Use-dependent fade and two-rate recovery of a naloxone-sensitive inhibition in the cat superior cervical ganglion

In anaesthetized cats, a short train to the cervical sympathetic trunk (CST), of frequency between 0.5 and 5.0 Hz, inhibited the postganglionic compound action potential (CAP) evoked by a test shock to the CST. When the CST was split into two bundles, the inhibition was obtained both homosynaptically and heterosynaptically. The inhibition was antagonized by naloxone and enhanced by peptidase inhibitors. Leu-enkephalin (ENK), injected into the arterial supply of the superior cervical ganglion (SCG) depressed the CAP. The ENK-evoked inhibition was antagonized by naloxone, enhanced by peptidase inhibitors and was occluded by the train-evoked inhibition. After prolonged stimulation of the CST (5-20 min at 5 Hz), the inhibition produced by a short train was depressed (faded). The fade was greater the longer the stimulation. After 20 min of stimulation the inhibition was absent. At this time the depressant effect of ENK was unchanged. When only one bundle of the split CST was stimulated at 5 Hz for 20 min, only the inhibition produced by that bundle faded, although both bundles converged onto a common set of ganglion cells. Thus, the fade is not due to receptor desensitization but more likely to failure to release the inhibitory mediator by the overstimulated axons. When, after 20 min of 5 Hz stimulation, no further stimuli were applied, the inhibition recovered in 60 min (fast recovery). However, recovery was slower when stimulation lasted longer than 20 min. Recovery took three days when stimulation lasted 80 min (slow recovery). The inhibition was markedly depressed after application of colchicine to the CST three days earlier.(ABSTRACT TRUNCATED AT 250 WORDS)

Optical limiting by chemically enhanced bacteriorhodopsin films

The optical limiting properties of a thin film (~150 microm) of chemically enhanced bacteriorhodopsin under cw laser illumination is investigated. The effective nonlinearity n(2) of the film is measured with the z-scan method. Anomalous absorption at different wavelengths as a function of illumination intensity is observed.

Mapping of the ben, ant and cat genes of Pseudomonas aeruginosa and evolutionary relationship of the ben region of P. aeruginosa and P. putida

Genes responsible for the utilization of benzoate, anthranilate or catechol (ben, ant, cat) of Pseudomonas aeruginosa PAO were mapped precisely using a cosmid clone carrying all these genes. Genes were localized either by subcloning and complementation or by Tn5 mutagenesis and mapping of the Tn5 insertions. To achieve this, a novel Tn5 mutagenesis procedure was developed by constructing a Tn5 insertion derivative of the Escherichia coli strain S17-1. Preliminary mapping of the ben cat genes of P. putida PPN was accomplished by complementation using a PPN cosmid bank. Sequence homology was demonstrated by Southern hybridization between the ben regions of both P. aeruginosa and P. putida, implying an evolutionary relationship of this chromosomal region of these two pseudomonads.

Photosensitization with anticancer agents. 18. Perylenequinonoid pigments as potential photodynamic therapeutic agents: preparation and photodynamic properties of amino-substituted hypocrellin derivatives

Perylenequinonoid pigments have demonstrated several photodynamic therapeutic advantages over the commonly used hematoporphyrin derivatives. Certain new amino-substituted hypocrellin B derivatives have been prepared, and both direct and reductive aminations of hypocrellin B are described. The photophysical and photochemical properties of the amino-substituted hypocrellin B derivatives were investigated, and their significantly enhanced red absorptivities and strong 1O2-generating functions qualify them as promising photodynamic therapeutic agents. In addition, the superoxide anion radical was also determined to be implicated in the photosensitization of the amino-substituted hypocrellin B derivatives.

Bradyrhizobium japonicum rhizobitoxine genes and putative enzyme functions: expression requires a translational frameshift

Some strains of Bradyrhizobium japonicum produce rhizobitoxine, a phytotoxin that causes foliar chlorosis on susceptible host plants. We have previously obtained Tn5-induced rhizobitoxine null mutants of B. japonicum. DNA sequence analysis of the region surrounding two Tn5 insertions identifies two overlapping open reading frames. The first open reading frame (rtxA) predicts a 54-kDa protein for which the N-terminal 280 residues have sequence similarity to serine: pyruvate aminotransferase. The sequence homology to aminotransferase is consistent with the involvement of this gene in serinol production, a likely intermediate in rhizobitoxine biosynthesis. Previously, a mutant in this open reading frame was shown not to make serinol. The predicted amino acid sequence of the second open reading frame (rtxB) has similarity to yeast O-acetylhomoserine sulfhydrolase. This enzyme function is similar to that required for dihydrorhizobitoxine synthase. The DNA sequence shows that the rtxB open reading frame overlaps rtxA, suggesting that expression of rtxB requires a -1 translational frameshift. Protein expression experiments demonstrate production of an RtxAB fusion protein. The ability of the overlapping rtxA and rtxB sequences to promote a translational frameshift was confirmed in a heterologous expression system. In Escherichia coli, this frameshift appears to be unusually efficient, occurring at a frequency of 80-90%.

Cadmium-induced arteriolar constriction in skeletal muscle microcirculation

Cadmium, an environmental pollutant, is known to induce hypertension in animal models, in part via an increase in peripheral vascular resistance. Since prior studies have investigated the vascular effects of cadmium using large, nonresistance arteries, we directly assessed cadmium's action on resistance size arterioles in skeletal muscle using the intact rat cremaster muscle preparation. Cadmium evoked a concentration-dependent constriction of the large arterioles (120 to 50 microns in diameter) but elicited no change in the diameter of smaller arterioles (30 to 15 microns). Blockade of alpha-adrenergic receptors did not diminish the constrictor response of the larger arterioles to cadmium, but bathing the cremaster muscles with a solution containing low calcium attenuated the arteriolar constriction to cadmium. Calcium repletion caused the arterioles to constrict further. These observations provide the first direct evidence that cadmium constricts resistance arterioles in skeletal muscle. The cadmium constriction: (1) is selective for the large arterioles, (2) is not mediated by alpha-adrenergic receptors, and (3) is influenced by the extracellular level of calcium. We conclude that arteriolar constriction in skeletal muscle tissue may play a role in the hypertensive actions of cadmium.

Chiroinositol deficiency and insulin resistance. III. Acute glycogenic and hypoglycemic effects of two inositol phosphoglycan insulin mediators in normal and streptozotocin-diabetic rats in vivo

Two insulin mediators, inositol phosphoglycans, were isolated from bovine liver by methods previously developed for rat liver, i.e. chromatography on an AG 1 x 8 ion exchange column and selective elution with HCl at pH 2.0 and 1.3. The pH 2.0 mediator containing D-chiroinositol stimulated pyruvate dehydrogenase phosphatase, whereas the pH 1.3 mediator containing myo-inositol inhibited cAMP-dependent protein kinase. Each mediator was further purified by thin layer and Bio-Gel P4 column chromatography and injected ip into normal fed rats together with [U-14C]glucose. After 2.5 h, diaphragms were removed, and glycogen isolated. Insulin mediators, like insulin, stimulated [U-14C]glucose incorporation into glycogen by 150-160% in a dose-dependent manner in the nanomolar range. Mediators injected iv in the nanomolar range into low dose streptozotocin-diabetic rats decreased plasma glucose 30-45% in 30-60 min, with a return to basal concentrations after 150-180 min. These in vivo insulin-like effects of mediator were observed without changes in serum insulin concentrations. The pH 2.0 mediator was 50-100 times more active (per nmol organic phosphate) than the pH 1.3 mediator in the ip diaphragm glycogenesis assay. Mediator effects on diaphragm were completely blocked by preincubation with an immunopurified inositol phosphoglycan antibody. Both mediators were equally active iv in lowering plasma glucose (per nmol inositol) at concentrations comparable to those of insulin.

Mitochondrial DNA mutation associated with aging and degenerative disease

Previous theories of aging based on somatic mutation neglected mtDNA, which has a high propensity for mutational error. Knowledge of yeast mtDNA mutations and their functional effects, and of human mtDNA mutations identified in the mitochondrial cytopathies, provides for a concept of aging based on the cumulative effect of mutations affecting human mtDNA. An essential feature of this concept is heteroplasmy, representing mixtures of normal and mutant mtDNA at the cellular and mitochondrial level, resulting in a "tissue mosaic" of focal bioenergetic deficits. Direct evidence for the concept is provided by (i) focal loss of staining for mitochondrially encoded enzymes, such as cytochrome c oxidase, in tissues of aged individuals (humans and rats) and (ii) an age-related increase in deletional mutations in mtDNA demonstrable by application of the polymerase chain reaction to DNA templates from individuals of different ages.

[A case-control study of colorectal cancer in Beijing]

A case-control study was conducted among 250 persons suffering from cancer of the colon and rectum (CRC) in the urban area of Beijing from Jan 1, 1988-June 30, 1989 to explore the risk factors for CRC. 500 neighbour residents were matched as control. The chi-square test and conditional logistic Regression analysis show that high consumption of meat, oil, low occupational physical activity and psychological stress were risk factors of CRC. A trend of increased odds ratio (OR) of CRC with high meat intake and a trend of decreased OR with increased occupational physical activity were found. The high consumption of vegetables and the habit of eating uncooked fresh vegetables showed a protective effect on CRC. The results of the study support the CRC etiological hypotheses of "fat-bile acid action" and "deficiency of dietary fibres".

Selective IgM deficiency and abnormal B-cell response in a foal

Selective IgM deficiency was diagnosed in a 3-month-old Standardbred colt that was referred for chronic respiratory tract disease. Immunoglobulin quantification revealed normal IgG and IgA concentrations, but undetectable IgM concentration. Stimulation of blood lymphocytes with the T-cell mitogens concanavalin A and phytohemagglutinin yielded results within the normal range. However, stimulation with the B-cell mitogen lipopolysaccharide produced no response. A B-cell defect similar to that associated with several immunodeficiency disorders in people was suggested as the cause of the IgM deficiency in this colt.

Clinical value of lung scintigraphy with Tc-99m gluconate in distinguishing benign from malignant lung diseases

One hundred patients were studied with three-phase lung scintigraphy with Tc-99m gluconate. The results showed that there were statistically significant differences between benign and malignant lung lesions in the intensity of accumulation, the blood supply index ratio, and the radioactive uptake ratio. However, no difference was observed between the benign lung lesions and the healthy lungs. Analysis of false negatives and false positives revealed that false negatives had something to do with the cell types of the malignancies, in addition to the relatively small size of the lesions; the false positives were mostly caused by acute inflammation, for which obstructive pneumonitis might be responsible in part. It is concluded that Tc-99m gluconate is tumor-avid and can be used as an agent for positive imaging of lung cancer, because quantitative parameters, blood supply index ratio, and radioactive uptake ratio are more objective in distinguishing malignant lung lesions from benign ones, and are of relatively higher sensitivity and specificity. Thus, lung scintigraphy with Tc-99m gluconate provides an efficient supplementary measure for differentiating between malignant and benign lung lesions.

[Bacterial microcolony and its primary applications]

A new rapid and useful microcolony technique was developed by using cellulose-acetate membrane as a supporter. The bacteria were inoculated on the membrane and cultivated for 3-6h. Then the membrane was rendered, fixed and colored. The microcolonies were observed and counted under the microscope. By using this technique the microcolonies of 139 strains of bacteria were observed. 72 strains of Staphylococcus were differentiated by means of observing the characteristics of the microcolonies. The correlation rate between the microcolony method and the routine method was 90.28%. This technique was also first used to determine the bacteria numbers in urine within 6h, and the advantages of it were significant compared with the plate count method.

Mitochondrial DNA mutation and the ageing process: bioenergy and pharmacological intervention

A comprehensive hypothesis concerning the contribution of mitochondrial DNA (mtDNA) mutations to the human ageing process is reviewed and the implications for cellular bioenergy loss and pharmacological therapy are considered. The central idea is that random mutations in the population of mtDNA molecules of each cell occur throughout life, and that this is a major contributor to the gradual loss of cellular bioenergy capacity within tissues and organs, associated with general senescence and diseases of ageing. An elaboration of four major aspects of the general proposition, together with relevant supporting data, is presented. (1) An extensive array of deletions in mtDNA of many tissues of humans and other mammals has been observed to occur in an age-related manner. (2) The preservation and selection of fully functional mtDNA molecules in the female germ line cells is proposed to occur via a human mtDNA cycle, in which selective amplification of a limited number of mtDNA templates occurs during oocyte development. This proposal explains the endowment of normal neonates with a mtDNA complement minimally contaminated by damaged mtDNA molecules. The phenomena of maternal inheritance and rapid fixation of sequence variants of mtDNA in mammals, as well as selection of cells based on mitochondrial function, are taken into account. (3) Tissue bioenergy mosaics result from accumulated mtDNA damage during ageing, representing different rates of cellular bioenergy loss within individual cells of a tissue. The random segregation of mtDNA during cell division will also further contribute to the tissue energy mosaic. Cells unable to meet their particular bioenergy demand will become non-functional, leading to cell death; the bioenergy threshold is different for the various cell types in the tissues of the body. (4) In order to bioenergetically resuscitate cells and tissues suffering from impaired mitochondrial functions as a result of the ageing process, we propose that redox compounds may be used therapeutically in the pharmacological configurations of a by-pass strategy or as a redox sink therapy. The role of these compounds is to maintain at least part of the mitochondrial respiratory chain function (by-pass) as well as to maintain adequate levels of cellular NAD+ (redox sink) for ATP synthesis, predominantly by the cytosolic glycolytic pathway, with some contribution from mitochondrial oxidative phosphorylation.

An apparently allosteric effect involving N2O with the nitrous oxide reductase from Wolinella succinogenes

It was shown that kcat for the benzyl viologen cation (BV+)-N2O oxidoreductase activity of nitrous oxide reductase from Wolinella succinogenes was 2-3 times greater at high N2O concentrations than at low. This effect of N2O on kcat exhibited a titration curve implicating a single secondary binding site for N2O with a Kd of 130-200 microM (Km with respect to N2O is about 2.5 microM). This work represents the first evidence of an apparently allosteric kinetic effect among nitrous oxide reductases. Its possible cause is discussed. BV+ was generated in these kinetic studies by addition of sub-stoichiometric amounts of dithionite. This means of reduction proved to be superior to the photochemical generation of BV+ that had been used previously with the enzyme. Mass spectrometric measurements suggested that the M(r) of the subunit of the enzyme is about 95,500 rather than 88,000.

Calmodulin stimulation of smooth muscle plasmalemmal vesicle Ca2+ uptake: direct or indirect effect?

Current evidence suggests that Ca(2+)-calmodulin-dependent protein kinase(s) may be involved in the regulation of smooth muscle contractility. The plasmalemmal Ca2+ pump plays an important role in smooth muscle contractility, and this pump is stimulated by calmodulin. However, it is not known whether this is due to direct activation, or calmodulin-dependent protein phosphorylation, or both. We tested these hypotheses using a plasma membrane vesicle preparation from porcine antral smooth muscle. Inclusion of calmodulin in the Ca(2+)-uptake assay decreased the free Ca2+ concentration at which Ca2+ uptake is 50% of the maximal rate (1.5 +/- 0.21 to 0.84 +/- 0.06 microM) of the Ca2+ pump for Ca2+, without changing maximal rate of Ca2+ uptake (Vmax) (8.0 +/- 1.1 to 8.4 +/- 0.7 nmol.min-1.mg-1). In contrast, prephosphorylation in the absence of Ca(2+)-calmodulin increased Ca(2+)-uptake rates at both low (pCa 6.0) and high Ca2+ concentration (pCa 5.0), suggesting an increase in Vmax. Further phosphorylation in the presence of Ca(2+)-calmodulin was not associated with any further increases in the Ca(2+)-uptake rates at pCa 6.0. However, inclusion of calmodulin in the Ca(2+)-uptake assays stimulated the rates (pCa 6.0) of both unphosphorylated and prephosphorylated vesicles to a similar extent. These findings suggest that the stimulation of the smooth muscle plasmalemmal Ca2+ pump by calmodulin is predominantly due to a direct effect via a mechanism distinct from that by plasma membrane phosphorylation.

Insulin mediator stimulation of pyruvate dehydrogenase phosphatases

A two stage assay for detecting insulin mediator based upon its stimulation of soluble pyruvate dehydrogenase (PDH) phosphatase to activate soluble pyruvate dehydrogenase complex (PDC) has been developed. This coupled assay determines the activation of PDC by monitoring production of [14C]CO2 from [1-14C]pyruvic acid. In addition to being more sensitive than the rat liver mitoplast assay previously used, it allows for the separation and investigation of the effects of mediator on the PDH phosphatases individually. It has been previously shown that the insulin mediator stimulates the most abundant PDH phosphatase, the divalent cation dependent PDH phosphatase, by decreasing the phosphatase's metal requirement (1). A metal independent PDH phosphatase has been found in bovine heart mitochondria. This phosphatase is not immunoprecipitated by antiphosphatase 2A antibody, it is not inhibited by okadaic acid, and it is not stimulated by spermine. However, it is stimulated (more than threefold) by insulin mediator prepared from isolated rat liver membranes. It is inhibited by Mg-ATP, with half-maximal inhibition at 0.3 mM; however, this inhibition is overcome by the insulin mediator.

Unusual selective immunoglobulin deficiency in an Arabian foal

A 10-month-old Arabian foal was evaluated for a suspected immunoglobulin (Ig) M deficiency. Decreased to nondetectable concentrations of IgM, IgA, and IgG (T), and a normal concentration of IgG, were present. Results of in vitro testing of the blood lymphocyte blastogenesis showed a weak response to the B-cell mitogen, lipopolysaccharide (LPS), but normal responses to T-cell mitogens. Results of postmortem examination showed synovitis of the left tibiotarsal and both scapulohumeral joints. Atrophy and edema of the lymph nodes and lymphocyte depletion in the thymus and spleen were seen. A subacute inflammatory infiltrate was observed in the kidney, synovium, liver, and brain. Etiologic agents were not identified. This case represents a previously unreported form of immunodeficiency disease in the horse.

Mechanism of impaired growth hormone secretion in patients with Cushing's disease

The function of the growth hormone-releasing hormone (GHRH)-growth hormone (GH) axis in Cushing's disease was studied by monitoring (a) the GH responses to GHRH loading and L-dopa loading, (b) the GHRH response to L-dopa loading, and (c) the daytime profiles of plasma GH concentration. GH release following GHRH and L-dopa was blunted in patients as compared to that in age-matched control subjects. However, GHRH release following L-dopa was similar in patients and controls. The plasma GH levels in four patients measured every 20 min by a highly sensitive immunoradiometric assay for GH showed pulsatile GH secretion at low levels during the observation period. These results indicate that GHRH release from the hypothalamus is preserved in patients with Cushing's disease, and support the hypothesis that glucocorticoid inhibits GH secretion by altering the hypothalamic somatostatin tone.

Physical and genetic mapping of the catA region of Pseudomonas aeruginosa

A prime plasmid has been used as the basis for the construction of a physical and genetic map of a 125 kb segment of the Pseudomonas aeruginosa PAO chromosome. Using pMO1811, a prime plasmid selected for the catA region, a series of Tn5 insertions were obtained which identified two new markers gcu (glycine utilization) and oap (organic acids and alcohols permeability) in the 125 kb region and located them in relation to other known markers of this region. A cosmid bank was constructed from the prime plasmid and an ordered array of cosmid clones for this region identified by restriction endonuclease mapping with EcoRI, HindIII and KpnI, as well as complementation mapping and chromosome walking. By Southern hybridization analyses, it was confirmed that the chromosomal insert carried by pMO1811 was flanked by single, tandemly arranged copies of IS21 and the orientation of the insert on this prime was determined. This cosmid bank provides a resource for the further analysis of this region of the P. aeruginosa genome.