Canine TIMP-2: purification, characterization and molecular detection

Matrix metalloproteinases (MMPs), which degrade tissues in health and disease are under the control of the tissue inhibitors of MMPs, the TIMPs. TIMP-2 is particularly important for control of MMP-2 and both have been implicated in many pathological processes from arthritis to tumour invasion. This study characterized and detected TIMP-2 from canine cells; including synovial fibroblasts and three tumour-derived canine cell lines, K1, K6 and DH82. Gelatin zymography demonstrated that pro-MMP-2 is produced by synovial fibroblasts and the three cells lines. Reverse zymograms showed that all the cell sources tested secrete both TIMP-1 and TIMP-2. The 22 kDa band was purified and n-terminal amino acid sequencing showed it to be highly homologous to equine and human TIMP-2. Analysis of purified canine MMP-2 and MMP-9 showed that TIMP-2 is associated, and co-purifies with MMP-2. Polymerase chain reaction, using consensus primers, was used to detect TIMP-2 mRNA from the cell sources and proved positive in all cases. This work highlights the importance of TIMP-2 as the main inhibitor for MMP-2 and, therefore, opens the possibilities of targeting TIMP-2 for therapeutic intervention against connective amino acid tissue degradation in a range of diseases.

Subjective assessment of blunt impacts

An important role of an eyewitness to an assault is to effectively quantify the degree of force used; yet evidence of this form is often subjective and relies on personal opinion. Twelve subjects were asked to strike a load cell with a wooden bat, using varying degrees of force. The strikes were recorded by video camera and 50 people observed the video and were asked to grade the strikes. On average 44% accurately assessed the severity of the strikes, whilst 26% over-estimated. Results suggest that the evidence of eyewitnesses should be treated with caution.

Dual effects of D-amphetamine on dopamine neurons mediated by dopamine and nondopamine receptors

By increasing dopamine (DA) release and activating feedback mechanisms, amphetamine and related psychostimulants are known to inhibit DA cell firing. Here, we report that D-amphetamine also has an excitatory effect on DA cells, which under control conditions, is masked by the inhibitory effect of D-amphetamine and is revealed when D2-like receptors are blocked. Thus, using in vivo single-unit recording in rats, we found that the selective D2 antagonist raclopride not only blocked the inhibition induced by D-amphetamine but also enabled D-amphetamine to excite DA cells. The excitation, expressed as an increase in both firing rate and bursting, persisted when both D1- and D2-like receptors were blocked by SCH23390 and eticlopride, suggesting that it is not mediated by DA receptors. The norepinephrine uptake blocker nisoxetine mimicked the effect of D-amphetamine, especially the increase in bursting, whereas the 5-HT uptake blocker fluoxetine produced no significant effect. Adrenergic alpha1 antagonists prazosin and WB4101 and the nonselective alpha antagonist phenoxybenzamine completely blocked increase in bursting induced by D-amphetamine and partially blocked the increase in firing rate. The alpha2 antagonist idazoxan and the beta antagonist propranolole, however, failed to prevent D-amphetamine from producing the excitation. Thus, revising the traditional concept, this study suggests that D-amphetamine has two effects on DA cells, a DA-mediated inhibition and a non-DA-mediated excitation. The latter is mediated in part through adrenergic alpha1 receptors.

Expression of two related viral early genes in Epstein-Barr virus-associated tumors

The transcription of two early "leftwardly" expressed genes carrying repetitive sequences, IR2 and IR4, has been studied for Epstein-Barr virus-associated tumors, and for established B-cell lines, using sequence-specific probes generated for this purpose. Whereas the IR4 transcript was identified in every tumor and cell line assessed (except B95-8, with a deletion that removes the gene), expression of the IR2 gene was restricted to B lymphocytes. Though the promoters for both transcripts lie within homologous regions (D(L) and D(R)) in the viral genome, the IR2 promoter appears more tightly regulated. Detailed characterization of the IR4 transcript from a nasopharyngeal carcinoma tumor, C15, identifies a sequence variant of this gene that differs from those reported for B cells; in situ hybridization methods show transcription to be restricted to a subset of cells, with the strongest signals seen adjacent to host stroma. As with B cells in culture (Y. Gao, P. R. Smith, L. Karran, Q. L. Lu, and B. E. Griffin, J. Virol. 71:84-94, 1997), chemical induction enhanced transcriptional expression of the IR4 gene in the C15 tumor, although staining for both the IR4 antigen and that of the virus lytic switch, Zta, gave negative results. In a Burkitt's lymphoma biopsy specimen, however, both proteins were found expressed, notably in the same subset of cells. The data here and elsewhere (Gao et al., J. Virol., 1997) are consistent with a block to intracellular transport of the transcript(s) and suggest nuclear roles for it in tumors, possibly in RNA processing and viral lytic replication. Both roles could be fulfilled in the absence of translation.

Development of disulfide peptide mapping and determination of disulfide structure of recombinant human osteoprotegerin chimera produced in Escherichia coli

Recombinant human osteoprotegerin chimera is a 90-kDa protein containing a human IgG Fc domain fused to human osteoprotegerin. The molecule is a dimer linked by two intermolecular disulfide bonds and contains eleven intramolecular disulfide bonds per monomer. A cysteine-rich region in osteoprotegerin contains nine disulfide bridges homologous to the cysteine-rich signature structure of the tumor necrosis factor receptor/nerve growth factor receptor superfamily. In this report, we have developed peptide mapping procedures suitable to generate disulfide-containing peptides for disulfide structure assignment of the fusion molecule. The methods employed included proteolytic digestion using endoproteinases Glu-C and Lys-C in combination followed by LC-MS analyses. Disulfide linkages of peptide fragments containing a single disulfide bond were assigned by sequence analysis via detection of (phenylthiohydantoinyl) cystine and/or by MS analysis. Disulfide bonds of a large, core fragment containing three peptide sequences linked by four disulfides were assigned after generation of smaller disulfide-linked peptides by a secondary thermolysin digestion. Disulfide structures of peptide fragments containing two disulfide bonds were assigned using matrix-assisted laser desorption ionization mass spectrometry with postsource decay. Both the inter- and intramolecular disulfide linkages of the chimeric dimer were confirmed.

Dynamics of stab wounds: force required for penetration of various cadaveric human tissues

It is often said that once the skin has been penetrated no further force is required to produce penetration of underlying tissues. This experimental study has used technology which was not available to earlier investigators to examine this issue in detail. The results confirm the importance of skin penetration but indicate that the penetration of other tissues may also require significant force.

Physiologic reflexes and their impact on resuscitation of the newborn

Most depressed newborn infants respond promptly to minimal intervention. When that does not happen, a thorough understanding of the physiologic reflexes that promote and prevent, prompt restoration of heart rate, blood pressure, and respiration is crucial. This article will review data demonstrating that lung inflation, in the purely mechanical sense, is a key element in a successful resuscitation. A complicated resuscitation is most often because of the caretaker's lack of awareness of basic cardiopulmonary physiology than to an unusually depressed infant.

Influence of age and strain on striatal dopamine loss in a genetic mouse model of Lesch-Nyhan disease

Lesch-Nyhan disease is a neurogenetic disorder caused by deficiency of the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT). Affected individuals exhibit a characteristic pattern of neurological and behavioral features attributable in part to dysfunction of basal ganglia dopamine systems. In the current studies, striatal dopamine loss was investigated in five different HPRT-deficient strains of mice carrying one of two different HPRT gene mutations. Caudoputamen dopamine concentrations were significantly reduced in all five of the strains, with deficits ranging from 50.7 to 61.1%. Mesolimbic dopamine was significantly reduced in only three of the five strains, with a range of 31.6-38.6%. The reduction of caudoputamen dopamine was age dependent, emerging between 4 and 12 weeks of age. Tyrosine hydroxylase and aromatic amino acid decarboxylase, two enzymes responsible for the synthesis of dopamine, were reduced by 22.4-37.3 and 22.2-43.1%, respectively. These results demonstrate that HPRT deficiency is strongly associated with a loss of basal ganglia dopamine. The magnitude of dopamine loss measurable is dependent on the genetic background of the mouse strain used, the basal ganglia subregion examined, and the age of the animals at assessment.

Regulation of cytoskeletal association by a basic amino acid motif in polyoma virus middle T antigen

The subcellular localization of many oncogenic proteins is thought to be important for their function. In the case of the middle T antigen of the DNA tumour virus, polyoma, localization to membranes in a specific manner is essential for its cellular transforming activity. To investigate factors that influence this localization, heterologous membrane targetting sequences were substituted for the middle T antigen transmembrane domain and the properties of the resulting proteins studied. Whereas C-terminal lipid modification derived from the H-ras CaaX box restored oncogenic activity to non-transforming truncated middle T antigen species, N-terminal myristylation from pp60c-src did not. Furthermore, a region, rich in basic amino acids and adjacent to the middle T transmembrane domain, was found to mediate association with detergent-insoluble cytoskeleton. Co-operation between the basic motif and neighbouring membrane binding domains resulted in specific localization of proteins to particular membrane sites, characterized by the association with subcellular structures, likely to be cytoskeletal in nature. These results demonstrate that the cellular localization of MT is regulated by at least two determinants, a transmembrane sequence which confers membrane binding and a basic motif which specifies a particular site within the membrane.

The effect of drugs commonly used in the treatment of equine articular disorders on the activity of equine matrix metalloproteinase-2 and 9

Loss of articular cartilage, which is the most important pathological lesion occurring in osteoarthritis, has been shown to be enzymatically mediated. The matrix metalloproteinases (MMPs) are a group of enzymes which have been implicated in this degradation of articular cartilage matrix. The use of pharmacological agents to inhibit this catabolic process in the joint is a potential route for therapeutic intervention. The gelatinase MMPs, MMPs-2 and 9, were purified by affinity chromatography from equine cell cultures. The ability of phenylbutazone, flunixin, betamethasone, dexamethasone, methylprednisolone acetate (MPA), hyaluronan, pentosan polysulphate and polysulphated glycosaminoglycan (PSGAG) to inhibit equine MMPs-2 and 9 were assessed by two degradation assays. Whilst some agents did have direct effects on MMP activity, these effects were only obtained at concentrations which were unlikely to be achieved for any length of time in vivo. It is improbable that any pharmacological agent, currently used in the horse, has a significant effect on gelatinase MMP activity.

Epidural analgesia for postoperative pain control in children

Ninety-eight continuous postoperative epidurals were administered to 87 children. The patients were divided into two groups: group I included 63 cases in which a 0.0625-0.25% solution of bupivacaine was continuously administered; group II included 35 cases in which a similar solution of bupivacaine mixed with 2-10 micrograms of fentanyl was administered. The dose of the epidural medication was titrated by the anesthesiologist according to the patient's age and anticipated level of postoperative pain. The average pain score for all patients for the first 48 h was 1.43. Supplemental analgesia averaging 0.132 mg intravenous morphine/kg/8 h was required in 49 cases (41 in group I and eight in group II). In group I, the average dose of supplemental analgesia was 0.144 mg intravenous morphine/kg/8 h, whereas in group II, it was only 0.056 mg intravenous morphine/kg/8 h. Continuous epidural analgesia is effective in controlling postoperative pain, and the addition of fentanyl reduces the need for systemic narcotics.

Delivery of high concentrations of inspired oxygen via Tusk mask

OBJECTIVES

Nonrebreather face masks (NRM) are frequently used in patients with respiratory distress and profound hypoxemia. A simpler modification to the partial rebreather face mask, using only two pieces of respiratory tubing or "tusks," has also been shown to increase FiO2 compared with the NRM in five normal subjects. Clinically, we have observed this modification to further increase PaO2 in critically ill patients already using the NRM in the intensive care unit. This study was designed to compare the Tusk mask with the NRM in both a larger group of normal subjects and in patients with underlying lung disease.

DESIGN

Prospective, randomized, crossover study.

SETTING

A university teaching hospital and tertiary care referral center.

SUBJECTS

Sixteen normal subjects (11 male and 5 female; age 30.4+/-6.8 [SD] yrs) and seven patients with interstitial lung disease (ILD) (3 male and 4 female; age 68.1+/-11.9 yrs).

INTERVENTIONS

Subjects and patients served as their own controls and were randomized to wear either the NRM or Tusk mask for a 30-min period. After a 60-min washout period, the other mask was applied.

MEASUREMENTS AND MAIN RESULTS

Arterial blood gas measurements were performed immediately before and at the end of each 30-min test period. Respiratory synchronization during the study period was achieved, using a metronome. In the normal subjects, PaO2 using the NRM and Tusk masks increased 290.0+/-57.1 torr (38.6+/-7.6 kPa) and 330.0+/-68.9 torr (44.0 +/-9.2 kPa), respectively (p=.032). PaO2 increased 293.4+/-38.0 torr (39.1+/-5.1 kPa) with the NRM and 378.4+/-61.7 torr (50.4+/-8.2 kPa) with the tusk mask (p=.001) in the patients with ILD. There was no statistically significant change seen in mean PaCO2 with either mask in either group. The mean PaO2 returned to within 6% of baseline in both groups after the washout period.

CONCLUSIONS

Both normal subjects and patients with compromised pulmonary function achieved a higher PaO2 using a Tusk mask than when using the conventional NRM, at the same oxygen flow rate. Patients with hypoxemia may obtain lifesaving benefit from the additional concentration of oxygen delivered via the Tusk mask.

Optimization of capillary chromatography ion trap-mass spectrometry for identification of gel-separated proteins

The current paradigm for protein identification using mass spectrometric derived peptide-mass and fragment-ion data employs computer algorithms which match uninterpreted or partially interpreted fragment-ion data to sequence databases, both protein and translated nucleotide sequence databases. Nucleotide sequence databases continue to grow at a rapid rate for some species, providing an unsurpassed resource for protein identification in those species. Ion-trap mass spectrometers with their ability to rapidly generate fragment-ion spectra in a data-dependent manner with high sensitivity and accuracy has led to their increased use for protein identification. We have investigated various parameters on a commercial ion trap-mass spectrometer to enhance our ability to identify peptides separated by capillary reversed phase-high performance liquid chromatography (RP-HPLC) coupled on-line to the mass spectrometer. By systematically evaluating the standard parameters (ion injection time and number of microscans) together with selection of multiple ions from the full mass range, improved tandem mass spectrometry (MS/MS) spectra were generated, facilitating identification of proteins at a low pmol level. Application of this technology to the identification of a standard protein and an unknown from an affinity-enriched mixture are shown.

Optimization of capillary chromatography ion trap-mass spectrometry for identification of gel-separated proteins

The current paradigm for protein identification using mass spectrometric derived peptide-mass and fragment-ion data employs computer algorithms which match uninterpreted or partially interpreted fragment-ion data to sequence databases, both protein and translated nucleotide sequence databases. Nucleotide sequence databases continue to grow at a rapid rate for some species, providing an unsurpassed resource for protein identification in those species. Ion-trap mass spectrometers with their ability to rapidly generate fragment-ion spectra in a data-dependent manner with high sensitivity and accuracy has led to their increased use for protein identification. We have investigated various parameters on a commercial ion trap-mass spectrometer to enhance our ability to identify peptides separated by capillary reversed phase-high performance liquid chromatography (RP-HPLC) coupled on-line to the mass spectrometer. By systematically evaluating the standard parameters (ion injection time and number of microscans) together with selection of multiple ions from the full mass range, improved tandem mass spectrometry (MS/MS) spectra were generated, facilitating identification of proteins at a low pmol level. Application of this technology to the identification of a standard protein and an unknown from an affinity-enriched mixture are shown.

Late G1 accumulation after 2 Gy of gamma-irradiation is related to endogenous Raf-1 protein expression and intrinsic radiosensitivity in human cells

We have previously reported a correlation between high endogenous expression of the protein product of the RAF-1 proto-oncogene, intrinsic cellular radiosensitivity and rapid exit from a G2/M delay induced by 2 Gy of gamma-irradiation. Raf1 is a positive serine/threonine kinase signal transduction factor that relays signals from the cell membrane to the MAP kinase system further downstream and is believed to be involved in an ionizing radiation signal transduction pathway modulating the G1/S checkpoint. We therefore extended our flow cytometric studies to investigate relationships between radiosensitivity, endogenous expression of the Raf1 protein and perturbation of cell cycle checkpoints, leading to alterations in the G1, S and G2/M populations after 2 Gy of gamma-irradiation. Differences in intrinsic radiosensitivity after modulation of the G1/S checkpoint have generally been understood to involve p53 function up to the present time. A role for dominant oncogenes in control of G1/S transit in radiation-treated cells has not been identified previously. Here, we show in 12 human in vitro cancer cell lines that late G1 accumulation after 2 Gy of radiation is related to both Raf1 expression (r = 0.91, P = 0.0001) and the radiosensitivity parameter SF2 (r = -0.71, P = 0.009).

An analysis of hypoxia in sheep brain using a mathematical model

Cerebral blood flow (CBF) increases as arterial oxygen content falls with hypoxic (low PO2), anemic (low hemoglobin) and carbon monoxide (CO) (high carboxyhemoglobin) hypoxia. Despite a higher arterial PO2, CO hypoxia provokes a greater increase in CBF than hypoxic hypoxia. We analyzed published data using a compartmental mathematical model to test the hypothesis that differences in PO2 in tissue, or a closely related vascular compartment, account for the greater response to CO hypoxia. Calculations showed that tissue, but not arteriolar, PO2 was lower in CO hypoxia because of the increased oxyhemoglobin affinity with CO hypoxia. Analysis of studies in which oxyhemoglobin affinity was changed independently of CO supports the conclusion that changes in tissue PO2 (or closely related capillary or venular PO2) are predictive of alterations in CBF. We then sought to determine the role of tissue PO2 in anemic hypoxia, with no change in arterial and little, if any, change in venous PO2. Calculations predict a small fall in tissue PO2 as hematocrit decreases from 55% to 20%. However, calculations show that changes in blood viscosity can account for the increase in CBF in anemic hypoxia over this range of hematocrits.

Efficacy of the cushing response in maintaining cerebral blood flow in premature and near-term fetal sheep

Fetal head compression during labor may increase intracranial pressure (ICP) and decrease cerebral perfusion pressure (CPP). An increase in mean arterial pressure (MAP) associated with the Cushing response normally acts to mitigate an ischemic insult when the increase in ICP approaches MAP. However, the premature fetus may be limited in its ability to increase MAP. We compared the efficacy of the pressor response in sustaining CPP, cerebral blood flow (CBF), and cerebral O2 consumption (CMRO2) in chronically catheterized fetal sheep at 0.6 gestation (92 d; n = 7) and 0.9 gestation (133 d; n = 7). When fetal ICP was increased to baseline MAP (41 +/- 3 mm Hg; +/-SEM) in 92-d fetuses, MAP increased by 7 +/- 2 mm Hg and remained stable during 30 min of constant ICP elevation; CBF decreased by 72% and CMRO2 decreased by 46%. In 133-d fetuses, MAP increased from 53 +/- 2 to 65 +/- 4 mm Hg at 3 min of elevated ICP; CBF decreased by 62% and CMRO2 decreased 30%. However, MAP continued to increase after 3 min and reached a stable level of 75 +/- 3 mmHg at 30 min in 133-d fetuses. The additional increase in MAP restored CBF and CMRO2 to baseline values. Plasma epinephrine and vasopressin concentrations increased between 6 and 33 min of elevated ICP to levels, exceeding those in 92-d fetuses. We conclude that the arterial pressure response to intracranial hypertension is present at 0.6 gestation but is less well developed than at 0.9 gestation in fetal sheep, possibly due to immaturity of the sympathoadrenal and vasopressin systems. Consequently, CBF and CMRO2 are not as well defended at mid-gestation against elevated ICP as might occur during difficult labor.

Determination of disulfide bonds in highly bridged disulfide-linked peptides by matrix-assisted laser desorption/ionization mass spectrometry with postsource decay

Matrix-assisted laser desorption/ionization mass spectrometry with postsource decay was used to generate fragment ions from peptide fragments containing heteropeptides linked together by two disulfide bonds. Postsource decay analysis of these peptide samples generates a series of singly charged fragment ions that, in addition to the peptide sequence ions, provide useful information for assigning disulfide arrangement in highly bridged disulfide-linked peptides. The assignment was made possible by fragmentation at peptide bonds between two Cys residues in a peptide that constitutes the highly bridged fragment, while retaining the disulfide linkage to the other peptide. Fragmentation using other types of instruments, such as quadrupole ion-trap mass spectrometry with collision-induced dissociation, usually did not generate such fragment ions. The data obtained from postsource decay also provide fragment ions derived from both symmetric and nonsymmetric cleavages of disulfide bonds. The present method is a highly sensitive technique which requires no further sample handling and should be complementary to other classical chemical methods. The method proved useful in facilitating the assignment of disulfide structure in tumor necrosis factor binding protein (TNFbp), which contains 162 amino acids and 13 disulfide bonds (Jones, M.; et al. Biochemistry, in press). Postsource decay analysis of large disulfide-containing peptides usually produces no fragmentation but generates a series of high-intensity ions derived from both symmetric and nonsymmetric cleavages of disulfide bonds.

Determination of tumor necrosis factor binding protein disulfide structure: deviation of the fourth domain structure from the TNFR/NGFR family cysteine-rich region signature

Tumor necrosis factor binding protein is a soluble molecule derived from the extracellular domain of the 55 kDa human tumor necrosis factor receptor, which can block the biological function of tumor necrosis factor by binding to the growth factor. This cysteine-rich molecule is subdivided into four domains, each containing six conserved cysteines that form three intrachain disulfide linkages known as the tumor necrosis factor receptor/nerve growth factor receptor family cysteine-rich region signature structure. In an effort to elucidate the molecular integrity of the molecule, we performed detailed analysis and searched for strategies to elucidate the complete disulfide structure of the E. coli-derived tumor necrosis factor binding protein and to determine the disulfide arrangement in the fourth domain of Chinese hamster ovary cell-derived molecule. The methods employed included various proteolytic digestions, peptide mapping, partial reduction, and assignment of disulfides by N-terminal sequencing and matrix-assisted laser desorption ionization mass spectrometry with post-source decay. The first three domains of the molecule were confirmed to have disulfide structures identical to the cysteine-rich region signature structure found in the above-mentioned receptor superfamily. The fourth domain has a different structure from the first three domains where the last four cysteines form two disulfide bonds in opposite positions.

An improved statistical methodology to estimate and analyze impedances and transfer functions

Estimating the mathematical relationship between pulsatile time series (e.g., pressure and flow) is an effective technique for studying dynamic systems. The frequency-domain relationship between time series, often calculated as an impedance (pressure/flow), is known more generally as a frequency-response or transfer function (output/input). Current statistical methods for transfer function analysis 1) assume erroneously that repeated observations on a subject are independent, 2) have limited statistical value and power, or 3) are restricted to use in single subjects rather than in an entire sample. This paper develops a regression model for transfer function analysis that corrects each of these deficiencies. Spectral densities of the input and output time series and the cross-spectral density between them are first estimated from discrete Fourier transforms and then used to obtain regression estimates of the transfer function. Statistical comparisons of the transfer function estimates use a test statistic that is distributed as chi2. Confidence intervals for amplitude and phase can also be calculated. By correctly modeling repeated observations on each subject, this improved statistical approach to transfer function estimation and analysis permits the simultaneous analysis of data from all subjects in a sample, improves the power of the transfer function model, and has broad relevance to the study of dynamic physiological systems.

Splicing by overlap extension by PCR using asymmetric amplification: an improved technique for the generation of hybrid proteins of immunological interest

Major histocompatibility complex (MHC) proteins play a central role in the immune recognition of antigen. The generation of hybrid MHC molecules has been of great value in elucidating the structure: function relationships of these key glycoproteins. In this report, the generation of cDNAs coding for seven such hybrid proteins is described. We have used the technique of splicing by overlap extension by the polymerase chain reaction (SOE by PCR) [Horton, R.M., Hunt, H.D., Ho, S.N., Pullen, J.K. and Pease, L.R. (1989) Engineering hybrid genes without the use of restriction enzymes: gene splicing by overlap extension. Gene 77, 61-68] to generate intermediate products of each of the components of the hybrid, tipped with a small sequence of the other, and then mixed these products in a second-stage PCR to produce the final spliced product. Where we were unable to generate final product, we introduced an additional step of asymmetric PCR synthesis to generate an excess of those strands which would anneal in the final PCR and found this to be effective. We noted a significant but manageable mutation rate, possibly contributed to by the tendency of DNA polymerase to add additional non-templated nucleotides [Hu, G. (1993) DNA polymerase-catalyzed addition of nontemplated extra nucleotides to the 3' end of a DNA fragment. DNA Cell Biol. 12, 763-770]. To avoid this, we modified our protocol to include a stage of blunting our intermediate products with T4 DNA polymerase prior to mixing them in the final PCR. We present this system as an effective mechanism to splice DNA.

Exit from G2 phase after 2 Gy gamma irradiation is faster in radiosensitive human cells with high expression of the RAF1 proto-oncogene

We have previously noted that high endogenous expression of the protein product of the full-length RAF1 proto-oncogene is related to relative intrinsic cellular radiosensitivity in 19 human cells lines in vitro. This appeared to be unrelated to the parameters of cell kinetics. In rodent and human cell lines transfected with dominant oncogenes, including Myc and MYC, Hras and HRAS and SV40, increased radioresistance has been accompanied by increased delay in progress through the G2 phase of the cell cycle after irradiation. We have thus examined the putative relationship between RAF1 expression and postirradiation perturbation of G2 phase in six of the human cell lines for which data have been reported previously. These lines exhibit a wide range of both radiosensitivity and Raf1 protein levels as measured previously by Western blotting. We report here that the cell lines whose cells appear to exit more rapidly from G2 phase are more radiosensitive (r = 0.91, P = 0.01) and express high levels of Raf1 protein (r = -0.93, P = 0.006).

Kinematics of four methods of stabbing: a preliminary study

Despite considerable research and development into stab-resistant clothing, no data exists which provides valid data for knife-body contact speeds which may be used to ensure that an appropriate and standard protection level is provided. Such data can only be obtained by a quantitative kinematic analysis of the stabbing movement. Two-dimensional video techniques (50 Hz) were used to record images of subjects (n = 10) performing each of four stabbing actions; Long Over (LO), Long Under (LU), Short Over (SO), Short Under (SU). Images were digitised from a minimum of ten frames pre-, to at least six frames post-blade entry. A two-way analysis of variance applied to selected kinematic parameters revealed significantly higher (P < 0.01) blade entry speeds for LO and LU as compared to SO and SU, respectively. This was due to the extra distance over which knife speed could be increased in the former conditions. Significantly greater shoulder joint angular velocities were found for LU and SU conditions, whilst for the elbow joint, conditions LO and SO were significantly greater (P = 0.000008). This suggests that the entry speeds during LO and SO are derived from a greater contribution from elbow extensor muscles, whilst those for LU and SU are derived from a greater contribution from the shoulder flexors. It was concluded that two separate kinematic strategies were employed by subjects, and that the maximum speed which may be generated during stabbing is influenced by the manner in which the knife is held.