Molecular characterization of a carbon transporter in plastids from heterotrophic tissues: the glucose 6-phosphate/phosphate antiporter

Plastids of nongreen tissues import carbon as a source of biosynthetic pathways and energy. Within plastids, carbon can be used in the biosynthesis of starch or as a substrate for the oxidative pentose phosphate pathway, for example. We have used maize endosperm to purify a plastidic glucose 6-phosphate/phosphate translocator (GPT). The corresponding cDNA was isolated from maize endosperm as well as from tissues of pea roots and potato tubers. Analysis of the primary sequences of the cDNAs revealed that the GPT proteins have a high degree of identity with each other but share only approximately 38% identical amino acids with members of both the triose phosphate/phosphate translocator (TPT) and the phosphoenolpyruvate/phosphate translocator (PPT) families. Thus, the GPTs represent a third group of plastidic phosphate antiporters. All three classes of phosphate translocator genes show differential patterns of expression. Whereas the TPT gene is predominantly present in tissues that perform photosynthetic carbon metabolism and the PPT gene appears to be ubiquitously expressed, the expression of the GPT gene is mainly restricted to heterotrophic tissues. Expression of the coding region of the GPT in transformed yeast cells and subsequent transport experiments with the purified protein demonstrated that the GPT protein mediates a 1:1 exchange of glucose 6-phosphate mainly with inorganic phosphate and triose phosphates. Glucose 6-phosphate imported via the GPT can thus be used either for starch biosynthesis, during which process inorganic phosphate is released, or as a substrate for the oxidative pentose phosphate pathway, yielding triose phosphates.

Molecular characterization of a carbon transporter in plastids from heterotrophic tissues: the glucose 6-phosphate/phosphate antiporter

Plastids of nongreen tissues import carbon as a source of biosynthetic pathways and energy. Within plastids, carbon can be used in the biosynthesis of starch or as a substrate for the oxidative pentose phosphate pathway, for example. We have used maize endosperm to purify a plastidic glucose 6-phosphate/phosphate translocator (GPT). The corresponding cDNA was isolated from maize endosperm as well as from tissues of pea roots and potato tubers. Analysis of the primary sequences of the cDNAs revealed that the GPT proteins have a high degree of identity with each other but share only approximately 38% identical amino acids with members of both the triose phosphate/phosphate translocator (TPT) and the phosphoenolpyruvate/phosphate translocator (PPT) families. Thus, the GPTs represent a third group of plastidic phosphate antiporters. All three classes of phosphate translocator genes show differential patterns of expression. Whereas the TPT gene is predominantly present in tissues that perform photosynthetic carbon metabolism and the PPT gene appears to be ubiquitously expressed, the expression of the GPT gene is mainly restricted to heterotrophic tissues. Expression of the coding region of the GPT in transformed yeast cells and subsequent transport experiments with the purified protein demonstrated that the GPT protein mediates a 1:1 exchange of glucose 6-phosphate mainly with inorganic phosphate and triose phosphates. Glucose 6-phosphate imported via the GPT can thus be used either for starch biosynthesis, during which process inorganic phosphate is released, or as a substrate for the oxidative pentose phosphate pathway, yielding triose phosphates.

Yersinia enterocolitica promotes deactivation of macrophage mitogen-activated protein kinases extracellular signal-regulated kinase-1/2, p38, and c-Jun NH2-terminal kinase. Correlation with its inhibitory effect on tumor necrosis factor-alpha production

The enteropathogenic bacterium Yersinia enterocolitica counteracts host defense mechanisms by interfering with eukaryotic signal transduction pathways. In this study, we investigated the mechanism by which Y. enterocolitica prevents macrophage tumor necrosis factor-alpha (TNFalpha) production. Murine J774A.1 macrophages responded to Y. enterocolitica infection by rapid activation of mitogen-activated protein kinases (MAPK) extracellular signal-regulated kinase (ERK), p38, and c-Jun NH2-terminal kinase (JNK). However, after initial activation, the virulent Y. enterocolitica strain harboring the Y. enterocolitica virulence plasmid caused a substantial decrease in ERK1/2 and p38 tyrosine phosphorylation. Simultaneously, the virulent Y. enterocolitica strain gradually suppressed phosphorylation of the transcription factors Elk-1, activating transcription factor 2 (ATF2), and c-Jun, indicating time-dependent inhibition of ERK1/2, p38, and JNK kinase activities, respectively. Analysis of different Y. enterocolitica mutants revealed that (i) MAPK inactivation parallels the inhibition of TNFalpha release, (ii) the suppressor effect on TNFalpha production, which originates from the lack of TNFalpha mRNA, is distinct from the ability of Y. enterocolitica to resist phagocytosis and to prevent the oxidative burst, (iii) the tyrosine phosphatase YopH, encoded by the Y. enterocolitica virulence plasmid, is not involved in the decrease of ERK1/2 and p38 tyrosine phosphorylation or in the cytokine suppressive effect. Altogether, these results indicate that Y. enterocolitica possesses one or more virulence proteins that suppress TNFalpha production by inhibiting ERK1/2, p38, and JNK kinase activities.

Cavitary cryptococcoma of the lungs and meningitis by Cryptococcus neoformans in a patient with AIDS

We report on a 39-year-old AIDS patient who presented a generalized cryptococcal disease with involvement of the lungs and central nervous system. Although the initial symptoms were mild and uncharacteristic, the radiological finding of cavernous destructions of the lungs (cryptococcoma) was detectable. The patient recovered after an initial 3 week therapy with amphotericin B and fluconazole followed by secondary prevention with fluconacole. The cavernous destructions receded within 4 months. Though the respiratory tract is the presumed port of entry for Cryptococcus neoformans, a cavernous destruction of pulmonary tissue without a diffuse infiltration of the lungs is a rare manifestation of cryptococcosis even in HIV patients.

From university student to registered nurse: the perennial enigma

Crucial issues related to the transition from university student to registered nurse are addressed, through a review of the literature. The considerable literature in this area indicates three distinct approaches in examining this question: there are personal and professional deficits which the new graduate must make up, the formal content of the university curriculum is deficient and must be replaced, the socio-political and professional contexts of practice constrains beginning practice. Each of these approaches is examined here in the expectation that uncovering these issues will encourage employers and educators to work together to resolve some of the current conflicts and difficulties inherent in the transition from university student to registered nurse. Various models of transition in current use are then explored, since support for the graduate is paramount for provision of a cost effective and efficient nursing service in a rapidly changing health service environment.

Cell-cycle arrest, micronucleus formation, and cell death in growth inhibition of MCF-7 breast cancer cells by tamoxifen and cisplatin

The induction of cell death along with cell-cycle arrest is one of the foremost mechanisms regulating cell growth. In the human breast carcinoma cell line MCF-7 we investigated two chemotherapeutic agents, the antiestrogen tamoxifen and the DNA-damaging drug cisplatin, for the relative contribution of these mechanisms to growth inhibition in culture. Growth kinetics and flow cytometry confirmed that tamoxifen at 1 microM acts mainly by arresting cells in the G0/G1 phase of the cell cycle. Compared to untreated controls, only a few more cells were detached from the monolayer and dead after a 5-day incubation. On the other hand, cisplatin at 1 microM did not induce the well-defined G2/M-arrest reported for other cell types, but resulted in a marked increase in the rate of cell death. A morphological feature observed, especially with cisplatin-treated MCF-7 cells, was the formation of numerous micronuclei (in up to 30% of the cells) and an increase in the number of binucleate cells (up to 20%). In both tamoxifen- and cisplatin- treated cultures, cell death appeared to occur by apoptosis, as indicated morphologically by cellular and nuclear shrinkage accompanied by DNA-condensation and ultimately the formation of DNA containing apoptotic bodies. However, no internucleosomal DNA degradation or endogenous endonuclease activity could be detected in the cells of the monolayer or in the mainly dead and detached cells of the culture supernatant. DNA fragmentation was only observed when isolated MCF-7 nuclei were incubated with exogenous endonucleases. However, as determined by reverse transcriptase/polymerase chain reaction amplification, MCF-7 cells do express the mRNA for DNase I, an endonuclease known to be involved in apoptosis. Thus, apoptosis is part of the growth-inhibitory process and occurs without apparent internucleosomal DNA fragmentation in MCF-7 cell cultures.

The immunomodulatory effects of antibiotics: in vitro and ex vivo investigations of 21 substances by means of the lymphocyte transformation test

Besides their antimicrobial activity antibiotics can modulate immune response. The paper provides original data about in vitro and in vivo influence of antibiotics on lymphocyte transformation test (LTT) and gives a comprehensive overview of literature data. In the study presented here the influence of several antimicrobial substances on unstimulated and PHA-stimulated lymphocyte transformation was investigated. The proliferative response was measured as (3H) thymidine uptake by lymphocytes. For initial screening the lymphocyte transformation test was performed on murine lymphocytes in vitro. As a whole 21 antimicrobial substances were tested including representative substances of the most important main groups. As a second step experiments were done with selected substances on human lymphocytes that had shown a distinct influence on murine cells in vitro. At therapeutic concentrations a pronounced stimulation of murine lymphocyte transformation was caused by carbapenems, aminothiazole cephalosporins and imidazoles. Purine analogs had only suppressive effects. However, the increased (3H) thymidine uptake in murine cells could not be regularly reproduced in human lymphocytes and in ex vivo experiments.

Differential contribution of Yersinia enterocolitica virulence factors to evasion of microbicidal action of neutrophils

The differential contribution of the virulence factors invasin, protein tyrosine phosphatase (YopH), cytotoxin (YopE), and adhesin (YadA) of Yersinia enterocolitica to evasion of the antibacterial activities of polymorphonuclear leukocytes (PMNs) (oxidative burst, phagocytosis, killing) was analyzed. We constructed virulence gene knockout mutants and a novel two-plasmid system allowing production and secretion of individual virulence factors. Wild-type Y. enterocolitica WA-314 harboring the virulence plasmid pYV08 resisted phagocytosis and killing by PMNs. Moreover, strain WA-314 was able to inhibit the neutrophil oxidative burst upon stimulation with opsonized zymosan independently on preincubation with normal human serum or YadA-specific serum. These phenotypic properties of strain WA-314 were differentially affected when mutants impaired in YadA production or Yop secretion were used. A more detailed analysis revealed that YopH plays the dominant role in suppression of the antibacterial action of PMNs without damaging the cells. The YopH suppressing effect could be enhanced by coproduction of YopE and YadA. The contribution of YadA is attributed to the adhesin function promoting interaction with PMNs under both opsonizing and nonopsonizing conditions. In contrast, invasin seems to mediate only opsonin-independent interaction with PMNs. Taken together, our results demonstrate that YopH, YopE, and YadA act in concert towards neutrophil attack to enable extracellular survival of Y. enterocolitica in host tissue.

Dissection of the Yersinia enterocolitica virulence plasmid pYVO8 into an operating unit and virulence gene modules

The structural genes encoding the Yop proteins of Yersinia enterocolitica are scattered around on the virulence plasmid (pYV). The genes which are required for transactivation, secretion and translocation of the Yopos are encoded in one cluster known as the lcr-region of pYV. After the introduction of an additional SalI restriction site into pYV of Y. enterocolitica serotype O8, we were able to clone and isolate the whole lcr-region on the mobilizable low copy vector pSUP102. Analysis of this construct in a plasmidless WA-strain showed that all Yops being encoded inside the lcr-region (YopN, YopB, YopD and the V-antigen) were secreted into the culture supernatant. Moreover, this lcr-fragment was able to promote secretion of other Yops encoded by a second recombinant plasmid. Thus the translocation and function of single Yops can be studied.

'You're more your own boss': nurses' experiences of agency work

Agency nurses and their work has received little attention in research in Australia. The study seeks to expand on the current literature from the United Kingdom and the United States that is predominantly personal accounts of individual nurses' experiences of agency work. The descriptive study explores four registered nurses' experiences of working through a nursing agency. Findings identified that agency work met the needs of the four women at that particular time in their lives. The concept of control over work scheduling, as described in much of the literature, was experienced by all four women. However, they indicated a lack of professional autonomy and isolation in their practice. Issues such as accessing continuing education and maintaining skills were identified as problems associated with agency work.

[Infections in diabetes mellitus]

Diabetes mellitus is one of the most frequent metabolic distortions predisposing for infectious diseases. Characteristic features of patients with diabetes mellitus are dysfunctions of professional phagocytes, in particular of polymorphonuclear leucocytes. Infections of skin and soft tissue in particular of the lower extremities, rhinocerebral mucormycosis, invasive external otitis and urinary tract infections are typically associated with diabetes mellitus. Frequently, a rapidly progressive infection requires urgent surgical intervention and parenteral antimicrobial therapy. Short-interval metabolic controls, improvement of metabolic functions, extended vaccination and strict hygiene measures are supportive to prevent infections or to reduce a complicated outcome of infections.

[Determination of parasite-specific antibodies during human schistosomiasis--diagnostic relevance]

Sera from patients with schistosomiasis (Schistosoma mansoni or S. haematobium) were examined for the presence of parasite specific antibodies (total antibodies), specific IgE and IgG4 antibodies by means fo ELISA technique using antigens prepared from adult worms of S. mansoni. Individuals from tropical countries who had no schistosomiasis and blood donors from Germany were studied for comparison. Significantly higher levels of specific antibodies were given by sera from patients with schistosomiasis than by controls in the tests for total antibodies, IgE and IgG4. The use of these results in diagnosis is compared and assessed with microscopic-parasitological methods.

[L-tryptophan-associated chronic eosinophilia-myalgia syndrome treated with cyclosporin]

After 2 weeks of ingestion of 130 g L-Tryptophan a 52 year old female develops an Eosinophilia Myalgia Syndrome with acute onset of deep venous thrombosis of forearm and possible initial cardiac manifestation featuring intermittent sinustachykardia. This is followed by a severe chronic disease (follow-up 15 months) with diffuse scleroderma and sensomotoric polyneuropathia. The deep muscle biopsy-specimen shows mononuclear infiltration of fascia and interstitial myositis with rare eosinophils. A blood eosinophilia (900/ul) occurs only in the initial acute onset of the illness. Plasma level of Kynurenine is significantly high (4000 pmol/ml), collagenneosynthesis is activated (Procollagen type III peptid 0.927 U/ml). No significant clinical improvement was seen with Acathioprine (100 mg/d) and Prednisolon (40-60 mg/d), after treatment with Ciclosporin scleroderma regresses completely, polyneuropathy is persisting.

Effect of Low Root Medium pH on Net Proton Release, Root Respiration, and Root Growth of Corn (Zea mays L.) and Broad Bean (Vicia faba L.)

The effect of low pH on net H(+) release and root growth of corn (Zea mays L.) and broad bean (Vicia faba L.) seedlings was investigated in short-term experiments at constant pH. Broad bean was more sensitive to low pH than corn: the critical values (pH values below which net H(+) release and root growth ceased) were pH 4.00 (broad bean) and pH 3.50 (corn) at 1 millimolar Ca(2+). Both proton release and root growth were progressively inhibited as the medium pH declined. Additional Ca(2+) in the root medium helped to overcome the limitations of low pH for net H(+) release and root growth. Potassium (for corn) and abscisic acid (for broad bean) increased both net H(+) release and root growth rate at the critical pH value. It is concluded that poor root growth at low pH is caused by a lack of net H(+) release that may decrease cytoplasmic pH values. Inhibited net H(+) release at high external H(+) activity is not due to a shortage of energy supply to the H(+) ATPase. Instead, a displacement of Ca(2+) by H(+) at the external side of the plasmalemma may enhance reentry of H(+) into root cells.

Inhibition of DNA primase and polymerase alpha by arabinofuranosylnucleoside triphosphates and related compounds

Inhibition of DNA primase and polymerase alpha from calf thymus was examined. DNA primase requires a 3'-hydroxyl on the incoming NTP in order to polymerize it, while the 2'-hydroxyl is advantageous, but not essential. Amazingly, primase prefers to polymerize araATP rather than ATP by 4-fold (kcat/KM). However, after incorporation of an araNMP into the growing primer, further synthesis is abolished. The 2'- and 3'-hydroxyls of the incoming nucleotide appear relatively unimportant for nucleotide binding to primase. Polymerization of nucleoside triphosphates by DNA polymerase alpha onto a DNA primer was similarly analyzed. Removing the 3'-hydroxyl of the incoming triphosphate decreases the polymerization rate greater than 1000-fold (kcat/KM), while a 2'-hydroxyl in the ribo configuration abolishes polymerization. If the 2'-hydroxyl is in the ara configuration, there is almost no effect on polymerization. An araCMP or ddCMP at the 3'-terminus of a DNA primer slightly decreased DNA binding as well as binding of the next correct 2'-dNTP. Changing the primer from DNA to RNA dramatically and unpredictably altered the interactions of pol alpha with araNTPs and ddNTPs. Compared to the identical DNA primer, pol alpha discriminated 4-fold better against araCTP polymerization when the primer was RNA, but 85-fold worse against ddCTP polymerization. Additionally, pol alpha elongated RNA primers containing 3'-terminal araNMPs more efficiently than the identical DNA substrate.

[The fine structure of the nucleus of the hypoglossal nerve of sheep and goats]

In the small domesticated ruminants the nucleus of the hypoglossal nerve is situated in close relationship to the median line in the middle of the elongated medulla. The nucleus is divided by the obex into a rostral and a caudal portion. In the sheep, four distinct subnuclei can be recognized, whereas in the dwarf goat great variations in the arrangement of cell groups exists. In both animals large and medium sized neurons are observed. The large neurons are characterized by densely packed small organelles. The medium sized neurons vary between a pale and an electron dense type. According to the size and morphology of the vesicles three types of synaptic contacts can be differentiated. Synapses of type 2 contain clear round and flattened vesicles and are partially accompanied by subsurface cisterns.

Influence of cefpodoxime on selected immunological functions and bacterial pathogenicity factors in vitro

The influence of a new oral cephalosporin cefpodoxime, on several interactions of the host-parasite relationship was investigated. Pretreatment of polymorphonuclear granulocytes (PNG) with cefpodoxime at therapeutical dosage in vitro did not have a significant effect on chemotaxis and luminol-dependent chemiluminescence. On the other hand, human serum did not exert a considerable effect on the bactericidal activity of cefpodoxime on Klebsiella pneumoniae and Staph. aureus. Serum resistance of Klebsiella pneumoniae was not altered after pretreatment with cefpodoxime 1/16 MIC (0.03 micrograms/ml) for 3 to 27 hours.

[Microbial spectrum and microbiological diagnosis of infectious endocarditis]

Still streptococci play the most important role as causatives of infective endocarditis. As change in composition of patient groups has taken place gradually pathogens like Staphylococcus epidermidis, enterococci, gram-negative rods and Candida species become more and more important now. Providing high-level accuracy if applied according to current rules blood culture is yet the basis for endocarditis caused by popular bacterial pathogens. If infection due to Candida species is suspected additional measuring of antibody response may be helpful in supporting the tentative diagnosis. Rare pathogens like Rickettsiae and Mycoplasma sp. must be considered for differential diagnosis, as infections caused by these organisms are to be identified by serological methods in first line.

[Clinical-parasitological experiences in Cameroon]

Clinical-parasitological experiences collected 1989 in Cameroon during a 6-weeks lasting medical work are reported. Malaria tropica is by far the greatest problem due to the impossibility of an effective epidemiologic control, further to rising drug resistances. Beside malaria there are plenty of other parasitoses, but they are more restricted to lower social groups and to certain geographic regions--to the extreme Northern part of Cameroon in particular. Furthermore the actual situation depends also from epidemiologic control programmes. So the trypanosomiasis seems to be under epidemiologic control, the onchocerciasis in opposite to it has been increased again due to the absence of an effective control programme at present.

Infective endocarditis at a hospital of the University of Kiel, 1958-1987

The clinical courses of 214 patients with infective endocarditis treated between 1958 and 1987 at the First Medical Hospital of the University of Kiel (FRG) were analyzed retrospectively. A decrease in the incidence of endocarditis occurred during the 30-year observation period. The mean age of patients was 48 years, and men were more frequently affected than women. In the course of the investigation, a rise in isolated aortic valve disease was noted, whereas the number of patients with isolated involvement of the mitral valve and combined mitral-aortic valvular defects declined. Streptococci (57%) were the most frequent pathogens isolated; as opposed to their increase, the percentages of Staphylococcus aureus and enterococci decreased. Otolaryngological, dentogenic and urogenital diseases were most frequently held to be responsible for the development of infective endocarditis. Prior cardiosurgical interventions became increasingly significant as a cause of the disease. In this connection, a rising percentage of endocarditis cases was linked with prosthetically replaced heart valves. Complications and concomitant symptoms of endocarditis included the development of heart failure, cerebral embolism and encephalitis, splenomegaly, and renal inflammation. Finally, the marked decrease in mortality contrasted with a simultaneous rise in the number of endocarditis cases achieving full recovery.

Alcohol withdrawal syndrome--an auto-immune disease? A neuroimmunologic model for pathogenesis of alcohol withdrawal symptoms

A neuroimmunologic model of alcohol withdrawal symptoms is developed according to which these may be considered as an idiopathic auto-immune disease. During the alcohol abuse period of non-addicts, homeostasis may alter pathologically by gradual adaptation of the organism: auto-sensitisation develops and finally leads to the breakdown of auto-immune tolerance of the structural modifications set by alcohol withdrawal. The immunosystem regards the existing assimilation of alcohol as self, the withdrawal of alcohol as non-self. Alcohol withdrawal may be considered as an acknowledged physical stressor, and physical stressors as potential triggers of auto-immune diseases. Some so-called alcohol-induced diseases may originate in the pathogenic effects of preceding auto-immune responses to repeated alcohol withdrawals. Neuroimmunologic preconditions of potential auto-immune diseases exactly fit the alcohol withdrawal situation. Neuroimmunologic diseases themselves show close analogies respectively to alcohol withdrawal symptoms as well as to some alcohol-induced diseases. The myelin basis protein is assumed to be a potential auto-allergen. Finally withdrawal symptoms being the expression of physical dependence on alcohol, the model may highlight the very nature of physical dependence.