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Biomedical subjects

J Lacombe

Publications and source records attributed to J Lacombe.

At least 19 recordsLinked to original sources
PubMed2002

Comparison of somatostatin receptor expression in human gliomas and medulloblastomas.

The expression of the five somatostatin receptor subtypes, sst1-5 was compared on tissue containing glial tumours (glioblastomas or oligodendrogliomas), medulloblastomas, and on normal human cortex. By semiquantitative reverse transcription coupled to polymerase chain reaction, the receptor expression profiles were high in cortex and in tissue containing oligodendrogliomas. It was moderate in medulloblastomas. Tissue containing glioblastomas displayed lower expression of somatostatin receptor subtypes, sst1 and sst3 being mostly expressed. By 125I-Tyr0DTrp8 somatostatin-14 or 125I-Leu8DTrp22 Tyr25 somatostatin-28 autoradiography combined with synaptophysin immunohistochemistry, it was possible to differentiate between isolated tumoral cell component infiltrating the cerebral parenchyma (cortex or white matter) and tumoral tissue (without residual parenchyma) in glioblastomas or oligodendrogliomas. Glial tumoral tissue per se presented few somatostatin receptors. By contrast, medulloblastoma tumoral cells exhibited numerous octreotide sensitive somatostatin receptors. sst2 immunocytochemistry demonstrated immunostaining of neuronal cells and neuropile; sst2 and sst3 immunostaining was identified on glioblastoma proliferating vessels endothelial cells and on medulloblastomas tumoral cells. Faint sst2 immunostaining among glial tumoral cells was due to microglia, while glioma cells did not significantly stain. In summary, medulloblastoma tumoral cells express sst2/sst3 receptors at a high level while glioma cells do not. In gliomas, sst expression is restricted to endothelial cells on proliferating vessels (displaying both sst2 and sst3 receptors), including parenchyma and reactive microglia (only sst2). The differential expression of sst2/sst3 receptors on gliomas and medulloblastomas has implications for the therapy of these tumours.

Adolescent↗
PubMed2000

The Kex2p proregion is essential for the biosynthesis of an active enzyme and requires a C-terminal basic residue for its function.

The Saccharomyces cerevisiae prohormone-processing enzyme Kex2p is biosynthesized as an inactive precursor extended by its N-terminal proregion. Here we show that deletion of the proregion renders Kex2p inactive both in vivo and in vitro. Absence of the proregion impaired glycosylation and stability and resulted in the retention of the enzyme in the endoplasmic reticulum. These phenotypes were partially complemented by expression of the proregion in trans. Trans complementation was specific to Kex2p proregion because expression of any of the seven mammalian prohormone convertase propeptides had no effect. These data are consistent with a model whereby Kex2p proregion functions as an intramolecular chaperone and indicate that covalent linkage to the protein is not an absolute requirement for proregion function. Furthermore, extensive mutagenesis revealed that, in addition to their function as proteolytic recognition sites, C-terminal basic residues play an active role in proregion-dependent Kex2p activation.

Amino Acid Sequence↗
PubMed1989

An arterial prosthesis from Argentina: the Barone Microvelour arterial graft.

The manufacture of a polyester vascular prosthesis in the southern hemisphere is a new development in the global dissemination of this maturing technology. Hence the recent introduction of the Barone Microvelour arterial graft from Argentina has highlighted the need for a comparative in vitro and in vivo study to compare its structure and performance with that of existing commercial products. Following a series of laboratory tests and implantations as a thoracoabdominal bypass in dogs, the Barone Microvelour has been identified as a strong graft constructed after the style of early weft-knitted designs. It provides an equivalent sequence and rate of healing to that of other polyester knitted grafts.

Animals↗
PubMed1988

Cardiovascular changes during the sleep-wake cycle in spontaneous hypertensive rats and their genetically normotensive precursors.

Blood pressure and heart rate were recorded in spontaneously hypertensive rats (SH) and in their genetically normotensive precursors (WKY) during the sleep-wake cycle using a computer-assisted method. Similar results were obtained in both strains: (a) No significant difference was observed in blood pressure values between slow-wave-sleep (SWS) and the last 2 min of the preceding wakefulness (W) episode within the complete cycle; blood pressure then increased during PS. (b) Heart rate values during SWS were significantly lower than those computed for W; a further fall of heart rate was observed during paradoxical sleep (PS) only in hypertensive rats. (c) During SWS the blood pressure and heart rate variability was significantly lower than during W and PS. In addition, blood pressure variability values during the three sleep-wake states were lower in hypertensive than in normotensive rats. These data suggest that there are no qualitative differences in the mechanisms that control circulation during sleep in normotensive and spontaneous hypertensive rats.

Animals↗
PubMed1988

Computer analysis of cardiovascular changes during sleep-wake cycle in Sprague-Dawley rats.

Blood pressure (BP) and heart rate (HR) were recorded in seven Sprague-Dawley rats during a total of 491 normal sleep-wake cycles with the use of a computer-assisted method developed for this study. Significant changes of BP, HR, and BP variability (BPV) were found between the three states within the cycle, i.e., wakefulness (W), slow-wave sleep (SWS), and paradoxical sleep (PS). The highest BP, BPV, and HR values were found during W. Then all cardiovascular (CV) variables fell during SWS, whereas BP and BPV rose again during PS. The fall of BPV observed during SWS was the most important CV change observed within the cycle. These state-dependent CV changes suggest that, in the rat, circulation during the sleep-wake cycle is controlled by the same central factors that operate in cats. In addition, significant BP and HR modifications between different cycles have been found. On the other hand, BP and HR differences between animals were also observed. The latter differences were found to be stable across the states, but no significant relation was found between BP and HR within any state. Thus the present data also suggest that BP and HR measurements are influenced not only by state-dependent factors but also by at least three different factors that are each independent of the state: one leads to BP and HR values that are influenced by the cycle the animal is in and the other two influence, respectively, the ranking of the individual's BP and HR levels within the population.

Animals↗
PubMed1986

[Transcutaneous oxygen tension and apnea during sleep stages in normal infants and infants at risk for sudden infant death syndrome].

The relationship between chronic hypoxemia and sudden infant death syndrome (SIDS) has been reported by several authors. In order to study the influence of the apnea-time during a sleep state on transcutaneous oxygen tension (tcPO2), we have studied polygraphically 30 full-term infants (10 controls, 10 SIDS siblings and 10 near-miss for SIDS), aged from 5 to 13 weeks. No significant difference was observed either for apnea-time or tcPO2 between infant-groups studied in different sleep states. We could not find any correlation between apnea-time and tcPO2 in all groups of infants studied during different states of sleep. It is therefore concluded that in normal and at risk for SIDS infants, tcPO2 levels during sleep states cannot be explained only by the apnea-time.

Blood Gas Monitoring, Transcutaneous↗
PubMed1986

Polysomnograms and cardiopneumograms in SIDS research.

Polysomnographic (PSG) and cardiopneumographic (CPG) recordings are commonly used in research on sudden infant death syndrome (SIDS). PSG and simultaneous CPG recordings were compared in order to clarify two practical problems: reliability of sleep state evaluation with CPG and comparability of the number of respiratory pauses evaluated by these two recording techniques. This comparison shows that: (1) evaluation of sleep states by CPG technique is only reliable for quiet sleep and (2) there was a significant difference in the number of pauses, the evaluation with PSG being systematically higher than with CPG. The abnormalities found or suspected in CPG home recordings must be confirmed by PSG in the laboratory.

Heart Function Tests↗
PubMed1986

Intraspinal lipomas with spina bifida. Prognosis and treatment in 73 cases.

The authors present a series of 73 cases of intraspinal lipomas in the lumbosacral region. Sixty-four patients were operated on, 43 of these under intraoperative monitoring of neural function. The results of this series and of major series published in the past 10 years demonstrate both the potential severity of these lesions (which are responsible for progressive neurological deficits in 56% of affected cases) and the benignity of their surgical treatment. The authors emphasize the usefulness of systematic early surgical treatment of these lesions.

Adolescent↗
PubMed1984

Factors causing acute shunt infection. Computer analysis of 1174 operations.

A series of 1174 operations performed on 802 hydrocephalic children was analyzed in an effort to find the factors causing acute postoperative infection. Culture of the cerebrospinal fluid (CSF) samples during the operation was positive in 33 cases. These cases were excluded from the series. Ninety infections were observed in the remaining 1141 operations, an overall rate of 7.9%. Most of these infections were meningitis (56 cases). Staphylococcus epidermidis was the bacterium most frequent identified (44%). Statistically significant relationships were found between shunt infection and the following factors: 1) age: infection was 2.6 times as frequent before 6 months than after 1 year of age (p = 0.03); 2) poor condition of the skin; 3) presence of intercurrent seats of infection at the time of surgery; 4) type of operation: the rate of infection was 8.4% in primary shunt insertions, 5% in shunt revisions, and 17.5% in reinsertions following shunt removal for infection (p = 0.0001); 5) end of the shunt requiring revision: an infection rate of 7.7% followed revision of the ventricular catheter alone, and 2.6% followed revision of the other end alone (p = 0.012); and 6) postoperative wound dehiscence or scalp necrosis. The surgical team involved was poorly correlated with the rate of infection (p = 0.12). No statistically significant relationships have been found between infection and 1) etiology of hydrocephalus: 2) sex; 3) recent neurosurgical operation before the shunt procedure; 4) preoperative presence of an external drainage tube or CSF fistula; 5) lumbar or ventricular taps, or ventriculography; 6) number of previous operations performed on the shunt; 7) time (month and year) of operation; or 8) sugar level and cell count in the CSF.

Cerebrospinal Fluid Shunts↗
PubMed1981

[Intra-sleep awakenings in relation to habitual sleep length and modifications of the sleep-wake rhythms (author's transl)].

The number of episodes of intervening wakefulness, their duration and their sleep stage occurrence were analyzed in the sleep recordings of 19 young (19-23 years), good sleepers. There were 5 long sleepers (LS), 5 short sleepers (SS) and 9 regular sleepers (RS). The experimental protocol included 2 reference nights, a night sleep recovery (after 36 h of wakefulness) and a day sleep recovery (after 24 h). The night following the day sleep recovery was also recorded. The duration of waking episodes was very stable and was independent both of type of sleeper and of situation. The histogram of these durations seemed to follow an exponential law. The number of awakenings varied according to the individual, the habitual sleep length (SS had very few) and the situation (such as length of prior wakefulness or circadian factors).

Adult↗
PubMed1981

[Intra-sleep awakenings in poor sleepers, 20 to 30 years of age. Correlation with anxiety level and personality (author's transl)].

Recordings were made from 43 poor sleepers between the ages of 20 and 30 for at least 4 consecutive nights. Three subject groups were formed on the basis of the awakenings occurring up to the sixth hour of sleep. The first group, with an average of 61 min wakefulness, is characterized by the abundance of long-lasting waking periods. The second group, with 18 min average wakefulness, showed the highest absolute number of awakenings, almost all of which were very brief. The third group, with 6 min average wakefulness, showed a slightly lower number of awakenings, but these were almost exclusively micro-waking periods. The temporal distribution of the waking periods was also different in the first group, in which the longest waking periods occur during the first hour of sleep and remain elevated until the fifth hour of sleep. The latency for falling asleep is particularly high for this group. A correlation exists between the amount of time awake up until the sixth hour of the night and the subject's anxiety level and the neuroticism index. 65% of the subjects obtained pathological scores on one or more MMPI scales. According to the order of frequency these were scales Sc, Pd and Pt. No preferential profile was found.

Adult↗
PubMed1980

Vasomotor origin of intracranial pressure waves in hydrocephalic infants.

By measuring cerebral blood volume (CBV) and intracranial pressure (ICP) variations at the same running time during sleep, it has been demonstrated that the ICP wave which appears during the REM sleep in hydrocephalic infants is produced by intracerebral vaso-dilatation. Nine infants with stabilized hydrocephalus were investigated by non-invasive means: REM phases were distinguished with the usual polysomnographic electrodes. Intracranial pressure was measured with a fontanel palpation transducer and CBV variations were obtained by recording 99mTc activity at the head level after in vivo labelling of red cells with 99mTc--pertechnetate. The time-activity curves, obtained from regions of interest and selected on the sequential radioisotope images, show that an increased ICP wave, occurring during the REM period, is related to a simultaneous increase in the blood volume, limited to the cerebral sector and not to the area of the external carotid artery.

Blood Volume↗
PubMed1978

[Sleep in children with episodic sleep phenomena: a comparison with the normal child].

(1) The sleep pattern of 23 children, aged 5-12 years, with episodic nocturnal phenomena (night-terrors, somnambulism, rhythmic movements) was recorded during two successive nights. It was compared with that of a group of 21 normal children of the same age. (2) In the pathological group, slow wave sleep (SLP, stages 3 and 4) was significantly shortened during the 2 nights. This deficit mainly involved the first 3h of sleep. (3) As for the slow wave sleep, REM sleep (SP) modifications prevailed during the first hours of sleep. The first REM period was delayed and preceded by more numerous and atypical partial REM periods. The duration of the first REM period increased faster as a function of its latency than in the normal child. (4) In contrast with this difficulty for REM sleep to occur during the first part of the night, the subsequent REM sleep pattern was similar in the 2 groups (total REM sleep duration, mean REM period duration, mean REM cycle duration). For equal latencies, REM periods had similar duration. Finally, the total REM sleep amount was a linear function of the total sleep time, with more or less identical coefficients for the two groups. (5) The part played by these modifications during the first hours of sleep in the occurrence of night terrors and somnambulism is discussed.

Child↗
PubMed1978

[Measuring intracranial pressure with a fontanelle palpation transducer (author's transl)].

The accuracy and reliability of a non-invasive method for the measurement of intracranial pressure through the fontanelle without puncture was tested during 12 or even 24 hours recordings. Wealthall and Smallwood modified aplanation transducer was first used. A metal frame had to be developed in order to secure the transducer rigidly over the fontanelle so that the recording could take place with the infant in any position and completely free of its movements. Simultaneous recordings of extradural or intraventricular pressure have shown the measurements were accurate to about 1 or 2 cm H2O in a neurosurgical environnement (i.e large fontanelles with pressure over 10 cm H2O). For smaller fontanelles or low or even negative intracranial pressure, a smaller transducer seems to be needed. The preliminary test of a plane strain gauge transducer that partially fills this need is shown.

Circadian Rhythm↗