Trophic effects by epidermal growth factor on duodenal mucosa and exocrine pancreas in rats

Epidermal growth factor (EGF) is a potent growth factor with possible implications on the regulation of pancreatic secretion and duodenal absorption but also on pancreatic tumor growth. In the present study the growth effect on duodenal mucosa and pancreas by a 14-day continuous infusion of three different doses of EGF (4, 30 and 60 micrograms EGF/kg/24 h) was studied in rats. The EGF content in duodenal mucosa and pancreatic tissue was significantly increased by 30 and 60 micrograms/kg/24 h of EGF while plasma levels were only marginally increased. Neither duodenal mucosal nor pancreatic weights were changed but DNA content in both tissues was increased with the higher EGF doses. Long-term EGF infusion has moderate trophic effect on duodenal mucosa and the pancreas. There is a high tissue uptake of EGF, specially in duodenal mucosa. The hyperplasia seems to be related to tissue levels of EGF but not to plasma levels.

Spontaneous malignant transformation of fibrous dysplasia

OBJECTIVE

To evaluate the clinical and radiological findings in diagnosing spontaneous malignant transformation of fibrous dysplasia.

METHODS

Fifteen cases of sarcomatous transformation proved by operation and pathological examinations were found in a group of 356 patients with fibrous dysplasia, and their radiological manifestations were retrospectively studied. The 15 cases included 8 osteosarcomas, 5 fibrosarcomas and 2 chondrosarcomas. All the 15 patients were known to have long-standing fibrous dysplasia, but no radiation therapy was ever received. Eleven patients had polyostotic fibrous dysplasia and 4 had monostotic type.

RESULTS

Malignant transformation most frequently occurs in the cystic expansive lesion of the long tubular bone. Pains, swelling and late appearance of a bony mass are the main clinical manifestations. The early radiological features of sarcomatous transformation in fibrous dysplasia are moth-eaten or cystic areas of osteolysis located in the involved bone. The cortical destruction and gradual formation of a soft tissue mass that contains tumor-bone are highly suspicious of osteosarcomatous transformation, while ring-like and spotty calcification in the tumor matrix is indicative of chondrosarcoma. Fibrosarcoma usually shows simple osteolytic destruction.

CONCLUSIONS

According to the clinical radiological findings, patients of sarcomatous transformation can be detected in the early stage. These radiological findings may be used as a clue for differentiating various kinds of sarcomatous transformation.

Phase labeling of C-H and C-C spin-system topologies: application in constant-time PFG-CBCA(CO)NH experiments for discriminating amino acid spin-system types

Triple-resonance experiments facilitate the determination of sequence-specific resonance assignments of medium-sized 13C,15N-enriched proteins. Some triple-resonance experiments can also be used to obtain information about amino acid spin-system topologies by proper delay tuning. The constant-time PFG-CBCA(CO)NH experiment allows discrimination between five different groups of amino acids by tuning (phase labeling) independently the delays for proton-carbon refocusing and carbon-carbon constant-time frequency labeling. The proton-carbon refocusing delay allows discrimination of spin-system topologies based on the number of protons attached to C alpha and C beta atoms (i.e. C-H phase labeling). In addition, tuning of the carbon-carbon constant-time frequency-labeling delay discriminates topologies based on the number of carbons directly coupled to C alpha and C beta atoms (i.e. C-C phase labeling). Classifying the spin systems into these five groups facilitates identification of amino acid types, making both manual and automated analysis of assignments easier. The use of this pair of optimally tuned PFG-CBCA(CO)NH experiments for distinguishing five spin-system topologies is demonstrated for the 124-residue bovine pancreatic ribonuclease A protein.

Novel covalent chaperone complexes associated with human chorionic gonadotropin beta subunit folding intermediates

Molecular chaperones facilitate the folding of proteins in the endoplasmic reticulum (ER) of mammalian cells. The glycoprotein hormone chorionic gonadotropin beta subunit is a secretory protein whose folding in the ER has been demonstrated (Huth, J. R., Mountjoy, K., Perini, F., and Ruddon, R. W.(1992) J. Biol. Chem. 267, 8870-8879). Because folding of wild type hCG-beta subunit occurs in the ER with a t1/2 = 4-5 min, stable association of ER chaperones with hCG-beta have been difficult to detect probably because they have a short half-life. However, beta-chaperone complexes containing the ER chaperones BiP, ERp72, and ERp94 have been detected in slow folding mutants of hCG-beta subunit that lack both of the N-linked oligosaccharides (Feng, W., Matzuk, M. M., Mountjoy, K., Bedows, E., Ruddon, R. W., and Boime, I. (1995) J. Biol. Chem. 270, 11851-11859). The questions addressed here are 1) whether the detection of chaperone-containing complexes is related to the absence of carbohydrate or to the rate of hCG-beta subunit folding, 2) whether such complexes are dead-end or whether they lead to formation of a secreted, mature hCG-beta form, and 3) what the nature of the hCG-beta-chaperone binding is. The data obtained indicate that the amount of detectable hCG-beta-chaperone complexes correlates with the rate or extent of folding, that the complexes of hCG-beta with ER chaperones lead to the formation of secretable beta, and that the complexes of hCG-beta with chaperones involve the formation of intermolecular disulfide bonds.

Phase labeling of C-H and C-C spin-system topologies: application in PFG-HACANH and PFG-HACA(CO)NH triple-resonance experiments for determining backbone resonance assignments in proteins

Triple-resonance experiments can be designed to provide useful information on spin-system topologies. In this paper we demonstrate optimized proton and carbon versions of PFG-CT-HACANH and PFG-CT-HACA(CO)NH 'straight-through' triple-resonance experiments that allow rapid and almost complete assignments of backbone H(alpha), 13C(alpha), 15N and H(N) resonances in small proteins. This work provides a practical guide to using these experiments for determining resonance assignments in proteins, and for identifying both intraresidue and sequential connections involving glycine residues. Two types of delay tunings within these pulse sequences provide phase discrimination of backbone Gly C(alpha) and H(alpha) resonances: (i) C-H phase discrimination by tuning of the refocusing period tau(a_f); (ii) C-C phase discrimination by tuning of the 13C constant-time evolution period 2T(c). For small proteins, C-C phase tuning provides better S/N ratios in PFG-CT-HACANH experiments while C-H phase tuning provides better S/N ratios in PFG-CT-HACA(CO)NH. These same principles can also be applied to triple-resonance experiments utilizing 13C-13C COSY and TOCSY transfer from peripheral side-chain atoms with detection of backbone amide protons for classification of side-chain spin-system topologies. Such data are valuable in algorithms for automated analysis of resonance assignments in proteins.

VDAC/porin is present in sarcoplasmic reticulum from skeletal muscle

In this study we demonstrate the existence of a protein with properties of the voltage-dependent anion channel (VDAC) in the sarcoplasmic reticulum (SR) using multiple approaches as summarized in the following: (a) 35 and 30 kDa proteins in different SR preparations, purified from other membranal systems by Ca2+/oxalate loading and sedimentation through 55% sucrose, cross-react with four different VDAC monoclonal antibodies. (b) Amino acid sequences of three peptides derived from the SR 35 kDa protein are identical to the sequences present in VDAC1 isoform. (c) Similar to the mitochondrial VDAC, the SR protein is specifically labeled by [14C]DCCD. (d) Using a new method, a 35 kDa protein has been purified from SR and mitochondria with a higher yield for the SR. (e) Upon reconstitution into a planar lipid bilayer, the purified SR protein shows voltage-dependent channel activity with properties similar to those of the purified mitochondrial VDAC or VDAC1/porin 31HL from human B lymphocytes, and its channel activity is completely inhibited by the anion transport inhibitor DIDS and about 80% by DCCD. We also demonstrate the translocation of ATP into the SR lumen and the phosphorylation of the luminal protein sarcalumenin by this ATP. Both ATP translocation and sarcalumenin phosphorylation are inhibited by DIDS, but not by atractyloside, a blocker of the ATP/ADP exchanger. These results indicate the existence of VDAC, thought to be located exclusively in mitochondria, in the SR of skeletal muscle, and its possible involvement in ATP transport. Together with recent studies on VDAC multicompartment location and its dynamic association with enzymes and channels, our findings suggest that VDAC deserves attention and consideration as a protein contributing to various cellular functions.

Ryanodine receptor/calcium release channel conformations as reflected in the different effects of propranolol on its ryanodine binding and channel activity

1. Propranolol, a beta-blocker, inhibited or stimulated ryanodine binding to both the membrane-bound and purified ryanodine receptor (RyR) depending on the assay conditions. At high NaCl concentrations, propranolol increased the number of ryanodine-binding sites (Bmax) with no effect on the binding affinity. In the presence of 0.2 M NaCl, ryanodine binding was inhibited by propranolol. Half-maximal inhibition was obtained at 1.2 mM and complete inhibition at 2 mM propranolol. The inhibitory effect of propranolol obtained at low NaCl concentration was not restored by increasing the NaCl concentration to 1 M. 2. Modulators of the RyR that are known to alter its conformational states, such as adenine nucleotides, Ca2+ concentration and pH, modified the effect of propranolol on ryanodine binding. In the presence of propranolol and at low NaCl concentrations, ryanodine binding was inhibited and showed no Ca(2+)-, pH-, or time-dependence. 3. Propranolol immediately and completely blocked the channel opening of RyR reconstituted into a planar lipid bilayer. Propranolol-modified non-active channel was reactivated to a subconductive state (about 40% of the control conductance) by ATP. 4. Competition experiments between lidocaine (a stimulatory drug) or tetracaine (an inhibitory drug) and propranolol at 0.2 or 1.0 M NaCl, respectively, suggest the existence of different interaction sites for local anaesthetics and propranolol. 5. These results suggest that propranolol interacts directly with the RyR and modifies its ryanodine binding and single-channel activities. Propranolol effects are altered by the RyR conformational state, suggesting its possible use as a conformational probe for RyR.

Antitumor activity of daphnane-type diterpene gnidimacrin isolated from Stellera chamaejasme L

The daphnane-type diterpene gnidimacrin, isolated from the root of the Chinese plant, Stellera chamaejasme L., was found to strongly inhibit cell growth of human leukemias, stomach cancers and non-small cell lung cancers in vitro at concentrations of 10(-9) to 10(-10) M. On the other hand, even at 10(-6) to 10(-5) M, the small cell lung cancer cell line H69 and the hepatoma cell line HLE were refractory to gnidimacrin. The agent showed significant antitumor activity against murine leukemias and solid tumors in an in vivo system. In K562, a sensitive human leukemia cell line, gnidimacrin induced blebbing of the cell surface, which was completely inhibited by staurosporine at concentrations above 10(-8) M, and arrested the cell cycle transiently to G2 and finally the G1 phase at growth-inhibitory concentrations. It inhibited phorbol-12,13-dibutyrate(PDBu) binding to K562 cells and directly stimulated protein kinase C (PKC) activity in the cells in a dose-dependent manner (3-100 nM). Although activation of PKC isolated from refractory H69 cells was observed only with 100 nM gnidimacrin, the degree of activation was lower than that produced by 3 nM in K562 cells. Our results suggest that gnidimacrin acts as a PKC activator for tumor cells and that this mechanism may be responsible for its antitumor activity.

The action of carboxyl modifying reagents on the ryanodine receptor/Ca2+ release channel of skeletal muscle sarcoplasmic reticulum

In this work we show that ryanodine binding to junctional sarcoplasmic reticulum (SR) membranes or purified ryanodine receptor (RyR) is inhibited in a time- and concentration-dependent fashion by prior treatment with the carboxyl reagent dicyclohexylcarbodiimide (DCCD). Exposure of the membrane-bound RyR to the water soluble carboxyl reagents 1-ethyl-3 (3-(dimethylamino) propyl carbodiimide (EDC) or N-ethyl-pheny-lisoxazolium-3'-sulfonate (WRK) only slightly affects their ryanodine binding capacity. The amphipathic reagent N-ethoxy cabonyl-2-ethoxy-1,2-dihydroquinaline (EEDQ) inhibited ryanodine binding at relatively high concentrations. DCCD-modification of the SR decreased the binding affinities of the RyR for ryanodine and Ca2+ by about 3- and 18-fold, respectively. The single channel activity of SR membranes modified with DCCD and then incorporated into planar lipid bilayers is very low (5-8%) in comparison to control membranes. Application of DCCD to either the myoplasmic (cis) or luminal (trans) side of the reconstituted unmodified channels resulted in complete inhibition of their single channel activities. Similar results were obtained with the water soluble reagent WRK applied to the myoplasmic, but not to the luminal side. The DCCD-modified non-active channel is re-activated by addition of ryanodine in the presence of 250 microM Ca2+ and is stabilized in a sub-conductance state. With caffeine, ryanodine re-activated the channel in the presence of 100 microM of Ca2+. The results suggest that a carboxyl residue(s) in the RyR is involved either in the binding of Ca2+, or in conformational changes that are produced by Ca2+ binding, and are required for the binding of ryanodine and the opening of the Ca2+ release channel.

Hepatitis B immunization: a potential incentive to HIV vaccine trial participation in Thailand?

To assess the effectiveness of hepatitis B immunization as an incentive to retention in HIV seroincidence studies and future HIV vaccine trials in northern Thailand, subjects enrolled in three HIV seroincidence cohorts were screened for hepatitis B markers and seronegatives were offered free hepatitis B immunization. Cohorts studied included female commercial sex workers (CSWs), male sexually transmitted disease (STD) patients, and recently discharged military conscripts. Subjects who agreed to the immunization program were compared with those not enrolled to determine the utility of immunization as an incentive to cohort retention. Full immunization was achieved for 273 (89.5%) of 305 vaccinees; only 323 (60.6%) of 533 subjects not immunized completed the same follow-up visits (OR = 1.49, 95% and CI = 1.27, 1.75). Hepatitis B vaccination was a significant incentive for completion of the follow-up program. The vaccination program had the greatest effect on the CSWs; a similar effect was seen for male STD patients, but not for discharged conscripts. Despite the immunization program, follow-up rates at 12 months were similar in the immunized and nonimmunized groups.

Marital fertility control among the Qing nobility: implications for two types of preventive check

Demographers, as early as Malthus, have assumed that the preventive checks, delayed marriage and celibacy, were absent in traditional China. In this paper on the Qing (1644-1911) imperial lineage, we demonstrate that, instead, there may have been a different, more 'modern' preventive check: fertility control within marriage. Marital fertility of lineage couples during the eighteenth and nineteenth centuries was low to moderate. Such low fertility was the product of three behavioural mechanisms: late starting, early stopping and, most significantly, long spacing. Couples apparently regulated their fertility according to their economic resources and the sex of their surviving children. Moreover, they did so, we suggest, by regulating their coital frequency. Deliberate fertility control, in other words, was already within the 'calculus of conscious choice' for some Chinese well before this century. the speed of contemporary sinitic fertility transitions may accordingly be attributed to the fact that they did not require a change in attitudes, only the diffusion of new incentives and effective technologies.

Study of UV-bleached channel-waveguide performance in nonlinear optical polymer films

We report studies on UV-photobleached optical channel waveguides in nonlinear optical polymer films. The nonlinear optical polymer used is poly(methyl methacrylate)/DR1 side-chain polymer. The effective indices of the channel waveguides are measured with the prism-coupling technique, along with the effective indices of bleached and unbleached polymer films. The effective-index method was used to predict the effective indices of the channel waveguides from measurements of the slab waveguides, without detailed knowledge of the index distributions in the polymer films. Some local stress-related effects on the boundaries of the channel waveguides caused by the UV-bleaching process are identified by comparison between direct channel measurement and prediction. It is found that the technique used in this study can be employed to predict the performance of channel waveguides processed such that they have no excessive internal stress distributions.

Modeling photobleached optical polymer waveguides

One of the most efficient ways to prepare nonlinear optical polymer channel waveguides is by photobleaching. To control the index profile precisely and to design and improve the performance of active electro-optical devices, modeling of the photobleaching process is important. We report our phenomenological bleaching model, which uses a stretched exponential time dependency technique that predicts the index profile for polymer channel waveguides and present design rules for active optical switches and modulators. One way to verify the bleaching model is to calculate the effective index and compare this with our measured effective index obtained with prism-coupling techniques. The bleaching model shows good agreement with experiments.

The asparagine-linked oligosaccharides of the human chorionic gonadotropin beta subunit facilitate correct disulfide bond pairing

The role of asparagine (N)-linked oligosaccharide chains in intracellular folding of the human chorionic gonadotropin (hCG)-beta subunit was determined by examining the kinetics of folding in Chinese hamster ovary (CHO) cells transfected with wild-type or mutant hCG-beta genes lacking one or both of the asparagine glycosylation sites. The half-time for folding of p beta 1 into p beta 2, the rate-determining step in beta folding, was 7 min for wild-type beta but 33 min for beta lacking both N-linked glycans. The p beta 1-->p beta 2 half-time was 7.5 min in CHO cells expressing the beta subunit missing the Asn13-linked glycan and 10 min for the beta subunit missing the Asn30-linked glycan. The inefficient folding of hCG-beta lacking both N-linked glycans correlated with the slow formation of the last three disulfide bonds (i.e. disulfides 23-72, 93-100, and 26-110) to form in the hCG-beta-folding pathway. Unglycosylated hCG-beta was slowly secreted from CHO cells, and beta subunit-folding intermediates retained in cells for more than 5 h were degraded into a hCG-beta core fragment-like protein. However, coexpression of the hCG-alpha gene enhanced folding and formation of disulfide bonds 23-72, 93-100, and 26-110 of hCG-beta lacking N-linked glycans. In addition, the molecular chaperones BiP, ERp72, and ERp94, but not calnexin, were found in a complex with unglycosylated, unfolded hCG-beta and may be involved in the folding of this beta form. These data indicate that N-linked oligosaccharides assist hCG-beta subunit folding by facilitating disulfide bond formation.

The epidemiology of HIV and syphilis among male commercial sex workers in northern Thailand

OBJECTIVE

To examine the prevalence and incidence of HIV and syphilis, and risk behaviors for these infections, among 1,172 male commercial sex workers (CSW) followed prospectively from 1989 to 1994 in Chiang Mai, northern Thailand.

METHODS

Twice yearly visits were conducted by the Thai Ministry of Public Health at all cooperating gay bars and clubs (17 sites) in Chiang Mai City as part of a national HIV sentinel surveillance. Men and boys who agreed were followed prospectively. Sentinel visits included an interview, HIV pre-test counseling, HIV and syphilis serology, condom distribution, and referral for post-test counseling. Participation was voluntary, confidential, and individual HIV results were available only to participating subjects. A total of 219 CSW were seen at least twice, allowing for incidence estimates based on 100 person-years (PY).

RESULTS

Median age of male CSW was 20 years. Median time of work as a CSW was 4 months. Most men (57.6%) described themselves as heterosexual. Median number of clients was 2.5 per week, and reported condom use with clients was low: 42% reported inconsistent or no condom use, while 58% reported always using condoms. Reactive Venereal Disease Research Laboratory results were 7.6%, overall, but showed a declining trend. HIV prevalence was 1.4% in June 1989, 13.9% in June 1990, and 20.1% in December 1993, and showed a significant increasing trend. There were 27 incident HIV infections in 227.3 PY of observation, for an overall incidence during the 4.5-year period of 11.9 per 100 PY (95% confidence interval, 7.42-16.38).

CONCLUSION

Male CSW in northern Thailand are at high risk for HIV despite current prevention efforts. The majority are heterosexual, which may be an important epidemiologic link in the spread of HIV between male CSW users and heterosexual women in Thailand.

Asparagine-linked oligosaccharides facilitate human chorionic gonadotropin beta-subunit folding but not assembly of prefolded beta with alpha

To determine the role of asparagine (N)-linked oligosaccharide chains in protein folding and assembly, the well established hCG-beta in vitro folding and assembly assays were used to analyze how the human CG (hCG) beta-subunit devoid of one or two N-linked glycans folds and assembles under different conditions. Two approaches were used: 1) site-specific mutagenesis of hCG-beta synthesized in Chinese hamster ovary cells transfected with beta-mutants lacking the asparagine glycosylation sites; and 2) enzymatic deglycosylation of hCG-beta synthesized in JAR cells with peptide N-glycosidase F or endoglycosidase H. In both cases, [35S]cysteine-labeled beta-subunits were used as substrates to measure the conversion of the hCG-beta folding intermediate p beta 1 into p beta 2 and assembly of p beta 2 with urinary alpha. Using the mutated substrates from Chinese hamster ovary cells, it was found that 60% of wild-type p beta 1 (two N-linked glycans), 60% of p beta 1 missing the Asn13-linked glycan, 40% of p beta 1 missing the Asn30-linked glycan, and 10% of p beta 1 missing two N-linked glycans were converted to the corresponding p beta 2, respectively. With the enzymatically deglycosylated substrate from JAR cells, 90% of p beta 1 (two N-linked glycans), 70% of p beta 1(1) (one N-linked glycan), and 10% of p beta 1(0) (without N-linked glycan) folded into p beta 2 under cysteamine and cystamine redox conditions with or without protein disulfide isomerase. These data demonstrate that at least one N-linked glycan is required for efficient folding of hCG-beta and that the Asn30-linked glycan is more important than Asn13-linked glycan for hCG-beta folding. It also was shown that the composition of N-linked glycans of hCG-p beta 1 did not change protein folding, since hCG-beta substrates with high mannose oligosacharides folded as efficiently as beta-substrates containing sialylated complex oligosaccharides. Moreover, assembly of the already folded, assembly-component folding intermediate, p beta 2, was not affected by removal of one or both of the N-linked glycans of the beta-subunit. These data thus show that N-linked glycans play their most important role in the folding component of the folding and assembly pathway for hCG-beta.

[The antitumor activities of gnidimacrin isolated from Stellera chamaejasme L]

Gnidimacrin, a diterpene compound, isolated from the methanol extract of Stellera chamaejasme L, showed significant antitumor activities against mouse leukemia P-388 and L-1210 in vivo. At the dosages of 0.02-0.03mg/kg ip, the in increase in life span (ILS) was 70% and 80%, respectively. Gnidimacrin was also active against murine solid tumors in vivo, such as Lewis lung carcinoma, B-16 melanoma and colon cancer 26. It showed ILSs of 40%, 49% and 41% at the dosages of 0.01-0.02mg/kg ip, respectively. Gnidimacrin strongly inhibited cell proliferation of human cancer cell lines such as leukemia K562, stomach cancers Kato-III, MKN-28, MKN-45, and mouse L-1210 by the MTT assay and colony forming assay in vitro. The IC50 of gnidimacrin was 0.007-0.00012microgram/ml. It is concluded that gnidimacrin is the principal antitumor element in Stellera chamaejasme L. with strong antitumor activities.

Solution NMR structure of the major cold shock protein (CspA) from Escherichia coli: identification of a binding epitope for DNA

Sequence-specific 1H and 15N resonance assignments have been determined for the major cold shock protein (CspA) from Escherichia coli with recently developed three-dimensional triple-resonance NMR experiments. By use of these assignments, five antiparallel beta-strands were identified from analysis of NMR data. Strands 1-4 have a classical 3-2-1-4 Greek key beta-sheet topology and there are two beta-bulges, at positions Lys10-Trp11 and Gly65-Asn66. Three-dimensional structures of CspA were generated from NMR data by using simulated annealing with molecular dynamics. The overall chain fold of CspA is a beta-barrel structure, with a tightly packed hydrophobic core. Two-dimensional isotope-edited pulsed-field gradient 15N-1H heteronuclear single-quantum coherence spectroscopy was used to characterize the 15N-1H fingerprint spectrum with and without a 24-base oligodeoxyribonucleotide, 5'-AACGGTTTGACGTACAGACCATTA-3'. Protein-DNA complex formation perturbs a subset of the amide resonances that are located mostly on one face of the CspA molecule. This portion of the CspA molecular surface includes two putative RNA-binding sequence motifs which contribute to an unusual cluster of eight surface aromatic side chains: Trp11, Phe12, Phe18, Phe20, Phe31, His33, Phe34, and Tyr42. These surface aromatic groups, and also residues Lys16, Ser44, and Lys60 located on this same face of CspA, are highly conserved in the family of CspA homologues. These isotope-edited pulsed-field gradient NMR data provide a low-resolution mapping of a DNA-binding epitope on CspA.

Cloning and expression of a novel acidic calponin isoform from rat aortic vascular smooth muscle

The actin-binding protein calponin has been implicated in the regulation of smooth muscle contraction. We have isolated cDNA clones encoding a novel acidic calponin isoform from rat aortic vascular smooth muscle cells. The initial 273 residues of the deduced 330 amino acid polypeptide (M(r) 36,377) are highly homologous to basic smooth muscle calponin isoforms, but the remaining 57 residues at the carboxyl terminus comprise a unique and strongly acidic domain. The sequence of the acidic domain shows high homology (93.3% identity) to the partial sequence of HUMXT01244, an unidentified human hippocampal gene product (Adams, M., Dubnick, M., Kerlavgne, A. R., Moreno, R., Kelly, J. M., Utterback, T. R., Nagle, J. W., Fields, C., and Venter, J. C. (1992) Nature 355, 632-634). Transcripts encoding acidic calponin are expressed in cultured rat aortic vascular smooth muscle cells and in non-muscle and smooth muscle tissues of adult rat. Based on its calculated M(r) and the tissue distribution of its expression, acidic calponin is an excellent candidate for a previously detected non-muscle calponin homolog (Takeuchi, K., Takahashi, K., Abe, M., Nishida, W., Hiwada, K., Nabeya, T., and Maruyama, K. (1991) J. Biochem. (Tokyo) 109, 311-316). Like basic calponin isoforms, acidic calponin synthesized in a bacterial expression system bound F-actin. However, unlike basic calponin, the acidic isoform did not interact with Ca2+/calmodulin, indicating a functional distinction between the muscle and non-muscle forms.

Total and methyl mercury levels in human scalp hairs of typical populations in China by NAA, GC(EC), and other techniques

The contents of total and methyl mercury in scalp hair samples of 1179 fishermen living in a typical Hg-polluted region in northeast China and 27 lying-in women and their newborns in Beijing have been determined by INAA, GC(EC), and other techniques. Only 18 of all fishermen had Hg contents above 5 micrograms/g, which indicates that the Hg pollution there has been substantially alleviated. The longitudinal Hg patterns of the lying-in women showed a gradually lowering tendency during pregnant period. Further, the Hg contents of the newborn babies generally were above or close to those of their mothers, confirming the mechanism that the methyl Hg, an organic species of Hg with high toxicity, is readily able to penetrate the placental barrier and to accumulate in the fetus. Thus, the mercury poison has occurred at the early stage of pregnancy.

Photorefractive damage thresholds in Ti:LiNbO(3) channel waveguides

The photorefractive effect in titanium-in-diffused LiNbO(3) waveguides is studied both experimentally and theoretically. Measurements of mode size and transmitted optical power as a function of input optical power are presented. The diffusion constants in the diffusion model and the unknown parameters in Kukhtarev's model are determined from measurements of the near-field intensity profiles at low and at high intensity levels. These parameters can then be used to predict waveguide behavior as a function of the input power level. The simulated behavior closely resembles that observed experimentally. Calculated corrections for thermally induced index perturbation show that the thermal effects are higher-order corrections to the dominant photorefractive effect.