Optimal control policy for probabilistic Boolean networks with hard constraints

It is well known that the control/intervention of some genes in a genetic regulatory network is useful for avoiding undesirable states associated with some diseases like cancer. For this purpose, both optimal finite-horizon control and infinite-horizon control policies have been proposed. Boolean networks (BNs) and its extension probabilistic Boolean networks (PBNs) as useful and effective tools for modelling gene regulatory systems have received much attention in the biophysics community. The control problem for these models has been studied widely. The optimal control problem in a PBN can be formulated as a probabilistic dynamic programming problem. In the previous studies, the optimal control problems did not take into account the hard constraints, i.e. to include an upper bound for the number of controls that can be applied to the captured PBN. This is important as more treatments may bring more side effects and the patients may not bear too many treatments. A formulation for the optimal finite-horizon control problem with hard constraints introduced by the authors. This model is state independent and the objective function is only dependent on the distance between the desirable states and the terminal states. An approximation method is also given to reduce the computational cost in solving the problem. Experimental results are given to demonstrate the efficiency of our proposed formulations and methods.

The patella as an unusual site of renal cell carcinoma metastasis

We report a rare case of renal cell carcinoma with metastasis to the patella in a 49-year-old man, who presented with seven months of left knee pain after a fall. Only two similar cases have been reported. Patellar metastasis is rare because it has a relatively poor blood supply and microemboli would have been sieved out by the pulmonary circulation. Patellectomy is the usual treatment for such cases. We suspect that the preferential metastasis in our patient is a result of tropism. Our treatment for this patient is unique. We opted for a patella-preserving operation involving the use of cryotherapy, as this treatment modality preserved the quality of life. An opportunistic biopsy one year later confirmed the absence of active disease within the patella. This case uniquely provides human in vivo histological confirmation that an intralesional procedure with local and systemic adjuvant therapy effectively controls local disease.

Export of toxic chemicals - a review of the case of uncontrolled electronic-waste recycling

This paper reviews the concentrations of persistent organic pollutants such as flame retardants (PBDEs), dioxins/furans (PCDD/Fs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and heavy metals/metalloid concentrations of different environmental media at Guiyu, a traditional rice-growing village located in southeastern Guangdong Province (PR China), which has turned into an intensive electronic-waste (e-waste) recycling site. Incomplete combustion of e-waste in open air and dumping of processed materials are the major sources of various toxic chemicals. By comparing with existing data available in other areas and also guidelines adopted in different countries, it is obvious that the environment is highly contaminated by these toxic chemicals derived from the recycling processes. For example, the monthly concentration of the sum of 22 PBDE congeners contained in PM(2.5) (16.8ngm(-3)) of air samples at Guiyu was 100 times higher than published data. In order to safeguard the environment and human health, detailed investigations are urgently needed, especially on tracking the exposure pathways of different toxic chemicals which may affect the workers and local residents especially mothers, infants and children.

Effect of Bone Material Properties on the Initial Stability of a Cementless Hip Stem: A Finite Element Study

In previous finite element studies of cementless hip stems reported in the literature, the effect of bone quality on the initial micromotion and interface bone strain has been rarely reported. In this study, the effect of varying cortical and cancellous bone modulus on initial stem micromotion and interface bone strain was examined and the potential consequence of these changes on bone ingrowth and implant migration was reported. A finite element (FE) model of a total hip replacement (THR) was created and the Young's moduli of cortical and cancellous bone were systematically varied to study the relative effect of the quality of both types of bone on the initial stability of a cementless THR. It was found that the initial micromotion and interface bone strain in a THR was significantly affected by the overall stiffness of the femur. In other words, both the reduction of the modulus of cortical and cancellous bone caused an increase in the initial micromotion and interface bone strain. This suggests that for FE studies to be truly predictive, a range of bone quality must be examined to study the performance envelope of a particular stem and to allow comparison with clinical results.

Profiling of protein kinases in the neoplastic transformation of human ovarian surface epithelium

OBJECTIVE

The aim of this study was to study the pattern of protein kinase expression in a culture model of epithelial ovarian carcinogenesis.

METHODS

Cultures of normal human ovarian surface epithelium (OSE), OSE from women with BRCA1 mutations, a cell culture model of preneoplastic (SV40 T-antigen-immortalized, nontumorigenic) and neoplastic (SV40-E-cadherin transfected, tumorigenic) OSE, and three ovarian cancer cell lines were used to represent OSE phenotypes of different genetic backgrounds and at different, progressive stages of neoplastic transformation. The protein kinase network signaling was studied by Western blotting, simultaneously using multiple antibodies for specific protein kinases.

RESULTS

High levels of cGMP-dependent protein kinase were found in normal and preneoplastic OSE, but were absent in neoplastic OSE. In contrast, expression of MEK6 was detected exclusively in neoplastic OSE. The expressions of casein kinase II (CK2), p38 mitogen-activated protein kinase (MAPK), cyclin-dependent kinase, and the phosphatidylinositol 3-kinase (PI3K) effectors Akt2 and p70 S6 kinase (S6K) were several-fold higher in neoplastic OSE than in normal OSE, whereas the expressions of the MAPKs extracellular signal-regulated kinases ERK1 and -2 were unchanged. Importantly, constitutive phosphorylation of Akt2 and p70 S6K, as found in neoplastic OSE, was also observed in overtly normal OSE from women with predisposing BRCA1 gene mutations.

CONCLUSIONS

These data demonstrate that different repertoires of downstream signaling proteins, particularly those of the MEK6-p38 MAPK-CK2 pathway and the PI3K pathway, are correlated with phenotypic manifestations of a cell culture model of OSE at progressive stages in the development of ovarian cancer. Changes in PI3K effectors are already found in overtly normal OSE from women with BRCA1 mutations.

Ovarian surface epithelium: biology, endocrinology, and pathology

The epithelial ovarian carcinomas, which make up more than 85% of human ovarian cancer, arise in the ovarian surface epithelium (OSE). The etiology and early events in the progression of these carcinomas are among the least understood of all major human malignancies because there are no appropriate animal models, and because methods to culture OSE have become available only recently. The objective of this article is to review the cellular and molecular mechanisms that underlie the control of normal and neoplastic OSE cell growth, differentiation, and expression of indicators of neoplastic progression. We begin with a brief discussion of the development of OSE, from embryonic to the adult. The pathological and genetic changes of OSE during neoplastic progression are next summarized. The histological characteristics of OSE cells in culture are also described. Finally, the potential involvement of hormones, growth factors, and cytokines is discussed in terms of their contribution to our understanding of the physiology of normal OSE and ovarian cancer development.

Rabbit sex hormone-binding globulin: expression in the liver and testis during postnatal development and structural characterization by truncated proteins

Although sex hormone binding globulin (SHBG) is found in the blood plasma of adult humans and rabbits and the gene is expressed in their livers, it is not detected in the plasma of adult rodents nor is it expressed in adult rodent livers. Thus the rabbit represents a good model to study the metabolism and function of SHBG in the blood. We have used a cloned rabbit SHBG cDNA to detect mRNA expression in rabbits during the postnatal period, and to construct truncated SHBG proteins for structure/function analysis. The SHBG mRNA appeared in the testis as early as 3 days after birth. The level increased gradually in abundance throughout postnatal development, and attained a maximum at 12 weeks of age when the gonads were fully matured. In contrast, SHBG mRNA in the livers of male and female animals increased to a maximum by 4 weeks of age, and were maintained at this level until 12 weeks before subsiding to the initial levels. The increase and decrease in SHBG mRNA levels in the liver were accompanied by similar changes in serum SHBG. This suggests that SHBG in the blood circulation comes from the liver and this might also provide a source of SHBG for the male reproductive tract before formation of the blood-testis barrier. To elucidate the minimal sequence of rabbit SHBG responsible for steroid-binding, a panel of 13 truncated SHBG proteins was constructed, expressed in Escherichia coli, and biochemically purified for study. It was shown that the complete protein sequence of rabbit SHBG was important for maintaining a stable steroid-protein complex. Unlike human SHBG for which a truncated protein of the first 206 residues of the 373 amino acid protein can still bind steroid, removal of 43 or more residues from the C-terminus of rabbit SHBG completely abolished steroid-binding.

Fatal chemotherapy associated Clostridium difficile infection--a case report

Clostridium difficile associated diarrhoea or Pseudomembranous colitis occasionally occurs without prior antibiotic usage. While the association of chemotherapy and Clostridium difficile infection has previously been well recorded, the true incidence is unknown. We report a case of Clostridium difficile associated diarrhoea after chemotherapy for lung cancer. The fatal outcome in this case and the increasing use of chemotherapy in this country highlights the need to have a high index of suspicion in any case of unexplained diarrhoea post chemotherapy. A review of the literature is presented.

Ovarian surface epithelium: biology, endocrinology, and pathology

The epithelial ovarian carcinomas, which make up more than 85% of human ovarian cancer, arise in the ovarian surface epithelium (OSE). The etiology and early events in the progression of these carcinomas are among the least understood of all major human malignancies because there are no appropriate animal models, and because methods to culture OSE have become available only recently. The objective of this article is to review the cellular and molecular mechanisms that underlie the control of normal and neoplastic OSE cell growth, differentiation, and expression of indicators of neoplastic progression. We begin with a brief discussion of the development of OSE, from embryonic to the adult. The pathological and genetic changes of OSE during neoplastic progression are next summarized. The histological characteristics of OSE cells in culture are also described. Finally, the potential involvement of hormones, growth factors, and cytokines is discussed in terms of their contribution to our understanding of the physiology of normal OSE and ovarian cancer development.

Coexpression of hepatocyte growth factor-Met: an early step in ovarian carcinogenesis?

Since autocrine regulation of HGF-Met is implicated in many forms of human cancer, we investigated whether the predisposition to develop ovarian cancer in women with hereditary ovarian cancer syndromes involves changes in the expression of HGF-Met by the tissue of origin of epithelial ovarian cancers, the ovarian surface epithelium (OSE). We compared cultures of normal OSE from women with (FH-OSE) (n=20) and with no (NFH-OSE) (n=48) family histories of ovarian cancer, SV40 Tag immortalized OSE lines (IOSE, n=5) and ovarian cancer cell lines (n=3). Cultures derived from 21/22 women with NFH-OSE and 13/13 women with FH-OSE expressed Met mRNA initially. After two to three passages, Met was downregulated in 37% of NFH-OSE cultures but persisted in 100% of FH-OSE cultures and ovarian cancer lines, like other epithelial differentiation markers that are stabilized in FH-OSE and neoplasia. HGF and Met mRNA were concomitantly expressed by NFH-OSE from only three of 32 women but in FH-OSE from eight of 13 women, and also in five of five IOSE and two of three ovarian cancer lines. Conditioned media from FH-OSE, but not NFH-OSE, contained immunoreactive HGF and induced cohort migration which was inhibited by neutralizing HGF antibody. Several signaling molecules of the PI3K pathway, including Akt2 and p70 S6K, were constitutively activated in FH-OSE from six of six women but in NFH-OSE from only four of eight women. Exogenous HGF was mitogenic in OSE, and that effect was regulated through the MAP kinase (ERK1/ERK2) and FRAP/p70 S6K pathways. The proliferative response to HGF was greater in NFH-OSE than in FH-OSE cultures. The results show that FH-OSE cultures differ from NFH-OSE by increased stability of Met expression and by HGF secretion. Constitutive phosphorylation of kinases and a diminished growth response to HGF suggest the presence of autocrine regulation in FH-OSE. In analogy with other cell types where an autocrine HGF-Met loop has been implicated in tumorigenic transformation, this change in FH-OSE may play a role in the enhanced susceptibility to ovarian carcinogenesis in women with hereditary ovarian cancer syndromes.

The sedative and electroencephalographic effects of regional anaesthesia

We studied sedation scores, the processed electroencephalogram and mean arterial pressure pre-operatively in patients before and after spinal (n = 15) and lumbar epidural (n = 15) anaesthesia. We compared them with changes occurring over time in a control group (n = 15), using the responsiveness component of the Observer Assessment of Alertness and Sedation rating scale. The electroencephalographic variables studied were bispectral index, 95% spectral edge frequency, median frequency and the power distribution between frequency bands alpha, beta, theta and delta. No differences were detected within groups in sedation scores before and after intervention, or between groups at either stage. No between-group differences were detected in electroencephalographic variables. In the spinal group, spinal anaesthesia caused an increase in bispectral index, 95% spectral edge frequency, median frequency and beta frequencies, and a decrease in delta frequencies and mean arterial pressure. The increase in beta frequencies is similar to that seen in patients with low plasma concentrations of midazolam and may represent subclinical sedation.

Hepatocyte growth factor promotes in vitro scattering and morphogenesis of human cervical carcinoma cells

OBJECTIVE

Hepatocyte growth factor (HGF) enhances cell dissociation and morphogenesis in many forms of carcinomas including some, but not all, cervical carcinomas. In this study, we examined the effects of HGF on two cervical cancer cell lines, derived from the same tumor, with different growth patterns in vivo and in vitro.

METHODS

Two cell lines, derived from the same cervical carcinoma, express spinous (C-4I) and basal (C4-II) squamous cell differentiation, respectively. A cell scattering assay was used to determine whether HGF would stimulate cell dissociation and motility. The morphogenetic capacity of HGF was assessed in collagen gel cultures, expression of the HGF receptor c-Met by Western blot analysis, and cadherin expression by immunofluorescence microscopy.

RESULTS

HGF-induced cell scattering was intense in C-4II, but limited in C-4I cultures. In collagen gels, C-4I cells formed large, spherical compact colonies with necrotic centers while C-4II cells formed small, irregular colonies with no necrosis. HGF induced proliferation and branching morphogenesis in both lines, but more prominently in C-4II cultures. There was no difference in c-Met or E- and P-cadherin expression between C-4I and C-4II cultures, but the lines differed in their signal transduction responses to HGF. The scatter response was mediated primarily by phosphatidylinositol 3-kinase in line C-4I, but by mitogen-activated protein kinase in line C-4II. HGF induced collagen gel contraction by C-4 cells, demonstrating for the first time that HGF has the capacity to induce this function.

CONCLUSIONS

The HGF-induced cell dispersion, morphogenesis, and collagen gel contraction in two cervical carcinoma cell lines were greatly influenced by differences between the lines in differentiation-associated properties. These properties, which include variations in extracellular matrix, junctional proteins, and signal transduction, may also modulate HGF action in vivo and thus determine patterns of invasiveness and growth of cervical carcinomas.

Effects of load carriage on heart rate, blood pressure and energy expenditure in children

Fifteen male primary school children, aged 10 years, were selected to carry school bags of 10, 15 and 20% of their own body weights, where 0% body weight was used as a control. Maximum oxygen uptake (VO2max) tests were conducted on a motorized treadmill using a continuous incremental protocol. During the load carrying test, subjects walked on a treadmill at 1.1 m s(-1) for 20 min at each load condition. Blood pressures were measured before, immediately following, and at 3 and 5 min after every trial. Heart rate and expired VO2 were recorded before, during and 5 min after walking using a cardiopulmonary function system. The results showed a significant difference in oxygen uptake, energy expenditure and the recovery of blood pressure rise for between 10 and 20% body weight load conditions. The carrying weight of a school bag for children could be recommended as 10% of body weight because it was not significantly different from 0% load in the metabolic cost.

Jupiter: Aerosol Chemistry in the Polar Atmosphere

Aromatic compounds have been considered a likely candidate for enhanced aerosol formation in the polar region of Jupiter. We develop a new chemical model for aromatic compounds in the Jovian auroral thermosphere/ionosphere. The model is based on a previous model for hydrocarbon chemistry in the Jovian atmosphere and is constrained by observations from Voyager, Galileo, and the Infrared Space Observatory. Precipitation of energetic electrons provides the major energy source for the production of benzene and other heavier aromatic hydrocarbons. The maximum mixing ratio of benzene in the polar model is 2x10-9, a value that can be compared with the observed value of 2+2-1x10-9 in the north polar auroral region. Sufficient quantities of the higher ring species are produced so that their saturated vapor pressures are exceeded. Condensation of these molecules is expected to lead to aerosol formation.

Constitutive and conditional cadherin expression in cultured human ovarian surface epithelium: influence of family history of ovarian cancer

Epithelial ovarian carcinomas arise in a simple mesothelium (ovarian surface epithelium, OSE) but exhibit properties of oviductal and endometrial epithelia. Thus, during malignant progression, their differentiation proceeds from simple to complex, in contrast to carcinomas in other tissues. Related changes in OSE of women with a history of familial ovarian cancer indicate that this aberrant differentiation is initiated very early in neoplastic progression. The mechanisms underlying this process are not understood. Because cadherins are known regulators of differentiation, we investigated the relationship of the cadherins E, N and P to OSE morphology, growth patterns and differentiation in cultures of normal and metaplastic OSE from women with (FH-OSE) and without (NFH-OSE) a family history of ovarian cancer and in the ovarian carcinoma lines OVCAR-3 and CaOV3. We used immunofluorescence, RT-PCR, in situ hybridization and Western blotting. Our results define N-cadherin as the constitutively expressed cadherin of normal and metaplastic OSE and indicate that P-cadherin is undetectable while E-cadherin expression is conditional and related to genotype, stage of neoplastic progression and growth pattern. The altered expression of E-cadherin in apparently normal OSE of women with hereditary ovarian cancer syndromes in conjunction with the known capacity of E-cadherin to induce epithelial characteristics implicates this adhesion molecule as a possible inducer of the aberrant Mullerian differentiation which characterizes epithelial ovarian carcinomas. Abnormal differentiation in such (pre)-neoplastic tissues may represent an early, irreversible, non-mutational step in ovarian epithelial neoplastic progression.

Conformational preferences in a benzodiazepine series of potent nonpeptide fibrinogen receptor antagonists

Previously, we reported the direct design of highly potent nonpeptide 3-oxo-1,4-benzodiazepine fibrinogen receptor antagonists from a constrained, RGD-containing cyclic semipeptide. The critical features incorporated into the design of these nonpeptides were the exocyclic amide at the 8-position which overlaid the Arg carbonyl, the phenyl ring which maintained an extended Gly conformation, and the diazepine ring which mimicked the gamma-turn at Asp. In this paper, we investigate conformational preferences of the 8-substituted benzodiazepine analogues by examining structural modifications to both the exocyclic amide and the seven-membered diazepine ring and by studying the conformation of the benzodiazepine ring using molecular modeling, X-ray crystallography, and NMR. We found that the directionality of the amide at the 8-position had little effect on activity and the (E)-olefin analogue retained significant potency, indicating that the trans orientation of the amide, and not the carbonyl or NH groups, made the largest contribution to the observed activity. For the diazepine ring, with the exception of the closely analogous 3-oxo-2-benzazepine ring system described previously, all of the modifications led to a significant reduction in activity compared to the potent 3-oxo-1, 4-benzodiazepine parent ring system, implicating this particular type of ring system as a desirable structural feature for high potency. Energy minimizations of a number of the modified analogues revealed that none could adopt the same low-energy conformation as the one shared by the active (S)-isomer of the 3-oxo-1, 4-benzodiazepines and 3-oxo-2-benzazepines. The overall data suggest that the features contributing to the observed high potency in this series are the orientation of the 3-4 amide and the conformational constraint imposed by the seven-membered ring, both of which position the key acidic and basic groups in the proper spatial relationship.

Neurocysticercosis--case report and literature review

A 30-year-old Indian migrant worker presented with seizures at the National University Hospital. A CT-scan of the brain showed multiple calcifications and cysts consistent with neurocysticercosis. Plain radiographs of the humeri and femora also revealed multiple soft tissue calcifications. He was given a course of anti-helminthic therapy and started on anti-epileptics. Neurocysticercosis is a common cause of seizures in endemic areas and must be considered in the differential diagnosis of epilepsy involving the members of the large community of migrant workers in Singapore.

Rabbit sex hormone binding globulin: primary structure, tissue expression, and structure/function analyses by expression in Escherichia coli

Sex hormone binding globulin (SHBG) is a homodimeric plasma protein found in mammals that binds sex steroids with high affinity and regulates their bioavailability. The protein is identical in structure and properties to the androgen binding protein (ABP) found in the male reproductive tract. We have isolated a 1245-base pair rabbit SHBG cDNA encoding a reading frame for a signal peptide followed by a protein of 367 amino acids, which shares 79.0, 68.1 and 63.2% amino acid identity with the corresponding human, rat and mouse proteins respectively. Northern blot and hot-nested PCR analyses indicated that rabbit SHBG is produced from a 1.6 kilobase mRNA in the liver of both sexes and in the testis. The rabbit SHBG cDNA was inserted into pGEX-1 lambda T for expression of a glutathione S-transferase/SHBG fusion protein in Escherichia coli. The bacterial product bound 5 alpha-dihydrotestosterone (DHT) in the same manner as the corresponding protein in serum. The dissociation constants (Kd) for rabbit and human SHBGs produced in E. coli were 11.1 +/- 1.1 nM and 2.1 +/- 0.6 nM respectively, and rabbit SHBG formed a less stable protein-steroid complex (t1/2 = 5 min) than human SHBG (t1/2 > 60 min). Unlike human SHBG, rabbit SHBG does not bind estradiol with high affinity. To aid in the identification of differences in the sequences of rabbit and human SHBG, which determine species differences in steroid-binding affinity and specificity, chimeras containing the 5'-terminal half of SHBG from one species and 3'-terminal half of SHBG from the other species were constructed and expressed. It was found that the chimeric proteins assumed similar steroid-binding affinity and specificity as the wild-type proteins when the amino (N)-terminal half of SHBG was derived from the same species. Replacement of the carboxyl (C)-terminal half of rabbit SHBG by the corresponding region of the human molecule increased the integrity of its steroid-protein complex. This supports the concept that amino acids within the N-terminal half of SHBG constitute the steroid-binding domain while the C-terminal half of the molecule may provide structural stability to the protein and its steroid-binding site.

Sport specific fitness testing of elite badminton players

There is a scarcity of descriptive data on the performance capacity of elite badminton players, whose fitness requirements are quite specific. The purpose of this paper is to investigate the physiological response of elite badminton players in a sport-specific fitness test. Twelve Hong Kong national badminton team players performed a field test on a badminton court. Six light bulbs were connected to a programming device causing individual bulbs to light up in a given sequence. The players were instructed to react to the flashes by running towards them, and striking shuttles mounted in the vicinity of the bulbs. Exercise intensity was controlled by altering the interval between successive lightings. A low correlation (r = 0.65) was found between the results of the field test and the rank-order list of subjects, based on an objective on-field physiological assessment and subjective ranking. This may be explained by the requirements of other factors besides physical fitness which contribute to success in elite level badminton competition. These factors may include, for example, technical skill, mental power, and aesthetic judgements on the court. Maximum mean (s.d.) heart rate data (187(8) beats.min-1) and blood lactate values (10.4(2.9) mmol.l-1) in this study showed that players were under maximal load during the field test. From the testing data, it seems reasonable to speculate that the intensity of level 3 (20 light pulses.min-1; 3.0 s.pulse-1) and level 4 (22 light pulses.min-1; 2.7 s.pulse-1) simulates the requirement of actual games energy expenditure of the Hong Kong badminton players exercising at close to their anaerobic threshold. The results also show that an estimate of fitness can be derived from measurements involving exercise closely resembling that which is specific for the sports activity in question. Improved training advice and guidance may result from such studies.

Physiological profiles and sport specific fitness of Asian elite squash players

There is a scarcity of descriptive data on the physiological characteristics of elite Asian squash players. The purpose of this study was to evaluate the physiological profile and sports specific fitness of Hong Kong elite squash players. It was conducted before the selection of the Hong Kong national squash team for the 1992 Asian Squash Championship. Ten elite squash players were selected as subjects for the study. Maximum oxygen uptake was measured using a continuous treadmill running test. A sports specific field test was performed in a squash court. The following means (s.d.) were observed: height 172.6(4.3) cm; weight 67.7(6.9) kg; body fat 7.4(3.4)%; forced vital capacity (FVC) 5.13(0.26) litres; maximum oxygen uptake (VO2max) 61.7(3.4) ml.kg-1.min-1; anaerobic threshold (AT) 80.2(3.3)% of VO2max; alactic power index 15.5(1.8) W.kg-1; lactic work index 323.5(29.4) J.kg-1, peak isokinetic dominant knee extensor and flexor strengths 3.11(0.29) Nm.kg-1 and 1.87(0.18) Nm.kg-1. The results show that the Hong Kong squash players have relatively high cardiorespiratory sports specific fitness and muscle strength which may be one of the key factors that contributed to the success of the Hong Kong team in the Asian Championship.

Cardiorespiratory fitness and isokinetic muscle strength of elite Asian junior soccer players

There is a scarcity of descriptive data on the physiological characteristics of elite Asian junior soccer players. The purpose of this study was to evaluate the cardiorespiratory fitness and isokinetic muscle strength of elite junior soccer players in Hong Kong. It was conducted in conjunction with the selection of the Hong Kong team to the 1989 Gothia Cup held in Sweden. Twenty-one top junior soccer players were selected as subjects for the study. The following means (+/- SD) were observed: age 17.3 +/- 1.1 years; height 172.5 +/- 6.2 cm; weight 62.8 +/- 7.0 kg; body fat 5.2 +/- 1.8%; forced vital capacity (FVC) 4.6 +/- 0.6 L; maximum oxygen uptake (VO2max) 58.6 +/- 2.9 ml.kg-1.min-1; anaerobic threshold (AT) 76.7 +/- 10.2% of VO2max; peak isokinetic dominant knee extensor and flexor strengths 3.28 +/- 0.37 Nm.kg-1 and 1.84 +/- 0.24 Nm.kg-1; hamstring to quadriceps peak torque ratio (H/Q) 56 +/- 0.6% measured at 60 degrees s-1. Hong Kong players appeared to have comparable aerobic power, light body weight, poor flexibility and above average isokinetic muscle strength compared to other international junior soccer players. Training programs to improve the contralateral knee muscle imbalance and to increase the fast speed movement capability of the non-dominant knee flexors are recommended.

Comparison of 3H- and 125I-radioimmunoassay and gas chromatography/mass spectrometry for the determination of delta 9-tetrahydrocannabinol and cannabinoids in blood and serum

Blood and serum specimens from 100 subjects in a driving study were tested for the presence of delta 9-tetrahydrocannabinol (THC) by 3H- and 125I-labeled RIA and GC/MS. The specimens were also analyzed for 11-nor-9-carboxy-delta 9-tetrahydrocannabinol by the two RIA methods. Blind quality control specimens containing THC were included with each batch of subject specimens and sent coded to three participating laboratories. The methods were assessed for accuracy, reproducibility, detectability, specificity, and the results correlated. It was found that serum was a better matrix than blood for determination of cannabinoids. The three methods gave parallel but significantly different quantitative results, apparently due to calibration problems. However, each technique was capable of measuring THC concentrations up to three hours after usage.

An evaluation of HPLC for the screening and quantitation of benzodiazepines and acetaminophen in post mortem blood

High performance liquid chromatographic (HPLC) methods have been developed for the analysis of benzodiazepines, some of their metabolites and for acetaminophen in post mortem blood. The methods include a single-step extraction and the use of internal standards for quantitation. Two different columns, mu-Bondapack C18 and mu-Bondapak phenyl with two different mobile phases are described. The methods presented are sensitive, reproducible, relatively selective, and have been used regularly in forensic toxicological analysis.

Environmental degradation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

Herbicide formulations containing known amounts of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and exposed to natural sunlight on leaves, soil, or glass plates lost most or all of the TCDD during a single day, due principally to photochemical dechlorination. Despite the known persistence of pure TCDD, it is not stable as a contaminant in thin herbicide films exposed to outdoor light.

Photodecomposition of Chlorinated Dibenzo-p-Dioxins

The toxic herbicide impurity 2,3,7,8-tetrachlorodibenzo-p-dioxin and its homologs decomposed rapidly in alcohol solution under artificial light and natural sunlight, the rate of decomposition depending upon the degree of chlorination. However, photodecomposition was negligible in aqueous suspensions and on wet or dry soil.