Modification of surface composition of Actinomyces viscosus T14V and T14AV.

The morphology and serology of Actinomyces viscosus T14V and T14AV were compared. When grown in supplemented tryptic soy broth, the virulent strain (T14V) possessed an extensive network of cell surface fibrils. In this medium, the avirulent strain (T14AV) possessed a microcapsule, absent on strain T14V, and a comparatively small number of surface fibrils. Mild acid extraction (Lancefield procedure) solubilized common antigenic components on both strains as well as components detectable only in the virulent strain T14V (virulence-associated antigens 1 and 2). When grown in Socransky chemically defined medium or Carlsson complex medium, the avirulent strain possessed increased amounts of surface fibrils and virulence-associated antigens. Whole cells and extracts of avirulent cells grown in Socransky medium absorbed antibodies to virulence-associated antigens with approximately the same efficiency as did whole cells and extracts of strain T14V, suggesting antigenic similarity between the two cell types. The results strongly support the hypothesis that observable differences between A. viscosus strains T14V and T14AV represent quantitative, rather than qualitative, differences in particular cell surface components. In addition, the magnitude of these differences can be modified by changing growth conditions.     

Cephalometric analyses and flow-volume loops in obstructive sleep apnea patients

Fifteen patients with obstructive sleep apnea syndrome (OSAS) and 10 controls were studied. Polygraphic monitoring during sleep confirmed the presence or absence of OSAS. Ten OSAS patients and five controls had cephalometric analysis and 12 OSAS patients and five controls had a flow-volume loop study during wakefulness. Seven OSAS patients were submitted to both analyses. Flow-volume loops were unable to detect extrathoracic airway obstruction in six out of 12 OSAS patients. One control was found with positive results. Six out of seven subjects with positive flow-volume loops were overweight (greater than or equal to 30% ideal weight). Cephalograms were very useful in demonstrating mandibular deficiencies in OSAS patients. The length of the soft palate and the position of the hyoid bone, together with the measurement of the posterior airway space, are criteria of great interest in OSAS patients. Cephalometric analysis is recommended in all OSAS patients scheduled for surgical procedure. None of these tests, however, whether alone or in combination, is capable of identifying all cases of OSAS.     

Blood Pressure and Heart Rate Changes Accompanying Classical Eyeblink Conditioning In The Rabbit (Oryctolagus Cuniculus)

In two experiments employing 38 rabbits differential classical conditioning of heart rate, blood pressure, and corneoretinal potential (CRP) response were examined using l-sec and 4-sec interstimulus intervals ISI respectively. The conditioned response consisted of HK decelerations and DP depressor responses early in conditioning. However, many, but not all, animals revealed pressor responses and HR accelerations after the CRP discrimination was acquired. Significant correlations were also obtained between BP pressor responses, HR accelerations, and the frequency of CRP CRs. These results were discussed within the context of the orienting and defense reflexes.     

Pedigree study of familial Alzheimer disease

Twenty-one families with familial Alzheimer disease were ascertained in a dementia clinic and assessed by multiple family interviews. Eight autopsies were reviewed. The age of onset varied from 25 to 85. Seven pedigrees showed evidence of 3 generation transmission. Paternal age of the founders of 4 lines which could be assessed was higher than controls.     

Selective vulnerability of unmyelinated fiber Schwann cells in nerves exposed to local anesthetics

When peripheral nerves of experimental rats are exposed to local anesthetics, distinctive and reproducible pathologic changes occur involving the perineurial sheath and endoneurial contents. Application of intermediate strength concentrations of the local anesthetics, 2-chloroprocaine, lidocaine, etidocaine, and intermediate or high concentrations of procaine to the surface of rat sciatic nerves resulted in the following changes. By 48 hours, the perineurial sheath exposed to the drug was disrupted and became permeable to granulocytes which infiltrated the subjacent endoneurium in conjunction with edema formation in the endoneurial interstitium. Application of 10% procaine to exposed nerve resulted in extensive demyelination. The most striking pathologic change occurring with either intermediate or high doses was accumulation of lipid droplets in Schwann cells, a phenomenon that occurred often in myelin-producing Schwann cells but much less frequently in unmyelinated fiber Schwann Cells. Lipid accumulation appears to be one of several reactive changes that affect Schwann cells of myelinated fibers and is dose-dependent. On the other hand, while reactive changes were infrequently seen in unmyelinated fiber Schwann cells, these cells appeared more susceptible to injury as shown by electron microscopy. Injury to Schwann cells by local anesthetics is temporary because these cells can replicate quickly. Autoradiographic studies of thymidine incorporation 1 week after procaine administration to the sciatic nerve showed intense proliferation of Schwann cells, but no such activity in controls. These findings support the view that their neurotoxic properties may account in some part for the function of local anesthetics, that Schwann cells of small unmyelinated fibers are more vulnerable to these agents than those of myelinated fibers, and that destruction of their supporting cells is followed by vigorous mitotic activity in the endoneurium.     

Prolonged vitamin C supplementation and recovery from eccentric exercise

We have previously shown that vitamin C supplementation affects recovery from an unaccustomed bout of demanding exercise, with the most pronounced effect being that on plasma interleukin-6 concentration. However, because of the proposed role of interleukin-6 in the regulation of metabolism, it was unclear whether this represented a reduced response to muscle damage or some form of interaction with the metabolic demands of the activity. Therefore, the aim of the present study was to investigate the effect of the same form of supplementation on a bout of exercise that initiated similar muscle damage but had a low metabolic cost. Fourteen male subjects were allocated to either a placebo (P) or a vitamin C (VC) group. The VC group consumed 200 mg of ascorbic acid twice a day for 14 days prior to a bout of exercise and for the 3 days after exercise. The P group consumed identical capsules that contained 200 mg lactose. Subjects performed 30 min of downhill running at a gradient of –18% and recovery was monitored for up to 3 days after exercise. Plasma VC concentrations in the VC group increased following supplementation. Nevertheless, downhill running provoked a similar increase in circulating markers of muscle damage (creatine kinase activity and myoglobin concentration) and muscle soreness in P and VC groups. Similarly, although downhill running increased plasma interleukin-6, there was no effect from VC supplementation. These results suggest that vitamin C supplementation does not affect interleukin-6 concentrations following eccentric exercise that has a low metabolic component.     

Molecular Cloning of a 32-Kilodalton Lipoprotein Component of a Novel Iron-Regulated Staphylococcus epidermidis ABC Transporter

Our previous studies identified two iron-regulated cytoplasmic membrane proteins of 32 and 36 kDa expressed by both Staphylococcus epidermidis and Staphylococcus aureus. In this study we show by Triton X-114 phase partitioning and tritiated palmitic acid labelling that these proteins are lipoproteins which are anchored into the cytoplasmic membrane by their lipid-modified N termini. In common with those of some other gram-positive bacteria, these highly immunogenic lipoproteins were released from the bacterial cell into the culture supernatants, with release being promoted by growth of the bacteria under iron-restricted conditions. Immunoelectron microscopy with a monospecific rabbit antiserum to the 32-kDa S. epidermidis lipoprotein showed that the majority of the antigen was distributed throughout the staphylococcal cell wall. Only minor quantities were detected in the cytoplasmic membrane, and exposure of the lipoprotein on the bacterial surface was minimal. A monoclonal antibody raised to the 32-kDa lipoprotein of S. aureus was used in immunoblotting studies to investigate the conservation of this antigen among a variety of staphylococci. The monoclonal antibody reacted with polypeptides of 32 kDa in S. epidermidis and S. aureus and of 40 kDa in Staphylococcus hominis. No reactivity was detected with Staphylococcus lugdunensis, Staphylococcus cohni, or Staphylococcus haemolyticus. The gene encoding the 32-kDa lipoprotein from S. epidermidis has been isolated from a Lambda Zap II genomic DNA library and found to be a component of an iron-regulated operon encoding a novel ABC-type transporter. The operon contains three genes, designated sitA, -B, and -C, encoding an ATPase, a cytoplasmic membrane protein, and the 32-kDa lipoprotein, respectively. SitC shows significant homology both with a number of bacterial adhesins, including FimA of Streptococcus parasanguis and ScaA of Streptococcus gordonii, and with lipoproteins of a recently described family of ABC transporters with proven or putative metal ion transport functions. Although the solute specificity of this novel transporter has not yet been determined, we speculate that it may be involved in either siderophore- or transferrin-mediated iron uptake in S. epidermidis.     

Integrity of the dissociated adult cardiac myocyte: gap junction tearing and the mechanism of plasma membrane resealing

Summary Dissociation of adult cardiac myocytes by collagenase perfusion techniques requires separation of the junctional contacts that link the cells physically, electrically and metabolically in the intact heart. Gap junctions, one of three types of intercellular junction present at the cardiac intercalated disc, are not split into their component membranes when myocytes are dissociated; they are ripped from the plasma membrane of one cell, to be retained by its neighbour. Partitioning of junctions in this way might be expected to constitute a serious threat to the ionic integrity of dissociated myocytes, but in practice, high yields of functionally intact cells, suitable for experimental studies, are routinely obtained. To explain this apparent paradox, repair mechanisms, operating to seal the membrane lesions caused by gap junction tearing, have been hypothesized, but evidence for their existence has previously been lacking. Using freeze-fracture electron microscopy, the present study identifies repair sites as smooth membrane domains that are continuous with the neighbouring plasma membrane, thus forming intact seals. That these structures are not chemically-induced artefacts is demonstrated by their presence in myocytes that were frozen directly from the living state. Subsarcolemmal vesicle clusters, detected in thin sections and freeze-fracture replicas, are associated with the smooth sealing domains. These structures may represent either rounded-up fragments of mechanically disrupted membrane or structures concerned with the synthesis of new lipid. From their freeze-fracture morphology, the sealing domains appear to be lipid-rich and protein-poor. Cytochemical studies using Ruthenium Red, cationized ferritin and lectins show in addition that they have a lower content of negatively-charged membrane components than the neighbouring plasma membrane, and that the carbohydrate residues normally associated with plasma membrane glycolipids and glycoproteins are absent.