding of taurocholate, this loop becomes less mobile and assumes a different conformation. The other bile salt binding site is located remote from the active site. In both structures, BAL forms similar dimers with the active sites facing each other.

CONCLUSIONS

Bile salts activate BAL by binding to a relatively short ten-residue loop near the active site, and stabilize the loop in an open conformation. Presumably, this conformational change leads to the formation of the substrate-binding site, as suggested from kinetic data. The BAL dimer observed in the crystal structure may also play a functional role under physiological conditions.

Clinical and experimental study on therapeutic effect of Weixibaonizhuanwan on gastric precancerous lesions

AIM

To study the therapeutic effect of Weixibaonizhuanwan on gastric precancerous lesions.

METHODS

Thirty-six patients with gastric precancerous lesions were treated with Weixibaonizhuanwan for 3 mo. Thirteen (36.1%) patients presented with mild atrophic gastritis, 14 (38.9%) with moderate atrophic gastritis, and nine (25.0%) with severe atrophic gastritis. Twenty-two (61.1%) and 27 (75.0%) of the cases were accompanied by intestinal metaplasia (IM) and dysplasia (DYS), respectively. Twenty of the 36 patients were men and 16 were women, ranging from 30 to 67 years in age, with 61.1% of the patients being 40-59 years old. The duration of the disease in these patients ranged from 3 mo to 21 years, with 20 (55.6%) patients experiencing durations of the disease between 5 and 10 years. The clinical manifestations of the disease in these patients included fullness of the abdomen (31 cases), abdominalgia (27 cases), anorexia (30 cases), eructation (26 cases), pantothenic acid (6 cases), and loose stool (9 cases). Patients were treated with Weixibaonizhuanwan and symptom improvement, level of atrophy of the gastric mucosa, and IM and DYS progression were analyzed.

RESULTS

After a 3-mo treatment with Weixibaonizhuanwan, seven patients experienced recovery. The treatment was effective in 11 cases, improved symptoms in 13 cases, and was ineffective in five cases. The overall efficacy rate was 86.1%. In patients with mild atrophic gastritis (n = 13), 11 improved into superficial gastritis and two experienced no improvement. In 14 cases of moderate gastritis, four cases improved into superficial gastritis and seven turned into mild atrophic gastritis, with three patients experiencing no improvement. Among severe atrophic gastritis patients (n = 9), five improved into moderate atrophic gastritis after treatment and four experienced no improvement. The overall efficacy rate in chronic atrophic gastritis patients was 77.8%. Among 9 patients with IM, IM disappeared in six cases, whereas three cases showed no improvement after treatment. In cases with moderate IM (n = 10), IM disappeared in two, turned into mild IM in five, and showed no change in three. Out of four cases with IM, one case turned into moderate IM and three showed no change. The overall efficacy rate in IM patients was 63.6%. Out of 16 cases of mild DYS, DYS disappeared in 11, whereas five cases showed no change. Out of nine cases of moderate DYS, DYS disappeared in two and turned into mild DYS in five cases, with two patients experiencing no change after treatment. No improvement was observed in the two cases of severe DYS after treatment. The overall efficacy rate in DYS patients was 66.7%. After treatment, expression of carcinoembryonic antigen (CEA) and proliferating cell nuclear antigen (PCNA) in gastric mucosa significantly decreased (P < 0.01). Before treatment, cancer staging of these patients by positive CEA expression was I, II, III, and IV in 13, 12, 9, and 2 cases, respectively. After treatment, the number of cases per stage changed to 25, 7, 3, and 1, respectively. Similarly, before treatment, staging by positivity of PCNA expression was I, II, III, and IV in 16, 11, 10, and 4 cases, respectively, and changed to 21, 9, 5, and 1, respectively, after treatment.

CONCLUSION

The use of Weixibaonizhuanwan in the treatment of gastric precancerous lesions showed promising therapeutic effects in patients after 3-mo treatments.

The evaluation of developmental toxicity of chemicals exposed occupationally using whole embryo culture

The purpose of this study was to employ the whole embryo culture (WEC) system to evaluate the developmental toxicity of industrial chemicals. Five chemicals including lead, cadmium, vinyl chloride, 1,2-dichloroethan, and carbon disulphide were tested in our laboratory both in vitro and in vivo (except lead). In vitro studies showed that cadmium and lead were teratogenic in the rat; whilst carbon disulphide, 1,2-dichloroethan and vinyl chloride mainly induced embryo growth retardation. The in vitro effects on development of the five industrial chemicals were similar to the effects in vivo. The in vitro effects were studied by three different exposure routes, direct exposure--chemicals added to the culture medium; indirect exposure--serum prepared from treated rats then used as culture medium, and pre-exposure--embryos treated maternally then explanted into control (untreated) culture medium. Comparing these three different exposure routes suggests that the last exposure route is the most effective when using WEC to evaluate developmental toxicity of industrial chemicals. The effects on embryo development of culturing in sera prepared from subjects occupationally exposed to antineoplastic drugs (ADs) was also tested by the WEC system. Embryos were cultured with human serum that was thought to contain ADs or ADs' metabolic materials (serum taken from nurses routinely handling ADs), to evaluate the effects of ADs on embryo development. Embryos (9.5-day) cultured with serum from 11 female nurses who had been handling ADs for 2-17 years in the oncology department all survived, but showed slight growth retardation. Embryos cultured with serum from 30 healthy and unexposed people served as controls and embryo development in their serum was normal.

Indirect validation of benzene exposure assessment by association with benzene poisoning

We present a validation study of a quantitative retrospective exposure assessment method used in a follow-up study of workers exposed to benzene. Assessment of exposure to benzene was carried out in 672 factories in 12 cities in China. Historical exposure data were collected for 3179 unique job titles. The basic unit for exposure assessment was a factory/work unit/job title combination over seven periods between 1949 and 1987. A total of 18,435 exposure estimates was developed, using all available historical information, including 8477 monitoring data. Overall, 38% of the estimates were based on benzene monitoring data. The highest time-weighted average exposures were observed for the rubber industry (30.7 ppm) and for rubber glue applicators (52.6 ppm). Because of its recognized link with benzene exposure, the association between a clinical diagnosis of benzene poisoning and benzene exposure was evaluated to validate the assessment method that we used in the cohort study. Our confidence in the assessment method is supported by the observation of a strong positive trend between benzene poisoning and various measures, especially recent intensity of exposure to benzene.

A cohort study of cancer among benzene-exposed workers in China: overall results

A large cohort study of 74,828 benzene-exposed and 35,805 unexposed workers employed between 1972 and 1987 in 12 cities in China were followed to determine mortality from all causes and the incidence of lymphohematopoietic malignancies and other hematologic disorders. Benzene-exposed study subjects were employed in a variety of occupations, including painting, printing, and the manufacture of footwear, paint, and other chemicals. All-cause mortality was similar in the benzene-exposed and unexposed comparison group. Statistically significant excess deaths were noted among benzene-exposed subjects for leukemia (RR = 2.3, 95% CP 1.1-5.0), malignant lymphoma (RR = 4.5, 95% CI: 1.3-28.4), and nonneoplastic diseases of the blood (RR = 95% CP 2.5-infinity), and a marginally significant excess was noted for lung cancer (RR = 1.4, 95% CI: 1.0-2.0). Risk was significantly elevated for the incidence of all lymphohematopoietic malignancies (RR = 2.6, 95% CI: 1.5-5.0), malignant lymphoma (RR = 3.5, 95% CI: 1.2-14.9), and leukemia (RR = 2.6, 95% CI.. 1.3-5.7). Among the leukemia subtypes, only acute myelogenous leukemia (AML) incidence was significantly elevated (RR = 3.1, 95% CI: 1.2-10.7), although nonsignificant excesses were also noted for chronic myelogenous leukemia (CML) (RR = 2.6, 95% CI: 0.7-16.9) and lymphocytic leukemias (RR = 2.8, 95% CI.. 0.5-54.5). Significant excesses were found for aplastic anemia (RR = infinity, 95% CI: 2.2-co) and myelodysplastic syndrome (RR = infinity, 95% CI: 1.7-infinity). Employment in benzene-associated occupations in China is associated with a wide spectrum of myelogenous and lymphocytic malignant diseases and related disorders. Investigations continue to assess the nature of these associations.

Equal vibrotactile sense thresholds of the fingers and its diagnostic significance for hand-arm vibration syndrome

The vibrotactile sense thresholds (VSTs) of the middle fingers of 60 healthy persons and 97 patients with Hand-Arm Vibration Syndrome (HAVS) or subclinical HAVS were measured quantitatively. Intermittent vibratory irritations were adopted, with vibration stimulus frequencies at 8, 16, 31.5, 63, 125, 250, and 500 Hz. The equal VST contours of the fingers were mapped. Results showed that the VSTs of the normal group were not correlated with sex or handedness. From 8 Hz to 250 Hz the equal VST contours of the normal group were relatively flat; at more than 250 Hz the contours began an abrupt ascent. The VST values had a logarithmic rising tendency with the increasing age of subjects. In the equal VST contours the frequency of the most sensitive threshold value was 125 Hz in the normal group and 8 Hz in the HAVS group. The patients' VST values were higher than that of the healthy persons. The vibrotactilegram showed that the VST values of the patient groups first shifted at high frequencies and VST loss displayed a "V"-type hollow at 125 Hz and 250 Hz. The quantitative test method of VST was a valuable auxiliary detection method for HAVS. The "V"-type hollow of VST was an early clinical manifestation of HAVS.

Characterization of a dinucleotide repeat in the 92 kDa type IV collagenase gene (CLG4B), localization of CLG4B to chromosome 20 and the role of CLG4B in aortic aneurysmal disease

Proteolytic imbalance may play a role in the pathogenesis of abdominal aortic aneurysms (AAA). CLG4B, which encodes the 92-kDa form of type IV collagenase, is a candidate gene for AAA. We genotyped a polymorphic dinucleotide repeat in the 5' flanking region of CLG4B in 94 unrelated Caucasian controls and in 127 unrelated Caucasian AAA cases. Eight alleles were detected in 188 control chromosomes with an observed heterozygosity of 0.68. There was no significant difference in allele distribution between cases and controls. We genotyped the dinucleotide repeat in 10 CEPH reference pedigrees and performed pairwise linkage analysis with markers on each of the 22 human autosomes. Lod scores between 10.45 and 20.29 were observed with markers spanning chromosome region 20q11.2-q13.1. Further support for assignment of CLG4B to chromosome 20 was provided by analysis of human-rodent somatic cell hybrids. This work describes a highly polymorphic marker in the CLG4B gene and assigns this gene to chromosome 20.

[Determination of finger vibrotactile threshold and its significance in patients with hand-arm vibration syndrome]

Vibrotactile sense threshold (VST) of the end of the middle fingers in 97 patients with established or suspected hand-arm vibration syndrome and 60 healthy controls was determined, and finger VST contour and vibration damage curve were plotted. Results revealed the most sensitive frequencies of VST were 8 Hz for the patients and 125 Hz for the controls, respectively. VST in the patients with hand-arm vibration syndrome was higher than that in the controls, and the threshold shift was initially at high frequency with a "V" dip at 125 Hz and 250 Hz. So, the authors think determination of VST is an auxiliary method used for diagnosis of hand-arm vibration syndrome.

[Bone metastasis of cervical carcinoma after treatment: analysis of 73 cases]

From Jan 1971 to June 1985, 3,943 patients with cervical cancer in stages I-III were treated in our hospital, bone metastasis developed in 73 cases (1.85%). 69.86% (51/73) of the metastasis occurred within 2 years after treatment. The most common site of bone metastasis were the vertebral column and pelvic bone. The more advanced clinical stage, the higher metastasis rate. The metastasis rate of nodular-infiltrative tumor was higher than that of exophytic type and ulcerative type 91.78% (67/73) of these patients died within 18 moths of metastasis with a mean survival of 8.9 months. If radiotherapy and chemotherapy were given, the mean survival can prolonged to 12.8 months. The most common route of bone metastasis was via lymphatics.

[Clinical study on circulating antisperm antibodies in women with recurrent abortion]

Couples with a history of recurrent spontaneous abortions (RSA) were analyzed for circulating antisperm antibodies (Ab) with an enzyme-linked immunosorbent assay (ELISA), a Franklin-Dukes (F-D) and a sperm immobilization test(SIT). The three tests were positive in 31.5%, 25.9% and 18.5% for wives and 24.1%, 11.1% and 7.4% for husbands in RSA couples. There was a statistical significance (P less than 0.01) as compared with the control group. The ELISA method was found to be most sensitive, and the positive rate of antisperm antibodies in wives was higher than that in husbands. The Ab titer of RSA group varied within 1:8 approximately 1:512, with 60% above 1:32. The pregnant weeks (P greater than 0.05) did not seem to affect the antisperm Ab titer, nor did the aborting frequency. Our study suggests that antisperm Ab is one of the important causes of RSA in women.

[Trace element contents in the transparent lens and the senile cataract lens]

The contents of trace elements Zn, Mn, Cu and Fe in 38 senile cataract lenses and 37 transparent lenses were determined by atomic absorption spectrophotometry. It was found that the contents of the elements in senile cortical cataract lenses were markedly different from those in transparent lenses. Comparing transparent lenses with senile nuclear cataract lenses, there was only difference in the content of Mn. It was therefore inferred that the occurrence of senile cataract was directly related to the deficiency of trace elements.