Biomedical subjects

P Vos

Publications and source records attributed to P Vos.

72 records · Page 4Linked to original sources

PubMed1988

Sites of action of mu-, kappa- and sigma-opiate receptor agonists at the feline ileocecal sphincter.

The sites of action of several opiate agonists at the feline ileocecal sphincter (ICS) were studied. Dose-response curves for the relatively specific ligands for the mu-, kappa-, and sigma-receptors were determined using morphine (mu-receptors), dynorphin-(1-13) (kappa-receptors), and N-allylnormetazocine (sigma-receptors). Each agonist results in a contractile ICS response. The ICS responded stereospecifically to the levo-isomer of N-allylnormetazocine. Atropine (30 micrograms/kg) or naloxone (100 micrograms/kg) antagonized the ICS response to morphine and to (-)-N-allylnormetazocine. Higher doses of naloxone were required to inhibit the ICS response to dynorphin. Neither atropine nor tetrodotoxin inhibited the ICS response to dynorphin. The ICS response to dynorphin was enhanced after tetrodotoxin. Morphine tachyphylaxis inhibited the ICS response to (-)-N-allylnormetazocine and vice versa. The ICS response to morphine was unaffected by vagotomy but inhibited by trimethaphan camsylate. This study suggests that dynorphin (kappa-receptor) acts at a smooth muscle receptor to mediate contraction and a neural receptor to mediate relaxation, while (-)-N-allylnormetazocine acts at the ICS via a mu-receptor. mu-Receptor activation causes ICS contraction via a cholinergic pathway.

Animals↗

PubMed1988

Response of luteinizing hormone secreting pituitary adenoma to a long-acting somatostatin analogue.

A large pituitary tumour was discovered in a 20 year old man who came to medical attention because of grand-mal seizures. The tumour produced biologically active LH as demonstrated by supranormal plasma LH and plasma testosterone values. Free alpha-subunit values were also elevated. In contrast, plasma FSH was in the lower normal range. Transsphenoidal operation failed to remove all tumour tissue. Detailed studies were carried out in the postoperative period. TRH and GnRH administration were associated with a rise of plasma LH and alpha-subunit, whereas plasma FSH was low and unresponsive. Bromocriptine treatment was ineffective. In contrast, both during and after treatment with SMS 201-995 for 6 weeks, a decrease of basal plasma LH values was observed. Furthermore, the administration of a single dose of SMS 201-995 reproducibly induced a decrease of plasma LH lasting for a period of about 6 h. The study suggests that SMS 201-995 may be useful in the treatment of patients with gonadotrope cell adenomas.

Adenoma↗

PubMed1987

In vitro expression of a full-length DNA copy of cowpea mosaic virus B RNA: identification of the B RNA encoded 24-kd protein as a viral protease.

Double-stranded cDNA was synthesized from B component RNA of cowpea mosaic virus and cloned into appropriate vectors. Using four clones, together representing the entire B RNA sequence, a full-length DNA copy was constructed and subsequently positioned downstream of a phage SP6 or T7 promoter. RNA molecules transcribed from this full-size DNA copy using SP6 or T7 RNA polymerase were efficiently translated in rabbit reticulocyte lysates into a 200-kd polypeptide similar to RNA isolated from viral B components. Moreover this polypeptide was rapidly cleaved into 32-kd and 170-kd polypeptides, exactly like the 200-kd polypeptide encoded by viral B RNA. In vitro transcription and translation of a DNA copy in which an 87-bp-long deletion in the coding sequence for the 24-kd polypeptide was introduced revealed that the 24-kd polypeptide bears the proteolytic activity involved in the primary cleavage of the B RNA-encoded polyprotein.

Journal Article↗

PubMed1987

[3H]ketanserin labels 5-HT2 receptors and alpha 1-adrenoceptors in human and pig brain membranes.

The binding characteristics of [3H]ketanserin (a reported selective radioligand for serotonin 5-HT2 receptors) and [125I]BE 2254 (which labels selectively alpha 1-adrenoceptors) were characterized in brain frontal cortex membranes of pig and man. Saturation experiments indicated that both radioligands label apparently a homogeneous class of binding sites in human and pig fontal cortex membranes. Competition experiments with [125I]BE 2254 using 17 agonists and antagonists showed monophasic and steep curves in human and pig frontal cortex membranes. The pharmacological profile of these sites is typical of alpha 1-adrenoceptors. In competition experiments with [3H]ketanserin, most of the tested compounds displayed shallow or biphasic curves. In particular, alpha 1-adrenoceptor-selective antagonists (prazosin, WB 4101, BE 2254...) displaced with nanomolar affinity about 15 and 40% of the specific [3H]ketanserin binding in human and pig frontal cortex membranes, respectively. The minor component of [3H]ketanserin binding correlated highly significantly with [125I]BE 2254 binding in both membrane preparations. The major component of [3H]ketanserin binding to pig and human frontal cortex membranes correlated significantly with [3H]ketanserin binding in rat brain cortex membranes (which is essentially to 5-HT2 receptors). The present data demonstrate that [3H]ketanserin in nanomolar concentrations binds significantly to alpha 1-adrenoceptors in human and pig frontal cortex membranes; this suggests a rather limited degree of selectivity of ketanserin for 5-HT2 receptors in pig and human tissues.

Adrenergic alpha-Antagonists↗

PubMed1987

Proteolytic activity of the cowpea mosaic virus encoded 24K protein synthesized in Escherichia coli.

The function of the 24-kilodalton (24K) protein encoded by cowpea mosaic virus (CPMV) has been studied by constructing a bacterial expression plasmid that contained a cloned chimeric segment consisting of partial DNA copies of CPMV M-RNA (including sequences coding for both capsid proteins) and B-RNA (including sequences coding for the 24K protein). Viral sequences were transcribed from the phage T7 promoter phi 10 of plasmid pT7-6 using T7-RNA polymerase expressed from plasmid pGP1-2 present in the same cells. Upon inducing the synthesis of T7-RNA polymerase several new polypeptides that contained CPMV-specific sequences were expressed, as demonstrated by immunoprecipitation and immunoblotting. Furthermore a proteolytic activity was detected in induced cells which cleaved the viral protein sequences specifically at two glutamine-glycine sites. One of the cleavage products represented capsid protein VP23. The proteolytic activity was absent when an 87-bp deletion was introduced in the coding region for the 24K protein, indicating that this protein represented the protease involved in the proteolytic processing at those specific sites.

Cloning, Molecular↗

PubMed1987

[3H]ketanserin labels serotonin 5-HT2 and alpha 1-adrenergic receptors in human brain cortex.

The binding of [3H]ketanserin and [125I]BE 2254 [( beta-(4-hydroxyphenyl)ethylaminomethyl]tetralone) was characterized in human brain cortex membranes. As observed in saturation experiments, [3H]ketanserin (a reportedly selective serotonin 5-HT2 ligand) and [125I]BE 2254 (a selective alpha 1-adrenergic antagonists) labeled, apparently, a homogeneous class of high-affinity recognition sites. Competition experiments performed with [125I]BE 2254 and a series of 20 structurally different compounds resulted in steep and monophasic competition curves. In contrast, competition curves of these compounds for [3H]ketanserin binding were often shallow or biphasic, suggesting a heterogeneity of the sites labeled by [3H]ketanserin. In particular, alpha-adrenoceptor-selective ligands (e.g., prazosin, BE 2254, WB 4101, phentolamine) showed clearly biphasic curves displacing about 20% of [3H]ketanserin binding with nanomolar affinity. On the other hand, cinanserin, a selective 5-HT2 antagonist, showed nanomolar affinity for 80% of the sites labeled by [3H]ketanserin, and micromolar affinity for the other 20%. There was a highly significant correlation between [125I]BE 2254 binding and the minor component of [3H]ketanserin in human brain cortex membranes (r = 0.910, p less than 0.0001, n = 20). The data show that [3H]ketanserin binds in the nanomolar concentration range (1.5-1.8 nM) to both 5-HT2 and alpha 1-adrenergic receptors. Similar results were obtained in rat and pig brain membranes. The data suggest that ketanserin possesses a rather limited degree of selectivity in human tissue.

Binding, Competitive↗

PubMed1987

Selective regulation of beta-2 adrenergic receptors by the chronic administration of the lipophilic beta adrenergic receptor agonist clenbuterol: an autoradiographic study.

Many antidepressant drugs, when administered chronically to rats, have been shown to produce decreases in the density of beta adrenergic receptors in the central nervous system. The centrally active beta adrenergic receptor agonist clenbuterol is currently being evaluated clinically as an antidepressant. The chronic administration of this drug to rats resulted in a large decrease in the density of beta adrenergic receptors in some areas of the rat brain but not in others. Thus, autoradiographic studies revealed that the total density of beta adrenergic receptors in the molecular layer of the cerebellum, but not in layers 1 to 3 or layer 4 of the cerebral cortex, was decreased. To examine whether this regional selectivity occurred because of differences in plasticity of cerebellum and cortex or because cerebellum contains mainly beta-2 adrenergic receptors and cortex contains mainly beta-1 adrenergic receptors, separate analyses of the subtypes of beta adrenergic receptors were performed in each area. These experiments indicated that the decrease in receptor density was entirely specific for beta-2 adrenergic receptors, whereas the density of beta-1 receptors was unchanged. Thus, even in layers 1 to 3 and layer 4 of the cerebral cortex, beta-2 receptor density was decreased, with no change in beta-1 receptor density. Using the autoradiographic assay for ligand binding, it was shown that clenbuterol has equal affinity for beta-1 and beta-2 adrenergic receptors, indicating that the selective effect of this drug was not due to a selective affinity for beta-2 receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗

PubMed1986

Effect of repeated administration of clenbuterol on the regulation of beta-adrenoceptors in the central nervous system of the rat.

The effect of the centrally acting beta-adrenoceptor agonist clenbuterol on beta-adrenergic responsiveness, beta-receptor density and N-protein coupling was studied in the rat cerebral cortex (which contains primarily beta 1-receptors) and cerebellum (containing mostly beta 2-receptors). The objective was to determine whether clenbuterol's effect on these variables was similar to that produced by standard antidepressants. When given to rats repeatedly, clenbuterol caused a decrease in beta-adrenergic responsiveness in slices from either the cerebral cortex or the cerebellum. The decreased beta-responsiveness in the cerebellum was associated with a decrease both in the density of beta-receptors and in receptor/N-protein coupling. In the cortex, only reduced receptor/N-protein coupling was observed by in vitro ligand-binding methods. However, when quantitative autoradiography was employed, clenbuterol treatment was found to reduce the binding of [125I]iodopindolol to beta 2-receptors throughout the brain, whereas binding to beta 1-receptors was not reduced. The down-regulation of beta 2-receptors by clenbuterol is due to its acting centrally as a beta 2-agonist. Although clenbuterol has about an equal affinity for beta 1-receptors and beta 2-receptors, no evidence was found for agonist activity of this drug at beta 1-receptors in the cerebral cortex. The strategies described here should be helpful in investigating important properties of centrally acting beta-agonists that might have potential as antidepressants.

Animals↗

PubMed1986

Epidermoid cyst of the testis.

An epidermoid cyst of the testis is a rare benign lesion, representing about 1% of all testicular tumors. Most of the lesions occur between the age of 20 and 40 and present as a painless enlargement of the testis, or are found as a nodule on routine examination. Histopathologic findings consist of a cyst filled with keratin and lined by a squamous epithelium. There is evidence that this tumor is of germ-cell origin and represents monoepidermal differentiation of a benign teratoma. There is some discussion about treatment, but most authors perform radical orchiectomy.

Epidermal Cyst↗

PubMed1985

Ferritin in liver, plasma and bile of the iron-loaded rat.

Rats were loaded with iron. With overload, up to a 10-fold increase of the iron and ferritin protein content of the livers was measured. The plasma ferritin concentration increased gradually with the ferritin concentration in the liver. The ferritin concentration in the bile increased also and was in the same range as in the plasma. The ratio plasma ferritin concentration to bile ferritin concentration in individual rats decreased in the case of considerable iron overload. After intravenous injection of liver ferritin, less than 2% of the ferritin concentration that disappeared from the blood was found to be in the bile. Isoelectric focussing revealed that the microheterogeneity of liver and bile ferritin were identical, but slightly different from plasma ferritin. These results indicate that ferritin was not solely leaking from the plasma to the bile. Together with ferritin, iron accumulated in the bile. The iron content of the bile ferritin was in the same range as in fully iron-loaded liver ferritin. It is likely that ferritin in the bile is excreted by the liver and consists of normal iron-loaded liver ferritin molecules. In all circumstances, the amount of iron in the bile was much higher than could be accounted for by transport by the bile ferritin. The ferritin protein to iron ratio in the bile was 0.1-1.2, which was in the same range as was measured in isolated lysosomal fractions of the liver. Those results agree with the supposition that ferritin and iron in the bile are excreted by the liver though lysosomal exocytosis.

Alanine Transaminase↗

PubMed1984

Study of the genetic organisation of a plant viral RNA genome by in vitro expression of a full-length DNA copy.

The genetic approach for elucidating functions encoded by RNA plant viruses has been hampered by the lack of methods to select desired mutants following random mutagenesis. An alternative might be to copy RNA genomes into DNA and use methods for site-directed mutagenesis to modify specific regions of the DNA copy. Transcription of the DNA copy will subsequently produce viral RNA with desired mutations. We have constructed a full-length DNA copy of the smaller of the two cowpea mosaic virus (CPMV) RNAs, referred to as M RNA. The DNA copy was positioned downstream from the promoter of bacteriophage SP6 and using SP6 RNA polymerase, this copy and two derivatives of it containing a specific deletion and insertion, respectively, have been transcribed into RNA molecules which are efficiently translated in rabbit reticulocyte lysates. The results obtained show that the subsequent in vitro transcription and translation of DNA copies may be a powerful tool to unravel the genetic properties of viral RNA genomes.

Cloning, Molecular↗

PubMed1983

Primary structure and gene organization of the middle-component RNA of cowpea mosaic virus.

Middle component RNA (M RNA) of cowpea mosaic virus (CPMV) was transcribed into cDNA and double-stranded cDNA was inserted into the EcoRI site of plasmid pBRH2. The nucleotide sequence of inserts was determined, after subcloning in bacteriophages M13mp7, M13mp8 or M13mp9, by the dideoxy chain termination method. The complete sequence of CPMV M RNA, up to the poly(A) tail, is 3481 nucleotides long. The sequence contains a long open reading frame starting at nucleotide 161 from the 5' terminus and continuing to 180 nucleotides from the 3' terminus. The sequence does not contain a polyadenylation signal for the poly(A) tail at the 3' end of CPMV RNA. The initiation site at position 161 together with AUG codons in the same reading frame at positions 512 and/or 524 account for the two large colinear precursor polypeptides translated in vitro from M RNA. The amino acid sequence deduced from the nucleotide sequence suggests that both precursor polypeptides are proteolytically cleaved at glutaminyl-methionine and glutaminyl-glycine, respectively, to produce the two viral capsid proteins.

Base Sequence↗

PubMed1982

Molecular cloning and characterization of a complete DNA copy of potato spindle tuber viroid RNA.

Double-stranded cDNA has been synthesized from RNA of a severe strain of potato spindle tuber viroid using a synthetic oligodeoxyribonucleotide as a primer. Upon cloning in bacteriophage M13mp9, two recombinant phages were selected to construct a pBR322-derived plasmid containing a complete viroid DNA copy. Elucidation of the nucleotide sequence revealed four differences with the previously established sequence of another PSTV strain, three of which were base exchanges and one a deletion.

Base Sequence↗

PubMedDate not supplied

Contribution of heating, ventilation, and air conditioning airflow and conversation to the ambient sound in a neonatal intensive care unit.

Sound reduction strategies in the neonatal intensive care unit (NICU) must focus on the sources of excessive sound. We studied the relative contribution of personnel conversation and heating, ventilation, and air conditioning (HVAC) airflow by measuring several parameters of sound during four environmental conditions: unaltered ambient sound, HVAC airflow off, HVAC airflow and conversation off, and conversation off. All measurements were decreased by interrupting HVAC airflow and conversation. The reduction was greater when conversation was stopped. The method of sound reduction did not change the frequency distribution of sound. Attention to personnel conversation may be effective in lowering sound exposure in the NICU. The contribution of HVAC airflow should be measured in new constructions and renovations.

Air Conditioning↗

PubMedDate not supplied

Sound transmission into incubators in the neonatal intensive care unit.

OBJECTIVE: To measure the attenuation of sound by modern incubators. STUDY DESIGN: LEQ, LMAX, LPEAK, and frequency distribution were measured simultaneously inside and outside two recent model incubators. RESULTS: The attenuation of sound (outside minus inside) was 15 to 18 dBA with the motor off and 4 to 8 dBA with the motor on. There was a significant difference between incubators in their attenuation of sound. Octave band analysis showed attenuation in frequency bands of > 31.5 Hz with the motor off. With the motor on, the sound level inside the incubator was higher than outside at frequency bands of < 250 Hz. CONCLUSION: Caring for infants inside modern incubators reduces "averaged" sound exposure to levels near those recommended for the neonatal intensive care unit. Lower frequency sounds are louder inside the incubator and arise from the incubator motor.

Humans↗

PubMedDate not supplied

Prognosis for papillary serous carcinoma of the endometrium after surgical staging.

BACKGROUND: To investigate the pattern of failure and the prognosis following pathological staging for uterine papillary serous carcinoma (UPSC). PATIENTS AND METHODS: A retrospective review was conducted of 22 patients with UPSC, treated between 1989 and 1998 at a single institution. All patients were surgically staged. Two patients with advanced disease received chemotherapy only. Two patients with early-stage disease were followed without further treatment. Eighteen patients received postoperative irradiation; eight patients received whole abdominal irradiation (WART), and the remaining 10 patients, pelvic irradiation (PRT). In addition, seven of these patients received vaginal cuff irradiation with low-dose-rate or high-dose-rate brachytherapy. Toxicity, pattern of failure, and survival were evaluated and compared to the literature. RESULTS: Seven patients (32%) developed distant metastases, three out of seven (42%) after WART. Four out of seven patients who had distant metastases died from disease progression during subsequent chemotherapy. All patients with distant metastases had locally advanced-stage disease at presentation (six stage III, one stage IV). Four patients with pelvic recurrences developed concurrent (2) and subsequent (2) distant metastases. Three patients had isolated distant metastases. No patient with early stage-disease (stage I and II) died from disease progression. CONCLUSION: Pathological staging should be performed for all patients with UPSC to determine the prognosis as well as to tailor the treatment. The role of abdominal irradiation in the treatment of UPSC is yet to be determined; however, such an approach may not be necessary for the control of disease for patients with early-stage (I and II) disease. Patients with locally advanced-stage (stage III) disease are at risk of local regional failures and distant metastases despite WART. Therefore, the benefit of WART for advanced-stage disease is also questionable. Paclitaxel-based chemotherapy is currently being investigated in this setting.

Aged↗

PubMedDate not supplied

Establishing a noise measurement protocol for neonatal intensive care units.

OBJECTIVES: To compare three noise exposure measurement methods and determine the effect of location within the nursery, time of day, day of week, shift, and activities such as nursing shift change and physicians' rounds on noise measurements. STUDY DESIGN: We performed a noise distribution survey, central site measurements, and quadrant area measurements in our nursery. The measurements made were sound pressure level and hourly LEQ, LMAX, and L10. RESULTS: The noise distribution survey method was least useful because steady-state noise sources were the exception. Differences between central site and quadrant area measurements were minimal. There was no significant effect of time of day, shift change, or physician rounds on the noise measurements. CONCLUSIONS: In an open nursery with excessive noise levels central site measurements over a relatively short time accurately reflect the noise exposure. A protocol for measuring noise exposure in the neonatal intensive care unit is appended.

Female↗

PubMedDate not supplied

Peak noise distribution in the neonatal intensive care nursery.

OBJECTIVE: To measure short duration sounds (L(PEAK)) in the neonatal intensive care unit and describe their intensity, incidence, and periodicity in relationship to activities within the unit. STUDY DESIGN: We measured 1-minute L(PEAK) at four locations within the intensive care unit, accumulating 48 hours of data for each weekday. RESULTS: Thirty-one percent of the L(PEAK) exceeded 90 dB. For further analysis, the data were transformed to the proportion exceeding 90 dB. These values varied significantly with day, week, location, and time of day. During physician rounds, there was a 16% relative increase in L(PEAK). CONCLUSION: These data demonstrate the intensity, incidence, and periodicity of short duration sounds in the intensive care nursery. Short duration sounds are known to affect the infant's physiological and behavioral states and should be addressed in future recommendations for sound control and reduction strategies.

Health Facility Environment↗