Enhancement of hormonal activity with a monoclonal antibody specific to porcine growth hormone

Abstract

The potentiation of the biological effects of recombinant porcine growth hormone (pGH) by immunologic manipulation was investigated. A monoclonal antibody (mAb), designated PS‐7.6, was raised against pGH and repeatedly shown to enhance the responsiveness of hypophysectomized (hypox) rats to pGH. As a result, animals receiving a combination treatment of pGH and mAb PS‐7.6 together gained significantly more weight than those receiving the same doses of pGH alone. The enhancing action of the mAb was a rapid process and its effective doses ranged from 0.1 to 2 mg/injection. The ability of the antibody to augment the hormonal activity persisted beyond the 5‐day treatment period and the differences in net weight gain between treated and control animals remained significant for 28 days. Results from treatment frequency studies further suggested that pGH when complexed with mAb PS‐7.6 required fewer injections and produced a greater efficacy than being administered alone. Therefore, present findings suggest that mAb PS‐7.6 may prove useful for not only improving the efficiency of pGH, but also developing a novel formulation for sustained pGH release.     

Hydrocarbon-metabolizing activity of various mammalian cells in culture

Summary Two methods for determining the hydrocarbon-metabolizing enzyme activity of cultured mammalian cells were compared. The method designed to measure benzo[a]an-thracene-induced aryl hydrocarbon hydroxylase activity could detect and quantify enzyme activities in low passage rodent cells, but could not reproducibly detect levels in intermediate or high passage mouse, rat, or human cells. The method designed to measure the ability of a cell to convert benzo[a]pyrene from an organic-soluble to an aqueous acetone-soluble form proved to be more reproducible. This technique, when modified, was demonstrated to be an effective screening test for the detection of those lines with higher levels of hydrocarbon-metabolizing enzymes. Supported by the Council for Tobacco Research and Contract NIH 70-2068 within the Virus Cancer Program, National Cancer Institute, National Institutes of Health.     

Microcalorimetric assay of acetylcholinesterase

Comparative assays were made in a spectrophotometer and a microcalorimeter for the reaction between acetylcholinesterase (EC 3.1.1.7) and acetylthiocholine. The rate of light absorbance change and the rate of heat flow were measured from similar and simultaneous reactions in spectrophotometer and microcalorimeter, respectively. At the enzyme activity levels studied, i.e., 0.05–0.15 I.U. in calorimetry and 1–4 I.U. in spectrophotometry, the reaction rates were linear and showed first-order kinetics. A highly significant positive correlation was seen between the two methods (r = 0.997). More importantly, spectrophotometric assay with acetylthiocholine (which utilized a secondary reaction with chromagen, dithiobisnitrobenzoic acid) stood in highly significant positive correlation with calorimetric assays (which did not require a chromagen) either with the same substrate (r = 0.976) or with acetylcholine (r = 0.900). It appears that microcalorimetry can be used in preference to spectrophotometry for enzyme kinetic studies to overcome the complexity of reaction mixture and interference problems and with the advantage of using natural substrates.     

Regulation of cardiac cyclic GMP-dependent protein kinase

An assay method based on the ability of high concentrations of Mg²⁺ to stimulate phosphorylation of histone in the presence of low concentrations of ATP was developed for the measurement of cyclic GMP-dependent protein kinase activity ratios (activity -cyclic GMP/activity + cyclic GMP). In tissues which contain only trace amounts of cyclic GMP-dependent protein kinase, the basal activity ratios were high due to interference from a cyclic nucleotide-independent protein kinase. In order to study the regulation of the cardica cyclic GMP-dependent protein kinase, factors affecting the equilibrium between the active and inactive forms of the enzyme were determined. Since the rate of dissociation of cyclic GMP from its binding site(s) was relatively slow at 0–4°C at pH 7.0, the amount of time required to process tissue samples was the major limiting factor for preserving the equilibrium between active and inactive forms of the enzyme. Dilution of heart tissue extracts at 0–4°C did not significantly alter the activity ratio of the enzyme under conditions of basal or elevated cyclic GMP levels. Experiments using charcoal or exogenous cyclic GMP-dependent protein kinase in the homogenizing medium demonstrated that the release of sequestered cyclic GMP was not responsible for the elevation of the cyclic GMP-dependent protein kinase activity ratios by agents like acetylcholine. Therefore, the assay reflected in part, at least, the retention of kinase-bound cyclic GMP in the tissue extracts. The effects of acetylcholine and sodium nitroprusside on cyclic GMP levels, the cyclic GMP-dependent protein kinase activity ratios, and force of contraction were studied in the perfused rat heart. Both agents produced rapid, dose-dependent increases in cardiac cyclic GMP. Optimal concentrations of acetylcholine produced a 2–3-fold increase in the levels of cyclic GMP and an increase in the cyclic GMP-dependent protein kinase activity ratio. No significant effect of acetylcholine on cyclic nucleotide-independent protein kinase activity was observed. Associated witth the acetylcholine-induced protein kinase, factors affecting the equilibrium between the active and inactive forms of the enzyme were determined. Since the rate of dissociation of cyclic GMP from its binding site(s) was relatively slow at 0–4°C at pH 7.0, the amount of time required to process tissue samples was the major limiting factor for preserving the equilibrium between active and inactive forms of the enzyme. Dilution of heart tissue extracts at 0–4°C did not significantly alter the activity ratio of the enzyme under conditions of basal elevated cyclic GMP levels. Experiments using charcoal or exogenous cyclic GMP-dependent protein kinase in the homogenizing medium demonstrated that the release of sequestered cyclic GMP was not responsible for the elevation of the cyclic GMP-dependent protein kinase activity ratios by agents like acetylcholine. Therefore, the assay reflected in part, at least, the retention of kinase-bound cyclic GMP in the tissue extracts. The effects of acetylcholine and sodium nitroprusside on cyclic GMP levels, the cyclic GMP-dependent protein kinase activity ratios, and force of contraction were studied in the perfused rat heart. Both agents produced rapid, dose-dependent increases in cardiac cyclic GMP. Optimal concentrations of acetylcholine produced a 2–3-fold increase in the levels of cyclic GMP and an increase in the cyclic GMP-dependent protein kinase activity ratio. No significant effect of acetylcholine on cyclic nucleotide-independent protein kinase activity was observed. Associated with the acetylcholine-induced increase in cyclic GMP and the cyclic GMP-dependent protein kinase activity ratio was a reduction in the force of contraction. In contrast, nitroprusside produced little or no increase in the cyclic GMP-dependent protein kinase activity ratio despite increasing the level of cyclic GMP 8–10-fold. Nitroprusside also had no effect on contractile force. In combination, nitroprusside and acetylcholine produced additive effects on cyclic GMP levels, but protein kinase activation and force of contraction were similar to those seen with acetylcholine alone. The results suggest that the cyclic GMP produced by acetylcholine in the rat heart is coupled to activation of the cyclic GMP-dependent protein kinase, while that produced by nitroprusside is not.     

Terpenoid and morphological variability of Pinus quadrifolia and the natural hybridization with Pinus monophylla in the San Jacinto Mountains in California

Monoterpenoids from wood of Pinus quadrifolia and Pinus monophylla from south of the San Jacinto Mountains in southern California were analysed by gas-liquid chromatography (GLC). The number of needles per fascicle, the number of resin canals, and the number of abaxial and adaxial stomatal rows in the needles were determined. Percentages of mycrene, α-pinene, and to a minor extent of camphene, β-pinene, limonene, and β-phellandrene, the above mentioned morphological characteristics and previously obtained data were all used for identification and characterisation of species intermediacy in the San Jacinto area. It was concluded that many P. quadrifolia trees in the mixed Buck Ridge stand and some trees in two pure stands of the same area were hybrids and that sympatric and to a lesser extent allopatric introgression of P. monophylla into P. quadrifolia takes place in the San Jacinto region. Introgression of P. quadrifolia into P. monophylla could not be demonstrated.     

The influence of water depth and flow regime on phytoplankton biomass and community structure in a shallow,lowland river

Hydrobiologia - The taxonomic composition and biomass of phytoplankton in the San Joaquin River, California, were examined in relation to water depth, flow regime, and water chemistry. Without...     

Screening costramid libraries for chromosomal genes: an alternative interspecific hybridization method

Abstract Broad host-range RK2-based cosmid vectors ('costramids') are increasingly used in molecular genetic studies of Gram-negative soil bacteria such as Rhizobium spp. we describe a simple modification of existing methods, whereby a genomic library constructed in a stringently replicated vector can be screened for genes which are undetectable by colony hybridization due to background cross-hybridization. This method allows the use of 'heterologous' probes (interspecies hybridization) to isolate several presumptive genes of interest from a gene bank of Rhizobium sp. NGR234 made in the costramid pRK7813. These are a gene with homology to the citrate synthase gene ( gltA ) or Escherichia coli , the gene encoding δ-aminol evulinic acid synthase ( hemA ), and a gene or genes regulating dicarboxylate transport.