Comparison of Ashdown's medium, Burkholderia cepacia medium, and Burkholderia pseudomallei selective agar for clinical isolation of Burkholderia pseudomallei

Ashdown's medium, Burkholderia pseudomallei selective agar (BPSA), and a commercial Burkholderia cepacia medium were compared for their abilities to grow B. pseudomallei from 155 clinical specimens that proved positive for this organism. The sensitivity of each was equivalent; the selectivity of BPSA was lower than that of Ashdown's or B. cepacia medium.     

Bipedal distribution of human vestibular-evoked postural responses during asymmetrical standing

Galvanic vestibular stimulation (GVS) evokes responses in muscles of both legs when bilateral stimuli are applied during normal stance. We have used this technique to assess whether asymmetrical standing alters the distribution of responses in the two legs. Subjects stood either asymmetrically with 75 % of their body weight on one leg or symmetrically with each leg taking 50 % of their body weight. The net response in each leg was taken from changes in ground reaction force measured from separate force plates under each foot. The net force profile consisted of a small initial force change that peaked at ∼200 ms followed by an oppositely directed larger component that peaked at ∼450 ms. We analysed the second force component since it was responsible for the kinematic response of lateral body sway and tilt towards the anode. In the horizontal plane, both legs produced lateral force responses that were in the same direction but larger in the leg ipsilateral to the cathodal ear. There were also vertical force responses that were of equal size in both legs but acted in opposite directions. When subjects stood asymmetrically the directions of the force responses remained the same but their magnitudes changed. The lateral force response became 2-3 times larger for the more loaded leg and the vertical forces increased 1.5 times on average for both legs. Control experiments showed that these changes could not be explained by either the consistent (< 5 deg) head tilt towards the side of the loaded leg or the changes in background muscle activity associated with the asymmetrical posture. We conclude that the redistribution of force responses in the two legs arises from a load-sensing mechanism. We suggest there is a central interaction between load-related afferent input from the periphery and descending motor signals from balance centres.     

Malaria transmission and naturally acquired immunity to PfEMP-1

Why there are so few gametocytes (the transmission stage of malaria) in the blood of humans infected with Plasmodium spp. is intriguing. This may be due either to reproductive restraint by the parasite or to unidentified gametocyte-specific immune-mediated clearance mechanisms. We propose another mechanism, a cross-stage immunity to Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP-1). This molecule is expressed on the surface of the erythrocyte infected with either trophozoite or early gametocyte parasites. Immunoglobulin G antibodies to PfEMP-1, expressed on both life cycle stages, were measured in residents from an area where malaria is endemic, Papua New Guinea. Anti-PfEMP-1 prevalence increased with age, mirroring the decline in both the prevalence and the density of asexual and transmission stages in erythrocytes. These data led us to propose that immunity to PfEMP-1 may influence malaria transmission by regulation of the production of gametocytes. This regulation may be achieved in two ways: (i) by controlling asexual proliferation and density and (ii) by affecting gametocyte maturation.     

Intestinal metaplasia in endoscopic biopsy specimens of gastric mucosa

A total of 1412 consecutive cases of endoscopic gastric biopsy, carried out over a four year period, were reviewed and specimens were examined histochemically to determine the prevalence of intestinal metaplasia and its variants. Three types were characterised: complete intestinal metaplasia and two classes of incomplete intestinal metaplasia (type IIa and type IIb) depending on the absence or presence, respectively, of sulphomucins within mucin secreting columnar cells. Type IIb intestinal metaplasia was significantly more common in patients with gastric carcinoma (p less than 0.001) and in those with dysplasia (p less than 0.001) than in patients with benign gastric pathology. No such association was found with either type I or type IIa intestinal metaplasia. In addition to those present in the columnar cells of type IIb intestinal metaplasia, sulphomucins were also commonly found in goblet cells of all three types of metaplasia. The presence of sulphomucins in goblet cells, however, was not significantly associated with gastric carcinoma or dysplasia. The significance of the different types of intestinal metaplasia in relation to the pathological findings is discussed.     

The potentiating effect of rheumatoid arthritis serum in the immediate phase of nephrotoxic nephritis

Nephrotoxic nephritis induced in rats was employed as an experimental model to investigate the possible effects of rheumatoid factor on in vivo antigen–antibody reactions. Rats injected simultaneously with rheumatoid arthritis serum and rabbit nephrotoxic globulin showed a three-fold increase in immediate proteinuria compared with rats injected with nephrotoxic globulin alone. This potentiating effect of rheumatoid arthritis serum was evident even when the serum was injected 48 hr after the nephrotoxic globulin and was also apparent to a lesser extent in rats decomplemented by a prior injection of aggregated human IgG. Normal human serum had no effect on the proteinuria produced by a standard dose of nephrotoxic globulin while rheumatoid arthritis serum injected with normal rabbit globulin did not increase urinary protein excretion above baseline levels. In rats injected with rheumatoid arthritis serum and nephrotoxic globulin, human IgM (presumably rheumatoid factor) was detected by immunofluorescence on the glomerular basement membrane along with the nephrotoxic globulin and rat complement and persisted at this site for as long as 42 days after the initial injections. Rheumatoid factor activity was also recovered by elution from glomeruli isolated from rat kidneys 24 hr after the injection of rheumatoid arthritis serum and nephrotoxic globulin.     

Circulating immune complexes, complement and complement component levels in childhood Hodgkin's disease.

Serum levels of circulating immune complexes (CIC) assayed by the Raji cell radioimmunoassay, total haemolytic complement (TCH50), Clq and C3 were correlated with clinical stage, histological type, age, sex and treatment of eighty-six children with Hodgkin's disease over a period of 4 years. Most significant findings were the changes of levels of CIC, TCH50, Clq and C3 during disease activity and following treatment. Significant perturbations were also seen in association with relapse. Levels of C and CIC were significantly elevated (P less than 0.001) at the time of diagnosis prior to splenectomy and/or any treatment. In the group before treatment, 81 percent of CIC levels were above 16 micrograms/ml with a maximum value of 1120 micrograms/ml. During treatment 33 percent were still above normal with a maximum of 320 micrograms/ml. Within 1 year after cessation of treatment, 37 percent also remained above normal levels with a maximum of 240 micrograms/ml. At relapse prior to treatment, 63 percent were again elevated with a maximum of 1280 micrograms/ml. The most significant difference on TCH50 levels relates to treatment periods. Sera of patients with active disease who are previously untreated show elevation of TCH50 levels (P less than 0.001) (average 127 CH50 mu/ml. During and after treatment eht TCH50 levels drop to 96 and 102 CH50 mu/ml, as compared to normal control of 100 CH50 mu/ml. In sera of patients at the first, second or third relapse, the combined TCH50 levels are significantly different from controls and across treatment periods (P less than 0.005).     

Regulation of glutathione by oxidative stress in bovine pulmonary artery endothelial cells

Glutathione plays important roles as an intracellular antioxidant and in the maintenance of cellular thiol-disulfide balance. In addition, glutathione may regulate cell growth signaling induced by oxidative stress. We previously reported that cellular glutathione is up-regulated by bleomycin in bovine pulmonary artery endothelial cells. The present study examined effects of hydrogen peroxide (H(2)O(2)) on cell growth and glutathione levels. Exogenous addition of H(2)O(2) induced biphasic effects on cell growth; 1 micro M was stimulatory and >10 micro M was inhibitory. However, both growth-promoting and inhibitory levels of H(2)O(2) increased cellular glutathione levels. Whereas 1 micro M H(2)O(2) moderately but significantly increased glutathione, 30 micro M caused a more substantial increase. Like bleomycin, both concentrations of H(2)O(2) activated DNA binding of antioxidant response element (ARE), a regulatory element in the promoter of the gamma-glutamylcysteine synthetase heavy chain subunit, a key regulator of glutathione synthesis. However, only high concentrations of H(2)O(2) activated p44/42 mitogen-activated protein (MAP) kinase. Thus, cellular glutathione is up-regulated by H(2)O(2), perhaps via activating ARE-binding factors in a mechanism independent of MAP kinase. H(2)O(2)-mediated increase in glutathione and activation of ARE binding may play important roles in growth and death of pulmonary artery endothelial cells.     

Developmental aspects of complement components in the newborn. The presence of complement components and C3 proactivator (properdin factor B) in human colostrum

A deficiency of all nine complement (C) components in cord sera relative to maternal serum levels was demonstrated. At 4 days of age, C1q (measured immunochemically), C1, C2, C4 and C7 levels were increased markedly to maternal levels. C3 was the only C component which exhibited no significant change between birth and at 4 days of age. A marked deficiency of serum levels of C8 and particularly of C9 was evident at birth.

No haemolytic C was demonstrable in the colostrum from which lipids were previously removed. Functional C3 was measurable by immune adherence with EAC142 intermediate sheep cells. Functional C3PA using cobra venom-induced lysis of unsensitized guinea-pig erythrocytes was also present. Substantial amounts of C3, C4 and C3PA determined immunochemically were found at 24 hr after birth with rapidly decreasing levels at 48 and 72 hr. C1q and C5 were absent. No differences of C components were evident in sera between bottle and breast-fed infants for any of the nine components studied.

     

Effect of tonic voluntary activity on the excitability of human motor cortex.

1. The threshold for obtaining EMG responses after transcranial magnetic stimulation of the brain is reduced by voluntary contraction of the target muscle. The present experiments tested whether some of this effect is due to increased cortical, as opposed to spinal, excitability during the contraction. 2. Magnetic stimulation was delivered with a figure-of-eight coil oriented with the junction region along the interaural line and also (in 4 of 7 subjects) with a circular coil centred at the vertex. The intensity of the conditioning stimulus was subthreshold for evoking a motor response in the relaxed wrist flexor muscles of the forearm. The presence of a small descending corticospinal volley in both the relaxed and active conditions was detected by measuring the facilitation of test H reflexes elicited in the flexor muscles of the forearm. 3. In all subjects, magnetic stimulation with either coil facilitated the H reflex at conditioning-test intervals of -1 to -3 ms (median nerve stimulus before magnetic). This was followed by a long-lasting facilitation. In three of the seven subjects stimulation with the figure-of-eight coil elicited an additional, earlier peak of facilitation at a conditioning-test interval of -3 to -5 ms. 4. In all subjects, the threshold for obtaining facilitation of the H reflex using a conditioning-test interval of -1 to -3 ms was reduced, and the amount of facilitation was larger, if subjects performed a weak tonic voluntary contraction. In contrast, with a conditioning-test interval of -3 to -5 ms voluntary contraction had no effect on the threshold. 5. It is suggested that H reflex facilitation at the conditioning-test interval of -1 to -3 ms was produced by indirect activation of corticospinal neurones by the magnetic stimulus, whereas at -3 to -5 ms, the facilitation was produced by direct activation of corticospinal axons. It is concluded that tonic voluntary contraction of a target muscle decreases the threshold for indirect activation of corticospinal neurones but not for direct stimulation of their axons.