Pax-1 in the development of the cervico-occipital transitional zone

The Pax-1 gene has been found to play an important role in the development of the vertebral column. The cervico-occipital transitional zone is a specialized region of the vertebral column, and malformations of this region have frequently been described in humans. The exact embryonic border between head and trunk is a matter of controversy. In order to determine a possible role of Pax-1 in the development of the cervico-occipital transitional zone we studied the expression of this gene in a series of quail embryos and murine fetuses with in situ hybridization and immunohistochemistry. Pax-1 is expressed in all somites of the embryo, including the first five occipital ones. During embryonic days 3–5 the gene is down-regulated in the caudal direction within the first five somites, whereas more caudally Pax-1 is strongly expressed in the cells of the perinotochordal tube. In 5-day-old quail embryos, the cartilaginous anlage of the basioccipital bone has developed and there is no more expression of Pax-1 in this region. The fusion of the dens axis with the body of the axis also coincides with switching off of the Pax-1 gene. More caudally, the gene is continuously expressed in the intervertebral discs of murine embryos and therefore seems to be important for the process of resegmentation. Quail embryos do not possess permanent intervertebral discs. “Hyper-” or “hyposegmentation” defects may be explained by an over- or under-expression of Pax-1 during development. We also reinvestigated the border between the head and trunk in chick embryos by performing homotopical grafting experiments of the 5^th somite between chick and quail embryos. Grafted quail cells formed mainly the caudal end of the basioccipital bone. They were also located in the cranial half of the ventral atlantic arch, and only a few cells were found in the tip of the dens axis.     

Immunohistochemical studies on S-100 cells in the anterior pituitary gland of Sprague Dawley rats and spontaneous dwarf rats

The S-100 cells in the pituitary glands of adult male Sprague Dawley rats (SDs) and spontaneous dwarf rats (SDRs) were immunohistochemically examined using anti-S-100 and anti-S-100 monoclonal antibodies. The immunoreactive cells against S-100 protein were divided into three subtypes on the basis of their immunore-activity against subunits of S-100 protein: S-100 dominant type (the -type cell), S-100 dominant type (the \-type cell) and immunoreactive against both S-100 and S-100 (the -type cell). In the SD, -type cells represented 26% of the total S-100 immunoreactive cells (S-100 cells) and were localized in the peripheral area of the ventral region of the pituitary gland. This type of cell was observed forming clusters, with more abundant cytoplasm than the -type cell. The proportion of -type cells was 53%. They were diffusely distributed throughout the gland, and their processes were thicker than those of the -type cell. In the SDR, the proportion of -type cells was 55%, and they were observed throughout the gland. In contrast, -type cells totalled 12% and were localized in small areas of the central and peripheral region of the gland. The proportion of -type cells was 21% in the SD and 33% in the SDR and they were observed forming small clusters in both animal groups. The proportion of -type cells compared with the total of S-100-immunoreactive cells was significantly higher (P < 0.05) in the SDR than in the SD, while the proportion of -type cells was markedly lower (P < 0.05).     

Selection and properties ofPseudomonas aeruginosa variants resistant to beta-lactam antibiotics

The relation between basal and inducible-lactamase production and resistance to-lactam compounds was studied in five clinicalPseudomonas aemginosa isolates and their corresponding resistant variants selected in the presence of either piperacillin, ceftazidime or aztreonam. In all wild-type strains enzyme levels were barely detectable in the uninduced state and most-lactams, including sulbactam and clavulanic acid, exhibited poor induction potency. Imipenem proved to be the most potent inducer in both these strains and their resistant variants. In the variants selected by either piperacillin or ceftazidime enzyme production amounted to 1.28 units/mg protein of the cell-free supernatants following the addition of-lactams as inducers. Additionally, these variants exhibited the phenomenon of non-specific induction, i.e. the increase of enzyme production by either a complex nutrient medium or by addition of vitamins. Enzyme production in the aztreonam-resistant variants was identical to that in the wild-type strains with a single exception, where the entire derepression of-lactamase production in one of the variants took place. Derepression of the chromosomally mediated enzyme affects the susceptibility to ureidopenicillins more than that to carboxy-penicillins and cephalosporins, whereas the-lactamase-independent resistance results in increased resistance to all-lactams with the single exception of imipenem.     

Glucocorticoids modulate TGF-beta production by human fetal lung fibroblasts

TGF- is thought to play a central role in pulmonary fibrosis inducing fibroblast differentiation and extracellular matrix synthesis. In human lung fibroblasts, it is still unclear how various TGF- isoforms affect TGF- production and whether glucocorticoids, commonly used agents to treat fibrotic lung disease, modulate these processes. To this end, human fetal lung fibroblasts (HFLF) were cultured with various concentrations of glucocorticoids (budesonide, dexamethasone or hydrocortisone) with and without TGF-1, -2, or -3. Post-culture media were collected for ELISA assays of TGF-1, -2, and -3 . TGF- mRNA was assessed by real time RT-PCR. Smad 2, 3, and 4 and AP-1 complex (c-fos and c-Jun) cellular localization were evaluated by immunostaining. TFG-2 and -3 stimulated TGF-1 production significantly (p < 0.01 relative to control). TGF-1 stimulated TGF-2 production (p < 0.01 relative to control). TGF-3 was undetectable. Glucocorticoids significantly inhibited TGF-1 and TGF-2 production and reduced expression of the up-regulated TGF-1 and TGF-2 mRNA induced by exogenous TGF-1, -2, or -3 (p < 0.01 for each) but had no effect on Smads. Although c-jun-related nuclear staining was not intensified in TGF--stimulated cells, it was reduced by glucocorticoids. Thus, TGF- isoforms may stimulate production of various TGF- isoforms in the lung. Glucocorticoids then may block TGF- production by modulating mRNA levels and c-Jun.     

The role ofγδ T cells in the normal and disordered immune system

Summary A small population of T cells does not express the conventional T cell receptor characterized by the and polypeptide chains (TCR) but instead, two polypeptides termed and (TCR). This alternative receptor is able to recognize antigen. It appears early in T cell ontogeny, but its role in the thymus prior to the availability of TCR remains unclear. In selected sites such as skin or gut TCR predominates in mice which might suggest a role of T cells in the first line of defense against infection, T cells secrete lymphokines and display cytotoxic activity. However, their activation requirements may differ from what is known for T cells since MHC-nonrestricted and also CD4 and CD8 negative T cells have been described. Preferential activation by mycobacterial antigens possibly indicates a special repertoire of the T cells. In various diseases slightly increased numbers of T cells were found, but these preliminary studies have not yet provided evidence for a major pathogenetic role of T cells.List of abbreviations C constant region (immunoglobulin or TCR gene segment) - CD4 cluster of differentiation 4 (mainly on helper cells) - CD8 cluster of differentiation 8 (mainly on cytotoxic cells) - D diversity region (immunoglobulin or TCR gene segment) - DNA desoxyribonucleic acid - IL2 interleukin 2 - J joining region (immunoglobulin or TCR gene segment) - kD kiloDalton - MHC major histocompatibility complex - NK natural killer (cells) - RA rheumatoid arthritis - TCR T cell receptor - V variable region (immunoglobulin or TCR gene segment)     

Factors influencing serum neopterin and β2-microglobulin levels in a healthy diverse population

Sera and questionnaire data from a population-based random sample of healthy adults was used to evaluate factors influencing neopterin and 2-microglobulin (2m) values. Both neopterin and 2m levels increased with age and were higher among white than blacks (mean values for whites and blacks: neopterin, 5.06 vs 4.49 nmol/L; 2m, 1.36 vs 1.28 mg/L). Gender differences were noted for 2m but not neopterin values (2m males vs females: 1.37 vs 1.29 mg/L). Neopterin values were lower among current smokers than among nonsmokers (4.32 vs 5.16 nmol/L) and were higher among users of antihistamines (5.46 among users vs 4.65 nmol/L among nonusers). Neopterin and 2m were correlated in this healthy adult population (adjustedr=0.53,P=0.001), yet no other interrelationships with numerous biologic markers except between 2m and serum-soluble interleukin-2 receptor levels (adjustedr=.41,P=0.05) were observed. These findings provide important baseline information to consider before planning or evaluating studies utilizing neopterin or 2m levels.     

Immunoglobulin and T cell receptor gene rearrangements and in situ immunophenotyping in lymphoproliferative disorders

Summary We investigated for rearrangements of the immunoglobulin (Ig) heavy and light chain genes and of the T cell receptor (TCRT) and (TCr) genes 45 biopsy samples from a variety of lymphoproliferative disorders. They were diagnosed histopathologically and immunophenotypically as non-Hodgkin's lymphomas (NHLs) of the B cell type (19 cases), NHLs of the T cell type (3 cases), NHLs of undetermined cell type (3 cases), atypical lymphoid proliferation (1 case) and AIDS-related lymphadenopathies with florid polyclonal follicular hyperplasia (19 cases). A monoclonal proliferation of B cells was shown by DNA analysis in all 19 B cell NHLs. In two immunohistologically determined T cell NHLs (both diagnosed as mycosis fungoides) the cells had rearrangements of TCr gene, whereas in the third case (lymphoblastic NHL) the cells had rearrangements of Ig heavy chain and TCr and TCr genes. None of the B cell NHLs exhibited TCrand TCr gene rearrangement bands. All the undetermined cell NHLs demonstrated rearrangements of Ig heavy chain gene associated with the germ line TCrand TCr genes; in two cases light chain gene rearrangements were also found. The atypical lymphoid proliferation, in which the differential diagnosis was between a reactive or malignant process, and two out of 19 cases of florid polyclonal follicular hyperplasia showed a clonal B cell population by DNA analysis. This study indicates that there was a strong correlation between the rearrangements of specific genes and the immunophenotype of the NHL; moreover, DNA analysis of tissue biopsy specimens from phenotypically undetermined cell NHLs and from equivocal lymphoid proliferation using Ig and TCR gene probes yelded an answer in the cases analyzed. The significance of clonal B cell expansions found in two AIDS-related lymphadenopathies should be interpreted with caution.This work was supported in part by a Grant No 86.00644.44 from the Consiglio Nazionale delle Ricerche, Progetto Finalizzato Oncologia, Rome, and by the Associazione Italiana per la Ricerca sul Cancro, Milan, Italy     

Activation of atrial muscarinic K+ channels by low concentrations ofβγ subunits of rat brain G protein

Effects of G protein subunits from rat brain on cardiac K⁺ channel was examined in single atrial cells of guinea-pig, using patch clamp techniques. We found that 10 pM concentration of rat brain subunits preparation could activate the atrial muscarine receptor-gated K⁺ channel (I_K.ACh). Neither the detergent, CHAPS, used to suspend nor the boiled preparation activated I_K.ACh. Furthermore, preincubation of subunits preparation in Mg²⁺-free solution, which easily inactivated -GTP-S, did not affect -activation of I_K.ACh. We concluded, therefore, that subunits themselves can activate I_K.ACh.Supported by the grants from the Ministry of Education, Culture and Science of Japan and from the Calcium Signal Workshop on Cardiovascular Systems     

Application of the polymerase chain reaction to study the M protein(-like) gene family in beta-hemolytic streptococci

Evaluation of homologous regions of published M protein (emm) gene sequences from group A streptococci (GAS; Streptococcus pyogenes) was used to design three primer pairs for polymerase chain reaction (PCR) and three oligonucleotide probe sequences internal to the amplified products. One set of primers and corresponding probe should detect and lead to amplification of emm(-like) genes of virtually every type (all M), another (SOR^-M) should only amplify emm(-like) genes from GAS negative for serum opacity reaction (SOR) and the third (SOR⁺M) should expand only emm(-like) genes from SOR⁺ GAS. Using the all M primer pair for PCR on the genomic DNA from GAS of 29 different M types as well as from a group C and a group G streptococcal isolate, DNA fragments within the expected size range were amplified in every assay. All PCR products reacted with the all M probe. Related sequences were not detected in genomic DNA of an S. agalactiae and an Enterococcus faecalis isolate. Applying the SOR^-M and SOR⁺M primers to identical assays led to mutually exclusive amplification products. The SOR⁺M and SOR⁺M probes hybridized only to their corresponding products. Exceptions to this exclusivity were the SOR⁺ GAS of M types 3, 8, 27, 34, 42, 67, and 69, which consistently reacted only with the SOR⁺M primer/probe set. Analysis of sequence data from the amplified emm(-like) 2, 3, 18, and 19 genes revealed interesting specific features such as conserved gaps in the C-terminal sequence regions from SOR⁺ and the exceptional SOR^- GAS strains. These data indicate the existence of a subgroup of strains among SOR^- GAS and may advance our understanding of phylogenetic relationship between different serotypes of GAS.     

Partitioning of Cortical and Deep Cytoskeleton Responses from Transient Magnetic Bead Twisting

We attempted to estimate in living adherent epithelial alveolar cells, the degree of structural and mechanical heterogeneity by considering two individualized cytoskeleton components, i.e., a submembranous cortical cytoskeleton and a deep cytoskeleton (CSK). F-actin structure characterizing each CSK component was visualized from spatial reconstructions at low and high density, respectively, especially in a 10-m-cubic neighborhood including the bead. Specific mechanical properties (Young elastic and viscous modulus E and ) were revealed after partitioning the magnetic twisting cytometry response using a double viscoelastic solid model with asymmetric plastic relaxation. Results show that the cortical CSK response is a faster ( ₁ 0.7s), softer (E₁: 63-109 Pa), moderately viscous (₁: 7-18 Pa s), slightly tensed, and easily damaged structure compared to the deep CSK structure which appears slower (₂ min), stiffer (E₂: 95-204 Pa), highly viscous (₂: 760-1967 Pa s), more tensed, and fully elastic, while exhibiting a larger stress hardening behavior. Adding drug depolymerizing actin filaments decreased predominantly the deep CSK stiffness. By contrast, an agent altering cell–matrix interactions affected essentially the cortical CSK stiffness. We concluded that partitioning the CSK within cortical and deep structures is largely consistent with their respective functional activities. © 2003 Biomedical Engineering Society. PAC2003: 8716Ka, 8716Ac, 8380Lz     

Function associated transforming growth factor-β gene polymorphism in chronic beryllium disease

Chronic beryllium disease (CBD) is a rare occupational, granulomatous lung disease clinically resembling sarcoidosis. The immune response to beryllium is thought to depend on genetic susceptibility. Although a glutamic acid in position 69 of the human leukocyte antigen-DP chain (HLA-DPB1-Glu69) is associated with the development of CBD, it cannot fully explain susceptibility. It is likely that additionally other genes are involved in regulating the immune and inflammatory response in the pathogenesis of this disease. Functional gene polymorphisms (PMs) of the tumor necrosis factor (TNF)A and transforming growth factor (TGF) ₁ genes are suspected to modify the course of granulomatous disorders. We analyzed the TGF-₁ (codon 25) PM in 59 patients with CBD and 164 matched healthy controls, from two groups of European/Israeli and United States origin. Additionally, patients were genotyped for HLA class II gene variants and the TNFA (–308) PM. The most significant results were found for the TGF-₁ (codon 25) PM with a shift towards the low producing non-GG genotypes in the subgroup of European and Israeli patients with CBD (62.50% vs. 13.82% in healthy controls; P<0.001). This phenomenon was not observed in the group from the United States. Moreover, TGF-₁ (codon 25) PM genotype frequencies from United States CBD patients differed significantly from those of European and Israeli patients. In contrast, increased frequencies for the high producing TNFA2 allele were found only in the patients from the United States (28.20% vs. 8.96% in healthy controls; P<0.005) but not in the group of Europe and Israel. In conclusion, the increase in TGF-₁ (codon 25) PM genotype frequency associated with a low TGF- release suggests that immunoregulatory cytokines such as TGF- are involved in the pathogenesis of CBD. Moreover, based on the interaction of gene PMs associated with the control of the immune response, such as TNF- and TGF-₁, with a specific immune response gene such as HLA-DPB1-Glu69 or other HLA-class II PMs driving the immune response to Be, the present data suggest that a combination of different genetic backgrounds determine susceptibility for the same immunopathological reaction and disease.     

An α-mating-type-specific mutation causing specific defect in sexual agglutinability in the yeast Saccharomyces cerevisiae

We have identified a recessive -mating-type-specific gene agl causing agglutinability defect without significant effects on other sexual activities. a cells carrying agl showed sexual agglutination with cells but cells carrying agl showed sexual agglutination with neither cells nor a cells. cells carrying agl produced pheromone and responded to a pheromone just like wild cells. cells carrying agl showed a little decreased but significant mating ability when tested on solid media or membrane filter. The agl mutant is different from any -specific ste mutants found so far in many sexual activities. The agl gene is recessive, and unlinked to the mating type locus. Biological significance of the mating type agglutinability is discussed based on the results obtained with the mutant.     

Two types of potassium channel regulated by ATP in pancreatic B cells isolated from a type-2 diabetic human

Two types of K channel regulated by ATP were observed in pancreatic cells from a type-2 diabetic man. One type had a conductance of 67 pS at-70 mV in symmetrical 140 mM KCl and was inhibited by intracellular ATP with a half-maximal concentration of 40 M. ATP inhibition was antagonised by ADP. Tolbutamide inhibited the whole-cell K currents half-maximally at 25 M. This channel has properties similar to those found for the ATP-sensitive K channel in rodent and normal human cells. The second channel type observed was an ATP-activated K channel. It had a conductance of 37 pS at -70 mV in symmetrical 140 mM KCl and was activated half-maximally by 9 M intracellular ATP. This channel was unaffected by 1 mM tolbutamide. In cell-attached patches, one cell out of four tested responded to 20 mM glucose with depolarization. The role of the ATP-activated K channel with respect to the (patho)physiology of the cell is uncertain.     

Interaction of Newcastle disease virus strains differing in virulence with chicken red blood cell receptors

Summary Nine NDV strains belonging to lentogenic, mesogenic and velogenic groups were studied. Virus adsorption to chicken red blood cell (RBC) surface was performed at 4° C, and after a temperature shift from 4° to 37° C elution of pre-adsorbed virus and accumulation of free N-acetyl-neuraminic acid (NANA) split from RBC receptors as a result of neuramindase (Nase) activity was detected. In the case of high multiplicity of adsorption the elution was very fast (complete elution within 5 minutes) for all the strains irrespective of their virulence. Although physical saturation of RBC surface with the adsorbed virus was not achieved, a certain minimal (strain-specific) amount of the pre-adsorbed virus which splits a maximally possible (for a given strain) quantity of the NANA was found (a state of enzymatic saturation). Below a certain low multiplicity of adsorption elution was delayed for about 20–30 minutes while the accumulation of the split NANA began immediately after the temperature shift. This phenomenon was interpreted as a result of crawling of the adsorbed virions upon the RBC surface followed by browsing of RBC recptors and liberation of NANA. Thus, the Nase activity of the attached virus (in situ Nase activity) is a factor providing both elution and crawling of the virus (depending on the multiplicity of adsorption).Thein situ Nase activity of all the strains used was determined quantitatively by (1) parameters of enzymatic kinetics (V_max, K_m and K_m/V_max) and (2) parameters of enzymatic efficiency related to a certain quantity of the adsorbed virus, namely, per amount of: a) crawling virus, b) that providing enyzmatic saturation, and c) that equal to K_m. Computation of these parameters revealed inverse correlation between thein situ Nase activity and the strain virulence. Thus, these indications can bein vitro markers of thein vivo virulence.With 8 Figures     

Untersuchungen zur kurzzeitigen Induktions- und zyklischen Erhaltungstherapie beim inoperablen kleinzelligen Bronchialkarzinom

Zusammenfassung Seit Juli 1978 wurden 103 Patienten mit inoperablem kleinzelligem Bronchialkarzinom mit der Zytostatikakombination Adriamycin, Cyclophosphamid und Vincristin (ACO) behandelt. Im Stadium limited disease (n=64) erfolgte während des zweiten Chemotherapiekurses eine prophylaktische Schädelbestrahlung, nach dem vierten eine konsolidierende thorakale Bestrahlung. Nach Erreichen einer kompletten Remission erhielten die Patienten prospektiv randomisiert Etoposid oder keine weitere spezifische Therapie. Ein objektives Ansprechen konnte bei 88/100 auswertbaren Patienten erzielt werden. Im Stadium limited disease fanden sich 72%, im Stadium extensive disease nur 33% komplette Remissionen. Im Stadium limited disease betrug die hochgerechnete mediane Überlebenszeit 15,8, im Stadium extensive disease 9,3 Monate (p<0.005). Es leben noch 29 Patienten, 4 rezidivfrei länger als 24 Monate. Patienten mit kompletter Remission hatten eine statistisch signifikant (p<0.001) längere Überlebenszeit als Patienten mit geringerem Ansprechen. Regelmäßig traten gastrointestinale und hämatologische Nebenwirkungen auf, drei Patienten starben während der Induktionsphase an Infektionen. Die kurzzeitige Induktionsbehandlung verbesserte jedoch den Krankheitsverlauf subjektiv und objektiv. Bisher ist kein positiver Effekt der zyklischen Etoposid-Gabe nach ACO festzustellen.Vorliegende Untersuchungen wurden gefördert im Rahmen des Forschungsprogramms Arzneimittelentwicklung und -testung für die Krebstherapie des BMFT     

Der klinische Wert quantitativ-immunochemischer Bestimmungen verschiedener Proteine im Liquor cerebrospinalis

Zusammenfassung Es wird ein klinischer Erfahrungsbericht mit der quantitativ-immunochemischen Bestimmung verschiedener Liquorproteine vorgelegt. Untersucht wurde der Liquor bei 213 Krankheitsfällen und gearbeitet mit der radialen Immundiffusionsmethode nach Mancini et al. In sämtlichen Fällen wurden neben den üblichen Liquoruntersuchungen _G-Globulin, saures ₁-Glykoprotein, Haptoglobin und unter den liquorfremden Proteinen das _M-Globulin und das-Lipoprotein quantitativ bestimmt. Die wesentliche Bereicherung der klinischen Liquordiagnostik durch die aufgeführten Untersuchungen wird gesehen in der Erfassung der jeweiligen immunologischen Reaktionslage und einer genaueren Bestimmung der Permeabilitätsintensität bei Hirnschrankenstörungen. Ferner kann gelegentlich quantitativen Liquorproteinbestimmungen der Hinweis auf akute Krankheitsphasen, ausgedehnte Gewebsdestruktionen und auf abgelaufene Blutungen in die Liquorräume entnommen werden. Dem Nachweis des-Lipoprotein im Liquor sowie vielleicht auch der Höhe des _G-Globulingehaltes kommt schließlich ein klinisch-diagnostischer Wert bei Raumforderungen im ZNS-Bereich zu.

---

Summary This paper presents a clinical experience with the quantitative immuno-chemical analysis of different cerebrospinal fluid proteins. The CSF of 213 patients suffering from a CNS disease was examined. We used the radial immun diffusion method as described by Manciniet al. Besides the usual CSF examinations, _G-Globulin, acid ₁-Glycoprotein, and Haptoglobin were quantitatively determined in all cases. Of those proteins that under healthy conditions do not occur in the CSF the _M-Globulin and the-Lipoprotein were quantitatively evaluated, too. The essential additional value of the clinical CSF diagnostic procedures derived from those examinations is seen in the comprehension of the respective immunological reaction state as well as of a more exact evaluation of the permeability intensity in brain barrier system disturbances. Furthermore, quantitative CSF determinations can occasionally point to acute episodes of a CNS disease, an extensive tissue destruction, or to a CSF dysproteinosis following a bleeding into the CSF space. The proof of the existence of-Lipoprotein in the CSF, and perhaps also the level of the _G-Globulin, finally show a clinical-diagnostic significance in cases of space occupying lesions within the CNS.

     

Preliminary observations on the ultrastructure of supposed sexual stages of Babesia bigemina (Piroplasmea)

Summary The stages of Babesia bigemina developing in the tick's gut within the first 20 hours after repletion have been first described by Robert Koch in 1906. Due to their radial processes he called them strahlenkörper (spiky-rayed stages). These forms are probably stages of a sexual developmental phase of the parasite. Their fine structural feature is characterized by numerous micropores, abundant microtubules, and a singular structure called by us bright body. The so-called strahlen (spiky rays) are cytoplasmic processes supported by a bundle of long, parallel microtubules that are distributed randomly and not configurated to a 9+2 or another pattern. Their number varies between two and more than ten. In the parasite's body are cytoplasmic microtubules mainly arranged in arrays and bundles in the cortical cytoplasm. The parasite itself is delimited by a single unit membrane. Subpellicular microtubules or other typical pellicular structures of motile sporozoan stages were not detected. The numerous micropores are of the sporozoan type. They are connected with ingestive invaginations. The bright body is a large, circular, not membrane-bounded cytoplasmic area being electron-lucid and apparently lacking ribosomes; it contains microtubular elements. Long microtubules pass through the bright body, or radiate from it towards the surrounding cytoplasm; some tubules extend into strahlen. The possible significance of the ultrastructures is discussed in view of similar structures in other Babesia spp. and Theileria spp.     

Resistance toTrypanosoma cruzi infection in relation to the timing of IgG humoral response

The Biozzi high (BH) and low (BL) responder mice (Selection III) differeed in their susceptibility toTrypanosoma cruzi. The BH strain responded quickly to the infection, similar to the reaction of (CBA×C57B1/10)F₁ mice but in contrast to the susceptible BL strain. We suggest that the IgG response mounted by the host during the prepatent period of the infection is crucial to the outcome of the infection.     

Metabolic control of respiratory neuronal activity and the accompanying changes in breathing movements of the rabbit

Summary The property of the neuronal membrane to be permeable to metabolic modifiers of two regulatory enzymes has been utilized to manipulate the spike activity of inspiratory (I) and expiratory-inspiratory (EI) neurons of the bulbar respiratory centre. The neurons have been classified according to their response to lung distension or collapse (- or -type) and to hyperventilation (tonic firing denoted by +, cessation of activity by –). Using extracellular microelectrodes for single unit recording, the medulla oblongata was superfused with a metabolite-containing CSF. The various neuronal sub-types exhibited a differential activating or inhibitory response to one or several metabolic effectors. For example I ⁺ units were activated by 5 mM glucose-6-phosphate (G-6-P) and 3.5 mM 3-phosphoglycerate (3-PGA), which both inhibited I ⁺ neurons, while 5 mM AMP inhibited I ⁺ much more strongly than I ⁺ cells. The spike density of I ^– and I ^– neurons was increased in the presence of 2.5 mM fructose-6-phosphate and 3.5–5 mM AMP, but became reduced by G-6-P. In contrast, 3 mM fructose-1,6-diphosphate and 5 mM 3-PGA activated the I ^– but inhibited the I ^– neurons. The EI units were characteristically activated by 10 mM citrate, which inhibited all I-type neurons. Activations of the I and I neurons led to an accelerated respiratory rate and a higher tidal volume, while the opposite was true for EI neurons. Intravenous injection of metabolites could not duplicate the striking effects under local applications.Supported by the Deutsche Forschungsgemeinschaft, Grant Ch 25/1.     

ω-Grammotoxin blocks action-potential-induced Ca2+ influx and whole-cell Ca2+ current in rat dorsal-root ganglion neurons

Field-potential stimulation of rat dorsal-root ganglion (DRG) neurons evoked action-potential-mediated transient increases in intracellular free calcium concentration ([Ca²⁺]_i) as measured by indo-1-based microfluorimetry. Field-potential-evoked [Ca²⁺]_i transients were abolished by tetrodotoxin, and their dependence on stimulus intensity exhibited an abrupt threshold. -Conotoxin GVIA (-CgTx, 100 nM) inhibited action-potential-mediated Ca²⁺ influx by 79%, while nitrendipine (1 M) had little effect. -Grammotoxin SIA (-GsTx, 267 nM), a peptide toxin purified from the venom of the tarantula spider, Grammostola spatulata, blocked action-potential-mediated Ca²⁺ influx as effectively as did -CgTx, suggesting that -GsTx blocks N-type Ca²⁺ channels. In contrast to block by -CgTx, the block produced by -GsTx reversed upon washout of the peptide. -GsTx (270 nM) blocked 80%, and -CgTx (1 M) blocked 64%, of whole-cell Ca²⁺ current (I _Ca) elicited by step depolarization to 0 mV from a holding potential of –80 mV. -GsTx completely occluded inhibition of I _Ca by -CgTx. However, when applied after -CgTx, -GsTx produced an additional inhibition of 27%, indicating that -GsTx also blocked a non-N-type Ca²⁺ channel. BayK8644 (1 M) elicited an increase in I _Ca in the presence of maximally effective concentrations of -GsTx, suggesting that -GsTx does not block L-type channels. Thus, -GsTx displays a selectivity for Ca²⁺ channel subtypes which should prove useful for studying Ca²⁺ channels and Ca²⁺-channel-mediated processes.