Search PubMed⌕ Search

Biomedical subjects

J Krieger

Publications and source records attributed to J Krieger.

At least 109 records · Page 6Linked to original sources
PubMed1994

Probing olfactory receptors with sequence-specific antibodies.

Molecular cloning has revealed the structure of several putative odorant receptors. Chemically synthesized peptides, that correspond to a predicted extracellular domain of the encoded proteins, were employed to generate receptor-specific antibodies. Immunohistological approaches as well as Western-blot analysis confirmed the specificity of the antipeptide sera. Furthermore, deglycosylation experiments explained the observed discrepancy between the molecular mass of odorant receptors, as determined by SDS/PAGE and Western-blot analysis of ciliary proteins (M(r) 50,000), and the predicted protein size based on the deduced primary structure from cloned receptor genes (M(r) 30,000-35,000). Receptor proteins become phosphorylated upon odorant stimulation of olfactory cilia preparations; this was demonstrated by immunoprecipitation experiments employing the sequence-directed, receptor-specific antibodies. Functional assays revealed that the receptor-specific antibodies significantly attenuate second messenger signalling elicited by inositol 1,4,5-trisphosphate-inducing odorants, whereas activation of the cAMP cascade by appropriate odorants was not affected. These observation indicate that the sequence-specific antibodies not only recognize odorant receptors, but also discriminate between receptor subtypes coupling to different second-messenger pathways.

Amino Acid Sequence↗
PubMed1994

[Sleep apneas].

In its most frequent form, in which obstructive apneas are predominant, the sleep apnea syndrome appears more and more as a frequent disorder. Clinically, it can be easily suspected in a patient presenting with snoring and daytime sleepiness, provided that these symptoms are systematically sought. A firm diagnosis relies on polysomnographic recordings. Beyond these symptoms, which are social and professional handicaps, the severity of the disorder is related to its cardiovascular long-term complications. The standard treatment is based upon nasal continuous positive airway pressure, which is safe and efficient but constraining. Surgical treatments, which are not as safe nor as efficient, can be proposed when continuous positive airway pressure is not accepted.

Adolescent↗
PubMed1993

T cell receptor antagonism mediated by interaction between T cell receptor junctional residues and peptide antigen analogues.

A major objective of new rational immunosuppressive therapies is to be able to inhibit deleterious T cell responses in an Ag-specific manner. Recently, a novel approach to inducing Ag-specific nonresponsiveness in T cells, termed receptor or TCR antagonism, has been described. Several analogues of the influenza hemagglutinin (H3) peptide HA307-319 were shown to block recognition of the native HA307-319 peptide by a DR1-restricted T cell clone at concentrations 1,000- to 10,000-fold less than required to competitively inhibit HA307-319 binding to DR1. These Ag analogues that inhibited T cell recognition differed from the stimulatory antigenic peptide only at single positions. How such limited changes affect the ternary complex interactions of TCR, peptide, and DR remains unclear. In the present study, we have utilized two different DR5-restricted T cell clones that exhibit mutually exclusive specificities for HA peptides with or without substitutions at position 313 to investigate the molecular requirements for receptor antagonism. In this reciprocal model system, we show that a single peptide/DR complex can antagonize one T cell clone while stimulating another. A comparison of nucleotide sequences derived from the TCR of the T cell clones that were either antagonized or stimulated by the peptide analogue/DR5 complex indicated that the different responses of these T cells result from minor differences in the amino acid residues in junctional regions that most likely interact directly with position 313 of the peptide analogues. Our results suggest that TCR antagonism is an Ag-specific phenomenon in which T cells are inhibited by interactions involving TCR residues required for the recognition of conventional Ag and the altered residues in peptide analogues.

Amino Acid Sequence↗
PubMed1993

Cloning and expression of odorant receptors.

Myriads of odorous molecules that vary widely in structure are nevertheless readily detected and discriminated by the sense of smell, but how this is achieved by the olfactory system has been a long-standing puzzle. Several different models have been proposed, and previous observations indicate that the recognition sites for odorous molecules could be G-protein-coupled receptor proteins, an idea supported by the discovery of a new gene family that probably encodes a diversity of odorant receptors. Here we report the identification of new members of the gene family encoding putative odorant receptors and demonstrate that they are indeed transcribed in olfactory receptor neurons. Furthermore, the receptor-encoding complementary DNA is expressed in non-neuronal surrogate cells, which generate second messenger responses upon stimulation with appropriate odorants, indicating that the receptors recognize odorants and couple to G proteins of the host cells.

Amino Acid Sequence↗
PubMed1993

Arrestin-subtypes in insect antennae.

Arrestin is supposed to be involved in uncoupling receptor-mediated second messenger cascades. Clones encoding proteins homologous to arrestin have been isolated from antennal cDNA libraries of Locusta migratoria and Heliothis virescens. Based on the size and several characteristic motifs, the two proteins are considered as members of different arrestin subfamilies. One of the subtypes, which has also been found in Drosophila, lacks the regulatory acidic C-terminal. The putative site of interaction with phosphorylated receptors, a cationic region in the primary structure, is conserved in all identified arrestins from locust to human.

Amino Acid Sequence↗
PubMed1993

Odorant binding proteins of Heliothis virescens.

cDNA clones coding for three different binding proteins were isolated from an antennal library of Heliothis virescens. The deduced amino acid sequences showed only moderate homology to each other but shared several common structural features. Based on a comparison with the predicted primary structures of antennal binding proteins from different moth species, one of the clones (Hel-1) was found to encode a pheromone binding protein, whereas the two others (Hel-10 and -11) encode general odorant binding proteins.

Amino Acid Sequence↗
PubMed1993

[Sleepiness and sleep apnea syndrome. Analysis of 188 questionnaires (102 patients and 86 controls)].

A questionnaire was given to 102 obstructive sleep apnea patients and 86 controls. A somnolence index was defined by averaging the scores of the answers to eleven questions concerning sleepiness. This index separated patients and controls (P < 0.0001). It was correlated with the apnea + hypopnea index (r = 0.32, P < 0.001), the body mass index (r = 0.45, P < 0.001) and with an objective measurement of sleepiness obtained from a modified multiple sleep latency test (r = -0.54, P < 0.001). Depending upon the current occupation, the tendency to fall asleep decreased in the following order: watching TV, passenger in a means of transport, reading, attending a show, attending a meeting, driving a car, and eating. This order is the same in patients and controls, irrespective of their "overall sleepiness". Thus, the circumstances of falling asleep are indicative of the severity of sleepiness.

Adult↗
PubMed1993

Continuous positive airway pressure treatment. Effects on growth hormone, insulin and glucose profiles in obstructive sleep apnea patients.

The principal nocturnal GH peak normally coincides with the first episode of slow wave sleep (SWS). Obstructive sleep apnea (OSA) patients have low nocturnal GH levels which may be explained by their poor quality fragmented sleep but other factors are possibly involved. Obesity is frequently associated with OSA, and obese patients also manifest reduced GH secretion. The mechanisms reducing GH levels in obese subjects are not understood, but hyperinsulinaemia is a suggested factor. In this study nocturnal plasma and secretory GH profiles of OSA patients were examined in relation to the quality and quantity of sleep, together with plasma glucose and insulin levels. Eight OSA patients, (BMI 32.7 +/- 2.3 kg/m2), underwent 2 night studies. For one night no treatment was given and for the other continuous positive airway pressure (CPAP) treatment was administered for the first time. Blood was collected continuously throughout each night and plasma GH, insulin and glucose profiles established in 10 min interval samples. From the plasma data a deconvolution model was used to calculate GH secretion rates. Sleep was recorded during the studies. For the non-treatment night GH levels were low and increased significantly with treatment, p = 0.008 for plasma levels and p = 0.02 for secretion rates. Treatment significantly decreased the cumulative apnea duration and increased the quantity of SWS and Rapid Eye Movement (REM) sleep (p = 0.008), but the mean insulin and glucose profiles did not differ between the two nights. Individual GH plasma and secretion rates, on treatment, showed a tendency to correlate with the amount of SWS (p = 0.09).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Nocturnal pollakiuria is a symptom of obstructive sleep apnea.

An increased urine excretion has been reported in obstructive sleep apnea (OSA) patients, but it is not clear whether it results in an increased number of nocturnal micturitions. The present study was aimed at investigating the frequency of nocturnal micturitions in OSA patients using a standardized questionnaire prospectively given to 102 OSA patients and 86 healthy male subjects. The frequency of nocturnal micturitions was significantly greater in the OSA patients than in the healthy subjects (more than 70% of the OSA patients with an apnea+hypopnea index > 50 reported nocturnal micturitions more than twice a week versus less than 25% of the healthy subjects, p < 0.0001). The number of nocturnal micturitions was also greater in the OSA patients than in the healthy subjects. There was an effect of age on the frequency of nocturnal micturitions; however, when age-matched subsamples were considered, there was still a significant difference between OSA patients and healthy subjects. In a subgroup of 25 OSA patients reevaluated after at least 1 year of home treatment with nasal continuous positive airway pressure the reported frequency of nocturnal micturitions had significantly decreased (p < 0.001). These results suggest that investigations aimed at establishing a diagnosis of OSA should be part of the work-up of patients complaining of nocturnal pollakiuria.

Adult↗
PubMed1993

Towards an identification of odorant receptors.

The molecular nature and diversity of receptive sites for odorous molecules is a central unanswered issue in olfaction. Based on the enormous resolving power of the olfactory system, which enables the stereospecific discrimination of numerous compounds at low concentrations specific receptor proteins have been proposed. Due to the central role of G-proteins in olfactory signalling it has been predicted that odorant receptors might be members of the superfamily of receptor proteins with seven transmembrane domains. Upon application of degenerated oligonucleotides and the PCR-technology a number of putative odorant receptors have been cloned and sequenced. In situ hybridisation studies using receptor-specific probes have been performed and olfactory neurons specifically expressing a particular receptor subtype are topologically identified in the nasal epithelium of rats. Clones of interest are now being expressed in heterologous systems in order to demonstrate functional activity of these putative receptor proteins and to match defined odorants to identified receptors.

Amino Acid Sequence↗
PubMed1992

Expression of a pheromone-binding protein in insect cells using a baculovirus vector.

A cDNA encoding a pheromone-binding protein from the male silkmoth Antheraea pernyi has been integrated into the genome of the Autographa californica multiple nuclear polyhydrosis virus such that the transcription was under the control of the strong polyhedrin promoter. Recombinant pheromone-binding protein was expressed in a baculovirus-infected insect cell line (Sf9) and secreted from the cells into the culture medium. Using a two-step protocol, recombinant pheromone-binding protein has been isolated and purified to homogeneity. Pheromone binding of recombinant protein has been demonstrated using a tritiated analog of (E,Z)-6,11-hexadecadienyl acetate.

Affinity Labels↗
PubMed1992

Daytime sleepiness after long-term continuous positive airway pressure (CPAP) treatment in obstructive sleep apnea syndrome.

A modified maintenance of wakefulness test was performed in 58 patients with obstructive sleep apnea (OSA) syndrome before treatment and after long-term (554 +/- 28 days) home therapy with nasal continuous positive airway pressure (CPAP). Before treatment the patients had a shorter mean sleep latency than controls (16 +/- 1 vs. 27 +/- 1 min, mean +/- SEM, P less than 0.001). After treatment, the mean sleep latency increased to 20 +/- 1 min (P less than 0.002 as compared to baseline), but was still shorter than in controls (P less than 0.001). The incomplete normalization of the mean latency contrasted with the patients' claim that they no longer felt sleepy. The improvement in daytime alertness was significantly correlated with the reduction in sleep fragmentation after CPAP treatment and with the baseline mean sleep latency. These results support the hypothesis that sleep disruption related to respiratory events plays a role in the pathogenesis of daytime sleepiness.

Electrocardiography↗
PubMed1992

Long-term compliance with nasal continuous positive airway pressure (CPAP) in obstructive sleep apnea patients and nonapneic snorers.

In a prospective study aimed at evaluating objectively the compliance with nasal continuous positive airway pressure (CPAP) treatment, 233 obstructive sleep apnea (OSA) (apnea index, > 10 apneas/hour) patients and 36 nonapneic snorers were studied. The compliance to treatment was measured by the mean rate of use of the CPAP device, obtained from a built-in time counter. The follow-up period was 874 +/- 48 in OSA patients and 675 +/- 83 in snorers. CPAP was proposed to all OSA patients but only to those snorers who felt improved after an initial laboratory night on CPAP. Nineteen OSA patients refused CPAP. Of the 214 OSA patients who accepted CPAP, 181 are still on treatment, with a mean daily rate of use of 5.6 +/- 0.1 hours (mean +/- SEM); 22 patients stopped CPAP after a variable period of time; 10 patients died and one acromegalic patient was considered cured after hypophysectomy for a pituitary adenoma. Depending upon the definition of acceptable compliance, the compliance rate in this group was between 77% and 89%. The mean rate of use was correlated with indices of disease severity (apnea index, apnea+hypopnea index, minimal SaO2 during sleep, daytime PaO2, pulmonary artery pressure). Thirty-six nonapneic snorers accepted CPAP. In this group, 26 are still on CPAP, with a mean daily rate of use of 5.4 +/- 0.5 hours; one patient died; one underwent uvolopalatopharyngoplasty without follow-up; and eight stopped CPAP. The compliance rate in this group was between 58% and 78%. This study shows that CPAP is reasonably accepted by OSA patients as well as by nonapneic snorers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗