The switch from larval to adult globin gene expression in Xenopus laevis is mediated by erythroid cells from distinct compartments

The transition of hemoglobins during metamorphosis of Xenopus laevis involves replacement of the larval erythrocytes by adult ones, suggesting that the developmental control of this event depends upon the growth characteristics of the precursor cells. To identify the erythroid precursor cells and to investigate their developmental fate, we analyzed the distribution of stage-specific globin mRNAs by northern blotting in dorsal and ventral fragments of stage 32 embryos after in vitro culture as well as presumptive erythropoietic tissues of tadpoles during metamorphosis. The histological analysis shows that erythrocytes differentiate only in ventral fragments, suggesting that the ventral blood islands and most likely also the dorsolateral mesoderm are the primary sites of erythropoiesis. We also demonstrate that the first generations of erythrocytes, already express the predominating larval-specific alpha-globin mRNAs. The globin mRNA patterns obtained from presumptive erythropoietic tissues suggest an important role of circulating precursor cells in larval erythropoiesis, whereas the liver appears to be the main site of formation and maturation of the adult erythrocytes. Tentatively we propose that anuran erythropoiesis is dependent upon a self-perpetuating stem-cell line and that the larval and the adult erythrocytes are derived from successive generations of erythroid precursors, whose commitment may be imposed by the erythropoietic sites.

Chimeric gRNA-mRNA molecules with oligo(U) tails covalently linked at sites of RNA editing suggest that U addition occurs by transesterification

Chimeric RNA molecules were detected by polymerase chain reaction amplification of kinetoplast RNA using a 3' primer specific to mRNA and a 5' primer specific to guide RNA (gRNA), and directly by Northern analysis. Covalent linkage of the 3' oligo(U) tail of the gRNA to the mRNA occurs at editing sites. Chimeric molecules were isolated for NADH dehydrogenase subunit 7 and cytochrome oxidase subunits II and III. We propose that these molecules are intermediates in the editing process and that successive transesterifications result in the transfer of uridine residues from the gRNA 3' oligo(U) tail to an editing site, with the number of uridine residues determined by base pairing with adenine and guanine "guide" nucleotides in the gRNA.

Reaching in the dark: enhanced responses in posterior parietal cortex

In order to assess the relative importance of visual input to area 7 reach-related neuronal activity, a monkey was trained to reach to visual targets displayed on a video-monitor, both with and without visual feedback. Visual feedback was removed by having the monkey reach in darkness to a previously illuminated target. Of 19 reach-related cells recorded in area 7 both in the light and the dark, ten showed an enhancement of discharge in the dark. These included area 7b cells sensitive to screen contact and area 7a cells active during reach. Dark enhancement of active somatic responsiveness may partially compensate for the loss of visual guidance.

Guide RNAs in kinetoplastid mitochondria have a nonencoded 3' oligo(U) tail involved in recognition of the preedited region

Maxicircle-encoded guide RNAs (gRNAs) for cytochrome b and maxicircle unidentified reading frames 2 and 3 (MURF2 and MURF3) were isolated by hybrid selection and sequenced. All three gRNAs contained nonencoded 3' oligo(U) tails 5-24 nucleotides in length, with a mean length of approximately 15 nucleotides. Secondary structure calculations indicate a functional role of the 3' oligo(U) tail in stabilizing the initial hybrid formed between the gRNA and the preedited mRNA, and allowed the identification of potential mRNA recognition sites for an editing complex. In addition, isolated MURF2 gRNA-II could be 5' capped with [alpha-32P]-GTP and guanylyltransferase, suggesting that at least some gRNAs represent primary transcripts.

Survival of pig embryos flushed from the reproductive tract immediately or two hours after slaughter of donors

Four- to eight-cell embryos were collected from genital tracts of slaughtered gilts. Prepuberal donors were synchronized and superovulated by PMSG and hCG, inseminated and eventually slaughtered approximately 78 h after the expected time of ovulation. Genital tracts were flushed either immediately after slaughter (group A) or after 2 h storage at either 37 degrees C (group B) or 20 degrees C). Best results were achieved in group A, followed by group B and, by a wide margin, group C. Differences in viability of embryos became more evident with longer culture times.

A model for RNA editing in kinetoplastid mitochondria: "guide" RNA molecules transcribed from maxicircle DNA provide the edited information

A class of small RNA molecules possibly involved in RNA editing is present in the mitochondrion of Leishmania tarentolae. These "guide" RNA (gRNA) molecules are encoded in intergenic regions of the mitochondrial maxicircle DNA and contain sequences that represent precise complementary versions of the mature mRNAs within the edited regions. In addition, the 5' portions of several gRNAs can form hybrids with mRNAs just 3' of the preedited region. A model is presented in which a partial hybrid formed between the gRNA and preedited mRNA is substrate for multiple cycles of cleavage, addition or deletion of uridylates, and religation, eventually resulting in a complete hybrid between the gRNA and the mature edited mRNA.

Biochemical characterization and purification of the neuronal sodium-dependent noradrenaline transporter

The protein properties of the neuronal sodium-dependent noradrenaline (NA) transporter of PC12 (rat pheochromocytoma) cells and of bovine adreno-medullary cells were studied by means of binding of 3H-desipramine (3H-DMI). 3H-DMI binding was decreased by proteases, phospholipase A2, by disulfide reducing agents and by the sulfhydryl-group alkylating agent N-ethylmaleimide. The NA transporter was partially purified by anion exchange and affinity chromatography. Tritiated desmethylxylamine (3H-DMX) bound irreversibly and in a DMI-sensitive manner to two PC12 membrane proteins (32kd and 53kd) which may represent components of the NA transporter.

Functional and molecular characterization of a monoclonal antibody against the 165-186 peptide of human IL-1 beta

A synthetic peptide of human recombinant interleukin 1 beta (hrIL-1 beta) 165-186, which exhibits biological activity in the human fibroblast assay, was used as an immunizing antigen to obtain a murine monoclonal antibody (MoAb) termed FIB 1. This MoAb, an IgG1, reacts specifically with hrIL-1 beta, but not with hrIL-1 alpha, as measured in enzyme-linked immunosorbent assays (ELISA). The MoAb FIB 1 detects the characteristic 17 kDa IL-1 protein in Western blots. Binding to the antigen is specific, as deduced also from the close correlation of ELISA immunoreactivity with IL-1 biological activity. The anti-IL-1 beta 165-186 Ab specifically neutralizes the biological activity of hrIL-1 beta and native IL-1, as measured by the IL-1-induced proliferation of murine thymocytes and human fibroblasts and the IL-1-dependent IL-2 production by murine T cells (EL4-6.1). Fifty per cent of hrIL-1 beta activity (25 U/ml, or 0.25 ng/ml) has neutralized by less than 30 micrograms/ml of MoAb. Furthermore, FIB 1 recognizes intracellular IL-1 in lipopolysaccharide-stimulated human peripheral blood mononuclear cells. The anti-IL-1 beta 165-186 Ab does not react with the shorter IL-1 beta fragment 161-173 in solid-phase ELISA, therefore the binding region seems to be localized in the amino acid sequence VALGLKEKNLYLS. A sandwich-ELISA, using a polyclonal sheep anti-IL-1 beta 251-269 Ab as the capture antibody and an anti-IL-1 beta 165-186 MoAb as the detecting probe, allowed the determination of IL-1 beta from crude culture supernatants.

Depressor effects of muscarinic and non-muscarinic mediation induced by lateral hypothalamic stimulation in the cat

Transient sympathetically-mediated depressor effects were induced by stimulation of a small locus in the lateral hypothalamic peri-fornical region, medial to the fields of Forel. The ganglionic blocking agent, atropine methyl nitrate (ATMN), was used to show that muscarinic as well as non-muscarinic sympathetic ganglion receptor neurotransmission was involved. Evidence is presented that stimulation of this LH site co-activates a number of mechanisms and that depending on which of these are activated, the ganglionic blocking agent ATMN may either block, reverse or potentiate the depressor effect.

Inferior parietal lobule neurones related to eye and hand reach movements in rhesus monkey

Analysis was made on neuronal responses of the inferior parietal lobule to visual, jump, or 'reach' behavioral paradigm in 2 awake, trained rhesus monkeys. Preconditioning and antidromic electrical stimulation of medial and oral pulvinar LP nuclei and the arcuate gyrus aided the study. The results reveal two reach cell categories: one with no definable visual sensitivity (NVHRN) and one with visual receptive field responsiveness (VHRN). The VHRN reach cell firing is characterized by an early component. As the latter was observed only when the monkey reached loci inside but not outside of the cell-receptive field, it was equated with the cell visual receptive field response. This component could be voided by preconditioning stimulation of medial pulvinar or LP, the latencies of the VHRN responses becoming longer and comparable to NVHRN. If the consequences of reaching were nulled in any of a few different ways, such as preventing the monkey from reaching, disenabling the panel key, or denying the reward, a reach cell biphasic firing response showed no change in the first burst, but the second burst was absent, suggesting the latter's relation to satiation. If a jump cell's visual responses enhanced by the 'jump' paradigm were negated by preconditioning stimulation, the saccadic eye movement that otherwise followed the enhanced signals was replaced by another saccade, different in direction and amplitude, as if of other frames of reference. It seems, therefore, that the inferior parietal lobe system subserves in two types of reach behaviour: one with and one without visual guidance, playing perhaps a role in selecting strategies such as the dynamic option to do away with the visual guidance, if circumstances demand.

Sympatho-inhibitory mechanisms acting at sympathetic ganglia to attenuate hypothalamic-induced pressor effect in the cat

Pressor and tachycardic effects induced in the cat by stimulation of a lateral hypothalamic (LH) site, are shown to be mediated by sympathetic ganglia nicotinic receptor, and potentiated under atropine methyl nitrate sympathetic ganglia blockage. It is postulated that a sympatho-inhibitory pathway muscarinic ganglionic mechanism, co-activated by the LH stimulation, attenuates the pressor and tachycardic effects, the potentiation presumably being a manifestation of blockage of that mechanism.

A vocabulary for medical informatics

The terminology in medical informatics is evolving rapidly. The organizers of MEDINFO and SCAMC have used different sets of keywords to index their documents. Recognizing the limitations of this approach, members of those organizations joined with the National Library of Medicine in the creation of a better terminology for medical informatics. A hierarchical structure was placed on the terms to produce a thesaurus typical of the sort often used in the indexing and retrieving of documents. The building of this thesaurus began with an automatic merging of the thesaurus used by the Association of Computing Machinery and the Information Sciences component of the "Medical Subject Headings." This product was pruned by eliminating terms not related to those in the MEDINFO keyword list or not in the medical informatics literature. Further refinement of the thesaurus resulted from extensive discussions among the authors of this paper. The first major application of this terminology has been to the indexing of the articles in "MEDINFO-86 Proceedings." Major components of this medical informatics thesaurus also have been incorporated into the "Medical Subject Headings." This paper describes the process of preparing the thesaurus and presents an evaluation of its coverage of the "MEDINFO-86 Proceedings."

[Traumatic pneumatocele--a case report]

The posttraumatic pneumatocele is a rare intrapulmonary lesion following blunt thoracic injury. By means of a well documented case report this rare form of lung contusion is demonstrated and the clinically important differential diagnosis is discussed.

Processing in the external transcribed spacer of ribosomal RNA from Physarum polycephalum

The rDNA of the myxomycete Physarum polycephalum is transcribed to give a 13.3 kb precursor of ribosomal RNA. At 1.7 kb downstream of the primary initiation site there is a processing site or a second initiation site. This site was studied by S1-mapping, DNA sequencing and electron microscopy. None of these methods could conclusively distinguish between the two formal possibilities. However, capping experiments indicate that rapid processing is taking place at this site rather than reinitiation. In addition, primary transcripts and processed molecules were assayed throughout the synchronous mitotic cycle. During all interphase stages newly initiated transcripts of rDNA and products of the first processing step are present in similar amounts, indicating control of initiation and not of maturation as being the main regulatory step for the accumulation of mature rRNAs. During the brief period of mitosis the level of newly initiated rRNA precursors is lowered.

Tubulin mRNAs of Trypanosoma brucei

The tubulin genes of Trypanosoma brucei are located in a single, tightly packed cluster of ten tandemly arranged alternating alpha and beta-genes. No tubulin genes are detected outside the clustered array. Therefore, the cluster can be assumed to be the locus of tubulin gene expression. Single bands of alpha and beta-tubulin mRNAs are observed in cultured procyclic as well as in bloodstream trypanosomes. Both alpha and beta-tubulin mRNAs have distinct 5' termini, which carry a 35-nucleotide mini-exon sequence. The 3' termini of both mRNA populations are heterogeneous.

Manipulation reach and visual reach neurons in the inferior parietal lobule of the rhesus monkey

The characteristics of inferior parietal lobule (IPL) 'reach cell' responses were studied in the fixating monkey in order to obtain a clue to the function of this area in manipulative behavior. Two subclasses of reach neurons, one showing visual receptive field sensitivity, the other lacking such responsiveness are proposed as correlates of two types of reach behavior, one that takes place with, the other without visual guidance, respectively. Neuronal firing increment and/or firing decrement responses, stimulus-bound to reach behavior were obtained from either type of cell. These were presented as equivalent modes of signal encoding, on the basis of the transformability of neuronal firing increment to firing decrement response as a result of preconditioning stimulation of the oral pulvinar nucleus. Many of the responses obtained were bimodal and some were biphasic, i.e. consisting of incremental and decremental firing phases. As each such component was independently modifiable, they were regarded different signal entities. The multicomponental nature of the visual reach neuronal response was manifested when the reaching movement was into the receptive field of the neuron. Responses consisted then of an initial component, presumably visual, prefixed to a response component stimulus-bound to the reach-invoking stimuli. The early component occupied the same position as the visual response of the cell obtained with visual receptive field stimulation alone. Moreover, the early component could be negated by preconditioning stimulation of the LP and/or pulvinar targets, and then the residual response simulated the response of a non-visual reach neuron.(ABSTRACT TRUNCATED AT 250 WORDS)