Chloramphenicol induces the transcription of the major cold shock gene of Escherichia coli, cspA

A downshift in temperature or exposure of cells to certain inhibitors of translation has been shown to induce the synthesis of cold shock proteins in Escherichia coli. We characterized the induction of the major cold shock protein (CS7.4, the product of the cspA gene) of E. coli in response to a shift from 37 to 15 degrees C and in response to the addition of chloramphenicol at 15 degrees C. A pulse-labeling assay and primer extension experiments indicated that the cold shock treatment resulted in a transient increase in the level of the cspA transcript and a transient induction of CS7.4, while the addition of chloramphenicol resulted in a constitutive increase in the level of cspA transcript and constitutive production of CS7.4. The addition of rifamycin immediately following the temperature downshift or along with the addition of chloramphenicol repressed the transcription of cspA as well as the induced production of CS7.4. Furthermore, changes in the cspA mRNA level were coincident with changes in CS7.4 synthesis. These results indicate that the expression of cspA induced by cold shock and chloramphenicol is at the level of transcription but not at the level of translation. Measurement of the half-life revealed that the cspA mRNA induced by chloramphenicol was more stable than that induced by cold shock.

Relation of cardiovascular responses to mental stress and cardiac vagal activity in coronary artery disease

Forty-six patients with documented coronary artery disease were studied to examine the relation of cardiovascular reactivity to mental stress and cardiac vagal activity. Cardiac vagal activity was measured by means of frequency-domain analysis of heart rate variability with 48-hour out-of-hospital Holter monitoring. The amplitude of the high-frequency component (0.16 to 0.40 Hz) of heart rate variability is considered to be an index of cardiac vagal activity. Cardiovascular reactivity was measured in the laboratory during a 3-minute public speaking task. Results revealed that (1) the amplitude of the high-frequency component was significantly higher during sleep (24.6 +/- 11.3 ms) than during waking (18.2 +/- 8.0 ms) (p = 0.002); (2) compared to subjects with low diastolic blood pressure reactivity, those who displayed high diastolic blood pressure reactivity exhibited a significantly lower amplitude of the high-frequency component (19.2 +/- 6.9 vs 23.4 +/- 9.6 ms, p = 0.03). These results indicate that decreased cardiac vagal activity may contribute to the exaggerated diastolic blood pressure reactivity to mental stress in patients with coronary artery disease.

An essential yeast protein, CBF5p, binds in vitro to centromeres and microtubules

Yeast centromere DNA (CEN) affinity column chromatography has been used to purify several putative centromere and kinetochore proteins from yeast chromatin extracts. The single yeast gene (CBF5) specifying one of the major low-affinity centromere-binding proteins (p64'/CBF5p) has been cloned and shown to be essential for viability of Saccharomyces cerevisiae. CBF5 specifies a 55-kDa highly charged protein that contains a repeating KKD/E sequence domain near the C terminus, similar to known microtubule-binding domains in microtubule-associated proteins 1A and 1B, CBF5p, obtained by overexpression in bacterial cells, binds microtubules in vitro, whereas C-terminal deleted proteins lacking the (KKD/E)n domain do not. Dividing yeast cells containing a C-terminal truncated CBF5 gene, producing CBF5p containing only three copies of the KKD/E repeat, delay with replicated genomes at the G2/M phase of the cell cycle, while depletion of CBF5p arrests most cells in G1/S. Overproduction of CBF5p in S. cerevisiae complements a temperature sensitivity mutation in the gene (CBF2) specifying the 110-kDa subunit of the high-affinity CEN DNA-binding factor CBF3, suggesting in vivo interaction of CBF5p and CBF3. A second low-affinity centromere-binding factor has been identified as topoisomerase II.

Tissue-specific expression and chromosomal localization of the alpha subunit of mouse meprin A

Meprins, membrane-bound oligomeric metalloendopeptidases, contain alpha and/or beta subunits. Their activities have been found in the mouse and rat kidney. The cloned cDNA for the mouse alpha subunit of meprin A (EC cloned cDNA for the mouse alpha subunit of meprin A (EC 3.4.24.18) was used here to survey mRNA expression in kidney of different mouse strains and in various tissues of mice and rats. A single message of 3.6 kilobases was found in kidney of random bred (ICR) and inbred mice (C57BL/6, DBA/2) that contain high meprin A activity and in Sprague-Dawley rat kidney. The alpha subunit message was undetectable in the kidney of C3H/He and CBA mice, inbred strains that do not express meprin A activity. Therefore, meprin A activity in the kidney of mouse strains correlates with the amount of alpha subunit mRNA present. The 3.6-kilobase mRNA meprin alpha subunit message was also detected in the small intestine of the rat but not in mice. No message was detected in brain, heart, skeletal muscle, liver, lung, or spleen of mice or rats. Polymerase chain reaction amplification or Southern blot analysis of genomic DNA revealed that the gene for the alpha subunit is present in all mouse strains as well as in human, monkey, rat, mouse, dog, cow, rabbit, and chicken, but it was not detected in yeast. There is one gene copy present in the mouse genome. The gene was localized to mouse chromosome 17 centromeric to the major histocompatibility complex (H-2) by the interspecific backcrossing method. The localization of this allele to Mep-1, the gene previously found to regulate the expression of meprin A activity in mice, supports the proposal that Mep-1 is the structural gene for the alpha subunit.

Kinetics of binding and hydrolysis of a series of nucleoside triphosphates by actomyosin-S1. Relationship between solution rate constants and properties of muscle fibers

We have measured the steady state kinetics of hydrolysis and presteady state kinetics of binding of the nucleoside triphosphate GTP, CTP, aza-ATP (1-N6-etheno-2-aza-ATP), and ATP by rabbit skeletal actomyosin-S1. The maximum rates of steady state hydrolysis at 10 degrees C at low ionic strength are: CTP, 1.9 s-1 > ATP, 1.3 s-1 > aza-ATP, 0.19 s-1 > GTP, 0.03 s-1. A similar dependence of the rate of steady state hydrolysis upon nucleotide structure has been observed in isometrically contracting muscle fibers in the accompanying paper (Pate, E., Franks-Skiba, K., White, H., and Cooke, R. (1993) J. Biol. Chem. 268, 10046-10053) which strongly suggests that the same biochemical step that limits the maximum rate of hydrolysis of nucleoside triphosphates by actomyosin-S1 in solution also limits the rate of hydrolysis by isometrically contracting muscle fibers. The apparent second order rate constants for the dissociation of actomyosin-S1 by nucleoside triphosphates at 10 degrees C are: ATP, 2.7 x 10(6) M-1 s-1 > aza-ATP, 3.4 x 10(5) M-1 s-1 > GTP, 2.5 x 10(5) M-1 s-1 > CTP, 1.4 x 10(5) M-1 s-1. There is an excellent correlation between the second order rate constant for the dissociation of actomyosin-S1 in solution and the dependence of shortening velocity in glycerinated muscle fibers upon the concentration for ATP, aza-ATP, and CTP (as per accompanying article; Pate et al., 1993). We have used the second order rate constants obtained in solution for the dissociation of actomyosin-S1 by these nucleotides and shortening velocity data obtained with the same nucleoside triphosphates in glycerinated psoas fibers in the accompanying article (Pate et al., 1993) to determine the average distance over which cross-bridges remain attached during unloaded shortening to be 5-12 nm.

Isolation and characterization of a gene (CBF2) specifying a protein component of the budding yeast kinetochore

We have cloned and determined the nucleotide sequence of the gene (CBF2) specifying the large (110 kD) subunit of the 240-kD multisubunit yeast centromere binding factor CBF3, which binds selectively in vitro to yeast centromere DNA and contains a minus end-directed microtubule motor activity. The deduced amino acid sequence of CBF2p shows no sequence homologies with known molecular motors, although a consensus nucleotide binding site is present. The CBF2 gene is essential for viability of yeast and is identical to NDC10, in which a conditional mutation leads to a defect in chromosome segregation (Goh, P.-Y., and J. V. Kilmartin, in this issue of The Journal of Cell Biology). The combined in vitro and in vivo evidence indicate that CBF2p is a key component of the budding yeast kinetochore.

Effects of aluminium ion on root growth, cell division, and nucleoli of garlic (Allium sativum L.)

The effects of different concentrations of aluminium chloride on root growth, cell division, chromosome morphology and nucleoli in root tip cells of garlic (Allium sativum L.) were studied. The concentrations of aluminium chloride (AlCl(3)) used were 10(-5), 10(-4), 10(-3), 10(-2) and 10(-1) m. Aluminium chloride inhibited root growth and caused mitotic irregularities, including c-mitosis, anaphase bridges, and chromosome stickiness. Nucleolar material was extruded from the nucleus into the cytoplasm. Extrusion was observed in inner root meristem and root cap cells. The poisoning by Al(3+) of the root tip cells of Allium sativum may result from the uptake and accumulation of Al and inhibition of Ca uptake, distribution of physiological activities of calmodulin (CaM) and the inhibition of some enzyme reactions.

Correlation of p53 mutations with epidermal growth factor receptor overexpression and absence of mdm2 amplification in human esophageal carcinomas

Esophageal carcinomas from 24 patients, most of whom were smokers and consumed alcoholic beverages daily, were analyzed for mutations in exons 5-8 of the p53 tumor suppressor gene. Mutations were identified by polymerase chain reaction amplification and direct sequencing in 12 of 24 (50%) of the samples; almost half of the mutations were at A:T base pairs. Nuclear accumulation of p53 protein, determined by immunohistochemistry with the CM-1 polyclonal antibody, was observed in all cases in which a missense mutation in the p53 gene was detected. None of the 24 carcinomas had amplification of the mdm2 gene, an alternate pathway to p53 loss of function. Alterations involving three other cancer-related genes associated with human esophageal carcinogenesis, c-erbB-1/epidermal growth factor receptor (EGFR), c-myc, and retinoblastoma (Rb), were examined by Southern blot or immunohistochemical analysis in the same sample set to explore the possibility of a link between oncogene activation and loss of tumor suppressor function. While no associations were observed between amplification of the c-myc or EGFR genes and p53 abnormalities, a significant correlation (P < 0.01) was seen between the presence of p53 mutation and EGFR overexpression. Absence of Rb protein, measured immunohistochemically, was observed in four tumors, none of which had aberrations of the p53 gene.

Isolation and characterization of a highly malignant variant of the SW480 human colon cancer cell line

We found that the human colon cancer cell line SW480 consists of two distinct subpopulations which we have designated E-type (epithelial) and R-type (round). Pure cultures of each type were obtained by subcloning, and both have maintained their characteristic phenotypes for at least 1 year (40 passages). E-type cells are the major (> 98%) type in the parental SW480 cell line. They form flat epithelial-like colonies. In contrast, R-type cells, which constitute a minor fraction (< 2%) of the parental cell line, have a rounded shape and grow in clusters of piled-up cells. Compared to E-type cells or the parental SW480 cells, isolated R-type cells display decreased doubling time, loss of contact inhibition, less adhesiveness to culture plates, higher anchorage-independent growth in soft agar, and a much more aneuploid karyotype. When injected s.c. into nude mice, R-type cells produce much larger tumors within the same period of time than E-type cells, and the tumors are less differentiated than those produced by the E-type cells. Cell fusion experiments between R-type and E-type cells revealed that the R-type phenotype is dominant, and the results suggest that this is due to one or a few genetic changes. Taken together, these findings suggest that the R-type cells represent a more malignant variant of the E-type cells. They may be useful, therefore, for studying mechanisms involved in tumor progression.

Families of metalloendopeptidases and their relationships

Crystal structures available for four metalloendopeptidases have revealed zinc ligands for these enzymes. New sequence information has made it possible to compare the primary structures of the zinc-binding site in metalloendopeptidases. A scheme based on the zinc-binding site is proposed to classify metalloendopeptidases into five distinct families: thermolysin, astacin, serratia, matrixin, and snake venom metalloproteinases. Two histidines and one glutamate are zinc-ligands in the thermolysin family. Three histidines and one tyrosine are zinc ligands in the other four families, which are further distinguished by the identity of the residue following the third histidine and by the environment surrounding the tyrosine.

The 93-kilodalton protein of Borrelia burgdorferi: an immunodominant protoplasmic cylinder antigen

Using immunoblots, we identified proteins of Borrelia burgdorferi recognized by sera from 62 patients with either acute or chronic Lyme disease. In all groups studied, the 41-kDa flagellar protein and a relatively minor 93-kDa protein (p93) were the most commonly recognized antigens in patients with acute and chronic disease due to B. burgdorferi. A murine monoclonal antibody (MAb 181.1) was developed against p93, and the antigen was detected by immunoblot analysis in four European and American strains of B. burgdorferi. On two-dimensional gel electrophoresis, p93 had an apparent pI of 6.8. Immunoelectronmicroscopy with MAb 181.1 demonstrated that p93 is located within the protoplasmic cylinder compartment of the organism. The gene encoding p93 was retrieved from a phage expression library. The derived amino acid sequence of p93 confirmed chemical characterization of the antigen, including its amino-terminal peptide sequence. The derived amino acid sequence predicted it to be predominantly alpha helical. A prominent antigenic domain located at the carboxy portion of the protein was recognized by human and rabbit polyclonal antisera and human (MAb D4) and mouse (MAb 181.1) MAbs.

Neutrophil priming by hepatocyte growth factor, a novel cytokine

We demonstrate here that the recently defined cytokine hepatocyte growth factor (HGF) 'primes' human neutrophils. Recombinant human HGF over the concentration range 0.1-20 ng/ml increased the neutrophil response to f-met-leu-phe by up to 200%, and required only a short preincubation, 10 min producing the maximum effect. Priming was independent of changes in cytosolic-free calcium homeostasis. We conclude that HGF may be a physiologically important cytokine with 'priming' activity for neutrophils.

Entrainment of the locomotor rhythm by group Ib afferents from ankle extensor muscles in spinal cats

1. Previous studies have concluded that the timing of the locomotor rhythm can be strongly influenced by input from group Ib afferents from leg extensor muscles (Duysens and Pearson 1980; Conway et al. 1987). The main objective of the present study was to obtain additional evidence for this conclusion by examining the characteristics of entrainment of the locomotor rhythm by rhythmic stimulation of group I afferents and by rhythmic force pulses in the ankle extensor muscles. 2. A reduced, non-immobilized preparation was developed in spinal cats that allowed isometric contractions of ankle extensor muscles to be elicited by ventral root stimulation during the expression of locomotor activity. The same preparation was used to examine the influence of electrically stimulating group I afferents from the ankle extensors and the effect of rhythmically stretching these muscles. The locomotor rhythm was initiated by sustained mechanical stimulation of the perineum following the administration of Clonidine and, in some preparations, Naloxone. 3. The timing of the onset of flexor burst activity was examined during entrainment with saw-tooth and ramp-and-hold stretches of the ankle extensor muscles. Flexor bursts were initiated about 200 ms following the release from the stretch, and this latency was independent of the entrainment frequency. 4. The locomotor rhythm was readily entrained by rhythmic contractions of the ankle extensor muscles produced by ventral root stimulation provided the magnitude of the contractions was greater than about 10N. Repetitive stimulation of group I muscle afferents from the ankle extensors also entrained the locomotor rhythm, with the timing of motor activity being similar to that during entrainment with rhythmic muscle contractions. Burst activity in the ipsilateral extensors was coincident with the stimulus trains in both cases. This similarity argues for entrainment being produced mainly by input from group Ib afferents. 5. The functional implication of the results of this and previous studies is that input from group Ib afferents during the stance phase of walking acts to inhibit generation of flexor burst activity and to promote extensor activity. The proposal that a decline in Ib activity near the end of the stance phase is involved in regulating the stance to swing transition is discussed.

Mapping the major antigenic domains of the native flagellar antigen of Borrelia burgdorferi

Purified flagellar protein (p41) of Borrelia burgdorferi (strain B31) was subjected to chemical cleavage with hydroxylamine or proteolysis with V8 protease, endoproteinase Asp-N, or alpha-chymotrypsin. The resulting polypeptides were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and their positions in the published DNA sequence of the p41 protein were determined by amino-terminal sequencing and amino acid analysis. Epitope specificities of antibody binding by a monoclonal antibody raised by immunization of mice with purified flagella and pooled sera from patients with multiple erythema migrans, late Lyme borreliosis, or secondary syphilis were analyzed by Western blots (immunoblots) of peptides transferred to Immobilon polyvinylidene difluoride filters. The major epitope binding one murine monoclonal antibody (158) was localized to a carboxy-terminal domain that includes residues 300 to 336. The dominant epitopes binding human polyclonal antibodies are in the central portion of the molecule (residues 182 to 218) that is not conserved compared with other bacterial flagellins. Additional reactive epitopes were identified in the amino-terminal domain of the protein. Sera from patients with syphilis bound strongly to the amino-terminal conserved domain, providing a structural basis for cross-reactivity seen in standard enzyme-linked immunosorbent assays, but not to the central part of the molecule. Specific and cross-reactive antigenic determinants need to be considered in the design of improved immunodiagnostics for spirochetal diseases.

Analysis and expression of the Borrelia burgdorferi P/Gau fla gene: identification of heterogeneity with the B31 strain

The flagellin gene from the P/Gau strain of Borrelia burgdorferi was cloned and sequenced. The translated P/Gau flagellin protein differed from the flagellin of the B31 strain at 13 of 336 amino acids. This includes seven differences between amino acids 190-234, an immunodominant and specific region for B. burgdorferi. The entire flagellin molecule, as well as peptides of the internal portion of the protein which is more specific for B. burgdorferi, has been expressed in Escherichia coli using a pET7HIS.2 expression system. These peptides may be of great value for the development of sensitive and specific recombinant-based serological assays.

Amplification and expression of the human cyclin D gene in esophageal cancer

Amplification of the hst-1 and int-2 genes on chromosome 11q13 has previously been found in over 20% of human primary esophageal cancers. However, these two genes do not appear to be transcribed in appreciable amounts. Recently, the human cyclin D gene (also referred to as prad1) has been mapped to the 11q13 locus. Here, we report coamplification of the cyclin D and hst-1 genes in 5 of 20 (25%) human squamous esophageal tumors. We also detected significant levels of cyclin D transcription in two esophageal carcinoma cell lines, even though they did not express detectable amounts of hst-1 transcription. These findings provide the first evidence for the amplification of a cyclin gene in human esophageal cancer and suggest that an increase in cyclin D gene dosage could be an important factor in the pathogenesis of esophageal cancer. Additionally, because the 11q13 locus is found to be amplified in many types of human tumors, cyclin gene amplification could also play an important role in the development of other forms of human cancer.

The alpha subunit of meprin A. Molecular cloning and sequencing, differential expression in inbred mouse strains, and evidence for divergent evolution of the alpha and beta subunits

Meprin A, a membrane-bound oligomeric metalloendopeptidase, contains two different subunits, alpha and beta. We report here the cloning and sequencing of the alpha subunit cDNA. The translated polypeptide consists of 760 amino acids, including a preprosequence (77 amino acids) that precedes the NH2 terminus of the purified enzyme. The next 198 amino acids constitute the "astacin family" protease domain, which includes the astacin family signature sequence, HE(L,I)XHXXGFXHE(Q,H)XRXDRDX(Y,H)(V,I)X(I,V). An immunoglobulin/major histocompatibility complex protein signature was found at the end of the protease domain. At the COOH terminus of the alpha subunit, there is an epidermal growth factor-like domain, followed by a transmembrane domain, and six additional amino acids. Ten potential glycosylation sites have been identified, and at least three of those sites are glycosylated. Northern blot analyses of kidney tissue from C57BL/6 and C3H/He mice indicate that variations in meprin A activity in these strains reflect differences in the levels of the alpha subunit mRNA. Several internal peptide sequences obtained from the beta subunit indicate that it is approximately 50% identical to the alpha subunit. Furthermore, NH2-terminal sequence analyses (39 residues) indicate that rat and mouse alpha are 79% identical, rat and mouse beta are 74% identical, and that alpha and beta subunits for both species are 47% identical. These data indicate that alpha and beta are closely related products of divergent evolution.

The use of naloxone to facilitate the generation of the locomotor rhythm in spinal cats

The locomotor rhythm evoked by perineal stimulation in clonidine-treated acute and chronic spinal cats can be produced more easily when the opioid receptor antagonist naloxone is also administered. Naloxone increases the frequency of the locomotor rhythm and decreases the intensity of skin stimulation required for evoking the rhythm. A useful property of naloxone is that it can restore the locomotor rhythm when the rhythm wanes, thus prolonging the time period over which locomotor activity can be generated. Administration of naloxone without clonidine does not enable the locomotor rhythm to be generated by skin stimulation, but it does reduce the concentration of clonidine required for the expression of a robust rhythm and may increase the chance of a successful preparation. We conclude that naloxone is a useful pharmacological tool for studies on the locomotor pattern generator.

Alkali-Activated Fly Ash-Slag Cement Based Nuclear Waste Forms

This paper is based on the results of an in-progress research project on Alkali-Activated Cement System at MRL. The objective of this research is to establish the potential for large volume use of fly ash and slag as main components of the cement system. Alkali-activated Fly ash-slag Cement (AFC) was studied as a matrix for immobilization of nuclear waste. AFC is characterized by high early strength, high ultimate strength, low porosity, lower solubilities of the hydrates, and high resistance to chemical corrosion as well as to freezing and thawing. All these advanced properties are particularly favorable to the immobilization the nuclear wastes.

Collision-induced pulse shortening in a mode-locked linear-cavity NaCl color-center laser with an InGaAs/InP multiple-quantum-well saturable absorber

We report collision-induced reduction of pulse widths in a linear-cavity passively mode-locked NaCl color-center laser. Colliding-pulse operation reduced the pulse widths from 800 to 430 fs. Pulses collided in the InGaAs/InP multiple-quantum-well saturable absorber if the round-trip time from the absorber to the output coupler was less than 1.3 ns, which implies carrier recombination times of that order. Measurements of the gain experienced by two successive pulses indicated partial saturation of the NaCl gain medium.

DNA binding of CPF1 is required for optimal centromere function but not for maintaining methionine prototrophy in yeast

The centromere and promoter factor 1 (CPF1) binds specifically in vitro and in vivo to an octanucleotide (RTCACRTG). This sequence is found in the centromere DNA element I (CDEI) of yeast centromeres and upstream from a number of transcription units including MET25, GAL2 and TRP1. Inactivation of the CPF1 gene results in three phenotypes; slow growth, a partial loss of centromere function and methionine auxotrophy. These phenotypes correlate well with the known binding sites for CPF1 and have led to the suggestion that CPF1 functions as a kinetochore protein at centromeres and as a transcriptional activator at promoters such as MET25. By analysing transcription from the MET25, GAL2, and TRP1 genes in cpf1 strains, we demonstrate that CPF1 plays no direct role in their transcriptional regulation. Further evidence in support of this comes from the analysis of point mutations in the basic region of CPF1 that affect DNA binding. A strain expressing a non-DNA bound form of CPF1 is phenotypically Met+, shows normal growth rate but has sub-optimal centromere function. We conclude that a DNA-bound form of CPF1 is required for the kinetochore function but not for maintaining methionine prototrophy.

Rapid and sensitive nonradioactive detection of mutant K-ras genes via 'enriched' PCR amplification

We have developed a rapid and highly sensitive nonradioactive method for the detection of a mutant codon 12 human c-K-ras allele in the presence of as many as 10(4) copies of the wild type codon 12 allele. This sensitivity is achieved by selective polymerase chain reaction (PCR) amplification of mutant K-ras gene sequences employing a two stage procedure. The first stage entails the amplification of both K-ras mutant and wild type codon 12 sequences, followed by a selective restriction enzyme digestion of only wild type sequences. The second stage involves a subsequent amplification of undigested amplified fragments, enriched in mutant codon 12 sequences. These products are subject to restriction length polymorphism analysis for the detection of point mutations at codon 12. This technique is rapid, nonradioactive, and eliminates the need for either oligonucleotide hybridization or DNA sequencing. Variations of this selective amplification procedure may prove promising for the detection of specific point mutations in heterogenous cell populations.

Immunologic and structural characterization of the dominant 66- to 73-kDa antigens of Borrelia burgdorferi

The 66- to 73-kDa proteins of Borrelia burgdorferi are dominant immunogens and expressed in all strains of B. burgdorferi. The humoral response to these Ag occurs relatively early during the course of infection. Two-dimensional Western blot analysis of this group of Ag revealed them to consist of a tetrad of proteins with apparent molecular mass of 66, 68, 71, and 73 kDa. Furthermore, in this study we demonstrate the 66-kDa protein to be a potent inducer of lymphoproliferation in the patient immune to B. burgdorferi. Monospecific polyclonal antibodies and mAb demonstrate that each of these proteins was immunologically distinct. However, direct amino acid sequence of the 66- and 68-kDa Ag was almost identical and had a high level of sequence similarity to the GroEL heat-shock protein (Hsp60) of Escherichia coli and the 60-kDa immunodominant protein of Treponema pallidum. The amino terminal sequence of the 71- and 73-kDa proteins of B. burgdorferi was almost identical and these proteins had remarkable sequence similarity to the DnaK heat-shock protein of E. coli (Hsp70). It appears likely, therefore, that proteins related to the heat-shock family are potent immunogens of B. burgdorferi.

Immunologic and structural characterization of the dominant 66- to 73-kDa antigens of Borrelia burgdorferi

The 66- to 73-kDa proteins of Borrelia burgdorferi are dominant immunogens and expressed in all strains of B. burgdorferi. The humoral response to these Ag occurs relatively early during the course of infection. Two-dimensional Western blot analysis of this group of Ag revealed them to consist of a tetrad of proteins with apparent molecular mass of 66, 68, 71, and 73 kDa. Furthermore, in this study we demonstrate the 66-kDa protein to be a potent inducer of lymphoproliferation in the patient immune to B. burgdorferi. Monospecific polyclonal antibodies and mAb demonstrate that each of these proteins was immunologically distinct. However, direct amino acid sequence of the 66- and 68-kDa Ag was almost identical and had a high level of sequence similarity to the GroEL heat-shock protein (Hsp60) of Escherichia coli and the 60-kDa immunodominant protein of Treponema pallidum. The amino terminal sequence of the 71- and 73-kDa proteins of B. burgdorferi was almost identical and these proteins had remarkable sequence similarity to the DnaK heat-shock protein of E. coli (Hsp70). It appears likely, therefore, that proteins related to the heat-shock family are potent immunogens of B. burgdorferi.

Modulation of the cutaneous responsiveness of neurones in the primary somatosensory cortex during conditioned arm movements in the monkey

The present experiments were designed to investigate the neuronal mechanisms, at the level of the primary somatosensory cortex, which underlie the observation that somatosensory cortical potentials evoked by air puff stimuli directed at the forearm are decreased, in a nonspecific and widespread manner, during voluntary movements about the elbow. Unitary discharge was recorded from 131 cells receiving cutaneous input from the hairy skin of the forearm or hand (areas 3b and 1) of two monkeys trained to perform rapid movements of the contralateral arm (elbow flexion or extension). Evoked unitary responses to air puff stimuli applied to the centre of the cell's receptive field, at various delays before and after the onset of movement, were recorded. Movement produced a significant decrease in the short latency excitatory response to the air puff in 89% of the cells (117/131); the remaining 11% were not modulated by movement. This movement-related "gating" of cutaneous inputs occurred regardless of the response pattern of the cells to movement alone, being observed in 91% of the cells with no movement-related discharge, and 89% of those with movement-related discharge. The air puff responses of cells with inputs from the forearm and the dorsum of the hand were all similarly modulated by movement and the modulation was clearly present prior to the onset of movement (mean onset, -66 ms). Variation in the depth of modulation as a function of the direction of the movement, flexion or extension, was observed in only a very small proportion of the modulated units (16/117); most showed no relationship to direction. It is suggested that, in this experimental situation, much of the modulation appears to occur at a pre-cortical level since there was no relationship between the pattern of discharge of cells in relation to movement alone and the pattern of movement-related gating of their responses to the air puff. Effects which might be consistent with a cortical origin for the modulation were only infrequently observed. The present results are strikingly similar to those obtained using the evoked potential method, and thus support the hypothesis that in this task of rapid elbow movements, movement modulates the transmission of cutaneous signals from the hairy skin of the distal forelimb to primary somatosensory cortex in a nonspecific and widespread fashion.

Modulation of cutaneous cortical evoked potentials during isometric and isotonic contractions in the monkey

The effects of the direction of movement (flexion vs extension) and the nature of the motor task (isotonic vs isometric) on the modulation of sensory cortical evoked responses to cutaneous stimulation were investigated in one monkey. Sensory responses were assessed by measuring the magnitude of the short latency component of air puff-evoked potentials recorded intracortically in the arm representation of areas 3b and 1 in the primary somatosensory cortex. At most recording sites, it was found that the amplitude of the air puff-evoked potential was decreased in a non-specific manner by motor activity. Neither the timing nor the depth of the modulation were found to vary with either the direction or the type of contraction. The effects were widespread since inputs from practically the entire forelimb (hairy skin) were diminished during the motor tasks. These results thus show that the modulation was more closely linked to the central motor output than to the peripheral input generated by muscle force and/or limb displacement. It is suggested that signals originating from central motor structures, acting in a feedforward manner, play a major role in 'gating' cutaneous inputs during movement. It is further suggested that the centrally mediated effects are exerted via a final common pathway upon which the 'gating' signals converge.

[Comparative study of ventricular late potentials recorded on the body surface and epicardium in experimental myocardial infarction]

A noninvasive method for detecting ventricular late potentials (VLPs) was described. Signal averaging technique with high pass bidirectional digital filter was used to record signal-averaged electrocardiograms (SA-ECGs) on the body surface and epicardium. The SA-ECGs were performed with local ventricular electrograms (LVEs) simultaneously in order to compare the difference in records from the two methods. The LVEs have been recorded by epicardial composite electrodes. The signal averaging system was made in Fudan University (Shanghai) and Suzhou Medical College. Duration of filtered QRS (DQRS), duration of the under 40 microv low-amplitude signal (D40) and last 20 ms voltage of the filtered QRS (V20) were measured. VLPs were defined as the presence of two or more abnormal values. Experiments were performed on 20 anesthetized dogs with ligation of the left anterior descending artery. This study has demonstrated that: (1) DQRS greater than or equal to 60 ms, D40 greater than or equal to 20 ms, V20 less than or equal to 16 microv were considered as abnormal values. These values almost did not overlap with the values detected from normal epicardium and body surface; (2) VLPs were shown on the body surface in 12 of 18 dogs (66.6%) in 3 hours after coronary artery ligation, but decreasing to 42.8% (6/14) in 3-6 days later; (3) the fractionated ventricular electrograms were directly recorded on epicardium of the infarction region by composite electrodes and signal averaging system in late stage of myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)