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Biomedical subjects

S Daniel

Publications and source records attributed to S Daniel.

At least 91 records · Page 5Linked to original sources
PubMed1993

Different sets of afferents are demonstrated by the fluorescent tracers fast blue and rhodamine.

The fluorescent retrograde tracers Rhodamine B Isothiocyanate (RITC) and Fast Blue (FB) were injected either into the thalamic nucleus rotundus or into the complexus neck muscle in pigeons. Both in the rotundal and the peripheral motor preparations RITC yielded a 3-5 times larger number of afferent ipsilateral neurones than FB. While RITC additionally labelled a large number of contralateral afferents, virtually no labelled cells were detected contralateral to the injection site using FB. This selective omission of the contralateral input with FB was identical for both neural systems despite differences in injection volume, survival time, and transport length. In the present case, this structure-specific sensitivity of FB would lead to the erroneous conclusion that contralateral afferents are virtually non-existent in the visual tectofugal and the peripheral motor system. Thus, these results make it likely that the choice for a certain tracer may lead to different connectional interpretations of a neural system. Although the mechanism for these structure-specific sensitivity differences are unknown, it is suggested that tracers with lower effectivity like FB may be unable to label afferent structures with fewer axon terminals.

Afferent Pathways↗
PubMed1993

An aggressive philosophy in controlled ovarian stimulation cycles increases pregnancy rates.

To assess the effect of timing of human chorionic gonadotrophin (HCG) administration in ovarian stimulation cycles, the serum oestradiol concentration and follicle profile were compared with the clinical pregnancy rate in 582 ovarian stimulation-intra-uterine insemination (OS-IUI) cycles and 3917 in-vitro fertilization-embryo transfer (IVF-ET) cycles. The pregnancy rates increased exponentially with increasing oestradiol in both OS-IUI and IVF-ET cycles (R2 = 0.720, P < 0.001) but then decreased in OS-IUI cycles when the oestradiol concentration exceeded 5000 pmol/l (R2 = 0.936, P < 0.004) at HCG administration. In OS-IUI cycles the percentages of cycles with three or more mature follicles (> or = 18 mm diameter) increased up to an oestradiol concentration of 5000 pmol/l then declined, mirroring the pregnancy rate (R2 = 0.900, P = 0.01). The exponential increase in pregnancy rate with increasing oestradiol concentration in IVF-ET cycles suggests that high oestradiol concentration does not have a deleterious effect on endometrial receptivity. The decrease in pregnancy rate in OS-IUI cycles when oestradiol concentration exceeded 5000 pmol/l reflected fewer mature follicles, resulting from premature administration of HCG to avoid severe ovarian hyperstimulation syndrome (OHSS). We recommend that HCG administration be delayed until multiple follicles have reached maturity, and reducing the risk of severe OHSS by converting high risk OS-IUI cycles to IVF-ET, or if funds or facilities are unavailable, transvaginally draining all but four or five mature follicles.

Chorionic Gonadotropin↗
PubMed1992

Giant thoracoabdominal lymphangioma with features of lymphangiomyoma.

A 15-year-old girl who presented with cough and dyspnea was found to have a mediastinal tumor that clinically resembled a lymphangioma. The tumor was unusual for its large size and its histologic features, which showed smooth muscle proliferation, generally considered a feature of lymphangiomyoma.

Adolescent↗
PubMed1991

Activation of protein kinase C in lipid monolayers.

The potential of lipid monolayers spread at an air-water interface was investigated as a well defined membrane model able to support protein kinase C (PKC) association and activation. PKC association to a mixed phospholipid film (phosphatidylcholine, phosphatidylserine) could be detected by an increase of the monolayer surface pressure. This association was strikingly dependent upon the presence of submicromolar concentrations of Ca2+. The effect of Ca2+ resulted in an increase of the PKC penetration into the lipid core at a given permissive surface pressure as well as in a marked increase of the critical surface pressure (29-38 dynes/cm) above which the enzyme was excluded from the membrane. Inclusion of diacylglycerol or tetradecanoate phorbol acetate (TPA) did not modify the PKC-monolayer association in a detectable manner. PKC associated to the lipid layer exhibited the expected catalytic property and was fully activated when diacylglycerol or TPA was included in the membrane. PKC activity was highly dependent upon the surface pressure of the lipid monolayer, being optimal between 30 and 35 dynes/cm. Study of the compression isotherm of various diacylglycerol structures revealed that all potent PKC agonists exhibited an expanded liquid phase behavior with collapse pressure below 40 dynes/cm, in contrast to weak activators which showed condensed isotherms with high collapse pressure (approximately equal to 60 dynes/cm). These observations showed that the lipid monolayer system is well adapted to the study of the molecular mechanisms involved in the regulation of PKC activity at a model membrane interface. They are in line with the suggestion of a major role of Ca2+ in the association (translocation) of PKC to membrane in living cell and suggest that diacylglycerol (and TPA) might activate membrane-associated PKC through local change in the surrounding lipid phase organization.

Animals↗
PubMed1991

Screening for potassium channel modulators by a high through-put 86-rubidium efflux assay in a 96-well microtiter plate.

A rapid and sensitive 86Rb efflux assay to detect chemical compounds capable of modulating the ATP-dependent potassium (KATP) channel is described. This assay, which is performed in a 96-well microtiter plate, utilizes a substrate adherent cell line as the target, requires a small amount of 86Rb as the tracer, and is a suitable system for performing the biochemical and pharmacological characterization of the KATP-channel and its activators. Because this assay is amenable to automation, it presents a useful means for high-volume screening of chemical compounds on a routine basis.

Adenosine Triphosphate↗
PubMed1990

Organization of neck muscle motoneurons in the cervical spinal cord of the pigeon.

As a first step towards the analysis of the neural control of pecking behaviour in the pigeon, the cell bodies of neck muscle motoneurons were localized and their somatotopic organization in the cervical spinal cord examined. Fluorescent tracers were injected into single neck muscles and labelled motoneuron cell bodies identified. Labelled perikarya were arranged in longitudinal columns within layers VIII and IX of the ventral horn ipsilateral to the injection site. Cell bodies of neurons innervating different muscles formed distinct columns that extended mainly rostrally from the injection level. Labelling of adjoining portions of one muscle revealed one continuous column of cell bodies. Relative to the neck muscles, the motoneuron perikarya were arranged in a mediolaterally inversed pattern.

Amidines↗
PubMed1990

Sympathetic neural modulation of cardiac impulse initiation and repolarization in the newborn rat.

We injected neonatal rats with nerve growth factor, the antiserum to nerve growth factor, or placebo for the first 10 days of life. Our goal was to determine the relation between sympathetic innervation of the developing heart, the electrocardiographic expression of cardiac rhythm, and the response of the heart to alpha-adrenergic stimulation with phenylephrine. We were especially interested in the latter area because of the prior demonstration in isolated cell systems of sympathetic neural modulation of a 41-kDa GTP regulatory protein and alpha-adrenergic responsiveness. Ten- to 11-day-old rats treated with nerve growth factor had more complete sympathetic innervation, faster heart rates, and higher levels of the 41-kDa protein than the placebo group. Electrophysiological studies were performed on isolated ventricular septa superfused with Tyrode's solution at 37.0 degrees-37.5 degrees C. The electrophysiological response of septa to 10(-9) and 10(-8) M phenylephrine from the 10-11-day-old nerve growth factor group was comparable with that of 3-week-old control animals. In contrast, 10-11-day-old antiserum-treated rats had an abnormal innervation pattern, lower levels of the 41-kDa protein, and a more immature electrophysiological response to alpha-adrenergic stimulation than the placebo group. In addition, antiserum-treated rats had an abnormally prolonged electrocardiographic QT interval. Our results demonstrate for the first time in intact animals a direct link between sympathetic innervation and alpha-adrenergic receptor-effector coupling as well as the dependence on innervation of the modulation of impulse initiation by alpha-agonists. This sequence of developmental events may be important not only in the regulation of normal cardiac rhythm but also in the expression of certain pathological entities such as the congenital long QT syndrome and the sudden infant death syndrome.

Animals↗
PubMed1989

Cavernous angioma of the thoracic spinal cord with intra- and extramedullary components.

A 31-year-old male presented with a 1 year history of left leg weakness and right leg sensory changes. Myelography revealed a probable intramedullary lesion at T4 and CT confirmed its intramedullary nature. At operation an almost black, firm mass was found projecting from the dorsal aspect of the cord and was totally excised. Histological examination revealed it to be a cavernous angioma.

Adult↗
PubMed1987

Needle biopsy for muscle diagnosis and research: an Italian experience.

We report our experience of needle biopsy over the past two and a half, viz. 395 cases. We find that the technique meets the needs of diagnosis and research very satisfactorily. We describe its advantages over open biopsy and recommend it in preference to the latter, provided that the necessary technical skill for processing the sample is available.

Adolescent↗
PubMed1986

[Acute myopathy and hyperthyroidism].

A 40 year-old woman with a rapidly progressive proximal muscle deficit of all four limbs had an acute myopathy secondary to hyperthyroidism. Biopsy of the quadriceps femoris revealed signs of non specific muscle impairment with type II fiber atrophy. Treatment with methimazole and correction of the thyroid condition led to rapid disappearance of the disorders. Eighteen months later the clinical status was normal and a second quadriceps femoris biopsy showed that the muscle had normalized.

Acute Disease↗
PubMed1984

Two cases of hemorrhagic fever with renal syndrome in northern Greece.

Two cases of hemorrhagic fever with renal syndrome were diagnosed in woodcutters presumably exposed to wild rodents and their urine in a forest in northern Greece. The disease was characterized by acute renal insufficiency without hemorrhagic manifestations. One patient required hemodialysis, but both recovered without sequelae and developed a fourfold increase in titer of antibody to Hantaan virus, as determined by an immunofluorescence test. These are the first reported cases of hemorrhagic fever with renal syndrome in Greece.

Adult↗