RECFIT: a microcomputer-based nonlinear regression curve-fitting package for the quantitative resolution of beta-adrenoceptor subtypes and estimation of nonspecific binding

A dedicated nonlinear regression based curve-fitting packages has been developed for quantitative analysis of beta-adrenoceptor subtypes. A feature of this package is the provision to obtain initial parameter estimates using a conversational graphical technique where the user is prompted for parameter estimates, and the resulting curve is displayed over the data. Data are then fitted to a one- or two-binding site model with user-selected weighting and constraints on the parameters. A novel feature is the provision to estimate the nonspecific binding component in the assays as a parameter in the model. The printout for each model consists of the parameters and their standard deviations, estimates of the goodness of fit, an analysis of residuals, and a graph of the data points overlayed with the fitted curve. The nonlinear regression algorithm is based on that of Gauss-Newton. When unweighted, the values determined by RECFIT are essentially the same as those found using the BMDPAR programs on an ICL 2976 mainframe computer. The implementation is reasonably efficient; a typical run for a two-site fit, using nine data points and estimating nonspecific binding, took a total time of about 8 min, excluding data entry and derivation of initial estimates, 4 min for the fitting, 30 sec for graph generation, and 2-3 min for printing of the graph and data.

Alpha 2-adrenoceptors in human lymphocytes: direct characterisation by [3H]yohimbine binding

[3H]yohimbine, a potent and selective alpha 2-adrenergic antagonist was used to label alpha-adrenoceptors in intact human lymphocytes. Binding of [3H]yohimbine was rapid (t1/2 1.5 -2.0 min) and readily reversed by 10 microM phentolamine (t1/2 = 5 - 6 min) and of high affinity (Kd = 3.7 +/- 0.86 nM). At saturation, the total number of binding sites was 19.9 +/- 5.3 fmol/10(7) lymphocytes. Adrenergic agonists competed for [3H]yohimbine binding sites with an order of potency: clonidine greater than (-) epinephrine greater than (-) norepinephrine greater than (+) epinephrine much greater than (-) isoproterenol; adrenergic antagonists with a potency order of yohimbine greater than phentolamine greater than prazosin. These results indicate the presence of alpha 2-adrenoceptors in human lymphocytes.

Binding potencies of 3 new beta 2 specific blockers to beta receptors in the ciliary processes and the possible relevance of these drugs to intraocular pressure control

The binding potencies of 3 new beta 2 blocking drugs to beta receptors in the ciliary processes were studied by means of radioligand techniques. The drugs studied were IPS339, ICI118,551, and Sandoz L1 32-468. The order of potency of these drugs was IPS339 greater than Sandoz L1 32-468 greater than ICI118,551. The beta 2 dissociation constants (KDs) for these drugs were 0.90 nM, 6.60 nM, and 55 nM respectively. These results are compared with those for other adrenergic agents, including timolol. The potential role of topical beta 2 blockers in glaucoma is discussed.

Circadian variation in number and affinity of beta 2-adrenoceptors in lymphocytes of asthmatic patients

To determine whether circadian variation in adrenoceptor function might underlie the 'morning dip' in peak expiratory flow (PEF) rate and its abolition by salbutamol we measured indices of beta-adrenoceptor function (Bmax. and Kd), the ratio FEV1/FVC, and plasma cortisol at 08.00 and 18.00 hours on and off salbutamol (4 mg given orally every 4 h) in five extrinsic asthmatic patients and five normal volunteers. There was a significant circadian variation in receptor numbers (Bmax.) in both the control and asthmatic groups which was not abolished on treatment with salbutamol. Both groups appeared to compensate for loss of receptor number induced by salbutamol administration by increasing receptor affinity. For comparable combinations of drug/time, there was no significant difference between the control and asthmatic groups. We conclude that the 'morning dip' observed in asthmatic patients cannot simply be explained by changes in cell receptor number or affinity, as our results suggest that both groups have intact beta-adrenoceptor function. Nevertheless, our observations of the normal circadian rhythm has important implications for future studies of beta-adrenoceptors in asthmatic patients.

Intraoperative serum concentrations of cefazolin and cefoxitin administered preoperatively at different times

The effect of administration time on the serum concentrations of cefazolin and cefoxitin achieved during surgery was studied. Patients about to undergo elective surgery were randomly selected to receive one of four antibiotic prophylaxis regimens. Two of the regimens consisted of cefazolin 20 mg/kg i.v. (as the sodium salt) administered either "on call" to the operating room or with anesthesia in the operating room. The other two regimens were identical except that cefoxitin 30 mg/kg i.v. (as the sodium salt) was substituted for cefazolin. Intraoperative blood samples for analysis of serum concentrations were obtained at the time of surgical incision, one hour after incision, and at wound closure. Forty patients completed the study (10 patients received each treatment). Mean projected cefazolin concentrations at the time of incision and at wound closure for both two-hour and three-hour operations were significantly higher after administration with anesthesia than after "on-call" administration. For cefoxitin, differences in projected concentrations for "on-call" administration versus administration with anesthesia were significant at the time of incision and at wound closure in a two-hour operation. At times corresponding to initial incision, projected free-cefoxitin concentrations were higher than those of cefazolin; however, projected free-cefazolin concentrations were higher than free-cefoxitin concentrations at wound closure for two-hour and three-hour operations. To ensure that antibiotic is present in serum throughout a two- or three-hour surgical procedure, cefoxitin should probably be administered at the induction of anesthesia. Cefazolin administered "on call" appears to be acceptable for maintaining serum concentrations throughout surgery of this duration.

Pharmacokinetics and toxicity testing

The pharmacokinetic basis for the design of toxicity tests is discussed with reference to the absorption and clearance of drugs. The absorption and clearance of a wide range of drugs by laboratory animals and man has been examined and reviewed to provide a firm basis against which new drugs can be compared. Some pitfalls in either the empirical approach to toxicology or the incorrect interpretation of kinetic data are highlighted. An approach is outlined for the rational application of animal pharmacokinetic data in the assessment of the safety in man of a new therapeutic agent.

beta 2 microglobulin plasma levels reflect disease activity in rheumatoid arthritis

Elevated plasma levels of beta 2 microglobulin have been described in rheumatoid arthritis (RA) but their relationship to disease activity is unclear. In patients treated for 6 months with auranofin (AF) there was a significant fall (p less than 0.05) in beta 2M levels pari passu with improvement in disease activity as measured by a fall in C-reactive protein. In addition, 26 patients with mild RA had beta 2M levels within the normal range. It is concluded that beta 2M plasma levels reflect disease activity in RA.

Failure of sodium aurothiomalate and triethyl phosphine gold to cause renal tubular injury in rheumatoid arthritis: implications for the aetiology of gold-related nephropathy

The urinary excretion of two proteins, B-2-microglobulin (beta 2M) and N-acetyl-B-D-glucosaminidase (NAG) was measured in 25 patients with rheumatoid arthritis (RA) on nonsteroidal anti-inflammatory drugs (NSAID). Although beta 2M excretion was normal NAG excretion was raised. As NAG excretion by a group of osteoarthritis patients receiving similar doses of NSAIDs was normal, it is concluded that rheumatoid disease per se may be associated with mild renal tubular dysfunction. Twelve of the above 25 patients were then given oral triethylphosphine-gold (auranofin) 6 mg daily and urinary beta 2M and NAG were measured after 6 months' treatment. Urinary excretion of beta 2M and NAG was also measured in 13 patients with RA established on intramuscular sodium aurothiomalate (MGST) and NSAIDs. Neither auranofin nor myocrisin were found to further significantly increase beta 2M and NAG excretion. These results suggest that gold compounds are not toxic to renal tubular epithelium.

Development of the cytosolic defence system against microsomal lipid peroxidation in rat liver

Ascorbate-induced lipid peroxidation in rat liver microsomes reaches the adult level in 2-3 days. NADPH-induced peroxidation develops more gradually, in parallel with the activity of NADPH-cytochrome P-450 reductase, attaining adult levels by 10-12 days. The glutathione-dependent cytosolic enzyme activity which inhibits peroxidation is inhibited by bromosulphophthalein. The development of this system lags behind the development of microsomal lipid peroxidation between the ages of 2 and 20 days, allowing peroxidation to proceed.

Microprocessor assisted handling of oestrogen receptor assays

The use of an Apple II microcomputer equipped with a light-pen for interactive analysis of steroid receptor data is described. Processing times have been reduced to less than 5 minutes per patient from around 45-60 minutes by the manual method. Graphical outputs using full and part data sets with derived results are printed for subsequent verification by the Consultant Medical Biochemist. Data processing backlogs have been completely eliminated by this system. The program has, of course, general applicability to any analyses producing a linear correlation between the x and y parameters, and its use in oestrogen receptor analysis is detailed principally because of a considerable and increasing demand for such assays in our department.

Amino acid sequences of three bombesin-like peptides from canine intestine extracts

Amino acid sequences of three canine bombesin-like peptides were determined after sequential purification of an extract obtained from 820 g of intestinal muscle. These three peptides contained 27, 23, and 10 amino acid residues. The sequences of the two shorter forms were identical to the corresponding carboxyl-terminal sequence of the heptacosapeptide. The sequence of the largest peptide is H2N-Ala-Pro-Val-Pro-Gly-Gly-Gln-Gly-Thr-Val-Leu-Asp-Lys-Met-Tyr-Pro-Arg-Gly-Asn - His(Trp-Ala-Val-Gly-His-Leu-Met-CONH2). The sequence of the 23-residue peptide is H2N-Gly-Gly-Gln-Gly-Thr-Val-Leu-Asp-Lys-Met-Tyr-Pro-Arg-Gly-Asn-His-Trp-Ala- Val-Gly(His-Leu-Met-CONH2). The sequence of the decapeptide is: H2N-Gly-Asn-His-Trp-Ala-Val-Gly-His-Leu-Met-CONH2. Comparison of the 27-residue peptide with the known structure of porcine gastrin-releasing peptide, another bombesin-like heptacosapeptide, reveals four amino acid substitutions: canine bombesin-like peptide had Pro 4, Gly 5, Gln 7, Asp 12, whereas porcine gastrin-releasing peptide had Ser 4, Val 5, Gly 7, Ala 12. Radioimmunoassay of brain extracts after similar purification revealed the presence of similar large and small forms of immunoreactive bombesin peptides, but with apparent tissue concentrations of about 4% of those present in intestinal muscle. Canine bombesin-like peptides represent another example of mammalian neuropeptides existing in more than one biologically active molecular form.

Beta adrenergic receptors in pigmented ciliary processes

Beta adrenergic receptors from membrane fragments of pigmented sheep eyes were studied and characterised by ligand binding techniques after the removal of melanin. In a representative experiment the beta max (total number of beta receptors) was 394.9 fmol/mg protein. The receptor affinity (Ka) was 440 pM. The potency series of drugs to displace 125I-HYP from the receptors was timolol = (-) propranolol greater than (+) propranolol greater than salbutamol greater than practolol. beta 1 Receptors were not detected in the ciliary processes. beta 2 Receptors were the prominent adrenergic receptors present. The theory as to how beta blockers work in glaucoma, their site of action, and the potential role of beta 2 blockers for use in intraocular pressure control is discussed.

Prediction of IQ and language skill from perinatal status, child performance, family characteristics, and mother-infant interaction

193 basically healthy working-class and middle-class mothers and their infants participated in a 4-year longitudinal study which focused on the relative potency of several clusters of variables for predictions of intellectual and language outcome during the preschool years. The major results were: (1) Measures of perinatal or infant physical status were extremely weak predictors of 4-year IQ or language. (2) Assessments of child performance were poor predictors prior to 24 months, but excellent predictors from 24 months on. (3) Assessments of mother-infant interaction and general environmental quality were among the best predictors at each age tested, and were as good as measures of child performance at 24 and 36 months in predicting IQ and language. (4) Measures of the family ecology (level of stress, social support, maternal education) and parent perception of the child, especially when assessed at birth, were strongly related to child IQ and language within a low-education subsample, but not among mothers with more than high school education. Patterns of prediction were similar for 48-month IQ and 36-month receptive language; predictions were notably weaker for 36-month expressive language.

A Canadian community mental health program: a clerkship experience

The authors describe a consultation-liaison relationship between a community psychiatry outpatient service and private community family practitioners, including some problems and solutions that have arisen as a result of this relationship. A medical student clerkship in this consultation-liaison setting is particularly useful in orienting students to community aspects of psychiatric care in primary care practice. Since 50% of medical students from McMaster University enter some form of primary care activity, this exposure and sensitization to community mental health activities is especially relevant.

The mechanism of hepatotoxicity of a chromone carboxylic acid (FPL 52757) in the dog

1. The chromone carboxylic acid (6,8-diethyl-5-hydroxy-4-oxo-4H-1-benzopyran-2-carboxylic acid) is hepatotoxic in dogs (at 40 mg/kg per day). This toxicity did not appear to be mediated by a reactive metabolite, as the compound was not metabolized by the dog, and phenobarbitone pretreatment (20 mg/kg per day) protected rather than potentiated. 2. Other studies in the dog showed that the chromone caused increases in the biliary excretion of alkaline phosphatase (17-fold), gamma-glutamyl-transpeptidase (9-fold), and 5'-nucleotidase (13-fold) which paralleled the biliary concentration of the drug (up to 1.3 mg/ml) and was accompanied by a reduction in bile flow. 3. The excretion of the chromone into the biliary tract of the dog was shown to be saturable, and therefore high hepatocellular concentrations of the drug and subsequent liver damage could result. 4. The toxicity of the chromone when administered to rat by retrograde biliary infusion, and the lysis of erythrocytes in vitro, are related to detergent properties of the drug and add confirmatory evidence for a mechanism of toxicity in the dog. 5. It is concluded that the chromone itself is responsible for the toxicity in the dog due to its detergent properties causing damage to the hepatobiliary tract. The protection by phenobarbitone and also by methionine may have been due to an increased bile flow reducing biliary concentrations.

Metabolism and excretion of a chromone carboxylic acid (FPL 52757) in various animal species

1. The disposition of the chromone carboxylic acid (FPL 52757) in several species has been investigated. The compound is extensively metabolized by hydroxylation in rat, mouse, ferret, squirrel monkey, cynomolgus monkey, rabbit, hamster, stumped-tailed macaque and baboon (e.g. 50-100% in rat, cynomolgus monkey and squirrel monkey). 2. The plasma clearance of the chromone in rat, rabbit and squirrel monkey was 138, 44 and 59 ml/kg per h respectively. Plasma clearance by the dog was slower (13 ml/kg per h) and due mainly to elimination of unchanged compound. 3. As the dog is particularly susceptible to FPL 52757-induced hepatotoxicity the parent compound may be responsible. Species which clear the compound rapidly compared with the dog did not show a hepatotoxic response. 4. Although metabolism occurs in man the clearance is still slow (15 ml/kg per h) and may be one reason for human susceptibility to a mild hepatotoxic effect with the compound.

A monoclonal antibody recognizing a determinant common to HLA-A3 and A11

Spleen cells from a mouse immunized with an AML cell expressing HLA-A3 produced a hybridoma secreting an anti-HLA-A3, A11 monoclonal antibody, 26D3. By complement-dependent cytotoxicity at dilutions to 1:10(4) the ascites antibody lysed 13/13 A3, 15/15 A11, and 8 other lymphocytes from a panel of 98 donors. The 26 D3 immunoprecipitated a molecule consisting of subunits of 44,000 and 12,000 daltons. Monoclonality of the antibody was demonstrated by isoelectric focusing and protein A affinity chromatography.

Studies on paracetamol-induced lipid peroxidation

Post-mitochondrial supernatants isolated from livers of rats given a single large oral dose of paracetamol (800 mg/kg) showed rapid rates of lipid peroxidation when incubated in vitro. As a result of paracetamol administration the level of reduced glutathione (GSH) declined to approx. 20-25% of the peak physiological value. Addition of reduced GSH to the supernatant inhibited the peroxidation. Paracetamol-induced lipid peroxidation was inhibited in vitro by antioxidants (e.g. vitamin E) but was unaffected by superoxide dismutase and mannitol. N-acetyl cysteine and cysteamine inhibited lipid peroxidation in vitro in a cytosol-dependent manner in the absence of glutathione. Lipid peroxidation probably occurs simultaneously with the proposed covalent binding of the active metabolite of paracetamol. Since the former process is known to cause severe and extensive membrane damage, it may be a very important factor in paracetamol-induced liver necrosis.

Immunoglobulin concentrations in the duodenal fluids of infants and children. II. The effect of pancreozymin and secretin

A study was conducted to determine whether pancreozymin and secretin affect the levels of immunoglobulins in duodenal fluid of children. The subjects consisted of 45 infants and children without gastrointestinal disease. Ig-A concentrations in duodenal fluid were significantly increased (P less than 0.02) after secretion administration (2 U./kg) as compared to resting fluid levels (18.3 +/- 0.8 vs. 12.9 +/- 1.1 mg./gm. protein). Secretin also produced a significant increase (P less than 0.0002) in Ig-M duodenal fluid levels (25.5 +/- 3.6 vs. 13.8 +/- 1.4 mg./gm. protein). Duodenal fluid Ig-G concentrations were not significantly changed in response to secretin (30.7 +/- 2.3 vs. 29.1 +/- 1.2 mg./gm. protein) or to pancreozymin (29.0 +/- 0.8 mg./gm. protein). Pancreozymin administration (2 U./kg) produced a significant decrease (P less than 0.01) in Ig-A concentration (11.2 +/- 0.8 mg./gm. protein) and a significant increase (P less than .0002) in the Ig-M levels of human duodenal fluid (20.8 +/- 1.8 mg./gm. protein).