Cell death of asynaptic neurons in regenerating spinal cord

The weakly electric fish Sternarchus albifrons possesses a unique class of asynaptic neurons, the electromotor neurons, whose axons constitute the electric organ. The cell bodies of origin of the electrocyte axons are located in the spinal cord. Both spinal cord and electromotor neurons ( electrocytes ) regenerate after amputation of the tail. Sternarchus spinal cords which have regenerated for 1 or more years show a progression in number of perikarya of electromotor neurons along the rostro-caudal axis. The most recently regenerated region of the cord is at the caudal end, which consists of a tube of ependyma. Progressing rostrally along regenerated spinal cord from the caudal end, numerous cells are generated and large numbers of electromotor neurons differentiate. The maximum number of electromotor neurons per transverse section of regenerated cord is five times higher than in normal mature cord. Rostral to this, the number of electromotor neurons decreases gradually to the normal number near the transition zone (the border with unregenerated cord). As the more rostral regenerated cord has presumably had a longer period of regeneration, we conclude that excess numbers of electromotor neurons are generated initially, and that subsequently the number of these neurons is decreased by cell death. This conclusion is supported by the fact that younger regenerates (2-4 months) have larger-than-normal numbers of perikarya of electromotor neurons extending up to the transition zone (Anderson and Waxman , 1981). No evidence of migration or depletion of electromotor neurons from unregenerated cord rostral to the amputation has been observed. Since the axons of the electromotor neurons in Sternarchus do not normally form any synapses, this study provides evidence that factors other than synaptic competition must be responsible for determining cell death during regeneration of these spinal neurons.

Seasonal changes in white and brown adipose tissues in Clethrionomys gapperi (red-backed vole) and in Microtus pennsylvanicus (meadow vole)

Mass and gross composition of white and brown adipose tissues and of skeletal muscle were determined for C. gapperi and for M. pennsylvanicus from monthly samples of a 1-year period. Amounts of brown fat increased throughout autumn to a maximum in late winter and then declined to a minimum in the spring. Gross composition remained relatively constant throughout the year. Changes in white fat showed a trend similar to changes in brown fat. Relatively low mean values for muscle mass during summer were due to a change in the age structure of the vole population.

Aggregates of acetylcholine receptors are associated with plaques of a basal lamina heparan sulfate proteoglycan on the surface of skeletal muscle fibers

Hybridoma techniques have been used to generate monoclonal antibodies to an antigen concentrated in the basal lamina at the Xenopus laevis neuromuscular junction. The antibodies selectively precipitate a high molecular weight heparan sulfate proteoglycan from conditioned medium of muscle cultures grown in the presence of [35S]methionine or [35S]sulfate. Electron microscope autoradiography of adult X. laevis muscle fibers exposed to 125I-labeled antibody confirms that the antigen is localized within the basal lamina of skeletal muscle fibers and is concentrated at least fivefold within the specialized basal lamina at the neuromuscular junction. Fluorescence immunocytochemical experiments suggest that a similar proteoglycan is also present in other basement membranes, including those associated with blood vessels, myelinated axons, nerve sheath, and notochord. During development in culture, the surface of embryonic muscle cells displays a conspicuously non-uniform distribution of this basal lamina proteoglycan, consisting of large areas with a low antigen site-density and a variety of discrete plaques and fibrils. Clusters of acetylcholine receptors that form on muscle cells cultured without nerve are invariably associated with adjacent, congruent plaques containing basal lamina proteoglycan. This is also true for clusters of junctional receptors formed during synaptogenesis in vitro. This correlation indicates that the spatial organization of receptor and proteoglycan is coordinately regulated, and suggests that interactions between these two species may contribute to the localization of acetylcholine receptors at the neuromuscular junction.

Characterization of the genome of the agent of erythrocyte aplasia permits its classification as a human parvovirus

It has recently been established that infection with a virus is the most common cause of transient arrest of erythrocyte production in the bone marrow, leading to aplastic crisis, in persons suffering chronic haemolytic anaemias. The physical characteristics of this human virus have suggested that it may be a member of the Parvoviridae. We report here that extraction of nucleic acid from this virus under annealing conditions yielded a single species of double-stranded DNA 5.5 kb in length. Treatment with heat or alkali converted this DNA into a rapidly migrating form sensitive to the single-strand-specific nuclease S1. Extraction of the virion DNA under conditions of low ionic strength where annealing would not be expected to occur yielded DNA which comigrated with the 5.5 kb single-stranded molecule. The results indicate that this virus packages equal numbers of complementary DNA strands into separate virions. It is suggested that this virus can be classified as a member of the genus parvovirus.

Aplastic crisis due to parvovirus infection in pyruvate kinase deficiency

A thirteen-year-old boy with congenital haemolytic anaemia due to pyruvate kinase (PK) deficiency had an aplastic crisis. A serum parvovirus-like virus (SPLV) was demonstrated in the blood by electron microscopy and, subsequently, IgM and IgG antibodies to the prototype SPLV B19 were detected. In an attempt to define the level of erythropoiesis that is involved in parvovirus-induced bone marrow suppression, the levels of circulating early erythroid progenitors (burst forming units erythroid, BFU-E) were monitored during the crisis and recovery period. The virus-containing plasma inhibited the formation of BFU-Es from non-immune subjects and this effect was neutralised by convalescent serum. Colony forming units granulocyte-macrophage (CFU-GM) were also inhibited but this was probably non-specific since neutralisation did not reverse the effect. These experiments, together with the clinical data, suggest a selective effect of SPLV at the stage of erythroid progenitors.

Infection with parvovirus-like virus and aplastic crisis in chronic hemolytic anemia

From 1980 to 1982 seven adults with chronic hemolytic anemia were admitted to Cook County Hospital, Chicago, with aplastic crisis. Six of these patients had sickle cell anemia, the seventh patient had beta thalassemia intermedia. Virologic studies showed that six patients had acute infection with the human parvovirus-like virus; in the remaining patient the lack of appropriate specimens precluded viral diagnosis. We describe the features of the virus infection and accompanying erythroid aplasia, and discuss the role of parvovirus-like virus as the etiologic agent in the arrest of erythrocyte production.

Fine structure of regenerated ependyma and spinal cord in Sternarchus albifrons

The caudal-most regenerated spinal cord in Sternarchus albifrons consists solely of an ependymal tube. Ependymal cells are enlarged radially and are more numerous than in unregenerated cord. Projections of ependymal cell cytoplasm and Reissner's fiber fill most of the central canal. Small groups of neurites and cell processes filled with dense-cored vesicles lie between abluminal processes of ependymal cells. Rostral to this, additional cells appear dorsal and lateral to the inner ependymal layer. Some cell bodies contain numerous dense-cored vesicles. Larger bundles of neurites, some with synapses, are present. Invaginations of the peripheral edge of the cord create enclosed spaces lined with basal lamina. In the peripheral region, longitudinally oriented neurites extend through extracellular spaces or channels. The ventral portion at some levels of regenerated cord is completely filled with neurites, processes containing dense-cord vesicles, and capillaries. Similar masses of neurites and processes containing dense-cored vesicles lie outside the cord proper, in or near the meningeal layer. In rostral-most sections, the organization of regenerated spinal cord approaches that of normal cord, with the regenerated cord exhibiting groups of myelinated axons, differentiated fibrous astrocytes and oligodendroglia, cell bodies containing dense-cored vesicles, and differentiated electromotor neurons. These observations indicate a degree of pluripotency in some of the ependymal cells in adult Sternarchus. Moreover, they are consistent with a role of ependymal cells in the guidance of regenerating neurites.

Caudal spinal cord of the teleost Sternarchus albifrons resembles regenerating cord

The morphology of spinal cord in the caudal-most spinal segments of normal adult Sternarchus albifrons is different from that of more rostral adult cord. The caudal segments are strikingly similar to the regenerating spinal cord observed after amputation of the tail in Sternarchus. In the caudal-most vertebral segment of normal spinal cord, ependymal cells are radially enlarged and are more numerous than in more rostral adult cord. Large processes of the ependymal cells extend into the central canal, which also contains a prominent Reissner's fiber. Invaginations of the outer surface of the spinal cord, with the associated basal lamina, are common. Lateral to the immediate ependymal layer, extracellular spaces contain longitudinally oriented neurites. Cell bodies and cell processes filled with dense-cored vesicles occur throughout the caudal-most segment of spinal cord, and are especially concentrated in the ventral half, interspersed with numerous capillaries. In all these respects the caudal-most segments of normal adult spinal cord in Sternarchus closely resemble regenerating spinal cord of Sternarchus. In both regions, at least some of the ependymal cells retain the ability to divide and generate new neurons and glial cells.

The role of interferon in the NK cell killing of virus-infected target cells

Spleen cells from uninfected CBA mice are more cytotoxic for Sendai virus-infected L929 cells than for uninfected cells and the lymphocytes responsible have the properties of NK cells. Preincubation of spleen cells with culture supernatants from Sendai virus-infected L929 cells increases the cytotoxicity for uninfected target cells. This increase in cytotoxicity can also be produced by pretreatment with purified mouse interferon. The enhancing effect of both the infected culture supernatants and purified interferon can be neutralized with anti-interferon serum. It is concluded that the preferential killing of Sendai virus-infected L929 cells by NK cells is dependent on the induction of interferon and that interferon will increase NK cell cytotoxicity for uninfected target cells.

The emerging story of a human parvovirus-like agent

It is now seven years since Cossart and her co-workers reported finding a novel parvovirus-like agent (PVLA) infecting man. Although this virus was found as a systemic infection in both Dr Cossart's eleven subjects and a further four subjects described subsequently (Paver & Clarke, 1976; Schneerson, Mortimer & Vandervelde, 1980) it was not until 1981 that a clearly defined clinical syndrome was identified as attributable to infection with this agent. Work in the Departments of Microbiology and Haematology, King's College Hospital Medical School and collaboration with the MRC laboratory at Kingston, Jamaica has shown that infection with the PVLA is the major cause of aplastic crisis in children with sickle cell anaemia (Sergeantet al.1981, Andersonet al.1982a, b).

Occurrence of infection with a parvovirus-like agent in children with sickle cell anaemia during a two-year period

The occurrence of infection with a parvovirus-like agent during the period April 1979-May 1981 in children attending a single sickle cell clinic in London was investigated. Virus was detected in serum by counter-current immunoelectrophoresis (CIE) and immunoelectron microscopy (IEM). Viral antibody was detected by CIE and specific IgM antibody by an IgM-antibody capture assay. Of the 68 children studied nine presented in aplastic crisis and evidence of infection with the parvovirus-like agent at the time of the crisis was found in all nine. Eighteen of the other children were antibody-positive at some time during the study. In 11 children there was no evidence of recent infection; however, two of these had a history of aplastic crisis in previous years. The other seven seroconverted during the course of the study but did not show any haematological effects. Five of these had a primary infection, one appeared to have reinfection and in the seventh there were insufficient data to distinguish between the two. Possible explanations for the difference between those presenting with aplastic crisis and those with asymptomatic seroconversion are discussed.

The production of monoclonal antibodies to rubella haemagglutinin and their use in antibody-capture assays for rubella-specific IgM

Mice were immunized by three intraperitoneal and one intravenous injection of rubella haemagglutinin. Splenocytes from these mice were fused with the cells of a syngeneic myeloma cell line, and following culture for various periods of time, single-cell clones were derived by the technique of limiting dilution. A total of 139 clones were derived from 13 parent hybrid cultures. To date, four of these cloned cultures have been propagated as ascitic tumours in mice. The preparation of IgG from ascitic fluid and labelling of this antibody with 125I is described. Results indicate that the use of labelled monoclonal antibodies as indicator reagents in solid-phase IgM antibody capture assays for the detection of rubella-specific IgM results in enhanced performance of these tests.

Retrograde axon reaction following section of asynaptic nerve fibers

The asynaptic spinal neurons of the gymnotid teleost Sternarchus albifrons show several distinct characteristics of the retrograde reaction of the perikaryon (which corresponds to chromatolysis in mammals) following axotomy. Nuclei of affected cells are characteristically eccentric. Large bundles of neurofilaments, never seen in normal perikarya of these cells, become prominent following axotomy. There is a marked increase in the number and size of dense bodies in the affected perikarya. Large arrays of parallel rough endoplasmic reticulum, never seen in normal cells, are frequent in the axotomized neurons. These results demonstrate that disconnection from synaptic terminals is not a necessary condition for the retrograde reaction of the perikaryon following axotomy.

The development and use of an antibody capture radioimmunoassay for specific IgM to a human parvovirus-like agent

An IgM-antibody capture radioimmunoassay (MACRIA) was developed for the detection of IgM antibody specific for the human parvovirus-like agent B19. Diagnosis of infection with this agent by either antigen detection or antibody seroconversion had been made by counter-current immunoelectrophoresis (CIE) in 18 cases of aplastic crisis occurring in children with homozygous sickle-cell disease. The MACRIA described here gave positive results in 17 of these 18 cases; in the remaining case only an acute specimen taken from the patient during viraemia and late convalescent specimens taken 184 and 247 days after onset of illness were available. The test was used to investigate 20 further cases of aplastic crisis in which neither viral antigen nor antibody seroconversion could be detected by CIE. Detection of virus-specific IgM permitted diagnosis of infection with this parvovirus-like agent in 17 of these cases. In the remaining three cases only single serum specimens taken late in convalescence, 82 days or more after the onset of symptoms, were available. In addition to these 34 cases of aplastic crisis in which primary infection with this agent was diagnosed by MACRIA, seven cases of apparent 'silent' infection detected by CIE were investigated. The test permitted the discrimination between primary infection and re-exposure to the virus in six of these patients. The use of this assay has added a considerable weight of evidence implicating primary infection with this parvovirus-like agent as an important cause of aplastic crisis in children with sickle-cell disease. Furthermore, MACRIA permits diagnosis of infection when only single serum specimens taken up to ten weeks after infection are available. Thus the use of this test will significantly facilitate the investigation of other clinical syndromes of presumptive infectious aetiology.

Forced walking prepartum for dairy cows of different ages

Fifty-three 2-yr-old Holstein heifers and 63 cows from 3 to 7 yr old were exercised 5 days/wk for 8 wk before calving. Three treatments were: 1) control (no forced exercise); 2) walk 1.6 km/day; and 3) walk 8.0 km/day. Exercise was at 4.0 km/h in a circular lane with a motor-driven gate. Daily feed intake and weekly body weights were recorded during the prepartum period and 50 days postpartum. Daily milk production and semimonthly milk composition were recorded for the complete lactation. Exercise did not affect feed intake during the prepartum period. Weight gain was reduced during the dry period, more for older than for young cows, and particularly less gain for the longer distance. There was no benefit to production or feed efficiency from exercise for any age of cows. Production of protein and solids not fat was higher for combined ages of cows on the shorter than the longer distance. Protein percentage in milk for the lactation was higher for exercised than for control cows; solids-not-fat percentage in milk was higher for exercise for shorter than for longer distance; and fat percentage in milk was not affected by exercise. Number of services per conception and number of days open were less for exercised cows.

Outcome of asymptomatic infection with rubella virus during pregnancy

We have tried to detect prenatal infection in 34 infants whose mothers were re-infected with rubella virus during pregnancy and in six infants whose mothers had primary subclinical rubella during pregnancy. Two methods of assessment were used: first, serum obtained soon after birth was tested for IgM antibody; secondly, serum obtained after the age of 8 months was tested for specific IgG. The 34 women with re-infections had increases in IgG antibody titre but no IgM response. No evidence of prenatal infection was found in 33 of their 34 infants. One infant was found to have IgG antibody at the age of 11 months. This infant was IgM-negative at birth and had a rubelliform rash at the age of 5 1/2 months; it therefore probably contracted post- rather than pre-natal infection. Fetal infection from maternal re-infection during pregnancy is probably rare. The six women with primary subclinical rubella produced both IgG and IgM classes of antibody. Three of their six infants showed serological evidence of intrauterine infection. One, infected when its mother was 8 weeks pregnant, had clinical evidence of congenital rubella. Primary subclinical rubella during pregnancy therefore carries a significant risk of fetal infection. Because of the difference in outcome, great care should be taken to distinguish between primary infection and re-infection when investigating symptomless increases in antibody titre after contact with rubella during pregnancy.

Long-term results following coronary bypass operation. Importance of preoperative actors and complete revascularization

The initial 102 patients who underwent aorta-coronary bypass grafting between 1969 and 1971 were followed for a mean of 96 months (minimum follow-up 7 years). Preoperative variables predictive of survival at 5 years were stability of angina, previous heart failure, and left ventricular function. Stability of angina, previous heart failure, previous myocardial infarction, and smoking were important predictors of symptomatic status at 5 years. At operation, 62 patients had anatomic or technically complete revascularization, whereas 40 had incomplete revascularization. There was a significantly improved survival rate in those patients who were completely revascularized. The 5 year survival rate was 84% for completely revascularized patients compared to 96% for incompletely revascularized patient (p less than 0.02). This improvement in survival was continued to 9 years. There was also a significant improvement in asymptomatic status of the completely revascularized patients compared to the incompletely revascularized patients. At 2 years, 75% of the completely revascularized subjects were asymptomatic compared to 45% of the incompletely revascularized patients. However, this difference disappeared after 5 years. Thus complete myocardial revascularization is superior to incomplete revascularization in terms of survival and asymptomatic state. Preoperative variables may be useful in predicting postoperative results.

Morphology of regenerated spinal cord in Sternarchus albifrons

The tail of the gymnotid Sternarchus albifrons, including the spinal cord, regenerates following amputation. Regenerated spinal cord shows a rostro-caudal gradient of differentiation. Cross sections of the most distal regenerated cord show radially enlarged ependymal cells, relatively undifferentiated cells, and numerous blood vessels. More anterior sections contain well differentiated electromotor neurons, glial cells, and myelinated axons. The number of electromotor-neuron cell bodies in cross sections of regenerated spinal cord is three to six times the number in nonregenerated cord. Distinct tracts of axons, easily identifiable in normal cord, are not distinguishable in cross sections of regenerated cord. Some reorganization of the spinal cord also appears to take place anterior to the site of transection. Individual electromotor neurons in the regenerated spinal cord have morphologies largely similar to those of normal electrocytes, i.e., cell bodies are rounded, lack dendrites, have synapses characterized by gap junctions with presynaptic axons, and lack an unmyelinated initial segment. The presence of electromotor neurons with normal morphology in regenerated spinal cord correlates with the re-establishment of relatively normal electrocyte axon-Schwann cell relationships in the regenerating electric organ of this sternarchid.

Cell separation by antibody-coupled magnetic microspheres and their application in conjunction with monoclonal HLA-antibodies

The modification and efficiency of a technique for cell separation is described. This technique combines the specificity of serologic reactions with the strength and physical selectivity of a magnetic field. A monoclonal HLA-BW 6 antibody was coupled to 100 nm diameter Fe3O4 containing albumin microspheres via surface-incorporated St. aureus Protein-A. The mixture of HLA-BW 6 and -BW 4 human peripheral blood lymphocytes was incubated with these immunomicropheres and applied to a glass column located in a magnetic field. Only HLA-BW 4 lymphocytes passed through the column and were collected. The recovered cells were 97% viable.

Patterns of antibody reactivity against selected human leukemia cell lines

Absorption procedures which allow the production of a selectively cytotoxic anti-human lymphocyte serum are described. Although the production of a reagent whose reactivity is restricted. Although the production of a reagent whose reactivity is restricted exclusively to lymphocytes may be achieved by exhaustive absorption steps using fresh human erythrocytes, CML cells, and fetal liver cells, a more realistic alternative is the use of appropriately selected cultured human leukemia cell lines. Data are presented which show how these cell lines may be employed to selectively manipulate the cross-reactivity spectrum of ALS. Pre-treatment of donor bone marrow cells prior to transplantation with a selectively lymphocytotoxic ALS has been shown to allow transplantation of bone marrow across major histocompatibility barriers in rodents without the occurrence of GvH reactions, and it is the purpose of the present investigations to show that an analogous anti-human ALS can be prepared which possesses the required degree of selectivity to allow its application for human bone marrow transplantation.

Is it important to preserve the chordae tendinae and papillary muscles during mitral valve replacement?

To evaluate the importance of preserving chordae tendinae and papillary muscles to left ventricular function after mitral valve replacement, 12 dogs had Carpentier-Edwards or Björk-Shiley mitral valves inserted. Cardiopulmonary bypass, systemic hypothermia at 25 degrees C and cold cardioplegia were used. The period of anoxic arrest was 30 minutes. In six dogs, mitral valve replacement was performed after complete excision of the mitral valve. In the other six dogs the anterior leaflet was partially excised but all chordae tendinae and papillary muscles were left intact. Hemodynamic measurements, including left ventricular function following volume loading, were made preoperatively and postoperatively. Left ventricular angiograms were obtained postoperatively in all dogs. Preoperatively there was no significant difference in the left ventricular function curves in the two groups, but postoperatively the curves showed significant differences. In the group with preserved chordae tendinae, left ventricular function improved with volume loading to a left ventricular end-diastolic pressure of 20 mm Hg while in the group with divided chordae tendinae, function improved more slowly and ceased to improve after loading to an end-diastolic pressure of 15 mm Hg. The mean left ventricular ejection fraction following mitral valve replacement with preserved papillary muscles was 0.62 +/- 0.01 and with divided papillary muscles was 0.45 +/- 0.05 (P less than 0.05). The authors conclude that it is important to preserve chordae tendinae and papillary muscles when carrying out mitral valve replacement.

Fetal infection resulting from maternal rubella after the first trimester of pregnancy

We have tried to measure the incidence of prenatal infection in 304 infants whose mothers had had rubella at various times after the first 12 weeks of pregnancy. Two methods of assessment were used: first, serum obtained soon after birth was tested for specific IgM antibody; secondly, serum obtained after the age of eight months was tested for specific IgG. When maternal rubella occurred 12-16 weeks after the last menstrual period specific IgM antibody was detected in 28 out of 50 infants (56%). The proportion fell progressively to 12% after maternal rubella at 24-28 weeks, rose to 19% after rubella at 28-36 weeks and then to 58% when the illness occurred during the last month of pregnancy. In all, IgM antibody was detected in 77 out of 260 infants (29%). The fetus can thus be infected at any time during the second and third trimesters of pregnancy, but the risk varies at different stages.The figures for the prevalence of IgG antibody were greater throughout, because some infants had IgG who had previously lacked specific IgM. After maternal rubella at 12-16 weeks IgG antibody persisted in 22 out of 31 infants (71%). The proportion fell to 28% after rubella at 24-28 weeks and then increased progressively to 94% after rubella during the last month. In all, IgG antibody persisted in 94 out of 190 infants (49%). The true rate of fetal infection probably lies between the rates estimated from the presence of IgM antibody and the subsequent prevalence of IgG.Infants whose mothers had rubella at any time during pregnancy should be examined regularly for possible evidence of damage.

Interaction of Escherichia coli K88 antigen with porcine intestinal brush border membranes

The fimbria-associated Escherichia coli antigen, K88, was purified to homogeneity as determined by polyacrylamide gel electrophoresis and immunodiffusion. This polymeric antigen consists of noncovalently linked subunits, containing little or no carbohydrate, and has a monomeric molecular weight of 23,000. When a binding assay employing differential filtration was used, K88 formed complexes with isolated porcine intestinal brush border membranes. The formation of complexes was inhibited by glycoproteins with terminal N-acetylglucosamine and N-acetylgalactosamine residues and to a lesser extent by free N-acetylhexosamines. These amino sugars may play a role in the interaction of this pathogenic strain of E. coli with the intestinal epithelia of pigs.

Regeneration of spinal electrocyte fibers in Sternarchus albifrons: development of axon-Schwann cell relationships and nodes of Ranvier

The electrocyte fibers in the gymnotid Sternarchus albifrons are highly differentiated myelinated axons which exhibit several types of nodes of Ranvier and characteristically short internode lengths. In the present study, regeneration of the electrocyte fibers following removal of the tail was examined by electron microscopy. By 36 days following extirpation, the regenerating electrocyte axons exhibit Type I nodes of Ranvier, with a normal morphology, and Type II nodes of Ranvier with a large nonmyelinated gap and a polypoid elaboration of the axon surface. Moreover, in the regenerating axons the internode length: diameter ratios are quite small. Thus, relatively normal axons-Schwann cell relations and a relatively normal differentiation of the axon surface are achieved during regeneration of the Sternarchus electrocyte fibers.

The role of host responses in the recovery of mice from Sendai virus infection

The antiviral responses in mice to intranasal inoculation with Sendai virus are described. To investigate the relative importance of the humoral, cell-mediated and interferon responses, the pathogenesis of this infection was studied in animals which were immunocompetent, T cell-deprived or immunosuppressed with cyclophosphamide. Treatment with cyclophosphamide converted the mild, self-limiting infection observed in immunocompetent mice into a severe and frequently lethal pneumonic disease. This was associated with an enhanced interferon response but no detectable antibody or cell-mediated immune response. T cell-deprived mice suffer an infection of intermediate severity associated with an increased interferon response, a normal humoral immune response and no cell-mediated immune response. The implications of these results in relation to the role of the antiviral responses in recovery from Sendai virus infection are discussed.

Effect of catabolite repression on chemotaxis in Salmonella typhimurium

The chemotaxis of Salmonella typhimurium LT2-ST1, grown with different sole carbon sources toward ribose, allose, serine, aspartate, and glucose, was examined. Maximum chemotaxis toward serine, aspartate, and glucose were unchanged with either glucose or citrate as the carbon source. The height of the peak in the ribose response curve was 25% of a standard serine response when the bacteria were grown on citrate. However, when the bacteria were grown on glucose, the ribose response was 1% of the serine standard, and when on glycerol, 5%. Chemotaxis toward allose, a competitive inhibitor of ribose chemotaxis, was similarly affected. The amount of ribose binding protein, the receptor for ribose chemotaxis, was determined in bacteria grown on citrate, glucose, or glycerol. The amount of ribose-binding protein released from cells grown on glucose or glycerol was appreciably less than the amount released from cells grown on citrate. These data suggest that the observed effect on ribose chemotaxis is due to catabolite repression of ribose-binding protein and another component of the chemotactic system.

Comparison of immunofluorescence and radioimmunoassay for detecting IgM antibody in infants with the congenital rubella syndrome

Immunofluorescence (IF) and radioimmunoassay (RIA) have been compared as methods for detecting IgM antibody in 124 infants with confirmed or suspected congenital rubella. IF was used to test sucrose density gradient fractions and RIA to test fractions and whole serum. When fractions were tested IF and RIA were equally specific and distinguished clearly between IgM and IgG, but RIA was the more sensitive method. The RIA titre in whole serum was always greater than in the peak IgM fraction and there was no evidence that testing the serum, rather than the fraction, could result in failure to detect IgM. With some sera RIA gave low titres which became negative after absorption with IgG-coated latex beads. The mechanism of this 'false positive' effect, which may have been due to IgM with anti-IgG activity, was not investigated, but if it can be removed by absorption it need not reduce the specificity of the test. During the first 6 months of life IgM antibody was detected by RIA in 30 out of 32 unfractionated sera and by IF in fractions from 28 of these. After the age of 6 months IgM was found progressively less frequently and the greater sensitivity of RIA became a more obvious advantage: 17 out of 60 specimens were positive by RIA and 11 of these were negative by IF. RIA testing of whole serum appears to be an economical, specific and sensitive method for detecting IgM antibody in congenital rubella, of particular value when the titre of antibody is low.

Competency: the what, why, and how of it

Competency is a frequently used term in the physical therapy profession, but many physical therapists are unclear about its definition and its meaning in professional activity. This article describes the operational definition of competency as used in the practice of physical therapy by members of the Association; describes the development of the manual, Competencies in Physical Therapy: An Analysis of Practice; offers direction in possible uses of the manual; and suggests future uses for the manual in Association activity.

The nature of the effector cells of cell-mediated immune responses to Sendai and Kunz virus infections in mice

The development of virus-specific cell-mediated immune (CMI) responses to Sendai and Kunz virus infections of the respiratory tract of mice is described. In addition a heterotypic cell-mediated immune response develops during each of the virus infections. Cell depletion studies indicate that the effector cells of the virus-specific CMI responses are theta antigen bearing T lymphocytes. Similar studies of the heterotypic responses suggest that 2 cell types are involved, T lymphocytes and NK cells.

Falciparum malaria and pregnancy

During pregnancy an increase occurs in the prevalence and density of Plasmodium falciparum malaria. The increase relative to non-pregnant women remains fairly constant with age though there is an over-all decrease in prevalence and density in both groups with age. The increase is at a height relatively early in pregnancy and declines after mid-term. At the height of the malaria season in The Gambia less antimalarial antibody appears in cord bloods than in the early dry season when transmission is lower. Infants show an increase in malaria prevalence and density in the early dry season as compared to the mid-wet season while the remainder of the population shows a decrease.

Automated tests for the assessment of thyroid function

Fully automated methods have been developed for the determination of thyroxine and triiodothyronine levels, antibodies to thyroglobulin and the assessment of thyroid hormone binding proteins in serum, using a continuous flow radioimmunoassay system. In addition the feasibility of a partially automated assay for thyrotrophin levels has been demonstrated. These employ Auto Analyzer modules and antibodies covalently linked to a magnetisable solid phase support. Separation of bound and free antigen is achieved by applying an external magnetic field. The system currently operates at a rate of 30 samples/h and requires only 10 minutes incubation since it is not necessary to reach equilibrium. The results are similar to those obtained by conventional manual techniques, however the precision is improved and operator error eliminated.

Diarrhea and colitis in clindamycin-treated surgical patients

Responding to reports that diarrhea and pseudomenbranous colitis occurred relatively frequently among patients who received clindamycin, we initiated a program of surveillance in clindamycin-treated patients, including direct examination of the colon mucosa for inflammation or pseudomembranes and a patient follow-up by a nurse-epidemiologist. Observation of 145 patients having 161 consecutive clindamycin treatment episodes determined that unexplained diarrhea (two or more stools per day) occurred in 30 patients (21%), and more severe diarrhea (five or more stools per day) occurred in 12 patients (8%). Colitis was not identified at all. The absence of pseudomembranes was confirmed by direct examination of colon mucosa in 114 patients. Development of disabling diarrhea or colitis in association with clindamycin therapy is not a universal phenomenon.

Innate cytotoxicity of CBA mouse spleen cells to Sendai virus-infected L cells

The presence in the spleens of unsensitized CBA mice of cells that are spontaneously cytotoxic for Sendai virus-infected L cells was confirmed. This innate cytotoxic activity to virus-infected cells was shown to exhibit some H-2 restriction. Partial identity of only the D end of the H-2 gene complex between the target and effector cells was required to produce cytolysis. Attempts to characterize the kind of cell active in this system indicated that neither the theta antigen nor the surface immunoglobulin markers were present. Furthermore, the cells appeared to have no adherent or phagocytic properties. The relationship between the effector cells responsible for innate cytotoxicity to virus-infected cells and the natural killer (NK) cells spontaneously cytotoxic for certain tumor cells is discussed.

Effects of innervation on the distribution of acetylcholine receptors on cultured muscle cells

1. Myotomal muscle cells from embryos of Xenopus laevis were cultured as a monolayer either alone or together with neural tube cells from the same embryos. 2. Spontaneous twitching and contractions evoked by electrical stimulation of neural perikarya were observed only in nerve-contacted muscle cells, and could be abolished by curare or alpha-bungarotoxin. 3. Within 2 days in culture muscle cells not contacted by nerve developed one or more discrete patches of acetylcholine (ACh) receptors as revealed by staining with fluorescent conjugates of alpha-bungarotoxin. Similar patches were also seen when staining was carried out after paraformaldehyde fixation, suggesting that they were not induced by the dyetoxin conjugate. 4. Radioautography after labelling with [125I]alpha-bungarotoxin revealed patches with grain densities approximately twenty-five-old greater than over the remainder of the cell. 5. Fluorescent stain on innervated cells was restricted to the path of nerve-muscle contact and sometimes extended for greater lengths than the largest patches seen on non-contacted muscle cells. 6. Similar long bands of stain associated with nerve--muscle contacts were observed when cultures were grown in high concentrations of curare and carbachol which prevented spontaneous twitching. They were also seen in cultures in which the addition of neural tube cells was delayed for 2-3 days. 7. It is concluded that innervation caused receptors to accumulate at sites of nerve-muscle contact and that this process can operate independently of muscle activity.

Facility for exercising dairy cows

That dairy cows housed in confinement might benefit if they were exercised during the dry period prompted development of a facility for exercising dairy cows. Two methhods of the exerciser, which consist of a circular lane and a driving mechanism powered by a variable speed electric motor, are described. A speed of 3.5 k, per h provides a steady but comfortable pace for pregnant dairy cows and heifers. Many animals refused to go at speeds greater than 5.5 km per h.

Nerve-induced and spontaneous redistribution of acetylcholine receptors on cultured muscle cells

1. Theree-day-old cultures of myotomal muscle, obtained from embryos of Xenopus laevis, were stained with fluorescent conjugates of alpha-bungarotoxin and maintained in native toxin in order to ensure that ACh receptors subsequently inserted into the sarcolemma would not be stained. Neural tube cells were then added to the cultures. 2. When cultures were exmained 1-3 days later fluorescent stain was found to be associated with sites of nerve-muscle contact. In some cases the stain along the path of contact extended for greater distances than the patches of stain seen on non-contacted muscle cells. 3. The development of new areas of fluorescent stain at sites of nerve-muscle contact was confirmed by making successive observations on the same muscle cells over a period of a day. 4. Similar experiments on muscle cells not contacted by nerve revealed the formation of new receptor patches, usually in areas of cell growth. 5. The majority of fluorescent pathes on non-contacted muscle cells did not undergo changes in size or shape over the course of 1-2 days. However some examples of enlargement, shrinkage and disappearance were observed. 6. On the basis of these findings it is concluded that ACh receptors aggregate within the sarcolemma, spontaneously as well as in response to innervation. In the latter case extrajunctional receptors accumulate at the site of nerve contact thereby contributing to the development of high receptor density in the subneural muscle membrane. This process of receptors redistribution occurs in the absence of synaptic or contractile activity. 7. Possible mechanisms involved in the redistribution of ACh receptors are discussed in relation to those which appear to modulate ligand-induced changes in the distribution of lectin and immunoglobulin receptors.

Cell mediated immunity in experimental influenza and parainfluenza infection

Cell mediated immunity (CMI) to Sendai and Kunz viruses, determined by a 51Cr release assay of cytotoxicity, has been shown to develop during the course of these infections. This virus specific response is mediated by sensitised T cells, and takes place against a background of innate cell mediated immunity. The mediator of this innate cytotoxicity exhibits none of the characteristics of T, B or K cells, but bears close resemblance to the NK cell which is spontaneously cytotoxic for certain tumour cells. Removal of the virus specific CMI by T cell depletion produces a moderate immunosuppressive effect. The nature of this effect and the role of CMI in these infections are discussed.

Denervated skeletal muscle fibers develop discrete patches of high acetylcholine receptor density

Denervated skeletal muscle fibers of mice develop discrete patches of high acetylcholine receptor density. The patches vary in size from less than 1 micrometer up to 30 micrometers, depending on the muscle and the period of denervation. Within the patches the acetylcholine receptor density is some 20 times greater than elsewhere along the muscle fiber and probably approaches that in the subsynaptic membrane.

Stromal invasion of cancer in pedunculated adenomatous colorectal polyps: significance for surgical management

Fifty-three patients were treated for pedunculated adenomatous polyps that contained foci of invasive cancer confined to the stroma. This entity is a stage of malignant involvement intermediate between in situ carcinoma and frank infiltrative cancer that invades the muscularis mucosae. Metastases to regional lymphatics were not observed. Local removal of such lesions without regional lymphadenectomy is adequate treatment.

Cell-mediated immunity to Sendai virus infection in mice

The development of a cell-mediated immune response to Sendai virus infection in mice was examined by the use of a 51Cr release assay of cytotoxicity. A low level of "background cytotoxicity" to Sendai virus-infected L cells was found in the spleens of uninfected CBA mice. Spleen cells from Sendai-infected mice showed an elevated level of cytotoxicity against these target cells for a period of 5 weeks, commencing 4 days after infection of the mice. A more transient response was observed in the spleens of mice infected with a serologically distinct virus, the Kunz strain of influenza. This cross-reacting, cell-mediated immune response was intermediate between that observed in unsensitized and Sendai-sensitized spleen cells. The relevance of these cell-mediated immune responses to respiratory tract virus infections is discussed.

Intraoperative fiberoptic colonoscopy--"the difficult polypectomy"

An alternative to transcolonic polypectomy, transabdominally directed, transanal colonoscopic polypectomy, for patients who require polyp removal but in whose cases standard colonoscopic approach has failed is presented. The early results are excellent, and the method also can be applied to other patients who have colonic polyps who undergo procedures such as hysterectomy and cholecystectomy.