In vitro evaluation of combination of fluconazole and flucytosine against Cryptococcus neoformans var. neoformans

Amphotericin B and fluconazole are current acceptable therapies for cryptococcal meningitis; however, their effect remains suboptimal. The combination of fluconazole and flucytosine has yielded encouraging clinical results in human immunodeficiency virus patients with cryptococcal meningitis. To investigate the biological basis of this finding, we performed in vitro combination testing of fluconazole and flucytosine against 50 clinical strains of Cryptococcus neoformans var. neoformans. Synergy (fractional inhibitory concentration index of < 1.0) was observed in 62% of cases, while antagonism (fractional inhibitory concentration index of > 2.0) was not observed. For cases in which synergy was not achieved (autonomous or additive effects), the beneficial effect of the combination was still seen (i.e., there was still a decrease, although not as dramatic, in the MIC of one or both drugs when used in combination). The in vitro inhibitory action of flucytosine was greatly enhanced by the addition of fluconazole; the flucytosine MICs for Cryptococcus isolates were markedly decreased to concentrations which were severalfold lower than the achievable cerebrospinal fluid flucytosine concentration. On the other hand, the addition of flucytosine did not greatly enhance the in vitro activity of fluconazole if the initial fluconazole MIC for the isolate was > or = 8 micrograms/ml. Controlled clinical studies are warranted to further elucidate the potential utility of fluconazole-flucytosine combination therapy.

Prevention of autoimmune demyelination in non-human primates by a cAMP-specific phosphodiesterase inhibitor

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease of the central nervous system that serves as a model for the human disease multiple sclerosis. We evaluated rolipram, a type IV phosphodiesterase inhibitor, for its efficacy in preventing EAE in the common marmoset Callithrix jacchus. In a blinded experimental design, clinical signs of EAE developed within 17 days of immunization with human white matter in two placebo-treated animals but in none of three monkeys that received rolipram (10 mg/kg s.c. every other day) beginning 1 week after immunization. In controls, signs of EAE were associated with development of cerebrospinal fluid pleocytosis and cerebral MRI abnormalities. In the treatment group, there was sustained protection from clinical EAE, transient cerebrospinal fluid pleocytosis in only one of three animals, no MRI abnormality, and marked reduction in histopathologic findings. Rolipram-treated and control animals equally developed circulating antibodies to myelin basic protein. Thus, inhibition of type IV phosphodiesterase, initiated after sensitization to central nervous system antigens, protected against autoimmune demyelinating disease.

Antibiotic-resistant Acinetobacter meningitis in neurosurgical patients

Acinetobacter anitratus has emerged as one of the common pathogens responsible for postneurosurgical meningitis at the authors' institution. Seven patients with Acinetobacter meningitis were identified during the 4-year period of this study, five of whom acquired organisms susceptible only to imipenem and amikacin. Acinetobacter bacteremia occurred concomitantly in five patients. Despite late institution of therapy as a result either of organism misidentification on Gram stain or of unexpected acquisition of a highly resistant organism, the patients' outcome was favorable after the initiation of appropriate antibiotic therapy. Imipenem and amikacin, with or without intrathecal aminoglycosides, were effective in patients with resistant strains of Acinetobacter.

Resistance of human immunodeficiency virus type 1 to acyclic 6-phenylselenenyl- and 6-phenylthiopyrimidines

Acyclic 6-phenylselenenyl- and 6-phenylthiopyrimidine derivatives are potent and specific inhibitors of human immunodeficiency virus type 1 (HIV-1). The development of in vitro resistance to two derivatives, 5-ethyl-1-(ethoxymethyl)-(6-phenylthio)-uracil (E-EPU), was evaluated by serial passage of HIV-1 in increasing concentrations of inhibitor. HIV-1 variants exhibiting > 500-fold resistance to E-EPSeU and E-EPU were isolated after sequential passage in 1, 5, and 10 microM inhibitor. The resistant variants exhibited coresistance to related acyclic 6-substituted pyrimidines and the HIV-1-specific inhibitors (+)-(5S)-4,5,6,7-tetrahydro-5- pyrimidines and the HIV-1-specific inhibitors (+)-(5S)-4,5,6,7-tetrahydro-5- methyl-6-(3-methyl-2-butenyl)imidazo[4,5,1-jk]benzodiazepin-2(1H)- thione (TIBO R82150) and nevirapine, but remained susceptible to 3'-azido-3'-deoxythymidine, 2',3'-dideoxycytidine, 2',3'-dideoxyinosine, and phosphonoformic acid. DNA sequence analysis of reverse transcriptase (RT) derived from E-EPSeU-resistant virus identified a Tyr (TAT)-to-Cys (TGT) mutation at either codon 188 (Cys-188; 9 of 15 clones) or codon 181 (Cys-181; 5 of 15 clones). The same amino acid changes were found in RT from E-EPU-resistant virus, but the Cys-181 mutation was more common (9 of 10 clones) than the Cys-188 mutation (1 of 10 clones). Site-specific mutagenesis and production of mutant recombinant viruses demonstrated that both the Cys-181 and Cys-188 mutations cause resistance to E-EPSeU and E-EPU. Of the two mutations, the Cys-188 substitution produced greater E-EPSeU and E-EPU resistance. The predominance of the Cys-188 mutation in E-EPSeU-resistant variants has not been noted for other classes of HIV-1 specific RT inhibitors. HIV-1 resistance is likely to limit the therapeutic efficacy of acyclic 6-substituted pyrimidines if they are used as monotherapy.

Aspergillus peritonitis in a continuous ambulatory peritoneal dialysis patient. Case report and review of the literature

Aspergillus peritonitis is a rare but treatable complication of continuous ambulatory peritoneal dialysis. We report a case of Aspergillus peritonitis in a continuous ambulatory peritoneal dialysis patient and review the nine other cases reported in the literature. The course was often insidious, and the clinical manifestation and laboratory findings were similar to those of bacterial peritonitis. The distinctive feature of these cases was the persistence of symptoms despite broad-spectrum antibiotics. Catheter removal is of crucial importance in the management of this disease.

In healthy primates, circulating autoreactive T cells mediate autoimmune disease

A T cell response against myelin basic protein (MBP) is thought to contribute to the central nervous system (CNS) inflammation that occurs in the human demyelinating disease multiple sclerosis. To test whether MBP-reactive T cells that are normally retrieved from the circulation are capable of inducing CNS disease, MBP-reactive T cell clones were isolated from the peripheral blood of healthy, unimmunized Callithrix jacchus (C. jacchus) marmosets. This primate species is characterized by a natural chimerism of bone marrow elements between siblings that should make possible adoptive transfer of MBP-reactive T cells. We report that MBP-reactive T cell clones efficiently and reproducibly transfer CNS inflammatory disease between members of C. jacchus chimeric sets. The demyelination that is characteristic of experimental allergic encephalomyelitis induced in C. jacchus by immunization against human white matter did not occur after adoptive transfer of the MBP-reactive clones. It was noteworthy that encephalitogenic T cell clones were diverse in terms of their recognition of different epitopes of MBP, distinguishing the response in C. jacchus from that in some inbred rodents in which restricted recognition of MBP occurs. These findings are the first direct evidence that natural populations of circulating T cells directed against a CNS antigen can mediate an inflammatory autoimmune disease.

Meningitis due to Xanthomonas maltophilia: case report and review

Xanthomonas maltophilia is being increasingly recognized as an opportunistic pathogen in debilitated patients. We report a case of postoperative meningitis due to X. maltophilia and review the cases of X. maltophilia meningitis reported in the literature. Because X. maltophilia is often resistant to multiple beta-lactam agents, including cephalosporins and imipenem, trimethoprim-sulfamethoxazole appears to be the drug of choice for treatment of X. maltophilia meningitis.

Intraocular candidiasis in patients with candidemia. Clinical implications derived from a prospective multicenter study

PURPOSE

Intraocular infection caused by Candida species can have devastating visual consequences. With the emergence of Candida as a major nosocomial pathogen, the authors investigated the prevalence of ocular lesions in patients with candidemia and evaluated risk factors for eye involvement.

METHODS

This study is a prospective, multicentered, observational design. One hundred eighteen patients with candidemia were evaluated by the infectious disease service and received indirect ophthalmologic examination within 72 hours of a reported positive blood culture. Ocular findings were classified on the basis of objective, pre-determined criteria. Candida chorioretinitis was defined as the presence of focal, white, infiltrative chorioretinal lesions without vitreal involvement. Candida endophthalmitis was defined as chorioretinitis with extension into the vitreous or intravitreal "fluff balls."

RESULTS

In contrast to previous studies of patients with candidemia citing prevalence rates of endophthalmitis approaching 40%, no patients were shown to have endophthalmitis. Candida chorioretinitis was seen in 9% of the patients, all of whom received antifungal agents. The observation that chorioretinitis never progressed to endophthalmitis suggests that systemic antifungal agents provided adequate ocular therapy. Risk factors for Candida chorioretinitis include fungemia with Candida albicans (versus nonalbicans species), multiple positive blood cultures, visual symptoms, and immunosuppression. Twenty percent of patients had nonspecific ocular lesions not directly related to infection.

CONCLUSION

Patients with candidemia who have the risk factors noted above warrant formal ophthalmologic examination.

Listeria monocytogenes peritonitis in cirrhotic patients. Value of ascitic fluid gram stain and a review of literature

Listeria monocytogenes has been increasingly implicated in spontaneous bacterial peritonitis in patients with cirrhosis. This bacterium can be mistaken for diphtheroids and gram-positive cocci if special attention is not paid to the motility pattern and specific biochemical tests. Although the sensitivity of ascitic fluid Gram stain is low, we describe a case in which the Gram stain of the ascites fluid was positive. This issue is now pertinent given recent recommendations of third-generation cephalosporin antibiotics as empiric therapy for spontaneous bacterial peritonitis; Listeria is resistant to cephalosporin agents. A positive Gram stain could affect the empiric antibiotic therapy. We review the clinical presentation and outcome in nine other cases of Listeria peritonitis occurring in cirrhotic patients.

Mechanism of growth inhibition of mammary carcinomas by glucarate and the glucarate: retinoid combination

In synergistic combination 0.75 mmol/kg diet of N-(4-hydroxyphenyl) retinamide and 32 mmol/kg diet of glucarate inhibits the growth of primary rat mammary tumors, but are equally effective as single agents at 1.5 and 128 mmol/kg diet, respectively. Dose-response studies suggest that like retinoids, glucarate acts directly on tumor cells, rather than having an adjuvant effect. Although synergism is maintained down to at least 0.38 mmol/kg diet of the retinoid, experiments using Vitamin A-deficient diets indicates 128 mmol/kg glucarate acts independent of retinoid. Both alone and in combination, glucarate and retinoid inhibited the growth of human mammary tumor cells grown in the athymic mouse, the growth of rat mammary tumors in germfree rats and the hormone-independent MTW 9a/R rat mammary tumor. Like retinoids, glucarate suppresses protein kinase C and induces transforming growth factor-beta, in the mammary tumor cells.

Differential migration of astrocytes grafted into the developing rat brain

Fetal and neonatal astrocytes migrate in specific patterns when transplanted into the adult rat host brain. However, it is unclear whether these astrocytes demonstrate the same degree of mobility during early brain development. In the present study, neonatal cortical, hippocampal, and hypothalamic astrocytes were collected from the brains of 1- to 3-day-old rats and placed in tissue culture. After 14 to 21 days, cultures enriched in astrocytes were harvested and labelled with either the fluorescent dye Fast Blue or fluorescein-labelled latex beads. They were then transplanted into the right frontal cerebrum of neonatal rats at 2, 5, 8, and 11 days postpartum. Seven days after transplantation, animals were sacrificed and their brains were fixed by immersion in aldehydes, sectioned on a cryostat, and examined with fluorescence microscopy. Transplanted astrocytes migrated along the corpus callosum, internal capsule, glial limitans, ventricular linings, and hippocampal structure. Labelled cells were also found in the contralateral hemisphere in day 2 brains. Migration in a radial fashion from the injection site toward the periphery was a particularly obvious pattern, and was most pronounced in these younger hosts. In days 5 and 8 rat brains, astrocyte migration became more restricted to the hemisphere of implantation. In 11-day-old host brains, hemispheric restriction and other region-specific influences became manifest and specifically modulated migration. Radial migration was absent in the 11-day-old host group except for cells of cortical origin. The observed results demonstrate that neonatal cortical, hippocampal, and hypothalamic astrocytes transplanted into the neonatal cerebrum migrate in patterns that are more extensive than in the adult brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of human immunodeficiency viruses resistant to oxathiolane-cytosine nucleosides

The (-) enantiomers of 2',3'-dideoxy-5-fluoro-3'-thiacytidine [(-)-FTC] and 2',3'-dideoxy-3'-thiacytidine [(-)-BCH-189] were recently shown to inhibit selectively human immunodeficiency viruses (HIV) and hepatitis B virus in vitro. In the current study, the potential for HIV type 1 (HIV-1) resistance to these compounds was evaluated by serial passage of the virus in human peripheral blood mononuclear cells and MT-2 cells in the presence of increasing drug concentrations. Highly drug-resistant HIV-1 variants dominated the replicating virus population after two or more cycles of infection. The resistant variants were cross-resistant to (-)-FTC, (-)-BCH-189, and their (+) congeners but remained susceptible to 2',3'-dideoxycytidine, 3'-azido-3'-deoxythymidine, 3'-fluoro-3'-deoxythymidine, 2',3'-dideoxyinosine, phosphonoformate, the TIBO compound R82150, and the bis(heteroaryl)piperazine derivative U-87201E. Reverse transcriptase derived from drug-resistant viral particles was 15- to 50-fold less susceptible to the 5'-triphosphates of FTC and BCH-189 compared with enzyme from parental drug-susceptible virus. DNA sequence analysis of the reverse transcriptase gene amplified from resistant viruses consistently identified mutations at codon 184 from Met (ATG) to Val (GTG or GTA) or Ile (ATA). Sequence analysis of amplified reverse transcriptase from a patient who had received (-)-BCH-189 therapy for 4 months demonstrated a mixture of the Met-184-to-Val (GTG) mutation and the parental genotype, indicating that the Met-184 mutation can occur in vivo.

Misdiagnosis of appendicitis in tubally sterilized women

Sterilization by tubal occlusive methods has a small but definite incidence of failure which is not well recognized among general surgeons. As a result of the failure to appreciate the possibility of ectopic pregnancy after tubal ligation, right-sided abdominal pain in this patient population is commonly misdiagnosed as appendicitis. One such case is presented, and the literature is reviewed and discussed.

Complete oxidation of linear alkylbenzene sulfonate by bacterial communities selected from coastal seawater

Anionic surfactants, especially alkylbenzene sulfonates, are discharged into marine areas in great quantities. Because of their poor biodegradability, linear alkylbenzene sulfonates accumulate in seawater and sediments. Bacterial communities that can degrade surfactants were selected from coastal seawater contaminated by urban sewage. All the isolated strains consisted of gram-negative, strictly aerobic rods or helical bacteria. Some of these, though isolated from coastal seawater, did not need sodium for growth and appeared to be related to the genera Alcaligenes and Pseudomonas. Complete surfactant biodegradation was achieved by three important steps: terminal oxidation of the alkyl chain, desulfonation, and aromatic-ring cleavage. Only a few strains were able to carry out the first two steps. The aromatic ring was then cleaved by other strains that possess very specific enzymatic activities. Finally, a number of strains grew on short acids that were end-of-metabolism products of the others.

Legionellosis

Legionella is a common cause of community- and hospital-acquired pneumonia. New information on the pathogenesis of infection and the host immune response is reviewed. Specialized laboratory tests, especially culture, are necessary for diagnosis since the clinical presentation is nonspecific. New antimicrobial agents and innovative approaches to disinfection of water distribution systems are presented.

Altered formation of leukotriene B4 in vitro by synovial fluid neutrophils in rheumatoid arthritis

The synthesis of products of the 5-lipoxygenase pathway by synovial fluid (SF) and peripheral blood neutrophils of 12 patients with rheumatoid arthritis was compared in 3 experimental conditions using high performance liquid chromatographic analysis. Major differences were observed when blood and SF neutrophils were incubated with ionophore A23187, the formation of all 5-lipoxygenase products being lower (p less than 0.0005) in the SF neutrophils. Addition of exogenous arachidonic acid to the A23187 stimulated cells partially overcame the difference in 5-lipoxygenase product synthesis between the 2 neutrophil populations. In contrast, upon incubation with arachidonic acid alone, SF neutrophils produced significantly larger amounts of 5-lipoxygenase products. The increased reactivity of the SF neutrophil 5-lipoxygenase to arachidonic acid and the decreased 5-lipoxygenase product synthesis upon A23187 stimulation may be the consequence of the previous activation of the cells and 5-lipoxygenase product synthesis in situ.

Characterization of the priming effects of human granulocyte-macrophage colony-stimulating factor on human neutrophil leukotriene synthesis

Human granulocyte-macrophage colony-stimulating factor (GM-CSF) is an in vitro and in vivo stimulator of human bone marrow myelomonocytic precursor cells and mature granulocyte and macrophage effector cells. We have compared the effect of GM-CSF on the synthesis of 5-lipoxygenase products induced by the chemotactic peptide fMet-Leu-Phe and the calcium ionophore A23187 in human neutrophils. Although GM-CSF alone did not stimulate detectable synthesis of products of the 5-lipoxygenase pathway, pre-incubation of neutrophils with 200 pM GM-CSF for 1 hour at 23 degrees C enhanced synthesis of leukotriene B4, its all-trans isomers and omega-oxidation products, and 5-hydroxyeicosatetraenoic acid in response to both the calcium ionophore A23187 (1.5 microM), and the chemotactic peptide fMet-Leu-Phe (0.1 microM). This priming effect of GM-CSF was maximal after a 60 min incubation at 23 degrees C, or after a 30 min preincubation at 37 degrees C. The effect of GM-CSF was maximal using a concentration of 1 nM. Enhancement of the leukotriene synthesis stimulated by A23187 was only observed when the cells were stimulated by the ionophore for periods of 3 minutes or less. In contrast, the enhancing effect of GM-CSF was still apparent when cells were exposed to fMet-Leu-Phe for as long as 15 minutes. Furthermore, the enhancing effect of GM-CSF was ablated when neutrophils were stimulated with A23187 and exogenous arachidonic acid. However, co-addition of exogenous arachidonic acid with fMet-Leu-Phe did not entirely mask the effect of GM-CSF. Possible mechanisms of action of GM-CSF are discussed.

[Degradation of a commercial surface-active agent, in the presence of a complementary source of carbon, by a selected bacterial colony in a marine environment]

Bacterial communities that can degrade surfactants have been selected from coastal seawaters contaminated by urban sewages. Only the linear fraction of commercial anionic surfactants was quickly degraded, and a residual fraction representing 10% of the initial concentration always remained. The highest concentrations of surfactant tolerated by these communities depend on the nature of the co-substrate and on the degree of adaptation of the selected bacteria.

Secretory proteins from adrenal medullary cells are carboxyl-methylated in vivo and released under their methylated form by acetylcholine

The carboxyl methylation of secretory proteins in vivo was investigated in bovine adrenal medullary cells in culture. Chromogranin A, the major intragranular secretory protein in adrenal medullary cells, and other secretory proteins were found to be carboxyl-methylated within secretory vesicles. The in vivo labeling pattern using [methyl-3H]methionine and the in vitro labeling pattern using S-adenosyl-[methyl-14C]methionine of intravesicular secretory proteins were similar. The detection of methylated chromogranin A in mature secretory vesicles required 3-6 h, a time consistent with the synthesis and storage of secretory proteins in this tissue. Carboxyl-methylated chromogranin A was secreted from medullary cells by exocytosis via activation of nicotinic cholinergic receptor and recovered still under the methylated form in the incubation medium. Since protein-carboxyl-methylase is cytosolic, these results suggest that methylation of secretory proteins is a cotranslational phenomenon.

Effect of physical training on norepinephrine turnover in tissues of normal and diabetic rats

This study was designed to examine the influence of physical training on the norepinephrine turnover rate in heart, pancreas, liver, and gastrocnemius muscles of normal and diabetic male rats at rest. Diabetes was induced with the IV injection of streptozotocin (45 mg/kg) and physical training was done on a treadmill according to a ten-week program. Norepinephrine turnover rate of tissues was estimated by following over time the decay in the specific activity of norepinephrine after a single IV bolus of tritiated norepinephrine (30 microCi/kg). Plasma glucose, insulin, and glucagon levels were also measured at the time of death. Although training caused a reduction in the plasma glucose values of diabetic rats, no changes in norepinephrine turnover rate were observed after the conditioning program. On the other hand, diabetes was associated with a significant 30% to 40% decrease in the pancreatic norepinephrine turnover rate. It is concluded that the beneficial effects of physical training on diabetes mellitus cannot be explained by adaptive changes in the sympathetic nervous system activity and that further work will be necessary to elucidate the mechanism whereby streptozotocin diabetes diminishes the pancreatic norepinephrine turnover.

Plasma, adrenal, and heart catecholamines in physically trained normal and diabetic rats

This study was designed to evaluate the possibility that the enhanced insulin sensitivity of physically trained normal and diabetic rats is due to adaptive changes in the adrenergic system. Mild diabetes mellitus was induced in male Wistar rats with streptozocin (STZ, 45 mg/kg i.v.) and a 10-wk conditioning program was conducted by having the animals run on a treadmill. Rats were cannulated 16 h after the last period of exercise and blood sampling was obtained 48 h later for basal plasma glucose, insulin, epinephrine, and norepinephrine determination. Catecholamine measurements were also made in adrenals, atria, and ventricles from sedentary control, trained control, sedentary diabetic, and trained diabetic rats. The previously reported beneficial effect of physical training on diabetes mellitus was reproduced. While diabetes mellitus did not modify the catecholamine levels, the training program provoked an increase in plasma epinephrine concentrations, with a concomitant significant rise in adrenal epinephrine content. In heart tissue, the epinephrine values also tended to be increased by training although statistical significance was not reached. These data suggest that basal secretion of epinephrine is somewhat increased in trained rats. Whether this may trigger adaptive changes that could be involved in the beneficial effect of physical training on experimental diabetes mellitus remains to be elucidated.

Muscarinic cholinergic receptors in mouse pituitary tumor cells: prolonged agonist pretreatment decreases receptor content and increases forskolin- and hormone-stimulated cyclic AMP synthesis and adrenocorticotropin secretion

Muscarinic receptor activation on the AtT-20 clonal line of mouse pituitary corticotrophs, inhibits forskolin-stimulated cyclic AMP formation and adrenocorticotropin secretion. In this study, the effect of prolonged receptor stimulation with the muscarinic agonist oxotremorine was found to reduce, in a time-dependent manner, the ability of oxotremorine to inhibit the AtT-20 cell response to forskolin. Pretreatment with oxotremorine also reduced the density of muscarinic receptors without affecting the affinity of these sites for [3H]quinuclidinyl benzilate. In addition to desensitizing the muscarinic receptor, oxotremorine pretreatment also enhanced the ability of forskolin to stimulate cyclic AMP formation and adrenocorticotropin secretion. The apparent sensitizing effect on cyclic AMP synthesis, extended to other muscarinic agents as well as other secretory agonists, was dependent on the oxotremorine concentration used during pretreatment and required at least 2 hr of pretreatment. Enhancement of forskolin-stimulated cyclic AMP accumulation by oxotremorine pretreatment was blocked by cycloheximide and reversed by the muscarinic antagonist, (-)-scopolamine, or by a 5-hr recovery period after pretreatment. The data suggest that prolonged muscarinic receptor activation (rather than simple occupancy) leads to an enhancement of adenylate cyclase activity in AtT-20 cells; whether this effect is coupled to the progressive loss of the inhibitory function of the muscarinic receptor and the receptor down-regulation is unknown.

Effects of physical training on beta-adrenergic receptors in rat myocardial tissue

A diminished sympathetic activity has been related to training bradycardia seen at rest and during exercise. In order to evaluate if changes in heart adrenergic receptors can be one of the mechanisms by which the sympathetic responsiveness could be decreased by physical training, the number and affinity of beta-adrenergic receptors were determined in heart ventricular tissue of rats submitted to a 10-week running programme. Binding studies were done at different concentrations of (-)[3H] dihydroalprenolol (DHA) (0.5 to 14.4 nmol X litre-1) with ventricular membrane preparations from control and trained rats. Direct linear plot analysis revealed that physical training reduced the total number (1933 +/- 192 vs 2922 +/- 211 fmol X ventricles-1; P less than 0.01) density of beta-adrenergic receptors expressed either as fmol X mg-1 of membrane protein (34 +/- 3 vs 43 +/- 3; P less than 0.05) or as fmol X g-1 ventricle (1740 +/- 170 vs 2308 +/- 155; P less than 0.05). There was no significant change in the dissociation constant (3.11 +/- 0.14 vs 4.08 +/- 0.51 nmol X litre-1; P greater than 0.05). Basal plasma noradrenaline levels were not affected by training (116 +/- 18 vs 101 +/- 14 pg X cm-3; P greater than 0.10); however the adrenaline values were significantly higher in trained rats (91 +/- 16 vs 47 +/- 7 pg X cm-3; P less than 0.05). These data indicate that physical training induces changes at the level of beta-adrenergic receptors and this may partly explain the bradycardia seen in trained subjects and animals.