Personal respiratory protection against Mycobacterium tuberculosis

The present study investigated the simultaneous occurrence of emergent stimulus-response relations (functional equivalence) and stimulus-stimulus relations (stimulus equivalence). After being pretrained and tested on two symbolic match-to-sample tasks (X1-Y1, X2-Y2), 20 4- and 5-year-old children were trained to emit specified responses to pairs of stimuli (A1-R1, B1-R1, A2-R2, B2-R2) in one setting (original training) and to emit other responses to one member of each pair (A1-R3, A2-R4) in another setting (reassignment training). Of the 18 children who responded correctly on all trained tasks, 15 emitted the novel responses also in the presence of the nonreassigned stimuli (B1-R3, B2-R4). Eleven of these children also matched same-class stimuli with one another (A1-B1, A2-B2, and vice versa). Additional tests with four of these children documented the formation of conditional response-stimulus relations (R3-B1, R4-B2) in all four children, and of conditional response-response relations (R1-R3, R2-R4, and vice versa) in two of them. Children who did not show stimulus control transfer also failed to match same-class stimuli with one another. Present findings, together with those obtained in animal research, suggest that functional equivalence can imply but does not require stimulus equivalence.     

'Sheltered disruption' of Neurospora crassa MOM22, an essential component of the mitochondrial protein import complex

MOM22 is a component of the protein import complex of the mitochondrial outer membrane of Neurospora crassa. Using the newly developed procedure of 'sheltered disruption', we created a heterokaryotic strain harboring two nuclei, one with a null allele of the mom-22 gene and the other with a wild-type allele. Homokaryons bearing the mom-22 disruption could not be isolated, suggesting that mom-22 is an essential gene. The mutant nucleus can be forced to predominate in the heterokaryon through the use of specific nutritional and inhibitor resistance markers. Cultivation of the heterokaryon under conditions favoring the mutant nucleus resulted in selective depletion of MOM22. MOM22-depleted cells did not grow and contained mitochondria with an altered morphology and protein composition. Protein import into isolated, MOM22-depleted mitochondria was abolished for most precursor proteins destined for all subcompartments. In contrast, precursors of MOM19, MOM22 and MOM72 became inserted normally into the outer membrane, defining a novel MOM22-independent import pathway which remained intact in mutant mitochondria. Furthermore, the specific binding of the ADP/ATP carrier to the outer membrane was unaffected, but subsequent transport across the outer membrane did not occur. Our data show that MOM22 is an essential component of Neurospora cells specifically required for the biogenesis of mitochondria.     

Lung function measurement in general practice: a comparison of the Escort spirometer with the Micromed turbine spirometer and the mini-Wright peak flow meter

It is important that new types of spirometer for widespread clinical use are pragmatically evaluated in primary care. This study compared measurements taken by a new portable Fleisch pneumotachograph spirometer (known as the Escort) with those of the commonly used mini-Wright peak flow meter and the Micromed Pocket turbine spirometer. A pragmatic study was conducted in two phases during routine surgeries at Aldermoor Health Centre, Southampton. Phase I compared the new spirometer with the mini-Wright peak flow meter and Phase 2 compared the new spirometer and the turbine spirometer. One hundred patients aged 5-88 years (56 patients with a history of chronic respiratory complaints and 44 patients without) entered Phase 1, and 100 patients aged 6-82 years (62 patients with a history of chronic respiratory complaints and 38 patients without) entered Phase 2. Each patient contributed only once to each phase, but some entered both phases on separate occasions. Ninety-five percent limits of agreement (mean +/- SD) were wide for all comparisons. Graphical plots revealed trends towards higher Escort values as mean values rose compared with both mini-Wright and turbine readings for peak expiratory flow rate and forced expiratory volume in one second. Possible over-reading of peak expiratory flow rate with the mini-Wright meter at low mean values was also seen. Readings taken with these different types of meter cannot be interchanged with confidence in clinical practice. The clinical significance of the theoretically more accurate measures of lung function produced with the new meter, and indeed of spirometry itself, needs further investigation.     

Long-term low-dose calcitriol treatment in predialysis chronic renal failure: can it prevent hyperparathyroid bone disease?

In an uncontrolled open study 13 patients with moderate to preterminal renal failure were treated with low doses (average 0.36 micrograms/day) of calcitriol up to the time of renal transplantation, which was performed before dialysis had been initiated. A transiliac bone biopsy was obtained both at the start and at the end of the treatment period, the latter coinciding with renal transplantation. All patients who started calcitriol treatment at a creatinine clearance (Ccr) above 30 ml/min had normal bone histology at the time of transplantation, but this was not observed when calcitriol treatment was started at Ccr below 30 ml/min. The study suggests that full benefit of calcitriol at the bone level is obtained only if prophylactic administration is started early in the course of renal failure.     

Minimal invasive therapy of aneurysms of the superficial femoral artery and the popliteal artery

Percutaneous stent placement has been described for treatment of aneurysms as an alternative to surgical therapy. Literature reports of percutaneous minimal invasive therapy of peripheral aneurysms shall be reviewed and compared with our own results. Six male patients (51-69 years) with femoropopliteal occlusions related to aneurysms were treated percutaneously. In two cases Wallstents and in four cases polyester-covered nitinol stents were applicated. A clinical investigation including doppler-ultrasound was performed 24 hrs, 1, 3, 6, 12 and 24 months after the intervention. Stent placement succeeded in all cases. No adjunctive surgical treatment was necessary. Ankle-brachial-index (ABI) improved from 0.22 +/- 0.2 before to 0.74 +/- 0.2 24 hours after the intervention. One patient was lost for follow-up (Wallstent). A decrease of ABI and additional intraarterial angiography revealed stent-graft occlusion within one month (n = 2) and within three months (n = 1). One of these cases was successfully recanalized with local fibrinolysis therapy. In three patients patency of the stent persisted for 24 (+/- 2) months follow-up with three-vessel-supply of the calf. These results warrant further investigations for this minimal invasive method of percutaneous stent deployment as an alternative to surgical bypass treatment of femoropopliteal aneurysms. Time of hospitalization was reduced. At this time, surgical treatment of peripheral vascular aneurysms is gold standard.     

Tyrosine kinase inhibition produces specific alterations in axon guidance in the grasshopper embryo

Tyrosine kinase signaling pathways are essential for process outgrowth and guidance during nervous system development. We have examined the roles of tyrosine kinase activity in programming growth cone guidance decisions in an intact nervous system in which neurons can be individually identified. We applied the tyrosine kinase inhibitors herbimycin A and genistein to whole 40% grasshopper embryos placed in medium, or injected the inhibitors into intact grasshopper eggs. Both inhibitors caused interneuronal axons that normally would grow along the longitudinal connectives to instead leave the central nervous system (CNS) within the segmental nerve root and grow out toward the body wall muscles. In addition, herbimycin A produced pathfinding errors in which many longitudinal axons crossed the CNS midline. To study how this drug affected guidance decisions made by individual growth cones, we dye-filled the pCC interneuron, which normally extends an axon anteriorly along the ipsilateral longitudinal connective. In the presence of herbimycin A, the pCC growth cone was redirected across the anterior commissure. These phenotypes suggest that tyrosine kinase inhibition blocks a signaling mechanism that repels the growth cones of longitudinal connective neurons and prevents them from crossing the midline.     

Striate cortex extracts higher-order spatial correlations from visual textures

Spatial correlations define the statistical structure of any visual image. Two-point correlations inform the visual system about the spatial frequency content of an image. Higher-order correlations can capture salient features such as object contours. We studied "isodipole" texture discrimination in V1 to determine if higher-order spatial correlations can be extracted by early stages of cortical processing. We made epicortical, local field potential, and single-cell recordings of responses elicited by isodipole texture interchange in anesthetized monkeys. Our studies demonstrate that single neurons in V1 can signal the presence of higher-order spatial correlations in visual textures. This places a computational mechanism, which may be essential for form vision at the earliest stage of cortical processing.     

Developmental stages in experimental liver metastases: relation to invasiveness

We have previously reported that an invasive morphotype can be evoked in a rat colon carcinoma by transplanting it into pre-induced subcutaneous granulation tissue. We have now studied the interaction of the same tumor with liver tissue, which is extremely poor in connective tissue in comparison with the subcutaneous site. Tumor cells were injected into the portal system and the resulting experimental liver metastases were examined by electron microscopy and immunohistochemistry. Early metastases consisted of well-differentiated acini, fully surrounded by connective tissue that was derived from the periportal stroma. In a later stage, this connective tissue was overgrown by tumor cells and, almost immediately, acinar differentiation was lost. Most metastases eventually reached the liver capsule, which reacted by forming a layer of granulation tissue. Only in this layer, we observed invasion by thin tumor cell strands, which were often intimately associated with fibroblasts or with blood capillaries. The tumor cells remained smooth and rounded during this process. After fully penetrating the granulation tissue, the tumor cell strands reached the liver surface, where they formed poorly structured papillary masses that were nearly devoid of stroma. Our observations indicate that, even in a relatively homogeneous organ like the liver, the tumor-host interaction is highly complex and dynamic. They also confirm the notion that granulation tissue stimulates tumor invasiveness. Finally, they show that tumor cells can actively invade host tissues without exhibiting a "fibroblastic" morphology.     

Formulaic methods of estimating calorie requirements in mechanically ventilated obese patients: a reappraisal

We reviewed 410 cases, 365 males and 45 females, mean age 64 years, of inguinal and femoral hernia, from 1/1/1991 to 31/12/1994, repaired with Lichtenstein and Trabucco techniques. Recurrent hernias repaired were 36 (8,8%). Local anesthesia was used in 82% and follow-up has ranged from 6 months to 4 years. The meshes used are made with a single layer of polipropylene and the Trabucco plugs T1 were made by hand at the operating table. In our experience these two techniques are simple, but is very important, before application of the mesh, a correct dissection of inguinal region. We made a complete excision of cremasteric fibers preservig, if possible, the genital branch of the genitofemoral nerve. The transversalis fascia is introflected and sutured in direct hernia repair or when there are a loss of tissues. The preliminary results obtained with the "tension free" hernioplasty are satisfying. The most important complications were 9 hematomas and an important and persistent inguinal neuralgia in 1 case. There were no recurrences, but we must considered the short follow-up period.