The variable response of bacteria to free haemoglobin in the tissues

The local enhancement of infection by exogenous ferric iron, as ferric ammonium citrate, and by ferrous iron as guinea-pig haemoglobin, was assessed in studies with 55 strains of bacteria injected into the skin of guinea-pigs. The test organisms included Staphylococcus aureus, Streptococcus spp., Klebsiella spp., Escherichia coli and Pseudomonas aeruginosa. Four strains of Bacteroides spp. were tested with haemoglobin only. As previously reported with other strains, enhancement of infection by members of a given species by ferric iron was variable; in this study infection with only 11 of 59 strains was enhanced. Haemoglobin either of equal or lesser iron content was a more potent enhancer, affecting 27 of the 59 strains. The enhancement ranged from two-fold to 80-fold, the higher figures on the whole being characteristic of haemoglobin enhancement. Some few instances of depression by both haemoglobin and ferric ammonium citrate were noted. A few tests were made with systemic haemoglobin but the concentrations attainable were largely ineffective. Enhancement of infection did not appear to be related to the capacity of a strain to lyse or digest host red blood cells. In so far as guinea-pigs, whose antibacterial defences are lowered by ferric or ferrous iron, represent human subjects at risk of infection because of clinical circumstances characterised by excess of available iron--either exogenous or as a result of haemolysis--our results with organisms of a kind commonly associated with infection in hospitals suggest that only a small proportion of environmental bacteria can take advantage of any decreased resistance associated with iron excess.     

Single-column thalamocortical network model exhibiting gamma oscillations, sleep spindles, and epileptogenic bursts

To better understand population phenomena in thalamocortical neuronal ensembles, we have constructed a preliminary network model with 3,560 multicompartment neurons (containing soma, branching dendrites, and a portion of axon). Types of neurons included superficial pyramids (with regular spiking [RS] and fast rhythmic bursting [FRB] firing behaviors); RS spiny stellates; fast spiking (FS) interneurons, with basket-type and axoaxonic types of connectivity, and located in superficial and deep cortical layers; low threshold spiking (LTS) interneurons, which contacted principal cell dendrites; deep pyramids, which could have RS or intrinsic bursting (IB) firing behaviors, and endowed either with nontufted apical dendrites or with long tufted apical dendrites; thalamocortical relay (TCR) cells; and nucleus reticularis (nRT) cells. To the extent possible, both electrophysiology and synaptic connectivity were based on published data, although many arbitrary choices were necessary. In addition to synaptic connectivity (by AMPA/kainate, NMDA, and GABA(A) receptors), we also included electrical coupling between dendrites of interneurons, nRT cells, and TCR cells, and--in various combinations--electrical coupling between the proximal axons of certain cortical principal neurons. Our network model replicates several observed population phenomena, including 1) persistent gamma oscillations; 2) thalamocortical sleep spindles; 3) series of synchronized population bursts, resembling electrographic seizures; 4) isolated double population bursts with superimposed very fast oscillations (>100 Hz, "VFO"); 5) spike-wave, polyspike-wave, and fast runs (about 10 Hz). We show that epileptiform bursts, including double and multiple bursts, containing VFO occur in rat auditory cortex in vitro, in the presence of kainate, when both GABA(A) and GABA(B) receptors are blocked. Electrical coupling between axons appears necessary (as reported previously) for persistent gamma and additionally plays a role in the detailed shaping of epileptogenic events. The degree of recurrent synaptic excitation between spiny stellate cells, and their tendency to fire throughout multiple bursts, also appears critical in shaping epileptogenic events.     

Translocation (4;11) in acute myelogenous leukemia

A child with acute myelogenous leukemia is presented. Cytogenetic analysis of her leukemic cells revealed a (4;11)(q12;q23) translocation. The slight difference in the breakpoint on chromosome #4 from previously reported cases of t(4;11) may account for the degree of myeloid differentiation expressed. Acute leukemia associated with t(4;11) is a unique subgroup that originates in an early myeloid stem cell and carries a poor prognosis.     

Immune function did not decline with aging in apparently healthy, well-nourished women

Nutrition plays a crucial role in immune function. Most studies on age-associated changes in immunocompetence in healthy adults did not examine the nutritional status of participants extensively. Inadequate nutritional status may confound the relationship of aging and immune response. The purpose of this study was to examine age-related changes in parameters of acquired and innate immunity in healthy and generally well-nourished older (62-88 years) versus younger (20-40 years) women. Subjects were screened for participation using the health criteria of the SENIEUR protocol as well as a number of nutrition criteria related to undernutrition, and protein, iron, vitamin B12, and folate status. Young and old women did not differ in total T (CD3+), T-helper (CD4+), or T-cytotoxic (CD8+) cell number. However, older women tended to have lower T-cell proliferation response to concanavalin A (P < 0.10) and significantly reduced response to phytohemagglutinin (P < 0.05). No age-related changes were noted in natural killer cell number or cytotoxicity. Phagocytosis and subsequent oxidative burst activity also did not differ between young and old women. Most immune parameters were not compromised with aging in this cohort of apparently healthy, well-nourished women. These findings highlight the importance of simultaneous examination of health and nutritional status in studies of immune function with aging.     

CD4 lymphocytes in the blood of HIV(+) individuals migrate rapidly to lymph nodes and bone marrow: support for homing theory of CD4 cell depletion

Recent studies have provided evidence that macrophages from Th1-prone mouse strains respond with an M1 profile, and macrophages from Th2-prone mouse strains respond with an M2 profile, characterized by the dominant production of NO or TGF-beta 1, respectively. We have shown that peritoneal macrophages from IL-12p40 gene knockout mice have a bias toward the M2 profile, spontaneously secreting large amounts of TGF-beta 1 and responding to rIFN-gamma with weak NO production. Moreover, IL-12p40KO macrophages are more permissive to Trypanosoma cruzi replication than their wild-type littermate cells. Prolonged incubation with rIL-12 fails to reverse the M2 polarization of IL-12p40KO macrophages. However, TGF-beta 1 is directly implicated in sustaining the M2 profile because its inhibition increases NO release from IL-12p40KO macrophages. IFN-gamma deficiency is apparently not the reason for TGF-beta 1 up-regulation, because rIFN-gamma KO macrophages produce normal amounts of this cytokine. These findings raise the possibility that IL-12 has a central role in driving macrophage polarization, regulating their intrinsic ability to respond against intracellular parasites.     

Changes in muscle responses to stimulation of the motor cortex induced by peripheral nerve stimulation in human subjects

The aim of this study was to determine whether prolonged, repetitive mixed nerve stimulation (duty cycle 1 s, 500 ms on-500 ms off, 10 Hz) of the ulnar nerve leads to a change in excitability of primary motor cortex in normal human subjects. Motor-evoked potentials (MEPs) generated in three intrinsic hand muscles [abductor digiti minimi (ADM), first dorsal interosseous (FDI) and abductor pollicis brevis (APB)] by focal transcranial magnetic stimulation were recorded during complete relaxation before and after a period of prolonged repetitive ulnar nerve stimulation at the wrist. Transcranial magnetic stimuli were applied at seven scalp sites separated by 1 cm: the optimal scalp site for eliciting MEPs in the target muscle (FDI), three sites medial to the optimal site and three sites lateral to the optimal stimulation site. The area of the MEPs evoked in the ulnar-(FDI, ADM) but not the median-innervated (APB) muscles was increased after prolonged ulnar nerve stimulation. Centre of gravity measures demonstrated that there was no significant difference in the distribution of cortical excitability after the peripheral stimulation. F-wave responses in the intrinsic hand muscles were not altered after prolonged ulnar nerve stimulation, suggesting that the changes in MEP areas were not the result of stimulus-induced increases in the excitability of spinal motoneurones. Control experiments employing transcranial electric stimulation provided no evidence for a spinal origin for the excitability changes. These results demonstrate that in normal human subjects the excitability of the cortical projection to hand muscles can be altered in a manner determined by the peripheral stimulus applied.     

Modulation of stretch-evoked reflexes in single motor units in human masseter muscle by experimental pain

The interaction between muscle pain and motor function of the jaw has been examined in recent years, but the nature of the modulation of the short-latency stretch reflex by pain is not fully understood. In this study, the reflex responses to stretch were measured in single low-threshold motor units that were kept discharging at a constant frequency, before, during and after the induction of experimental pain in one masseter muscle by controlled infusion of hypertonic saline. The probability of evoking a reflex response in individual motor units in the painful muscle at near-monosynaptic latency was reduced by a mean of about 20%. However, the overall reflex response in the surface electromyogram of both the ipsi- and contralateral masseter muscles was greater during pain. This was apparently a secondary response to the pain-induced increase in pre-stimulus activity in the motoneurone pools of both muscles, because increased motoneurone excitability may facilitate stretch reflexes. It is concluded that the most likely explanation for the reduced reflex response of low-threshold masseter motor units during experimental pain is a tonic reduction in the fusimotor drive to the masseter spindles.     

Lymphocyte proliferation in response to acute heavy resistance exercise in women: influence of muscle strength and total work

Little is understood about the immune responses to heavy resistance exercise. The purpose of this investigation was to determine the influence of physical strength and the ability to do more total work on lymphocyte proliferation after an acute bout of heavy resistance exercise. A group of 50 healthy but non-strength trained women were recruited for the study and tested for their one repetition maximum (i.e. 1 RM or maximal mass lifted once). From the normal distribution of strength the top and bottom 8 women [mean age 22.5 (SD 3.1) years] were asked to volunteer to define our two groups (i.e. high strength and low strength). The two groups were significantly different (P<0.05) in 1 RM squat strength [low strength 39.9 (SD 4.6) kg, 0.65 (SD 0.08) kg·kg body mass^–1 and high strength 72.2 (SD 10.7) kg, 1.1 (SD 0.12) kg·kg body mass^–1] but were not significantly different in body mass, age, activity levels, and menstrual status (all in same phase). Each performed a resistance exercise protocol consisting of six sets of 10 RM squats with 2 min rest between the sets. The 10 RM loads and total work were significantly greater in the high strength group than in the low strength group. Blood samples were obtained pre-exercise and immediately post-exercise for test for lactate (significant increase with exercise) and cortisol (no changes) concentrations with no differences noted between groups. Immunological assays on the blood samples determined the incorporation of tritiated thymidine by lymphocytes in responses to concanavalin A (ConA), phytohemagglutinin (PHA), and pokeweed mitogen (PWM). Following the squat exercise, there was a significant decrease in lymphocyte responsiveness to PWM in the high strength but not in the low strength group for both total proliferation and proliferation adjusted per B or T cell. On the other hand, lymphocytes from the low strength group proliferated to a significantly greater extent (adjusted per T cell) in response to ConA and PHA. These data indicate that the heavy resistance exercise protocol reduced the lymphocyte proliferative responses only in the stronger group of subjects. This effect may have been due to the high absolute total work and the greater exercise stress created by the resistance exercise protocol in the high strength group. Therefore, individuals performing at the same relative exercise intensity (i.e. 10 RM) in a resistance exercise protocol may have different immune responses stemming from differences in absolute total work performance. Electronic Publication     

A framework for measuring costs to society of IgE-mediated food allergy

Both immunoglobulin E (IgE)-mediated food allergy and food intolerance can lead to many changes in personal behaviour and health care resource use which have important economic consequences. These costs will impact directly, indirectly and intangibly on both individuals and society in general. It is important to measure the cost of illness (COI) of food allergy as a first step in developing and evaluating measures to reduce and control the burden of illness. This paper outlines a framework for assessing COI of food allergy from different viewpoints. It offers a structure for identifying the different cost impacts on allergic and nonallergic consumers, food producers and society as a whole, and for scoping, measurement and valuation of relevant costs. Within this structure, the existing literature is reviewed. This review illustrates the lack of information and clear methodology for assessing costs of food allergy. The paper concludes that there is a need for a more structured research programme to generate data essential for future evaluations of procedures and technologies for the diagnosis, treatment and management of food allergy.