Influence of vertical posture development on the velocity properties of triceps surae muscle in normal children.

Contraction time and half-relaxation time of triceps surae muscle were studied in 9 normal children immediately after they began to stand alone and again 6 weeks later. The velocity properties of the muscle were recorded during isometric twitch induced by supramaximal indirect stimulation. The development of the vertical posture at the end of the first year was found to be associated with prolongation of the contraction time, reaching values observed in 3-year-old children and adults. During the same period the half-relaxation time did not change. Data are reported to show that the influence of the vertical posture on the contraction time is due to changes in the contractile properties of the muscle. It is assumed that the velocity properties of triceps surae are influenced by the long-term activation of the muscle in supporting the vertical posture.

[Staircase phenomenon in children with progressive muscular dystrophy and dermatomyositis]. / Fenomen lestnitsy u detei s progressiruiushchei myshechnoi distrofiei i dermatomiozitom.

The electrical and mechanical activity of the isometric twitch of flexor carpi ulnaris muscle during two per second indirect supramaximal stimulation for 90 sec was examined in 14 children with muscular distrophy and 8 children with dermatomyositis. The muscle electrical responses show no significant changes in the amplitude of its first negative phase. The first derivative of the dinamogram shows some of the following abnormalities in 8 of the examined children with muscular distrophy and in 2 of these with dermatomyositis: 1. Prolonged and increased negative staircase; 2. Insufficient or absent positive staircase potentiation. These abnormalities of the staircase phenomenon disclose disorders of the contractile function of the examined muscle.

Mapping the genome of rapeseed (Brassica napus L.). II. Localization of genes controlling erucic acid synthesis and seed oil content.

A F1 microspore-derived DH population, previously used for the development of a rapeseed RFLP map, was analysed for the distribution of erucic acid and seed oil content. A clear three-class segregation for erucic acid content could be observed and the two erucic acid genes of rapeseed were mapped to two different linkage groups on the RFLP map. Although the parents of the segregating DH population showed no significant difference in seed oil content, in the DH population a transgressive segregation in oil content was observed. The segregation closely followed a normal distribution, characteristic of a quantitative trait. Using the program MAPMAKER/QTL, three QTLs for seed oil content could be mapped on three different linkage groups. The additive effects of these QTLs explain about 51% of the phenotypic variation observed for this trait in the DH population. Two of the QTLs for oil content showed a close association in location to the two erucic acid genes, indicating a direct effect of the erucic acid genes on oil content.

Mapping the genome of rapeseed (Brassica napus L.). I. Construction of an RFLP linkage map and localization of QTLs for seed glucosinolate content.

A linkage map of the rapeseed genome comprising 204 RFLP markers, 2 RAPD markers, and 1 phenotypic marker was constructed using a F1 derived doubled haploid population obtained from a cross between the winter rapeseed varieties 'Mansholt's Hamburger Raps' and 'Samourai'. The mapped markers were distributed on 19 linkage groups covering 1441 cM. About 43% of these markers proved to be of dominant nature; 36% of the mapped marker loci were duplicated, and conserved linkage arrangements indicated duplicated regions in the rapeseed genome. Deviation from Mendelian segregation ratios was observed for 27.8% of the markers. Most of these markers were clustered in 7 large blocks on 7 linkage groups, indicating an equal number of effective factors responsible for the skewed segregations. Using cDNA probes for the genes of acyl-carrier-protein (ACP) and ß-ketoacyl-ACP-synthase I (KASI) we were able to map three and two loci, respectively, for these genes. The linkage map was used to localize QTLs for seed glucosinolate content by interval mapping. Four QTLs could be mapped on four linkage groups, giving a minimum number of factors involved in the genetic control of this trait. The estimated effects of the mapped QTLs explain about 74% of the difference between both parental lines and about 61.7 % of the phenotypic variance observed in the doubled haploid mapping population.

Deletion analysis of Bulgarian SMA families.

All three types of autosomal recessive spinal muscular atrophy map to chromosome region 5q13. Recent reports suggest that they are associated with deletions of two adjacent genes: SMN and NAIP. Here we report the first deletion analysis of Bulgarian SMA families. Homozygous deletion of exons 7 and 8 of the SMN gene were found in 85% of our patients, but the NAIP gene (exons 5 and 6) was deleted in only 26% of patients. To our knowledge, these frequencies are some of the lowest reported so far. The NAIP gene was deleted predominantly in severely affected patients (type I), while in the group with milder types SMA only deletions of the SMN gene were detected. Our phenotype-genotype correlation study confirmed that larger deletions are associated with more severe clinical course. The Bulgarian data support the thesis that the telomeric SMN gene could play a major role in determining SMA, while the NAIP or the centromeric SMN copy have a modifying effect on the phenotype.

Excitation-contraction latency in the muscles of children and adults.

Excitation-contraction latency in the fast flexor carpi ulnaris and in the slow triceps surae muscles was studied in healthy children aged one month, 10 months and three years, and in adults. The tests were carried out during isometric twitch following supramaximal indirect stimulation. Excitation-contraction latency was found to increase with age in both the fast and slow muscles. The latency is longer for the slow than the fast muscle. A positive correlation was found in the children between excitation-contraction latency and contraction time.

Dynamic properties of partially denervated muscle in children with brachial plexus birth palsy.

Contraction time, time to peak rate of tension development, half-relaxation time and maximum twitch tension of partially denervated flexor carpi ulnaris muscle were measured in children with brachial plexus birth palsy. The extent of weakness of the affected muscle was assessed by expressing its maximum twitch tension as a percentage of the tension of the contralateral normal muscle. Contraction time, time to peak rate and half-relaxation time were prolonged in children with severe weakness, while in children with moderate weakness only half-relaxation time was prolonged. The contralateral normal flexor carpi ulnaris muscle showed age differences in its contractile properties, while in the affected muscle such differences were not found. This result suggests that denervation at birth impairs normal development of muscle contractile properties.

Force and contraction time relation in skeletal muscles of children and adults.

The force and contraction time relation was studied in twitch isometric contraction of flexor carpi ulnaris muscle (FCU) and triceps surae (TS) in 5-week-old infants, 3-year-old children and adults. Contraction time (CT), duration of the plateau of active state (PAS), and time of the decline of active state (DAS) do not change with increasing force of contraction of FCU in all three age groups and in TS in 5-week-old infants. CT and DAS decrease with increasing force of contraction in 3-year-old children and in adults. PAS remains unchanged with increasing force of TS in 3-year-old children and decreases in adults, but considerably less than CT and DAS. Evidence is adduced supporting the view that CT changes with increasing force of TS depend mainly on the elastic properties of the muscle.

Congenital cataracts facial dysmorphism neuropathy syndrome, a novel complex genetic disease in Balkan Gypsies: clinical and electrophysiological observations.

During a study of hereditary motor and sensory neuropathy-Lom in Bulgaria, a previously unrecognized neurological disorder was encountered, mainly in Wallachian Gypsies, who represent a relatively recent genetic isolate. The disorder has been termed the congenital cataracts facial dysmorphism neuropathy (CCFDN) syndrome to emphasize its salient features. Fifty individuals from 19 extended pedigrees were identified and examined clinically and electrophysiologically. At least 1 patient from each family was admitted to the hospital in Sofia for full investigation. Pedigree analysis indicates autosomal recessive inheritance. The disorder is recognized in infancy by the presence of congenital cataracts and microcorneas. A predominantly motor neuropathy beginning in the lower limbs and later affecting the upper limbs develops during childhood and leads to severe disability by the third decade. Associated neurological features are a moderate nonprogressive cognitive deficit in most affected individuals together with pyramidal signs and mild chorea in some. Accompanying nonneurological features include short stature, characteristic facial dysmorphism, and hypogonadotrophic hypogonadism. Nerve conduction studies suggest a hypomyelinating/demyelinating neuropathy, confirmed by nerve biopsy. The CCFDN syndrome is thus a pleomorphic autosomal recessive disorder displaying a combination of neurological and nonneurological features.