The binding of calcium and yttrium ions to a glycoprotein from bovine cortical bone

The binding of Ca²⁺ and Y³⁺ to an acidic glycoprotein from bovine cortical bone, bone sialoprotein, was determined from the titration curves at I 0·2 in the presence and absence of the cations. The binding of Y³⁺ was greater than that of Ca²⁺. The value for the association constant, k, for the interaction with Y³⁺ increased with pH, from log k 2·93 at pH3·4 to log k 3·50 at pH4·4, and the number of binding sites/mol. increased from 4·6 at pH3·4 to 9·1 at pH4·4. It is proposed that the binding site consists of three carboxyl groups, but it is likely that the binding is a strong electrostatic interaction rather than a co-ordination linkage. A chondroitin sulphate–protein complex also extracted from bovine cortical bone interacted with Y³⁺ and Ca²⁺ to a similar extent as did bone sialoprotein. It is suggested that these materials are present in bone at the resting and resorbing surfaces and that they contribute to the deposition of yttrium, americium and plutonium at these sites.     

Naphthaquinone biosynthesis in moulds: the mechanism for formation of javanicin

1. The following compounds, added to the growth medium of Fusarium javanicum, were converted into labelled javanicin with the percentage incorporations noted in parentheses: [Me-¹⁴C]methionine (0·83); [1-¹⁴C]acetate (0·70); [2-¹⁴C]malonate (0·07). 2. Labelled samples of javanicin were degraded by Zeisel reaction, Kuhn–Roth oxidation and reaction with sodium hypoiodite; acetic acid obtained from the Kuhn–Roth reaction was further degraded by the Schmidt reaction. Labelled methionine was used only for the formation of the methoxyl group, and the remaining carbon atoms were derived by the acetate-plus-polymalonate pathway. The methyl group attached directly to the naphthaquinone ring is derived by the reduction of a carboxyl group. 3. The demonstration of this biosynthetic pathway supports the assignment of the methoxyl group at position 7.     

THE EFFECTS OF INJURY PREVENTION WARM-UP PROGRAMMES ON KNEE STRENGTH IN MALE SOCCER PLAYERS

The study investigates the effects of the 11+ and HarmoKnee injury prevention programmes on knee strength in male soccer players. Under-21-year-old players (n=36) were divided equally into: the 11+, HarmoKnee and control groups. The programmes were performed for 24 sessions (20-25 min each). The hamstrings and quadriceps strength were measured bilaterally at 60°·s^-1, 180°·s^-1 and 300°·s^-1. The concentric quadriceps peak torque (PT) of the 11+ increased by 27.7% at 300°·s^-1 in the dominant leg (p<0.05). The concentric quadriceps PT of HarmoKnee increased by 36.6%, 36.2% and 28% in the dominant leg, and by 31.3%, 31.7% and 20.05% at 60°·s^-1, 180°·s^-1 and 300°·s^-1 in the non-dominant leg respectively. In the 11+ group the concentric hamstring PT increased by 22%, 21.4% and 22.1% at 60°·s^-1, 180°·s^-1 and 300°·s^-1, respectively in the dominant leg, and by 22.3%, and 15.7% at 60°·s^-1 and 180°·s^-1, in the non-dominant leg. In the HarmoKnee group the hamstrings in the dominant leg showed an increase in PT by 32.5%, 31.3% and 14.3% at 60°·s^-1, 180°·s^-1 and 300°·s^-1, and in the non-dominant leg hamstrings PT increased by 21.1% and 19.3% at 60°·s^-1 and 180°·s^-1 respectively. The concentric hamstrings strength was significantly different between the 11+ and control groups in the dominant (p=0.01) and non-dominant legs (p=0.02). The HarmoKnee programme enhanced the concentric strength of quadriceps. The 11+ and HarmoKnee programmes are useful warm-up protocols for improving concentric hamstring strength in young professional male soccer players. The 11+ programme is more advantageous for its greater concentric hamstring strength improvement compared to the HarmoKnee programme.     

Thermal denaturation in acidic solutions of double-helical ribonucleic acid from virus-like particles found in Penicillium chrysogenum. A spectrophotometric study

1. Two species of double-helical RNA isolated from mycelium of Penicillium chrysogenum were titrated with acid at 25°C and 95°C (solvent 0.1m-sodium phosphate buffer). At 25°C denaturation occurred at about pH3. At 95°C in the denatured form cytosine residues titrated as a simple monobasic acid of pK3.9 compared with pK2.5 for the native form at 25°C. 2. On thermal denaturation in neutral and acidic solutions one species of RNA (38% rG·rC) `melted' in three distinct stages, equivalent to a mixture of three species, namely one of about 25% rG·rC, another of about 33% rG·rC and a third of about 46% rG·rC: the relative proportions were 0.25:0.35:0.40. 3. On thermal denaturation in acidic solutions the increase in the fraction of ionized cytosine residues concomitant with the `melting' of rG·rC base pair also affects the spectrum especially at 280nm and serves to enhance the contribution of rG·rC base pairs at this wavelength. The increment in ε_(P) at 280nm on `melting' an rG·rC base pair approaches 53501·mol<sup>−1</sup>·cm<sup>−1</sup> depending on pH, compared with 33501·mol<sup>−1</sup>·cm<sup>−1</sup> at pH7. In contrast ε<sub>(P)</sub> at 280nm is scarcely affected by `melting' rA·rU base pairs or by the protonization of adenine residues. 4. Changes in the spectrum of Escherichia coli rRNA on denaturation in acidic solutions were studied to yield the mole fractions of rA·rU and rG·rC base pairs `melting' at particular pH values.     

Effects of pH and temperature on the wild-type and a mutant form of Neurospora glutamate dehydrogenase

1. We confirm the observation of Bürk (1965) that Neurospora crassa NADP-linked glutamate dehydrogenase normally exists in an inactive form below pH7·0 and in a fully active form above pH8·0 in either tris or orthophosphate buffer. At pH7·4 the enzyme is about half activated at 25°. 2. The variety of the enzyme produced by the mutant am^2l shows a similar behaviour except that the transition is shifted about one pH unit in the alkaline direction. 3. The am^2l enzyme has previously been reported to be activated by brief warming to 30° in phosphate buffer at pH8·0. The wild-type enzyme shows a similar effect at pH7·0. In tris buffer this effect is much less pronounced. 4. The am^2l enzyme is extremely unstable at 47° at pH7·0; its stability is somewhat greater at lower pH, and is markedly increased by increasing the pH in the range 7·0–8·7. The wild-type enzyme also shows an indication of a stability minimum at pH7·0, but a temperature of 60° is needed for a measurable rate of inactivation. 5. The inactive form of the enzyme is much more subject to thermal irreversible denaturation than is the active form.     

Rates of entry and oxidation of acetate,glucose, d(?)-β-hydroxybutyrate,palmitate, oleate and stearate,and rates of production and oxidation of propionate and butyrate in fed and starved sheep

1. Rates of entry and oxidation of a range of metabolites have been measured in tracheostomized sheep (diet, 800g. of lucerne chaff and 100g. of maize/day) by combining isotope-dilution techniques with the continuous measurement of total respiratory gas exchange, and ¹⁴CO₂ production during the intravenous or intraruminal infusion of ¹⁴C-labelled substrates. 2. Mean entry rates in fed and starved (24hr.) sheep respectively, expressed as mg./min./kg. body wt.^0·75, were: glucose, 5·0 (range 4·8–5·1, 2 observations) and 3·8 (3·2–4·2, 4); acetate, 10·8 (9·1–13·5, 4) and 5·8 (1); d(−)-β-hydroxybutyrate, 1·4 (1) and 1·5 (0·8–2·4, 4); palmitate, oleate and stearate (starved sheep only) 1·0 (0·6–1·9, 7), 0·9 (0·2–1·6, 10) and 0·9 (0·5–1·1, 11) respectively. 3. Production rates of propionate and butyrate in continuously feeding sheep were 6·4 (4·7–8·3, 4) and 4·3 (3·4–6·1, 4) mg./min./kg.^0·75 respectively, and in starved (24hr.) sheep were 2·5 (2·2–2·9, 2) and 1·0 (0·8–1·2, 2) mg./min./kg.^0·75 respectively. 4. Calculated terminal values for the specific radioactivity of respiratory ¹⁴CO₂ during measurements of entry rates and production rates were used to calculate the contributions of individual substrates to overall oxidative metabolism. Mean values for fed and starved sheep respectively were: glucose, 9·1 (8·6–9·6, 2) and 11·2 (5·9–15·1, 4)%; acetate, 31·6 (26·8–38·1, 4) and 22·1 (1)%; d(−)-β-hydroxybutyrate, 10·4 (1) and 4·8 (1·9–7·7, 4)%; propionate, 23·0 (13·8–29·9, 4) and 7·1 (6·8–7·4, 2)%; butyrate, 16·5 (13·7–20·5, 4) and 5·3 (5·2–5·3, 2)%; palmitate, oleate and stearate (starved sheep only), 4·7 (2·0–7·7, 7), 4·0 (1·2–6·6, 10) and 4·4 (3·8–5·8, 9)% respectively. The sum of these values for individual substrates in fed and starved sheep, excluding that of β-hydroxybutyrate and after correction of the glucose value for the known interrelations of this substrate with propionate, accounted for 76% and 58% respectively of total production of carbon dioxide. 5. Calculations based on the proportion of substrate entry directly oxidized indicated that the substrates studied accounted for 63% (fed sheep) and 43% (starved sheep) of total energy expenditure measured by oxygen uptake. The contribution of β-hydroxybutyrate was excluded, and corrections were made for glucose–propionate interrelations, and for the different rates of oxidation of the methyl and carboxyl fragments of acetate. 6. The present results have been combined with those obtained earlier in this Laboratory to examine the relationships between rates of substrate entry and oxidation, and concentrations of substrate in blood. Rates of entry of acetate, glucose, d(−)-β-hydroxybutyrate, palmitate and oleate (but not stearate) were well correlated with concentration in blood, and substrate contribution to production of carbon dioxide showed a similar correlation to blood concentration, except with glucose. 7. It was concluded that the general technique is of potential value in providing valid quantitative parameters of animal metabolism.     

The metabolism of [2-14C]indole in the rat

1. [2-¹⁴C]Indole has been synthesized from [¹⁴C]formate and o-toluidine via N[¹⁴C]-formyltoluidine. 2. When fed to rats, the ¹⁴C of [¹⁴C]indole (dose 70–80mg./kg. body wt.) is fairly rapidly excreted, and in 2 days an average of 81% appears in the urine, 11% in the faeces and 2·4% as carbon dioxide in the expired air. 3. Radioactivity is excreted in the urine as indoxyl sulphate (50% of the dose), indoxyl glucuronide (11%), oxindole (1·4%), isatin (5·8%), 5-hydroxyoxindole conjugates (3·1%), N-formylanthranilic acid (0·5%) and unchanged indole (0·07%). The faeces contain indoxyl sulphate (0·4% of the dose) and indole (0·2%), but the major metabolites have not been identified. 4. Fed to rats with biliary cannulae an average of 5·6% of a dose of [¹⁴C]indole (20–60mg./kg. body wt.) is excreted in the bile in 2 days. Radioactivity is present as indoxyl sulphate (0·8% dose) and 5-hydroxyoxindole conjugates (0·6%). 5. Rats further metabolize indoxyl into N-formylanthranilic acid and anthranilic acid, and oxindole into 5-hydroxyoxindole. 6. With rat-liver microsomes plus supernatant under aerobic conditions, indole gives indoxyl, oxindole, possibly isatin, N-formylanthranilic acid and anthranilic acid, but under anaerobic conditions gives only oxindole. Similarly, under aerobic conditions, oxindole gives 5-hydroxyoxindole, anthranilic acid and o-aminophenylacetic acid. 7. Indole is metabolized by two pathways, one via indoxyl to isatin, N-formylanthranilic acid and anthranilic acid, and the other via oxindole to 5-hydroxyoxindole and possibly to o-aminophenylacetic and anthranilic acid. 8. The following new compounds are described: 4-hydroxy-2-nitrophenylacetic acid, 3-, 4- and 5-benzyloxy-2-nitrophenylacetic acid, 5- and 7-hydroxyoxindole and 5-aminoacridine indoxyl sulphate.     

Further observations on the production of amino acids by rat-liver mitochondria and other subcellular fractions

1. Rat-liver mitochondria showed a decrease in amino acid production after preparation in 0·25m-sucrose containing EDTA (1mm), but an increase in water content. When EDTA was replaced by Mn²⁺ (1mm) or succinate (1mm), both amino acid production and water content were lowered, whereas preparation in 0·9% potassium chloride caused an increase in both. 2. Amino acid production by rat-liver homogenates prepared in 0·9% potassium chloride or 0·25m-sucrose was similar (q_{amino acid} 0·047 and 0·042 respectively aerobically). After freezing-and-thawing q_{amino acid} values were approximately doubled, and approached that of a homogenate prepared in water. 3. All cations tested inhibited amino acid production by mitochondria, Hg²⁺ and Zn²⁺ being the most effective in tris–hydrochloric acid buffer. In phosphate buffer Mg²⁺ and Mn²⁺ had no effect. Of the anions tested only pyrophosphate and arsenate had any inhibitory effect at final concn. 1mm. 4. Iodosobenzoate (1mm) and p-chloromercuribenzenesulphonate (1mm) inhibited mitochondrial amino acid production by 70–80%, whereas soya-bean trypsin inhibitor, EDTA and di-isopropyl phosphorofluoridate inhibited by a maximum of 30%. Respiratory inhibitors had no effect. 5. Rat-liver homogenate and subcellular fractions each showed an individual pattern of inhibition when a series of inhibitors was tested. 6. Amino acid production by mitochondria was decreased by up to 50% in the presence of oxidizable substrate, apart from α-glycerophosphate and palmitate, which had no effect. CoA stimulated amino acid production in tris–hydrochloric acid but not in phosphate buffer, α-oxoglutarate abolishing the stimulation. 7. Cysteine and glutathione stimulated amino acid production by whole mitochondria by 30%, but only reduced glutathione stimulated production in broken mitochondria. 8. Adrenocorticotrophic hormone and growth hormone stimulated mitochondrial amino acid production by 21–24%, whereas insulin inhibited production by 25%. 9. Coupled oxidative phosphorylation increased amino acid production by up to 154% at 25° and 40°. The increase was abolished by 2,4-dinitrophenol. 10. Amino acid incorporation in mitochondria was accompanied by an increase in amino acid production, both being decreased by chloramphenicol. 11. Mitochondrial production of ninhydrin-positive material was increased in the presence of albumin. The biggest increase was noted for the soluble fraction of broken mitochondria. No increase was found in the presence of ¹⁴C-labelled algal protein or denatured mitochondrial protein.     

Enzymes in cancer: Asparaginase from chicken liver

1. A procedure for partial purification of asparaginase from chicken liver is presented. 2. The bulk of the enzyme is located in the soluble fraction of chicken liver. 3. Molecular weights of chicken-liver asparaginase and of the guinea-pig serum enzyme, estimated by gel filtration, were 306000 and 210000 respectively. The Michaelis constants (K_m) at 37° and pH8·5 were 6·0×10⁻⁵m and 7·2×10⁻⁵m respectively. 4. At 50° the chicken-liver enzyme was moderately stable, some activity being lost by aggregation; in dilute electrolyte solutions the activity rapidly diminished. 5. The anti-lymphoma effect of guinea-pig serum in mice carrying the 6C3HED tumour was confirmed. Chicken-liver asparaginase also showed an effect but in this case the enzyme preparation had to be administered repeatedly. 6. Guinea-pig serum asparaginase was stable for several days in mouse blood, after intraperitoneal injection, whereas chicken-liver asparaginase rapidly disappeared. 7. Aspartic acid β-hydrazide was shown to be a competitive inhibitor of chicken-liver asparaginase with K_i approx. 5·6×10⁻⁴m. In mice it produced an anti-lymphoma effect, as reported previously.     

Glucose metabolism in the superovulated rat ovary in vitro. Effects of luteinizing hormone and the role of glucose metabolism in steroidogenesis

1. Superovulated rat ovary slices from rats treated with 20μg. of luteininzing hormone/100g. body wt. 2hr. before death and from control animals have been incubated in vitro. Output of Δ⁴-3-oxo steroids (0·2μmole/g. wet wt./hr. in control tissue) was linear for 4hr., and was increased by approx. 70% in slices from luteinizing hormone-treated rats. Rate of oxygen consumption (90·0±4·6μmoles/g. wet wt./hr.) was linear for 3hr. and unaltered by luteinizing hormone treatment or addition of glucose (1mg./ml.) to the medium. 2. In slices from control animals, steady-state rate of glucose uptake was 78·0±2·9μg. atoms of carbon/g. wet wt./hr.; steady-state rates of lactate output, pyruvate output and incorporation of [U-¹⁴C]-glucose carbon atoms into carbon dioxide and total lipid extract were 60·7±0·9, 2·4±0·1, 18·0±1·1 and 0·7±0·1μg. atom of carbon/g. wet wt./hr. and accounted for 104·5±1·9% of the glucose uptake. In slices from luteinizing hormone-treated rats, glucose uptake and outputs of lactate, pyruvate and [¹⁴C]carbon dioxide were increased by approx. 25%, and 108·4±3·2% of the glucose uptake could be accounted for. 3. The total lipid extract was separated by thin-layer chromatography and saponification. Of the ¹⁴C incorporated into this fraction during incubation with [U-¹⁴C]glucose 97% was found in the fractions containing glyceride glycerol and less than 3% in the fractions containing sterols, steroids or fatty acids. Appreciable quantities of ¹⁴C were incorporated into these lipid fractions from [1-¹⁴C]acetate. 4. From a consideration of the tissue glycogen content, the specific activities of [¹⁴C]lactate and glucose 6-phosphate (C-1) derived from [1-¹⁴C]-, [6-¹⁴C]- and [U-¹⁴C]-glucose, and the ratio of [¹⁴C]carbon dioxide yields from [1-¹⁴C]glucose and [6-¹⁴C]glucose, it was concluded that there was no appreciable glycogenolysis or flow through the pentose phosphate cycle. 5. In ovary slices from both control and luteinizing hormone-treated animals, glucose in vitro raised the incorporation rate of ¹⁴C from [1-¹⁴C]acetate into sterols and steroids. Luteinizing hormone in vivo stimulated the incorporation rate in vitro but only in the presence of glucose. 6. In slices incubated in medium containing [³H]water, [¹⁴C]sorbitol and glucose (1mg./ml.), the total water space (865±7·1μl./g.) and the extracellular water space (581±22μl./g.) were unchanged by luteinizing hormone treatment in vivo but the glucose space was raised from 540±23·6μl./g. to 639±31·3μl./g. 7. Luteinizing hormone treatment was found to lower the tissue concentration of the hexose monophosphates and to increase the total activity of hexokinase, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase and possibly of phosphofructokinase. 8. The kinetic properties of a partially purified preparation of phosphofructokinase were found to be qualitatively similar to those from other mammalian tissues. 9. The results are discussed with reference to both the role of glucose metabolism in steroidogenesis and the mechanism by which luteinizing hormone increases the rate of glucose uptake.     

Purification of rabbit kidney cytokinase and a comparison of its properties with human urokinase

1. The cytokinase (tissue activator of plasminogen) content of several mammalian tissues was evaluated by a quantitative casein hydrolysis method. 2. An alkaline (pH10·5) extraction of cytokinase from rabbit kidney lysosome–microsome fraction, followed by chromatography on DEAE-cellulose at pH7·6 with stepwise or linear increase in concentration of phosphate buffer, gave an 86-fold purification of the enzyme. The purified material was non-proteolytic against casein and heated fibrin and was freeze-dried without significant loss of activity or solubility. 3. Cytokinase is a protein with E^0·1%_1cm.=0·87 at 280mμ, and does not possess sufficient hexose or sialic acid to be classified as a glycoprotein. It has S_20,w 2·9–3·1s and molecular weight 50000 when measured on a calibrated Sephadex G-100 column. It has an isoelectric point between pH8 and pH9, and is maximally active and stable at pH8·5. It is inactivated by heat at 78°. 4. Cytokinase and human urokinase have the same K_m value and are inhibited in a partially competitive manner by -aminohexanoic acid and aminomethylcyclohexanecarboxylic acid. They are also inhibited by cysteine and arginine, but are unaffected by iodoacetamide and p-chloromercuribenzoate. 5. On the basis of this and other evidence it is suggested that rabbit kidney cytokinase and human urokinase are similar, if not identical, enzymes.     

Technetium-99m in the Diagnosis of Thyrotoxicosis

The thyroid uptake at 20 minutes of intravenously administered Technetium-99^m (^99mTc) was measured in 117 patients with a standard scintillation counter. Patients were divided into three groups on the basis of clinical assessment, four-hour ¹³¹I uptake, triiodothyronine (T-3) resin uptake, and protein-bound iodine measurements.In 31 patients with no evidence of thyroid disease the mean ^99m Tc uptake was 1·8% ±S.D. 1·1%. In 32 patients with thyroid enlargement who were euthyroid the mean uptake was 2·5% ±S.D. 2·2%. In 54 thyrotoxic patients the mean uptake was 17·7% with a range of 4·1 to 44%, all cases having an uptake above the upper limit of normal (4·0%). These results agree closely with reported uptake studies using scanning techniques. In seven patients the extrathyroidal neck activity was measured by using a scanner, and the mean was 6·3% of the extrathyroidal total body radioactivity comparing favourably with an assumed 6% used in our calculations.We have shown that the measurement of the thyroid uptake of ^99mTc with a scintillation counter is of value, and that it is not necessary to use scanning techniques in the diagnosis of thyrotoxicosis. Advantages of ^99m Tc are minimal radiation, reduction in patient and laboratory time, and low cost.     

Purification and properties of diaminopimelate decarboxylase from Escherichia coli

1. Diaminopimelate decarboxylase from a soluble extract of Escherichia coli A.T.C.C. 9637 was purified 200-fold by precipitation of nucleic acids, fractionation with acetone and then with ammonium sulphate, adsorption on calcium phosphate gel and chromatography on DEAE-cellulose or DEAE-Sephadex. 2. The purified enzyme showed only one component in the ultracentrifuge, with a sedimentation coefficient of 5·4s. One major peak and three much smaller peaks were observed on electrophoresis of the enzyme at pH8·9. 3. The mol.wt. of the enzyme was approx. 200000. The catalytic constant was 2000mol. of meso-diaminopimelic acid decomposed/min./mol. of enzyme, at 37°. The relative rates of decarboxylation at 25°, 37° and 45° were 0·17:1·0:1·6. At 37° the Michaelis constant was 1·7mm and the optimum pH was 6·7–6·8. 4. There was an excess of acidic amino acids over basic amino acids in the enzyme, which was bound only on basic cellulose derivatives at pH6·8. 5. The enzyme had an absolute requirement for pyridoxal phosphate as a cofactor; no other derivative of pyridoxine had activity. A thiol compound (of which 2,3-dimercaptopropan-1-ol was the most effective) was also needed as an activator. 6. In the presence of 2,3-dimercaptopropan-1-ol (1mm), heavy-metal ions (Cu²⁺, Hg²⁺) did not inhibit the enzyme, but there was inhibition by several amino acids with analogous structures to diaminopimelate, generally at high concentrations relative to the substrate. Penicillamine was inhibitory at relatively low concentrations; its action was prevented by pyridoxal phosphate.     

The tissue content and turnover rates of intermediates in the biosynthesis of glycosaminoglycans in young rat skin

1. The tissue contents of hexose monophosphate, N-acetylglucosamine 6-phosphate, UDP-glucose, UDP-galactose, UDP-N-acetylglucosamine, UDP-N-acetylgalactosamine and UDP-glucuronic acid were determined in the skin of young rats less than 1 day post partum. Tissue-space determinations were used to calculate their average cellular concentrations. 2. The incorporation of [U-¹⁴C]-glucose into the intermediates was recorded with time and their rates of turnover were calculated. The results demonstrated product–precursor relationships along the pathway of hexosamine synthesis and that of hexuronic acid synthesis. The rates of synthesis of UDP-N-acetylhexosamine and UDP-glucuronic acid were 1·5±0·3 and 0·24±0·03mμmoles/min./g. of tissue respectively. These results indicated the average turnover time of the total tissue glycosaminoglycans to be about 5 days.     

Kinetics of thiamin cleavage by sulphite

Results are presented on the rate of thiamin cleavage by sulphite in aqueous solutions as affected by temperature (20–70°), pH(2·5–7·0), and variation of the concentration of either thiamin (1–20μm) or sulphite (10–5000μm as sulphur dioxide). Plots of the logarithm of percentage of residual thiamin against time were found to be linear and cleavage thus was first-order with respect to thiamin. At pH5 the rate was also found to be proportional to the sulphite concentration. In the pH region 2·5–7·0 at 25° the rate constant was 50m⁻¹hr.⁻¹ at pH5·5–6·0, and decreased at higher or lower pH values. The rate of reaction increased between 20° and 70°, indicating a heat of activation of 13·6kcal./mole.     

A Large-Scale Genetic Analysis Reveals a Strong Contribution of the HLA Class II Region to Giant Cell Arteritis Susceptibility

We conducted a large-scale genetic analysis on giant cell arteritis (GCA), a polygenic immune-mediated vasculitis. A case-control cohort, comprising 1,651 case subjects with GCA and 15,306 unrelated control subjects from six different countries of European ancestry, was genotyped by the Immunochip array. We also imputed HLA data with a previously validated imputation method to perform a more comprehensive analysis of this genomic region. The strongest association signals were observed in the HLA region, with rs477515 representing the highest peak (p = 4.05 × 10⁻⁴⁰, OR = 1.73). A multivariate model including class II amino acids of HLA-DRβ1 and HLA-DQα1 and one class I amino acid of HLA-B explained most of the HLA association with GCA, consistent with previously reported associations of classical HLA alleles like HLA-DRB1^∗04. An omnibus test on polymorphic amino acid positions highlighted DRβ1 13 (p = 4.08 × 10⁻⁴³) and HLA-DQα1 47 (p = 4.02 × 10⁻⁴⁶), 56, and 76 (both p = 1.84 × 10⁻⁴⁵) as relevant positions for disease susceptibility. Outside the HLA region, the most significant loci included PTPN22 (rs2476601, p = 1.73 × 10⁻⁶, OR = 1.38), LRRC32 (rs10160518, p = 4.39 × 10⁻⁶, OR = 1.20), and REL (rs115674477, p = 1.10 × 10⁻⁵, OR = 1.63). Our study provides evidence of a strong contribution of HLA class I and II molecules to susceptibility to GCA. In the non-HLA region, we confirmed a key role for the functional PTPN22 rs2476601 variant and proposed other putative risk loci for GCA involved in Th1, Th17, and Treg cell function.     

Involvement of carboxyl and phenoxyl groups in Cajanus cajan lectin-sugar interaction: interpretation of titration curves

Hydrogen ion titration of an affinity-purified mannose/glucose-specific lectin from Cajanus cajan seeds at 30°C and ionic strength of 0.15 was reported earlier by our lab (Salahuddin and Khan, 1998). Further work has been carried out on the systematic study of H⁺ titration of Cajanus cajan lectin at three different temperatures, i.e., 10°, 20°, and 30°C at ionic strength of 0.15. In all, 88 protons were dissociated reversibly in pH range 2–12. Different ionizable groups present in lectin were also determined with respect to their heat of ionization. Heat of ionization, H, for 43 carboxyl groups was 1.92 Kcal/mol, and for 7 phenoxyl groups, 6.84 Kcal/mol. Spectrophotometric titration was performed in the presence and absence of 0.1 M methyl -d-mannopyranoside to characterize the role of phenoxyl groups present at the active site. One phenoxyl group was found to be involved in carbohydrate binding. The presence of two carboxyl groups per subunit at the active site was confirmed by H⁺ titration in the presence and absence of 0.1 M methyl -d-mannopyranoside. Hemagglutinating and IgM precipitating activity was checked for the chemically modified carboxyl and phenoxyl group preparation. Loss of activity further confirmed the participation of carboxyl as well as phenoxyl groups at the active site. It is interesting to note the near-UV CD changes in the aromatic environment/conformation of the lectin in the presence of specific sugar, further indicating the possible participation of phenoxyl groups in the carbohydrate-binding pocket.     

The metabolism of methylcyclohexane

1. When [U-¹⁴C]methylcyclohexane is fed to rabbits (dose 2–2·5m-moles/kg. body wt.), 65% of the radioactivity is excreted in the urine as metabolites, 0·5% appears in the faeces and about 15% in the expired air, some 4–5% remaining in the body in about 60hr. after dosing. The 15% of the dose appearing in the expired air consists of unchanged methylcyclohexane (10%) and ¹⁴CO₂ (5%). The low output of ¹⁴CO₂ shows that reactions leading to complete oxidation of methylcyclohexane are of minor importance. 2. The main metabolite found in the urine was the glucuronide of trans-4-methylcyclohexanol which was isolated. Seven methylcyclohexanols were found in the urine as conjugated glucuronides. The amounts of these were determined by isotope dilution to be as follows: cis-2-, 0·6%; trans-2-, 1·2%; cis-3-, 11·5%; trans-3-, 10·5%; cis-4-, 2·4%; trans-4-methylcyclohexanol, 14·7%, cyclohexylmethanol, 0·3%. No 1-methylcyclohexanol was found. There was evidence also that a small amount (approx. 1%) of the hydrocarbon aromatized to benzoic acid, probably via cyclohexylmethanol and cyclohexane-carboxylic acid. 3. The pattern of hydroxylation and the various amounts of the isomers found suggest that the hydroxylation in vivo of methylcyclohexane is dependent on steric factors in the molecule, hydroxylation occurring to the greatest extent at the carbon atom furthest away from the methyl group.     

Antimicrobial Effects of Mustard Flour and Acetic Acid against Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella enterica Serovar Typhimurium

This study was designed to investigate the individual and combined effects of mustard flour and acetic acid in the inactivation of food-borne pathogenic bacteria stored at 5 and 22°C. Samples were prepared to achieve various concentrations by the addition of acetic acid (0, 0.5, or 1%) along with mustard flour (0, 10, or 20%) and 2% sodium chloride (fixed amount). Acid-adapted three-strain mixtures of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella enterica serovar Typhimurium strains (10⁶ to 10⁷ CFU/ml) were inoculated separately into prepared mustard samples stored at 5 and 22°C, and samples were assayed periodically. The order of bacterial resistance, assessed by the time required for the nominated populations to be reduced to undetectable levels against prepared mustards at 5°C, was S. enterica serovar Typhimurium (1 day) < E. coli O157:H7 (3 days) < L. monocytogenes (9 days). The food-borne pathogens tested were reduced much more rapidly at 22°C than at 5°C. There was no synergistic effect with regard to the killing of the pathogens tested with the addition of 0.5% acetic acid to the mustard flour (10 or 20%). Mustard in combination with 0.5% acetic acid had less bactericidal activity against the pathogens tested than did mustard alone. The reduction of E. coli O157:H7 and L. monocytogenes among the combined treatments on the same storage day was generally differentiated as follows: control < mustard in combination with 0.5% acetic acid < mustard alone < mustard in combination with 1% acetic acid < acetic acid alone. Our study indicates that acidic products may limit microbial growth or survival and that the addition of small amounts of acetic acid (0.5%) to mustard can retard the reduction of E. coli O157:H7 and L. monocytogenes. These antagonistic effects may be changed if mustard is used alone or in combination with >1% acetic acid.     

Isolation and Characterization of a Composite Plasmid Rms201 Mutant Temperature Sensitive for Replication

A mutant temperature-sensitive for R-plasmid replication, Rms201ts14, was isolated from composite plasmid Rms201 after mutagenesis of P1 transducing lysate with 100 mM hydroxylamine for 40 h at 37°C. When Escherichia coli ML1410(Rms201ts14)⁺ was grown at temperatures between 40 and 42°C in L broth, antibiotic-sensitive cells were segregated. When the incubation temperature of ML1410(Rms201ts14)⁺ in L-broth was shifted to 42 from 30°C, the increase in the number of antibiotic-resistant cells ceased 90 min after the temperature shift. However, the total number of cells continuously increased, and only 3% of the cells retained the plasmid at 5 h after the temperature shift to 42°C. At 30°C the amounts of covalently closed circular deoxyribonucleic acid per chromosome of Rms201ts14 and Rms201 were 3.8 and 6.3%, respectively. Incorporation of radioactive thymidine into the covalently closed circular deoxyribonucleic acid of Rms201ts14 did not take place at 42°C, whereas radioactive thymidine was incorporated into the covalently closed circular deoxyribonucleic acid of Rms201 at a rate of 4%/chromosome even at 42°C. The synthesis of plasmid covalently closed circular deoxyribonucleic acid in a cell harboring Rms201ts14 was almost completely blocked at 42°C. These results indicated that the gene(s) responsible for plasmid deoxyribonucleic acid replication was affected in the mutant Rms201ts14. Temperature-sensitive miniplasmid pMSts214, which has a molecular weight of 5.3 × 10⁶ and encodes ampicillin resistance, was isolated from Rms201ts14. Similarly, miniplasmid pMS201, which encodes single ampicillin resistance, was isolated from its parent, Rms201, and its molecular weight was 4.7 × 10⁶. These results indicate that the gene(s) causing temperature sensitivity for replication of Rms201 resides on the miniplasmid.