Hormonal regulation of the alpha-ketoglutarate dehydrogenase complex in the isolated perfused rat liver

The metabolic flux through the alpha-ketoglutarate dehydrogenase reaction in perfused livers was monitored by measuring the rate of 14CO2 production from [1-14C]alpha-ketoglutarate. The rates of 14CO2 production and glucose production from [1-14C]alpha-ketoglutarate were increased with increasing perfusate alpha-ketoglutarate concentrations. Vasopressin, angiotensin II, and the alpha 1-adrenergic agonist phenylephrine stimulated transiently by 2.5-fold the metabolic flux through the alpha-ketoglutarate dehydrogenase reaction in the presence and absence of Ca2+ in the perfusion medium. High concentrations of glucagon (1 x 10(-8) M) and 8-p-chlorophenylthio-cAMP (100 microM) (data not shown) also stimulated transiently the metabolic flux through the alpha-ketoglutarate dehydrogenase reaction. However, lower glucagon concentrations (1 x 10(-9) M) stimulated the rate of 14CO2 production from [1-14C]alpha-ketoglutarate only under conditions optimized to fix the cellular oxidation-reduction state at an intermediate level, when glucagon (1 x 10(-9) M)-mediated elevation of cAMP content was greater than that observed under highly oxidizing and reducing conditions. These data indicate that agonists which increase cytosolic free Ca2+ levels stimulate the metabolic flux through the alpha-ketoglutarate dehydrogenase complex. Furthermore, the data presented here demonstrate for the first time that physiological glucagon concentrations stimulate the metabolic flux through the alpha-ketoglutarate dehydrogenase reaction only under conditions known to be optimal for glucagon-mediated Ca2+ mobilization in the isolated perfused rat liver.     

Allelopathy due to purine alkaloids in tea seeds during germination

Summary During imbibition of whole tea seeds (6 days) two purine alkaloids, caffeine and theobromine, did not decrease in the seed coats and there was no increase in the seeds. In parallel with and after the breaking of seed coats there was a gradual release of caffeine from coats of germinating seeds. By contrast, when the seed was freed from the outer seed coat and soaked, imbibition of the seed required only 2 days and simultaneously caffeine was released from the inner seed coat. In such seeds, but not in whole seeds, growth of embryonic tissues (roots and shoots) was inhibited after the breaking of the inner seed coats. Nevertheless, caffeine increased more in such roots of the seedlings of decoated seeds than in roots of normal seedlings.     

Studies on the mechanism of T cell inhibition by the Pseudomonas aeruginosa phenazine pigment pyocyanine

Pseudomonas aeruginosa and its products have been shown to inhibit mitogen-induced human lymphocyte blastogenesis as measured by [3H]TdR uptake. The phenazine pigment pyocyanine has been identified as one of the inhibitors present in cellfree culture supernatants. To determine the mechanism of the inhibitory action of pyocyanine, we studied its effect on the early stages of T cell activation. Pyocyanine inhibited lymphocyte stimulation induced by specific antigens, the lectin concanavalin A and the calcium ionophore, ionomycin, suggesting that its inhibitory effect is not dependent on interference with the T cell antigen receptor complex itself. Using quin-2, we showed that pyocyanine did not interfere with the mitogen-induced increase in cytosolic-free Ca2+. We also showed that pyocyanine did not interfere with the function of calmodulin stimulated Ca2+-Mg2+ ATPase activity, indicating that the mechanism of action of pyocyanine differs from that of the structurally related phenothiazine compounds. Analysis of IL 2 production and IL 2 receptor expression clearly showed that pyocyanine inhibits the production of this essential lymphokine as well as the expression of IL 2 receptors on the T cell membrane. This inhibition is dose dependent and not due to cellular toxicity. There was parallel inhibition of growth in cell volume as well as [3H]TdR uptake. Thus, our results demonstrate that pyocyanine inhibits T cell proliferation by decreasing the production of the critical lymphokine IL 2 and by decreasing the expression of the IL 2 receptor. Local suppression of lymphocyte stimulation by phenazine pigments such as pyocyanine may interfere with cellular immune responses that may be necessary for eradication of chronic infection with P. aeruginosa.     

Health checks in general practice: another example of inverse care?

OBJECTIVE--To assess attendance at and the characteristics of patients attending health checks for cardiovascular disease offered in a general practice over a period of five years (1984-9). DESIGN--Medical record audit and postal questionnaire survey. SETTING--One general practice in Oxfordshire with a socially diverse population. PARTICIPANTS--1101 Men and 1110 women aged 35-64 registered with the practice. MAIN OUTCOME MEASURES--Age, sex, marital state, social class, smoking habits, alcohol consumption, and diet. RESULTS--Of the 2211 men and women in the target age group (35-64) in 1989, 1458 (65.9%) had been offered screening and 963 (43.6%) had attended for a health check. Attenders were more likely to be women, aged greater than or equal to 45, married, non-smokers, and of higher social class than patients who did not respond to the invitation. The relative likelihood of non-attendance was 1.24 for smokers, 1.20 for the overweight, 1.16 for heavy drinkers, and 1.28 for those with a less healthy diet, even after adjustment for age, sex, marital state, and social class. CONCLUSIONS--After five years of offering health checks, opportunistically (to men) and in the context of cervical smear tests (to women), less than half of the eligible patients had attended. The likelihood of acceptance of an invitation to attend was inversely related to the patient''s cardiovascular risk for all factors measured except age. A coherent strategy to reduce cardiovascular disease depends on more careful targeting of scarce health service resources and more emphasis on public health measures (such as dietary regulation and tobacco taxation). Doctors should be careful not to absolve the government of its public health obligations by substituting unproved preventive interventions aimed at the individual patient.     

Local production of fibronectin by ectopic human retinal cells

Summary The distribution of fibronectin mRNA and fibronectin in adult human retina and epiretinal membranes was investigated by in situ hybridisation and immunohistochemical techniques. The cells in normal adult retina contained little or no fibronectin mRNA and the retina only showed fibronectin immunoreactivity in retinal vessels. The cells in detached neuroretina did not contain fibronectin message but the vitreoretinal interface of the detached retina exhibited variable fibronectin immunoreactivity. Retinal glia, retinal pigment epithelium and fibroblast-like cells in membranes at the vitreoretinal juncture (epiretinal membranes) showed variable labelling with the fibronectin mRNA probe and all the membranes immunostained for fibronectin. No difference could be detected between membrane cell types in the intensity of labelling with the mRNA probe or for fibronectin immunoreactivity. The results indicate that cells in situ in attached and detached adult human retina do not produce fibronectin. Although fibronectin at the vitreoretinal juncture in retinal detachment is probably partly derived from plasma fibronectin resulting from breakdown of the blood-retinal barrier, ectopic retinal cells produce fibronectin and contribute to the glycoprotein in epiretinal membranes.     

Coevolution of self-fertilization and inbreeding depression. III. Homozygous lethal mutations at multiple loci.

We study the evolution of the rate of self-fertilization in response to deleterious mutations at multiple loci. Although partial selfing induces associations among loci even in the absence of linkage, associations among mutations at different loci are of a smaller order of magnitude than the mutation rate. Genotypes that carry homozygous lethal mutations in heterozygous form at i loci occur in frequencies of the order (Ti) mu i, in which T denotes the number of viability loci and mu the mutation rate. While associations between mutations at different loci remain small even under inbreeding, each viability locus develops an association with the modifier of the rate of self-fertilization that substantially affects the evolution of the breeding system. Positive associations between enhancers of selfing and haplotypes carrying multiple wild-type alleles and positive associations in heterozygosity between the modifier locus and the viability loci promote evolutionary increases in the rate of self-fertilization.     

Enigmatic Cyst-Forming Sporozoon in the Spinal Cord of a Dog

A female racing greyhound dog was presented to the clinic at the age of 3 months with a 2 months’ history of irregular hindleg movements and thin hindleg muscles. On examination 1 month later, a squatting standing posture, a week proprio-ceptive positioning reaction, and severe atrophy and pain of the lumbar and thigh muscles, were evident. The dog was sacrificed and necropsied. The adrenals, hindleg muscles, kidneys, myo-cardium, peripheral nerves, spinal cord, thyroid, and tonsils were fixed in 10 % neutral buffered formalin and processed for histo-pathology.