PubMed Health⌕ Search

Biomedical subjects

A Staal

Publications and source records attributed to A Staal.

At least 19 recordsLinked to original sources
PubMed1992

Evidence for the functional involvement of protein kinase C in the action of 1,25-dihydroxyvitamin D3 in bone.

In the present study the involvement of protein kinase C in the action of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on osteoblast-like cells and in the stimulation of in vitro bone resorption by 1,25(OH)2D3 was examined. Incubation for 24 h with 1,25(OH)2D3 potently stimulated osteocalcin synthesis by ROS 17/2.8 cells. This stimulation was inhibited (30-70% inhibition) by 25 microM of the protein kinase C (PKC) inhibitors 1-O-hexadecyl-2-O-methyl-rac-glycerol (AMG) and sphingosine without affecting basal osteocalcin synthesis. 1,25(OH)2D3-stimulated osteocalcin secretion by nontransformed isolated fetal rat osteoblasts was also inhibited (30-55%) by AMG. Also, AMG inhibited 10(-9) M 1,25(OH)2D3-induced up-regulation of vitamin D receptor in ROS 17/2.8 cells. Activation of PKC with phorbol 12-myristate 13-acetate (PMA) did not cause an increase in osteocalcin secretion, while only a small increase in cellular content of osteocalcin in ROS 17/2.8 cells was observed. Addition of PMA together with 1,25(OH)2D3 did not change the response to 1,25(OH)2D3. The PKC inhibitors were not toxic for the cells. 1,25(OH)2D3 did not stimulate diacylglycerol production in ROS 17/2.8 cells up to 5 min after administration. However, 4- and 24-h incubation with 10 nM 1,25(OH)2D3 increased phorbol ester binding in ROS 17/2.8 cells. 1,25(OH)2D3 potently stimulated bone resorption after 3 and 6 days of culture in fetal mouse long bones and calvaria. Both the PKC inhibitors AMG (25 microM) and staurosporine (50 nM) strongly inhibited (60-86% inhibition) 1,25(OH)2D3-stimulated bone resorption without affecting basal 45Ca release. These effects were not due to a cytotoxic effect of both PKC inhibitors. Nor is it likely that the effects of AMG and staurosporine are due to inhibition of cell proliferation as hydroxyurea did not affect 1,25(OH)2D3-stimulated bone resorption. The inhibition of 1,25(OH)2D3-stimulated bone resorption by PKC inhibitors suggests that besides osteocalcin synthesis PKC is also involved in other responses of 1,25(OH)2D3 in bone. 1,25(OH)2D3 does not directly activate PKC via an increase in diacylglycerol production but more likely via an increase in PKC. Together, the present study demonstrates a functional involvement of PKC in the action of 1,25(OH)2D3 in bone and bone cells which may have consequences for the development of 1,25(OH)2D3 analogs, e.g. with less hypercalcemic and relatively more antiproliferative activity.

Alkaloids↗
PubMed1991

'Atypical TIAs' may herald cardiac rather than cerebral events.

Sixty-four patients with atypical transient cerebral or visual symptoms that could not be classified as unequivocal TIAs nor as migraine, epilepsy or neurosis, were followed up for a mean of 3.75 years (range 11 months and 9 years, 240 patient years). Their mean age was 55 years. Only two patients suffered a (non-disabling) stroke, but eight patients had a major cardiac event: fatal myocardial infarction in three, sudden death in one and non-fatal myocardial infarction in four patients. Seven of these eight patients were known to have cardiovascular risk factors. Visual symptoms were relatively benign with regard to cardiac events (2 events in 28 patients), whereas dizziness alone and focal sensory symptoms alone were more strongly associated with subsequent cardiac complications (2 out of 4, and 4 out of 13 patients, respectively). In a control group of 185 patients with 'typical' TIAs or minor strokes, followed for a total of 233 patient years, seven patients had a ischaemic stroke, and only one a cardiac event. Our results suggest that patients with atypical transient cerebral deficits and cardiovascular risk factors may carry a low risk of subsequent stroke, but a high risk of major cardiac events.

Adult↗
PubMed1991

Epidemiology of lissencephaly type I.

In a cooperative study in The Netherlands 22 patients with lissencephaly type I were collected. In the period 1980-1988, the prevalence of lissencephaly type I in the Netherlands was 11.7 per million births (12.2 for females and 11.0 for males). The 5-year survival rate of patients with a complete or nearly complete agyria (grade 1 or 2) in this study was 54% compared to 91% in patients with a mixture of agyria with pachygyria or complete pachygyria (grade 3 or 4).

Abnormalities, Multiple↗
PubMed1990

Non-familial degenerative disease and atrophy of brainstem and cerebellum. Clinical and CT data in 47 patients.

We studied the clinical features of 47 patients with a non-hereditary degenerative disease and with atrophy of brainstem or cerebellum or both in CT scanning. There was no relation between the CT findings and duration or severity of the disease, nor with the kind of the neurological signs which comprised ataxia, a hypokinetic rigid syndrome, oculomotor abnormalities, upper and lower motor neuron signs, orthostatic hypotension and dementia. The 2 main diagnoses were olivopontocerebellar atrophy (OPCA), or a combination of OPCA and striatonigral degeneration (SND). The differential diagnosis with Parkinson's disease and progressive supranuclear palsy was discussed. We concluded, that a CT scan is warranted in all cases of suspected Parkinson's disease, especially in those without tremor, and in cases of motoneuron disease with broad-based gait. In our patients with mainly hypokinesia and rigidity, levodopa treatment had no or brief beneficial effects. If ataxia predominated, OPCA appeared the most sensible diagnosis; if a hypokinetic-rigid syndrome predominated, the diagnoses SND plus OPCA appeared the most suitable. We assessed the degree of atrophy on CT subjectively, because an interobserver study of 60 normal CT scans, did not produce reliable measurements.

Adult↗
PubMed1989

Anticipation in myotonic dystrophy: fact or fiction?

In 1918 Fleischer reported that after transmission from one generation to the next, myotonic dystrophy has an earlier onset and is more severe. The hypothesis put forward by Penrose in 1948 that 'anticipation' is caused by bias of index case selection was based on theoretical arguments only and has not been supported by clinical observations. This hypothesis was tested in a clinical and genetic study of 14 families with myotonic dystrophy. Excluding index patients, an earlier onset in the child was found in 98% of 61 parent-child pairs. A greater mean difference in age of onset was found with transmission via the father than via the mother. The comparison of the severity of the disease between parents and children was difficult because of the variation in symptoms but, in general, the disease was more severe in the child than in the parent. The penetrance of the abnormal gene was nearly complete in the 14 families combined, leaving little room for the observation of 'complementary' parent-child pairs in the future. Also in retrospect no complementary parent-child pairs were found in the first generations. Fertility was severely reduced only in the very early onset patient group and this selective infertility cannot be responsible for the total amount of anticipation observed. It is therefore concluded that anticipation may be inherent in the transmission of myotonic dystrophy. This has important consequences for genetic counselling.

Adult↗
PubMed1989

Reliability of the diagnosis of a first seizure.

We studied the interrater variability among three neurologists of the diagnosis of a seizure in 100 patients evaluated for a possible "first seizure." We found that use of simple descriptive diagnostic criteria and discussion among the neurologists themselves improved the diagnostic agreement.

Adolescent↗
PubMed1987

[Facial paralysis].

Explore the source record for details and available documents.

Adrenal Cortex Hormones↗
PubMed1978

Hereditary sensory neuropathy, a new type.

Two brothers with a new type of hereditary sensory neuropathy are described. The main clinical feature is late onset sensory ataxia without ulcerating acropathy or other autonomic abnormality. The older patient also has oculomotor dysfunction and extensor plantar responses.

Ataxia↗
PubMed1975

An unusual form of spinal muscular atrophy with mental retardation occurring in an inbred population.

Three sibs are described suffering from hereditary non-progressive spinal muscular atrophy with non-progressive mental retardation. One of them had in addition signs of pyramidal tract involvement. Muscular weakness was more pronounced proximally than distally and the neck muscles were severely involved. Th.ey all had small skulls and several associated congenital malformations were observed including syndactyly of the left hand in 1 patient. The patients belong to a small inbred community in the Netherlands. Erythropoietic protoporphyria was also present in the family but segregated independently. This combination of "congenital" mental retardation with "congenital" non-progressive spinal muscular atrophy is believed to represent a new syndrome, caused by a rare recessive gene.

Adult↗