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Biomedical subjects

J Vilkki

Publications and source records attributed to J Vilkki.

At least 19 recordsLinked to original sources
PubMed1992

Cognitive flexibility and mental programming after closed head injuries and anterior or posterior cerebral excisions.

Cognitive inflexibility and deficient mental programming are specifically related to frontal lobe lesions. The aim was to demonstrate that closed head injury (CHI) patients with brain lesions verified by computed tomography have such cognitive deficits, and are inferior in these respects to patients with posterior cerebral excisions mainly for tumours. This hypothesis was confirmed using a Category Identification and Sorting test as well as a measure of mental programming in a Spatial Learning task. Furthermore, CHI patients who had non-frontal parenchymal lesions were inferior by these measures to patients with posterior excisions. This result suggests that diffuse axonal lesion in CHI causes the deficits similar to those following frontal lobe excision.

Adolescent↗
PubMed1992

Cognitive test performances related to early and late computed tomography findings after closed-head injury.

Computed tomography (CT) findings from early (less than 24 hours) and late scan (6 months) after closed-head injury (CHI) were compared to cognitive test scores obtained on an average of 4 months after injury in a consecutive series of 53 patients. The presence of parenchymal lesion was associated with poor test results, indicating cognitive inflexibility and disinhibition of routine response tendencies in novel tasks. These deficits have previously been found to be related in particular to frontal-lobe dysfunction, but the present study did not support the hypothesis that frontal lesion is the principal cause of this impairment in CHI. Parenchymal lesions in the right and left hemisphere were associated with spatial and verbal deficits, respectively. Ventricular enlargement in the late CT was related to cognitive inefficiency, both being strongly associated with age. The results suggest that parenchymal lesion in the early CT is an indicator of diffuse axonal injury, which results in cognitive inflexibility during recovery.

Adolescent↗
PubMed1991

Mental programming after frontal lobe lesions: results on digit symbol performance with self-selected goals.

The aim of this study was to demonstrate that the inability to set adequate sub-goals in a cognitive task is a sensitive indicator of programming deficit after frontal lobe lesion. Sixty-one patients with focal cerebral lesions and 25 control subjects were studied with a modified Digit Symbol task, in which the score depended on the adequacy of the sub-goals set by the subject. This score was compared to that on the standard condition, in which the subject was requested to work as quickly as possible without self-selected goals. The results confirmed the prediction that patients with anterior lesions set less adequate sub-goals than patients with posterior lesions and, unlike the latter patients, have a more pronounced deficit on the performance with self-selected goals than on the standard condition. In particular patients with left frontal lobe lesions underestimated their capabilities in relation to task requirements.

Adult↗
PubMed1991

A new mtDNA mutation associated with Leber hereditary optic neuroretinopathy.

A single base mutation at nucleotide position 3460 (nt 3460) in the ND1 gene in human mtDNA was found to be associated with Leber hereditary optic neuroretinopathy (LHON). The G-to-A mutation converts an alanine to a threonine at the 52d codon of the gene. The mutation also abolishes an AhaII restriction site and thus can be detected easily by RFLP analysis. The mutation was found in three independent Finnish LHON families but in none of the 60 controls. None of the families with the nt 3460 mutation in ND1 had the previously reported nt 11778 mutation in the ND4 gene. The G-to-A change at nt 3460 is the second mutation so far detected in LHON.

Animals↗
PubMed1991

Optic atrophy in Leber hereditary optic neuroretinopathy is probably determined by an X-chromosomal gene closely linked to DXS7.

Leber hereditary optic neuroretinopathy (LHON) is a maternally inherited disease, probably transmitted by mutations in mtDNA. The variation in the clinical expression of the disease among family members has remained unexplained, but pedigree data suggest an involvement of an X-chromosomal factor. We have studied genetic linkage of the liability to develop optic atrophy to 15 polymorphic markers on the X chromosome in six pedigrees with LHON. The results show evidence of linkage to the locus DXS7 on the proximal Xp. Tight linkage to the other marker loci was excluded. Multipoint linkage analysis placed the liability locus at DXS7 with a maximum lod score (Zmax) of 2.48 at a recombination fraction (theta) of .0 and with a Zmax - 1 support interval theta = .09 distal to theta = .07 proximal of DXS7. No evidence of heterogeneity was found among different types of families, with or without a known mtDNA mutation associated with LHON.

Adult↗
PubMed1990

Analysis of mitochondrial ND4 gene DNA sequence in Finnish families with Leber hereditary optic neuroretinopathy.

A mutation in the mitochondrial DNA at nt 11,778 has recently been found in Leber hereditary optic neuroretinopathy (LHON), a maternally inherited ocular disease. The mutation is located in the ND4 gene encoding subunit 4 of the respiratory chain enzyme NADH dehydrogenase. The mutation was subsequently not found in 9 of the 20 known Finnish families with LHON, implying that there are at least two different mutations associated with the disease. Using direct sequencing of PCR-amplified mtDNA, we have now sequenced the entire ND4 region in the families without the nt 11,778 mutation to find the other mutations. No new mutations in the ND4 region were found, suggesting that the putative mtDNA mutation in these families may be in the coding regions for other subunits of NADH dehydrogenase enzyme. The sequence of ND4 gene as found to be highly homogeneous.

Animals↗
PubMed1990

Social outcome related to cognitive performance and computed tomographic findings after surgery for a ruptured intracranial aneurysm.

A series of 83 patients was examined with a battery of cognitive tests, a clinical interview, and computed tomography 1 year after surgery for a ruptured intracranial aneurysm. Disability on the Glasgow Outcome Scale (33%), failure to return to work (25%), impaired social relations (25%), and subjective or clinical mental impairment (56%) were found to be related to each other and to poor performance on cognitive tests, especially to verbal impairments in patients with left lateral infarctions and to memory deficits and cognitive inflexibility in patients with frontal medial infarctions. Furthermore, cognitive deficits and poor outcome were associated with diffuse brain damage. Depression and anxiety were unrelated to test performances, but were frequently reported by patients with right lateral infarctions.

Adult↗
PubMed1990

Segregation of mitochondrial genomes in a heteroplasmic lineage with Leber hereditary optic neuroretinopathy.

Relatively little is known about the factors maintaining mitochondrial DNA (mtDNA) sequence diversity in humans. A detailed understanding of the transmission genetics of mtDNA has been partly hampered by the lack of evidence for heteroplasmic individuals. Among families with Leber hereditary optic neuroretinopathy, we found a maternal lineage with individuals heteroplasmic for a single nucleotide change, and we were able to follow the segregation of polymorphic mitochondrial genomes over 3 generations. The results show that rapid segregation can occur but also that the level of heteroplasmy can be maintained from one generation to another. In this family the disease phenotype is associated with the mtDNA sequence change, confirming the involvement of the mutation in the disease.

Base Sequence↗
PubMed1989

Mitochondrial DNA polymorphism in Finnish families with Leber's hereditary optic neuroretinopathy.

Leukocyte mitochondrial DNA (mtDNA) from 17 Finnish families with Leber's hereditary optic neuroretinopathy and 70 maternally unrelated controls as well as skeletal muscle mtDNA from four of the Leber families and three controls was analyzed with 30 restriction enzymes. By this means, over 10% of the nucleotides of mtDNA were screened. No major deletion or insertion was found in any of the mtDNAs studied. The restriction fragment patterns of mtDNA showed no evidence of mtDNA heteroplasmy (mixture of different mtDNA types) in either blood or muscle cells. In all, 24 mtDNA types were observed in the material. In the maternal lines of Leber families, 11 mtDNA types were found, indicating no recent common maternal ancestor for the Finnish Leber families. In spite of several previously unknown polymorphisms, no mutation of mtDNA could be found exclusively in families with Leber's disease. However, a couple of mutations leading to amino acid replacements of mitochondrially encoded proteins were observed in certain Leber families only. These mutations have occurred in genes coding for subunits of NADH dehydrogenase, suggesting that a defect of the respiratory chain complex I may cause Leber's disease.

DNA, Mitochondrial↗
PubMed1989

Deficient programming in spatial learning after frontal lobe damage.

Patients with anterior or posterior brain damage and control subjects performed a spatial sequence learning task in which the score obtained depended on the subject's ability to set sub-goals appropriate for his learning capacity. The anterior group obtained lower scores and more frequently set inadequate sub-goals than the posterior group. No anterior vs posterior difference was found on a similar learning task in which another sequence was learnt by predetermined sub-goals. The result supported the hypothesis that frontal lobe lesions disturb programming or goal-based search for action structure on spatial learning.

Adult↗
PubMed1989

Perseveration in memory for figures after frontal lobe lesion.

The aim was to determine whether recurrent perseveration, i.e. the tendency to incorrectly repeat previous responses, is related to the site of cerebral lesion. Sixty-seven brain-damaged patients and 35 control subjects were studied with a modified Benton Visual Retention Test. Patients with anterior lesions made a higher number of recurrent perseverations than patients with posterior lesions. The results was in disagreement with the hypothesis that recurrent perseveration is associated with left posterior lesions.

Adult↗
PubMed1989

Differential perseverations in verbal retrieval related to anterior and posterior left hemisphere lesions.

Sixty-two patients with focal cerebral lesions and 11 control patients were examined using alternating tasks of learning, generation, and recall of words beginning with "K." The results supported the hypothesis that "recurrent" and "stuck-in-set" varieties of perserveration are related to posterior and anterior left hemisphere lesions, respectively. Patients with left posterior lesions usually failed to suppress the expression of previously generated words in the subsequent generation task, whereas patients with left anterior lesions stated a greater number of new (incorrect) words in the recall of previously learned words, presumed to indicate stuck-in-set perseveration of the previous generation performance.

Adult↗
PubMed1989

Speed-accuracy optimization in acquisition of figures after focal cerebral lesion.

Seventy-seven brain damaged patients and 14 control subjects performed a visual memory test in which the subjects had to reproduce geometric figures from memory after studying the design for 10 seconds (standard condition) and after an observation period subjectively necessary and sufficient for accurate reproduction (self-timed condition). The brain damaged patients were less efficient than the control subjects on the self-timed acquisition even when the covariance on the standard condition was taken into account. The prediction that frontal lobe damaged patients are inferior to posterior brain damaged patients on the speed-accuracy optimization of acquisition was true only in the right hemisphere damaged patients on the simple trials, suggesting that right frontal lobe damage disturbs voluntary attention. Visuospatial errors were typical for right hemisphere damaged patients, perservations for left frontal lobe damaged patients.

Adult↗
PubMed1989

Hemi-inattention in visual search for parallel lines after focal cerebral lesions.

Visual search and line orientation discrimination was studied in 67 brain-damaged and 15 control subjects, with the aim of demonstrating that hemi-inattention follows both left- and right-hemisphere damage even when confined to the frontal lobe. Both anterior and posterior lesions of either hemisphere caused inattention to the side contralateral to the lesion, this asymmetry being pronounced at the onset of search, especially in patients with anterior lesions. Hemi-inattention was associated with the overall inefficiency of line orientation discrimination and exploration as well as simple verbal performance in right-hemisphere-damaged patients, but tended to dissociate from these deficits in left hemisphere-damaged patients. Brain-damaged patients were inferior to the control subjects, and women inferior to men in the overall efficiency of exploration, but only women with right posterior lesions had a deficit in line orientation discrimination.

Attention↗
PubMed1989

Cognitive deficits related to computed tomographic findings after surgery for a ruptured intracranial aneurysm.

A consecutive series of 118 patients operated on for ruptured intracranial arterial aneurysms was studied. Ninety-six of them could be adequately examined with a battery of psychological tests and computed tomographic scans 1 year after a subarachnoid hemorrhage. Seventeen orthopedic control patients with no history of brain damage were also tested. The pattern of cognitive deficits was strongly related to the findings on the computed tomographic scans. Patients with left lateral infarctions had deficits on performances requiring verbal efficiency, including memory and classification tasks, whereas patients who had right lateral infarctions were poor on a visuoconstructional task (the copying of Rey's Figure). These deficits were pronounced when lateral infarction was associated with diffuse brain damage. Patients with frontal medial infarctions had low scores on memory tests; the inefficiency in verbal fluency, categorical reasoning, and memory was related to diffuse brain damage. The patients who had no infarctions did not differ significantly from the control group. Cognitive impairments after left lateral and frontal medial infarctions, as well as diffuse brain damage, correlated with the Glasgow Outcome Scale.

Brain↗
PubMed1989

Genetic heterogeneity in Leber hereditary optic neuroretinopathy revealed by mitochondrial DNA polymorphism.

The presence or absence of a recently observed mitochondrial DNA (mtDNA) mutation associated with Leber hereditary optic neuroretinopathy (LHON) was tested in 19 Finnish families with cases of LHON. Leukocyte and muscle DNA from individuals with optic atrophy, microangiopathy, or normal fundi from maternal lineages were studied by Southern blot analysis, using mouse mtDNA as a hybridization probe. The mtDNA mutation, detected as SfaNI site polymorphism, was seen in 10 of the 19 families. In one family, the mutation was seen only in the two affected individuals, indicating recent origin for the mutation. Nine families and 28 maternally unrelated controls did not show the mutation. The results imply that alternative mtDNA mutations are associated with LHON and that this genetic heterogeneity may be the cause of the interfamilial variation in the clinical expression of LHON. In the families showing the SfaNI site mutation, the mutation was homoplasmic in all individuals irrespective of their disease status, suggesting that the intrafamilial variation in the clinical expression is not due to different ratios of mutant versus normal mtDNA.

Blotting, Southern↗
PubMed1988

Human mitochondrial DNA types in Finland.

Variation in mitochondrial DNA (mtDNA) in a sample of 110 Finns was analyzed with six restriction enzymes, AvaII, BamHI, HaeII, HindII, HpaI, and MspI, by using total blood cell DNA probed with mouse mtDNA. Two new enzyme morphs were observed, one for HaeII and one for HindII. Double-digestion experiments indicated that the BamHI morphs 2 and 3 result from base changes leading to AvaII morphs 3 and 9, respectively. Of the ten different mtDNA types observed, defined by restriction fragment patterns, seven have been previously described in Caucasoid populations. The three new "Finnish" mtDNA types can be derived from Caucasoid lineages by single restriction site changes. The results were used to reconstruct a phylogenetic tree for Caucasoid mtDNA types defined by the enzymes used. The frequencies of mtDNA types were used to compute genetic distances between Finns, Italians, and Israeli Jews. The frequencies of both enzyme morphs and mtDNA types show that the Finnish population is highly homogeneous.

DNA Restriction Enzymes↗