Diaphragmatic and ventilatory responses to alveolar hypoxia and hypercapnia in conscious kittens.

Ventilation and electromyographic (EMG) activity of the diaphragm were recorded in unanesthetized kittens 2 and 10 wk of age during normoxia, hypercapnia (2 and 4% CO2), and hypoxia (12 and 10% O2). We measured integrated diaphragmatic EMG activity at end inspiration (DIAI) and end expiration (DIAE); the difference (DIAI-E), which represents the phasic change of the diaphragmatic activity, was considered responsible for a given tidal volume (VT). During hypercapnia, the 2-wk-old kittens increased minute ventilation (V) by increases in both VT and respiratory frequency (f), whereas the 10-wk-old kittens increased V primarily by an increase in VT. At both ages, DIAI and DIAI-E increased during hypercapnia, whereas DIAE did not change significantly. During hypoxia, in the young kittens, V and VT decreased while f increased markedly; in the older kittens, V, VT, and f did not change significantly. In kittens of both ages, DIAI increased during hypoxia; because diaphragmatic activity persisted into expiration, DIAE also increased. DIAI-E, as well as VT, was decreased in the young kittens, whereas in the older ones DIAI-E was slightly increased despite an unchanged VT. Finally, the ventilatory and diaphragmatic response to hypoxia changes with maturation in contrast to the response to hypercapnia. It is concluded that 1) the hypoxia-induced reduction of VT may result from prolongation of diaphragmatic activity into expiration, inasmuch as it induces a reduction of the phasic change of the diaphragmatic activity, and 2) because DIAI-E indirectly reflects central inspiratory output, a central mechanism should be involved in the reduced VT and V in response to hypoxia in newborns.     

Ventilatory and metabolic responses to cold and hypoxia in intact and carotid body-denervated rats.

The effects of hypoxia on thermoregulation and ventilatory control were studied in conscious rats before and after carotid denervation (CD). Measurements of metabolic rate (VO2), ventilation (V), shivering intensity (SI), and colonic temperature (Tc) were made in groups of eight rats subjected to three protocols. In protocols 1 and 2, at ambient temperature (Ta) of 25 and 5 degrees C, respectively, rats were exposed to normoxia and hypoxia [inspired O2 fraction (FIO2) 0.13-0.11]. In protocol 3, Ta was decreased from 25 to 5 degrees C in 30-min steps of 5 degrees C. Recordings were made in normoxia and hypoxia (FIO2 0.12). The results show that in both intact and CD rats 1) in normoxia, cold exposure increased VO2, V, and SI, and these increases were proportional to the decrease in Ta; 2) hypoxia induced only a transient decrease in SI, and, for a given Ta, VO2 was reduced whereas V and SI were increased; and 3) in CD rats, V increased less during cold exposure in both normoxia and hypoxia; VO2 and Tc were more depressed during hypoxia. It is concluded that 1) the interaction between Ta and FIO2 in the control of V is partly dependent on the carotid body afferents, 2) shivering thermogenesis may be transiently affected by hypoxia independently of the carotid body afferents, and 3) nonshivering thermogenesis may be directly inhibited by hypoxia, especially during cold exposure.     

Localization of P elements, copy number regulation, and cytotype determination in Drosophila melanogaster

Seventeen highly-inbred lines of Drosophila melanogaster extracted from an M' strain (in the P/M system of hybrid dysgenesis) were studied for their cytotype and the number and chromosomal location of complete and defective P elements. While most lines were of M cytotype, three presented a P cytotype (the condition that represses P-element activity) and one was intermediate between M and P. All lines were found to possess KP elements and only eight to bear full-sized P elements. Only the lines with full-sized P elements showed detectable changes in their P-insertion pattern over generations; their rates of gain and of loss of P-element sites were equal to 0.12 and 0.09 per genome, per generation, respectively. There was no correlation between these two rates within lines, suggesting independent transpositions and excisions in the inbred genomes. The results of both Southern blot analysis and in situ hybridization of probes made from left and right sides of the P element strongly suggested the presence of a putative complete P element in region 1A of the X chromosome in the three lines with a P cytotype; the absence of P copy in this 1A region in lines with an M cytotype, favours the hypothesis that the P element inserted in 1A could play a major role in the P-cytotype determination. Insertion of a defective 2 kb P element was also observed in region 93F in 9 of the 13 M lines. The regulation of the P-element copy number in our lines appeared not to be associated with the ratio of full-length and defective P elements.     

The origin of the membrane convolute in degranulating platelets. A comparative study of normal and "gray" platelets

Thrombin-stimulated normal platelets contain a membrane system of dilated channels with openings to the exterior. Whether these membranes originate from the surface connected system (SCS), the alpha-granules or internalized portions of the plasmalemma has not yet been defined. The present study traces in series of ultrathin sections the rearrangement of these membranes during shape change, degranulation and internalization of surface membranes in washed normal and "gray" platelets upon the stimulation with thrombin (1 IU/ml). Cationized ferritin (CF) was used as a surface marker in order to recognize internalized portions of the plasmalemma. Within the first seconds after stimulation, both normal and gray platelets changed their shape by extrusion of the SCS membranes. Simultaneously they started to internalize surface membrane and formed surface membrane invaginations closely attached to the outer rim of the cytoskeletal sphere which developed during the internal contraction. CF was internalized in these invaginations. CF was not observed within the system of dilated channels of stimulated platelets, however. Thrombin-stimulated gray platelets showed a markedly reduced number of dilated channels or none at all. This observation may be due to the fact "gray" platelets are deficient in alpha-granules. It is concluded that the dilated system of membranes in degranulated normal platelets originates from membranes of the alpha-granules which have performed compound exocytosis.     

Pattern analysis in Belgian limestone grasslands

Pattern analyses were made in several limestone grasslands of Belgium. Vegetation has been sampled in continuous transects. Monospecific patterns are defined by means of two non-parametric indices; multivariate analysis (reciprocal averaging) completed the analysis. The following kinds of pattern are described and explained: random, aggregate, clump, gap, stationary density variation, non-stationary density variation, gradient and many complex patterns. The multivariate analysis leads to a careful phytosociological study of the transects and to the definition of floristically homogeneous regions. Some particular points of pattern analysis, the problem of vegetation sampling and some perspectives are discussed.     

Targeted point mutation that creates a unique Eco RI site within the signal codons of the beta-lactamase gene without altering enzyme secretion or processing

A method has been developed for constructing site-specific mutations by using a strongly selectable marker on which to "piggy-back" a desired mutation that may be phenotypically silent. Using this approach, a new unique Eco RI restriction site has been generated at the beginning of the signal codons of the beta-lactamase gene of the plasmid pBR322. The consequential alteration of the second amino acid of the signal from Ser to Arg has no effect on either the transport or the processing of the beta-lactamase.     

Servo respirator constructed from a positive-pressure ventilator.

We have constructed an electronically controlled respirator from three commercially available components: a positive-pressure ventilator, a recorder pen motor, and a differential amplifier. Using negative feedback derived from a tracheal pressure signal, the instrument functions as a servo respirator which provides precise control of tracheal pressure. The system's power and response characteristics are well suited for ventilation of anesthetized cats and dogs. The servo respirator can be used as an externally controlled respiratory pump which provides flexibility in selection of the parameters of the ventilatory cycle. Alternatively, it can function as a "demand" respirator which generates transthoracic pressure proportional to efferent respiratory discharge.     

Sudden interruption of leaflet opening by ventricular contractions: a mechanism of mitral regurgitation.

The motion of both mitral cusps and the presence of valvular regurgitation during ventricular contractions were investigated in seven experiments on dogs in which radiopaque markers had been sutured to the cusps and the valve annulus 1-32 wk before the studies. Cineangiograms of the left ventricle were obtained during ventricular ectopic beats, interposed throughout the cardiac cycle (20-99% of cycle length) and during induced variations in the P-R interval (0-200 ms). Mitral regurgitation was observed only during a) weak, early ectopic beats (peak pressure below 34 mmHg) which were incapable of closing the cusps and b) when ventricular contractions suddenly interrupted normal leaflet motion toward the ventricle, during three well-defined periods of diastole (diastolic valve opening, diastolic rebound, and atrial opening). Valve closure following sudden reversal of cusp opening was slow and the leaflets often did not arrive simultaneously at their closed positions. These findings suggest that sudden interruption of leaflet opening by ventricular contractions is an important mechanism of transient mitral regurgitation in the normal heart.     

Role of Interaction and Nucleoside Diphosphate Kinase B in Regulation of the Cystic Fibrosis Transmembrane Conductance Regulator Function by cAMP-Dependent Protein Kinase A

Cystic fibrosis results from mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-dependent protein kinase A (PKA) and ATP-regulated chloride channel. Here, we demonstrate that nucleoside diphosphate kinase B (NDPK-B, NM23-H2) forms a functional complex with CFTR. In airway epithelia forskolin/IBMX significantly increases NDPK-B co-localisation with CFTR whereas PKA inhibitors attenuate complex formation. Furthermore, an NDPK-B derived peptide (but not its NDPK-A equivalent) disrupts the NDPK-B/CFTR complex in vitro (19-mers comprising amino acids 36–54 from NDPK-B or NDPK-A). Overlay (Far-Western) and Surface Plasmon Resonance (SPR) analysis both demonstrate that NDPK-B binds CFTR within its first nucleotide binding domain (NBD1, CFTR amino acids 351–727). Analysis of chloride currents reflective of CFTR or outwardly rectifying chloride channels (ORCC, DIDS-sensitive) showed that the 19-mer NDPK-B peptide (but not its NDPK-A equivalent) reduced both chloride conductances. Additionally, the NDPK-B (but not NDPK-A) peptide also attenuated acetylcholine-induced intestinal short circuit currents. In silico analysis of the NBD1/NDPK-B complex reveals an extended interaction surface between the two proteins. This binding zone is also target of the 19-mer NDPK-B peptide, thus confirming its capability to disrupt NDPK-B/CFTR complex. We propose that NDPK-B forms part of the complex that controls chloride currents in epithelia.     

L'ultrastructure du foie humain lors d'ictères idiopathiques chroniques

Summary The hepatocytes of 15 liver biopsies from 13 patients suffering from nonhemolytic constitutional jaundice were studied with respect to the presence of mitochondria with fibrillary inclusions or with vacuoles and to the presence of «paracrystalline cytoplasmic inclusions».Intramitochondrial fibrillary inclusions were found in all cases in quite various proportions, from 1 to 45% of the observed organelles. Intramitochondrial vacuoles were less frequent: they were observed only in three cases, and in one case only in more than 10% of the organelles. Mugnaini's paracrystalline inclusions, dispersed in the cytoplasm of the hepatocytes without outer membranes, were abundant in two cases.None of these morphological characters could be considered as pathognomonic and their origin is unknown: nevertheless their repartition in human liver in pathological conditions seems worthy of further study.

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Travail subventionné par le «Fonds National Suisse de la Recherche Scientifique».