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L Steen

Publications and source records attributed to L Steen.

At least 37 records · Page 2Linked to original sources
PubMed1993

Realizing the dream.

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Education, Dental, Continuing↗
PubMed1992

Alteration in molecular structure which results in disease: the Met-30 variant of human plasma transthyretin.

The structure of a variant transthyretin has been determined by X-ray crystallography at 2.3 A resolution in order to investigate those changes which lead to amyloid formation. This variant transthyretin, in which the internal valyl residue at position 30 is replaced by methionyl, is associated with the most common form of familial amyloidotic polyneuropathy (FAP). Comparison to the known structure of the normal transthyretin tetramer shows that the bulkier methionine residue 30 which lies between the nearly orthogonal beta sheets of the dimer, results in the sheets being displaced an average of 0.4 A. The internal structure of the sheets and of the monomer-monomer interface is maintained. Such global changes may affect the metabolic properties and the tendency towards polymerization of the mutant protein. These findings may form a basis for understanding other amyloid-deposition diseases.

Amino Acid Sequence↗
PubMed1992

Salivary hypofunction in patients with familial amyloidotic polyneuropathy.

Patients who suffer from familial amyloidotic polyneuropathy frequently complain of mouth dryness and an increased need for dental treatment. The aim of the present investigation was to study saliva secretion rate and composition and other factors related to the risk of dental caries in patients with familial amyloidotic polyneuropathy. Thirty patients with familial amyloidotic polyneuropathy volunteered for the study and were compared with a matched control group. Samples of unstimulated and stimulated whole saliva were collected in a standardized manner. The secretion rates were calculated, and the concentrations of electrolytes, glycoprotein markers, and proteins with antibacterial properties were analyzed. Dental caries and variables related to the risk of dental caries were also scored. The results show that familial amyloidotic polyneuropathy patients frequently have a decreased rate of saliva secretion and that the degree of salivary hypofunction is positively correlated to the progress of familial amyloidotic polyneuropathy. Forty-three percent of the familial amyloidotic polyneuropathy patients in this study had no detectable secretion of unstimulated saliva. A low secretion rate of stimulated saliva (< 0.7 ml/min) was found in 33% of the patients. The concentrations of salivary protein, amylase, lysozyme, salivary peroxidase, secretory IgA, hexosamines, sialic acid, fucose, phosphate, potassium, and the degree of protein glycosylation were higher in the familial amyloidotic polyneuropathy patients than in the control patients. We conclude that patients with familial amyloidotic polyneuropathy have a reduced saliva secretion and are subsequently at risk for increased development of dental caries.

Adult↗
PubMed1992

Influence of transcutaneous electrical nerve stimulation on memory in patients with dementia of the Alzheimer type.

This study examined the effect of transcutaneous electrical nerve stimulation (TENS) on memory in patients with dementia of the Alzheimer type. It was hypothesized that, in the early stage of the illness, electrical stimulation could activate the affected cortical regions by stimulating the neurotransmitter systems projecting to these areas. The results reveal that electrical stimulation improves the verbal long-term memory in these patients. Moreover, verbal fluency improves more in patients who received electrical stimulation than in patients who received control treatment. However, electrical stimulation does not influence the visual long-term memory of the patients, nor does it affect their verbal and nonverbal short-term memory. Underlying theoretical mechanisms are discussed.

Afferent Pathways↗
PubMed1992

Homozygosity for the transthyretin-Met30-gene in seven individuals with familial amyloidosis with polyneuropathy detected by restriction enzyme analysis of amplified genomic DNA sequences.

Familial amyloidotic polyneuropathy (FAP) with a mutation in position 30 of transthyretin (TTR) (previously called prealbumin) is an autosomal dominant inherited disorder characterized by varying degrees of peripheral neuropathy, nephropathy, gastrointestinal problems, and vitreous amyloid. We have earlier diagnosed homozygosity for the TTR-Met30-gene using Southern analysis in four Swedish individuals. We have found it possible to detect homozygosity for the Met-30 mutation by amplifying discrete regions of the TTR-gene using polymerase chain reaction (PCR), and the amplification products restricted with NsiI analysed by gel electrophoresis. Clinical data on seven homozygous individuals, including three new cases, are presented.

Aged↗
PubMed1992

Bile acid malabsorption caused by gastrointestinal motility dysfunction? An investigation of gastrointestinal disturbances in familial amyloidosis with polyneuropathy.

Gastrointestinal dysfunction due to autonomous neuropathy is a complication described in various diseases such as diabetes mellitus, multiple sclerosis, and familial amyloidosis with polyneuropathy. We present the results of a prospective investigation of bile acid malabsorption in 17 patients with familial amyloidosis by means of 75Se-labelled homocholic-tauro acid (SeHCAT). The diagnosis was in all cases verified by the DNA test for mutation of transthyretin in position 30. Small-intestinal biopsy specimens were examined for deposits of amyloid, and the presence of gastric retention was evaluated by gastroscopy. In addition, the patients were investigated for bacterial overgrowth by means of the bile acid breath test (BABT). A high frequency of abnormal BABT results (44%) was encountered. However, 65% also had abnormal low SeHCAT values, indicating bile acid malabsorption. Only two patients had abnormal BABT and normal SeHCAT results, indicating bacterial contamination of the small intestine. Bile acid losses increased with the duration of gastrointestinal symptoms. Significantly lower SeHCAT values were encountered in patients with gastric retention, whereas the occurrence of amyloid deposits in small-intestinal biopsy specimens was without effect on SeHCAT retention. Bile acid malabsorption is frequently encountered in familial amyloidosis with polyneuropathy and seems to be more closely associated with gastrointestinal motility dysfunction than with amyloid deposits in the intestinal mucosa.

Amyloidosis↗
PubMed1991

Biochemical effect of liver transplantation in two Swedish patients with familial amyloidotic polyneuropathy (FAP-met30).

Familial amyloidotic polyneuropathy (FAP) is an autosomal dominant inherited disorder characterized by progressive peripheral and autonomic neuropathy, associated with neural and systemic amyloid deposits. The amyloid fibrils contain a variant transthyretin (TTR) molecule (TTR met30), over 90% of which is produced in the liver. After liver transplantation in two patients with severe symptomatic FAP, only normal TTR was detectable in circulation. The two patients are being monitored at regular intervals, and, although in one patient there was no evidence of reduction in the quantity of amyloid present at 6 months, there had been no further progression of the neuropathy.

Adult↗
PubMed1990

Association of C3 and C4A complement types with familial amyloidotic polyneuropathy.

A mutant variant of the serum protein transthyretin (TTR-met30) appears to be a necessary but not sufficient condition for the development of familial amyloidotic polyneuropathy (FAP). We have studied a number of serum protein markers (alpha 1-antitrypsin, properdin factor B, C3, C4A, C4B, haptoglobin, transferrin and group-specific component) in FAP patients and healthy controls in an attempt to identify additional pathogenic factors which may influence the risk for developing FAP in male and female patients as well as the age of onset of the disease. Statistically significant associations were found in the complement systems C3 and C4A. The C3F variant was significantly increased in all FAP patients with a relative risk (RR) of 2.0, more pronounced in female patients (RR = 2.6) and patients with an early onset of the disease (RR = 4.5). In the FAP patients only the variants A3 and A4 were found in the C4A system. C4A3 was found in all patients, which was significantly higher than in the controls. The remaining serum protein systems showed no statistically significant associations with FAP. The results suggest that genetic variants of complement factors C3 and C4A may interact with the mutant TTR-met30 by modifying the expression and onset of FAP.

Age Factors↗
PubMed1988

Restriction fragment length polymorphism analysis of mutated transthyretin in vitreous amyloidosis.

Amyloid deposits of the vitreous are usually associated with familial amyloidotic polyneuropathy (FAP). Various mutated forms of transthyretin (prealbumin) seem to form the main amyloid fibril component. Five Swedish patients, all with vitreous amyloidosis but no systemic symptoms or family history of amyloidosis, were examined using restriction fragment length polymorphism analysis. Genomic DNA was tested with a transthyretin complementary DNA probe. After cleavage with Nsi1, two restriction fragment length polymorphism markers of 5.1 and 1.5 kilobase were detected in the patients but not in the control subjects. These observations indicate the same methionine for valine substitution at position 30 of the transthyretin molecule in patients with vitreous amyloidosis as seen in Swedish patients with FAP as well as in patients with FAP from Japan and Portugal, and patients of Swedish descent with FAP from the United States.

Aged↗
PubMed1988

Homozygosity for the transthyretin-met30-gene in two Swedish sibs with familial amyloidotic polyneuropathy.

Familial amyloidotic polyneuropathy (FAP) is an autosomal dominant inherited disorder. Recent biochemical studies have revealed that amyloid protein in FAP of Japanese, Swedish and Portuguese origin mainly consists of a variant transthyretin (TTR) (formerly called prealbumin) with one amino acid substitution of methionine for valine at position 30. In a 56-year-old man with typical polyneuropathy, gastrointestinal problems and vitreous amyloid, we diagnosed homozygosity for the TTR-met30-gene using RFLP analysis. In a family study, a sister presented the same homozygous RFLP pattern; however, in a careful clinical investigation we were not able to demonstrate any of the typical symptoms of FAP, nor could we demonstrate amyloid deposits in a biopsy skin specimen. This is the first report of homozygosity for the TTR-met30-gene, and it shows that the mutation of the protein involved in amyloid formation may be necessary but is clearly not sufficient for the clinical symptoms.

Adult↗
PubMed1988

Diagnosis of familial amyloidotic polyneuropathy in Sweden by RFLP analysis.

Genomic DNA from 17 Swedish patients with familial amyloidotic polyneuropathy (FAP), and 50 healthy controls were tested with a cDNA transthyretin probe. In seven of the patients, FAP was not reported in either of their parents. All 50 controls showed restriction fragments of 6.6 kb and 3.2 kb after cleavage with Nsil, while the 17 FAP patients showed RFLP markers of 5.1 and 1.5 kb. These observations indicate the same methionine for valine substitution at position 30 in Swedish patients with FAP as seen in patients with FAP from Japan, Portugal and FAP-patients of Swedish descent from USA. However, the mean onset of FAP symptoms for the 17 Swedish patients was found to be significantly later than for the patients from Japan, Portugal and USA.

Adult↗
PubMed1987

Nicardipine in the treatment of essential hypertension controlled 6-month-study comparing nicardipine with propranolol at rest and during exercise.

Thirty patients with mild to moderate essential hypertension entered a randomised double-blind parallel group study for 6 months to compare the effects of the new calcium channel blocker nicardipine 90 mg/day and propranolol 240 mg/day. Both drugs reduced systolic and diastolic blood pressures significantly in the supine and in standing positions. After 6 months of treatment, nicardipine had reduced the supine systolic and diastolic blood pressures by 16 and 17 mm Hg, respectively, and propranolol by 15 and 12 mm Hg. While propranolol treatment led to a marked decline in heart rate, nicardipine caused a small but statistically significant increase in heart rate throughout the study. Both drugs reduced blood pressure during maximal exercise, but propranolol had a greater effect. During exercise nicardipine did not affect the heart rate, whereas propranolol dramatically reduced it. Nicardipine did not produce any ECG changes at rest or during exercise. The side-effects for nicardipine were mild and were related to the vasodilatation induced by the drug. No abnormalities in routine blood chemical tests were found for either of the drugs. Nicardipine appears to be an effective single drug treatment for mild to moderate hypertension.

Adult↗
PubMed1987

Characterization of dolichol kinase from bovine thyroid microsomes.

Bovine thyroid microsomes are able to phosphorylate exogenous [1-3H]dolichol as well as endogenous dolichol. The properties and specificity of the dolichol kinase activity have been studied by following the phosphorylation of [1-3H]dolichol to [1-3H]DMP as well as the formation of [32P]DMP from endogenous dolichol and [gamma-32P]CTP. The dolichol kinase activity was not linear with respect to time and exhibited a neutral pH-optimum. Product formation was directly proportional to microsomal protein concentration up to 2.5 mg protein/incubation. The enzyme was found to depend on divalent cations for activity: Mg2+-ions being much more effective than Ca2+- and Mn2+-ions. In accordance, EDTA was strongly inhibitory. The enzyme exhibited specificity for CTP as phosphoryl donor and was found to be inhibited by the reaction product CDP. The apparent Km-value for exogenous dolichol amounted to 4 microM. Those for CTP were estimated to be 3.88 and 10.75 mM with exogenous [1-3H]dolichol depending on the source of CTP. With endogenous dolichol Km-values for CTP of 27.8 and 6.1 microM were calculated in respectively the absence and presence of 5 mM VO4(3-). Triton X-100 (0.15%) was necessary in the [1-3H]dolichol kinase assay (only 3% of enzymatic activity in the absence of detergent), while with [gamma-32P]CTP dolichol kinase detergent was only of minor influence (30% stimulation at 0.02% Triton X-100). The levels of the enzymatic activity could be doubled by the inclusion of 18-21 mM NaF [( 1-3H]dolichol kinase) as phosphatase inhibitor: VO4(3-) had practically no effect. In contrast with [gamma-32P]CTP dolichol kinase, the enzymatic activity could be enhanced 4-fold by addition of 5 mM VO4(3-) while F- resulted into no appreciable effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗