Plasma dopamine response to sympathetic activation in man: a biphasic pattern

We studied the plasma catecholamine response to standing and bicycle ergometric tests in 16 normal male subjects. During the standing test (performed in 10 subjects), we observed an early increase in plasma dopamine together with the fast increase in norepinephrine values; in the second half of this test (i.e. from 5 to 10 min of standing), we observed an increase in plasma dopamine levels. During the ergometric test (performed in 6 subjects), we observed a plasma dopamine increase at the maximal exercise; this persisted during the early recumbent recovery phase (6 min), despite the clear-cut decrease of both norepinephrine and epinephrine plasma levels. Our data are not in agreement with previous papers describing a simple increase in plasma dopamine after stimulation. This paper provides no informations regarding the mechanisms of this response of plasma dopamine. Other approaches must be used to study this aspect more directly.     

The effect of chronic iron deficiency on adrenal tyrosine hydroxylase activity.

Chronic nutritional iron deficiency of 2 to 5 weeks duration reduced the blood hemoglobin content to 30-50% of control values and resulted in an increase in rat adrenal tyrosine hydroxylase (TH) (EC 1.14.16.2) activity. Kinetic and mixing experiments indicated that this increase was due to an increase in enzyme protein. The body weight of iron-deficient rats ranged from 60 to 80% of control; this factor, however, was not responsible for the increase in adrenal TH as enzyme activity was directly proportional to final body weight. To determine whether the increase in adrenal TH in iron-deficient rats was due to increased sympathetic activity to the adrenal medulla, the splanchnic nerve was cut. The increased TH was still observed after adrenal denervation; this indicates that the mechanism of response to iron deficiency lies within the adrenal itself. Age of the rats is important in determining whether the increase in TH activity will occur.     

Increase in acetylation of spermidine in rat liver extracts brought about by treatment with carbon tetrachloride

Within three hours of the administration of hepatotoxic doses of carbon tetrachloride to rats there was a substantial increase in the ability of liver extracts to catalyze the accumulation of monoacetylspermidine when incubated with spermidine and acetyl-CoA. This increase was maximal by six hours and correlated with the period in which there was a pronounced fall in hepatic spermidine and concomitant increase in putrescine. During this time there is a large increase of the conversion of labeled spermidine into putrescine in the liver. These results therefore suggest that this conversion requires the prior acetylation of spermidine.     

Oedema in Rheumatoid Arthritis: Changes in the Coefficient of Capillary Filtration

The rate of formation of tissue fluid for a given increase of venous pressure and for a known volume of tissue has been measured in the forearm. There is a significant increase in this figure in rheumatoid arthritis and a still greater increase in patients who develop recurrent oedema. This increase could not be attributed to steroid or phenylbutazone therapy, nor to a fall in the serum albumin. The results imply that there is some generalized abnormality in capillary function in rheumatoid disease and that this change is not limited to the joints.     

Responses of respiration and photosynthesis of Scenedesmus protuberans Fritsch to gradual and steep salinity increases

The effect of an increase in salinity on the physiology of thehalotolerant chlorophyte Scenedesmus protuberans was studiedin light-limited continuous cultures. It was observed that agradual, as well as a steep increase in salinity resulted inlower biomass. However, the mechanisms by which this was achievedwere different. In the culture that was exposed to a gradualsalinity increase, respiration and the cellular protein contentof the culture were initially unaffected. However, this culturewas not able to maintain its cellular chlorophyll content and,consequently, gross and net photosynthesis decreased. The culturethat was exposed to a steep salinity increase rapidly reactedby increasing its respiration and cellular protein content,which is ascribed to an induction of osmoregulation. This culturewas able to maintain its gross photosynthesis rate. It is speculatedthat, in this species, a steep salinity increase induces a nearlyimmediate osmoregulatory response, allowing growth to continue.If the cells are exposed to a gradual salinity increase, inductionof osmoregulation lags behind and, consequently, photosynthesisand growth rate will be^* affected.     

Increase in dry weight and protein content inBrassica oleracea andNicotiana tabacum pith expiants daring short-term cultivation on simple media

The stem pith discs of kale and tobacco were cultured on simple sugar-mineral media. The dry weight of the expiants rose almost linearly for 20 days and was doubled in 10 to 12 days. Neither protein accumulation nor the increase in cell number are responsible for this relatively high increase in dry weight of discs. The accumulation of sugars or polysaccharides is thought to be the cause of this increase.     

Cosolvent control of substrate inhibition in cosolvent stimulation of beta-glucuronidase activity.

Bacterial β-glucuronidase exhibits a considerable increase in specific activity, upon addition of suitable organic cosolvents to aqueous systems. The effect is especially marked with three to five carbon alcohols; a nine fold increase was observed in this study using t-butanol in the range of 10% by volume of t-butanol in water. Most such increases were previously ascribed to cosolvent effects on V_max, i.e. to the catalytic steps. However, it is shown here that this enzyme is susceptible to marked substrate inhibition, and that half of the cosolvent induced activity increase is due to decreasing this inhibition. The other 50% of the activity increase probably does reside in cosolvent stimulation of V_max.     

Noise-induced vocal modulation in cotton-top tamarins (Saguinus oedipus)

The Lombard effect-an increase in vocalization amplitude in response to an increase in background noise-is observed in a wide variety of animals. We investigated this basic form of vocal control in the cotton-top tamarin (Saguinus oedipus) by measuring the amplitude of a contact call, the combination long call (CLC), while simultaneously varying the background noise level. All subjects showed a significant increase in call amplitude and syllable duration in response to an increase in background noise amplitude. Together with prior results, this study shows that tamarins have greater vocal control in the context of auditory feedback perturbation than previously suspected.     

Activation of a ribosomal protein S6 protein kinase in Xenopus oocytes by insulin and insulin-receptor kinase.

Previous studies in this laboratory have shown that insulin treatment of Xenopus oocytes leads to an increase in phosphorylation of ribosomal protein S6. To investigate the mechanism of this increase, S6 kinase activity was measured in lysates of oocytes exposed to insulin. Insulin caused a rapid 4- to 6-fold increase in S6 kinase activity, which was maximal by 20 min and which could be reversed by removal of insulin prior to homogenization. Dose-response curves showed a detectable increase in specific activity at 1 nM insulin with a maximal effect at 100 nM. Treatment of oocytes with puromycin did not prevent this increase in S6 kinase activity, suggesting activation rather than synthesis of the enzyme. DEAE-Sephacel chromatography of extracts from insulin-treated oocytes revealed two peaks of S6 kinase activity, and the specific activity of the peak eluting at 300 nM NaCl was increased 3-fold in oocytes treated with insulin. The same peak of S6 kinase activity was increased 40% within 10 min in oocytes injected with highly purified insulin-receptor kinase. These results indicate that the insulin-dependent increase in S6 phosphorylation is due, at least in part, to activation of an S6 protein kinase, and this activation may result from the action of the insulin receptor at an intracellular location.     

Cold exposure or chronic noradrenaline treatment induces an increase in the calmodulin-like immunoreactivity of brown adipose tissue of rats

Cell proliferation is often associated with an increase in calmodulin, the ubiquitous intracellular calcium receptor of non-muscle cells. A long lasting increase in the proliferative activity of brown adipose tissue is induced by cold exposure in the rat. The present work showed that this phenomenon is also associated with a rapid and long lasting increase in the calmodulin content of this tissue. It was equally shown that this increase can be reproduced by noradrenaline admini-stration.     

Climate disruption and parasite-host dynamics: patterns and processes associated with warming and the frequency of extreme climatic events

Levels of parasitism and the dynamics of helminth systems is subject to the impact of environmental conditions such that we may expect long term increases in temperature will increase the force of infection and the parasite's basic reproduction number, R0. We postulate that an increase in the force of infection will only lead to an increase in mean intensity of adults when adult parasite mortality is not determined by acquired immunity. Preliminary examination of long term trends of parasites of rabbits and grouse confirm these predictions. Parasite development rate increases with temperature and while laboratory studies indicate this is linear some recent studies indicate that this may be non-linear and would have an important impact on R0. Warming would also reduce the selective pressure for the development of arrestment and this would increase R0 so that in systems like the grouse and Trichostrongylus tenuis this would increase the instability and lead to larger disease outbreaks. Extreme climatic events that act across populations appear important in synchronizing transmission and disease outbreaks, so it is speculated that climate disruption will lead to increased frequency and intensity of disease outbreaks in parasite populations not regulated by acquired immunity.     

Splanchnic Nerve Transection Abolishes the Age-Dependent Increase of Neuropeptide Y-Like Immunoreactivity in Rat Adrenal Gland

Using an antiserum directed against porcine neuropeptide Y (NPY), a high concentration of NPY immunoreactivity (NPY-IR) was detected in rat adrenal gland. The level of NPY-IR in the adrenal gland was found to increase considerably with age. Biochemical characterization by reverse-phase HPLC indicated that this increase was due to accumulations of NPY and another molecular form of NPY-like immunoreactive peptide. Chronic denervation of the splanchnic nerve abolished this age-dependent increase of NPY-IR rat adrenal gland.     

Effect of Maternal Alcohol Consumption on the Lipid Composition of CNS in the Offspring

Maternal alcohol consumption at a level that does not affect calorie intake increases cholesterol concentration and content as well as incorporation of labeled glucose into cholesterol in the brain and spinal cord of newborn rat pups. Continued consumption of alcohol during lactation also affects the galactolipid concentration in the brain and spinal cord of pups at 21 days of age, and this increase seems mainly to be due to an increase in content of myelin lipids. Analysis of myelin shows that the concentration of phospholipids also increases in this fraction. The increase in incorporation of labeled glucose into these membrane lipids suggests an increase in the synthesis of these lipids, which prevents fluidization of the membrane by alcohol. That in the brainstem the increase in levels of cholesterol and galactolipids is higher than in other regions and that there is also an increase in content of sphingomyelin, phosphatidylcholine, and phosphatidylethanolamine suggest that the brainstem needs better protection against fluidization.     

Detection of Several Novel γ-Aminobutyric Acid-Containing Compounds in Human CSF

gamma-Aminobutyric acid (GABA) concentrations in human CSF are known to increase significantly after hydrolysis; however, the source of this increase has been unknown. Using either ion-exchange or reverse-phase chromatography coupled with on-line alkaline hydrolysis, we have shown 2-pyrrolidinone, the lactam of GABA, to be present in insufficient quantity to account for this increase. Subsequent experiments involving fraction collection of column eluents followed by acid hydrolysis and rechromatography demonstrated the presence of several previously undetected GABA-containing compounds.     

Induction of spermidine/spermine N1-acetyltransferase by methylglyoxal bis(guanylhydrazone)

The anti-tumor agent methylglyoxal bis(guanylhydrazone) was found to be a competitive inhibitor of spermidine/spermine N1-acetyltransferase with a Ki of about 8 microM. Treatment of rats with this drug lead to a very large increase in the total amount of spermidine/spermine N1-acetyltransferase in liver, kidney and spleen. The total increase as measured using a specific antiserum amounted to 700-fold in liver and 100-fold in kidney within 18 h of treatment with 80 mg/kg doses. At least part of this induction was due to a pronounced increase in the half-life of the acetyltransferase which increased from 15 min to more than 12 h. The very large increase in the amount of the enzyme is likely to overwhelm the direct inhibition, and a net increase in the acetylation of polyamines by this enzyme would be expected to occur after treatment with methylglyoxal bis(guanylhydrazone). The acetylated polyamines are known to be rapidly degraded by polyamine oxidase producing putrescine. Direct evidence that a substantial part of the increase in the content of putrescine in the liver of rats treated with methylglyoxal bis(guanylhydrazone) occurs via the induction of this acetylase/oxidase pathway was obtained. These results indicate that methylglyoxal bis(guanylhydrazone) affects cellular polyamine levels not only by means of its inhibitory effect on S-adenosylmethionine decarboxylase and diamine oxidase but also by the induction of spermidine/spermine N1-acetyltransferase. They also raise the possibility that the enormous increase in this enzyme which occurs with higher doses may contribute to the very severe toxicity of methylglyoxal bis(guanylhydrazone).     

Coupled computational analysis of arterial LDL transport -- effects of hypertension

Hypertension, a risk factor for atherosclerosis, increases the uptake of low density lipoproteins (LDL) by the arterial wall. Our objective in this work was to use computational modeling to identify physical factors that could be partially responsible for this effect. Fluid flow and mass transfer patterns in the lumen and wall of an arterial model were computed in a coupled manner, replicating as closely as possible previous experimental studies in which LDL uptake into the artery wall was measured in straight, excised arterial segments. Under conditions of both flow and no-flow, simulations predicted an increase in concentration polarization of LDL at the artery wall when arterial pressure was increased from 120 to 160 mmHg. However, this led to only a slight increase in mean LDL concentration within the arterial wall. However, if the permeability of the endothelium to LDL was allowed to vary with intra-arterial pressure, then the simulations predicted that the uptake of LDL would be enhanced 1.9-2.6 fold at higher pressure. The magnitude of this increase was consistent with experimental data. We conclude that the concentration polarization effects, enhanced by elevated intra-arterial pressure, cannot explain the increase in LDL uptake seen under hypertensive conditions. Instead, the data are most consistent with a pressure-linked increase in endothelial permeability to LDL.     

Synthesis of collagen by smooth muscle in the hyertrophic intestine

During hypertrophy of the small intestine of the guinea-pig at the oral side of an experimental stenosis, the individual intestinal segments do not increase in length but undergo a remarkable increase in weight (up to 7 times that of control segments). Concomitantly an increase in collagen content is found; this is usually larger than the increase in weight, and the concentration of collagen is therefore also increased. This effect is more noticeable in the muscle coat than in the wall as a whole. It is suggested, on the basis of histological observations, that some of this collagen is synthesized by smooth muscle cells.     

Effects of the histiophagous ciliate Philasterides dicentrarchi on turbot phagocyte responses

Philasterides dicentrarchi is an opportunistic histiophagous ciliate parasite causing systemic scuticociliatosis in cultured turbot (Scophthalmus maximus L.). This study investigated the effects of inoculation with live or killed trophozoites of this ciliate (plus 3% thioglycollate) on the in vitro phagocytic activity and respiratory-burst responses of inflammatory peritoneal leucocytes obtained from the fish thus treated. The phagocytic activity of leucocytes from fish inoculated with killed P. dicentrarchi was higher in the presence than in the absence of infected turbot serum (ITS). The effect of ITS was smaller in fish inoculated with live P. dicentrarchi, indicating modulation of the opsonic activity of ITS. Inoculation with live ciliates led to a significant increase in subsequent in vitro extracellular ROS production, but only when normal turbot serum (NTS) or ITS was included in the assay medium. Inclusion of live P. dicentrarchi in the medium abolished this increase, suggesting ROS-scavenging activity. Inoculation with live P. dicentrarchi led to a significant decline in subsequent in vitro intracellular ROS production; when NTS was included in the medium, there was a significant increase in intracellular ROS production, but no such increase was observed when ITS was included in the medium. Inoculation with live P. dicentrarchi alone did not increase subsequent in vitro NO? production in response to LPS; a significant increase was observed when NTS or ITS was included in the assay medium, but this increase was not affected by prior inoculation with P. dicentrarchi. These results suggest that the amphizoic nature of this parasite may reflect the ease with which it can develop mechanisms of evasion of the host immune response.     

Promotion of peroxidase activity in the cell wall of Nicotiana

Peroxidase catalyzes the oxidation of indole-3-acetic acid. The primary products of this reaction stimulate growth in plants. Therefore, our concept is that an increase in peroxidase activity will increase the effect of indole-3-acetic acid as a growth hormone. Our objective was to study the effect of 2,3,5-triiodobenzoic acid, a growth regulator, on isoperoxidases in the cell wall and cytoplasm of Nicotiana. Isoperoxidases from the cell wall and cytoplasmic fractions were separated by acrylamide gel electrophoresis. We found that 2,3,5-triiodobenzoic acid and indole-3-acetic acid increase peroxidase activity in the cell wall. Since both 2,3,5-triiodobenzoic acid and indole-3-acetic acid increase the activity of the same isoperoxidase, we conclude that 2,3,5-triiodobenzoic acid synergizes rather than antagonizes auxin action, and we suggest that this increase in indole-3-acetic acid oxidase activity sensitizes plant tissues to auxin.     

Endocrine changes during diapause development in the cabbage army moth Mamestra brassicae

Many insects undergo diapause to survive adverse seasons. Although the mechanism of diapause induction is the subject of extensive study, that of diapause termination remains poorly understood. In the present study, we show the endocrine processes leading to the termination of pupal diapause in Mamestra brassicae. Diapause of this insect is terminated if the pupae are exposed to a low temperature for several weeks. During this period, the prothoracic glands (PGs) of pupae acquire the potential to secrete sufficient ecdysteroids necessary for inducing adult development. The main endocrine changes observed under the low temperature conditions are: (i) the increase in activity of the PGs in two steps; (ii) the increase in responsiveness of the glands to prothoracicotropic hormone (PTTH); and (iii) two‐step increase in PTTH gene expression in the brain. The timing of the first and second increases in PG activity roughly coincides with that of the two steps of increase in PTTH gene expression, and the timing of the increase in the responsiveness of the PGs to PTTH coincides with the second, larger increase in PTTH gene expression. The ablation of the PGs prior to cooling pupae does not affect the increase in PTTH gene expression, whereas brain removal results in a failure to increase PG activity, strongly suggesting that PTTH is the master regulator of diapause development and termination.