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Biomedical subjects

S Tanner

Publications and source records attributed to S Tanner.

At least 19 recordsLinked to original sources

A study of Wilson disease mutations in Britain.

Wilson disease (WD) is an autosomal recessive disease of copper transport. The disease is caused by a large number of mutations in the ATP7B gene, some of which appear to be population specific, whereas others are found in probands from a variety of different ethnic backgrounds. This study presents the results of screening the ATP7B gene by SSCP and sequencing in order to define the spectrum of mutations seen in British referrals for WD. The 52 patients screened included 10 with a non-British mixed ethnicity origin. This study identified 19 novel mutations and 18 mutations that had been previously described. The novel mutations included seven nonconservative missense mutations, eight small insertions, or deletions causing frameshift, two nonsense mutations, and two splice-site mutations. Seven of the 10 mixed ethnicity patients harboured homozygous mutations, whereas only four of the larger British group were homozygotes. The detection rate by SSCP analysis in the British group of 42 consecutive unrelated WD probands was 70%. However, SSCP screening of just three exons (exons 8, 14, and 18) is predicted to identify 60% of mutations present in WD referrals.

Adenosine Triphosphatases↗

Control of myelination by specific patterns of neural impulses.

A cell culture preparation equipped with stimulating electrodes was used to investigate whether action potential activity can influence myelination of mouse dorsal root ganglia axons by Schwann cells. Myelination was reduced to one-third of normal by low-frequency impulse activity (0.1 Hz), but higher-frequency stimulation (1 Hz) had no effect. The number of Schwann cells and the ultrastructure of compact myelin were not affected. The frequency of stimulation that inhibited myelination decreased expression of the cell adhesion molecule L1, and stimulation under conditions that prevented the reduction in L1 blocked the effects on myelination. This link between myelination and functional activity in the axon at specific frequencies that change axonal expression of L1 could have important consequences for the structural and functional relationship of myelinating axons.

Action Potentials↗

Magnetic resonance of the neonatal brain.

We discuss the advantages of magnetic resonance (MR) technique in the study of the neonatal brain. Major results have been obtained concerning the understanding of the normal appearance of the developing brain. Bands of cells migrating to the cortex have been identified in the frontal periventricular white matter up to late gestation. MR can also identify the disappearance of the subependymal germinal matrix with increasing gestational age. With respect to the lesions of prematurity, subependymal germinal matrix hemorrhages were for the first time identified by MR underneath the posterior horns of the lateral ventricles. Subtle ischemic lesions of the periventricular white matter, not detected by brain ultrasound scan, are also described. Analysis of the lesions of the term neonates showed the role of MR in defining a more precise prognosis of infants who have sustained "birth asphyxia". The lesions can affect the basal ganglia, watershed areas of the white matter, and cortex. MR scans performed in the second week of life seem to show a stronger association with the outcome. Brain ischemic areas of the term neonates presenting with focal or multifocal seizures can also be detected by MR. These infarcted zones are usually located in the perfusion territory of the middle cerebral artery, more often in the left hemisphere. The timing of the scan is an important factor as the conventional MR can be negative in the first two-three days after the seizures. The diffusion-weighted imaging (DWI) is a new MR technique very sensitive to acute ischemic injury, and it may solve the problem of the scan timing.

Brain↗

MR features of developing periventricular white matter in preterm infants: evidence of glial cell migration.

PURPOSE: MR imaging of the brain is increasingly used in the investigation of the newborn, but little information is available on the normal appearance of the developing brain. We scanned a series of newborn infants in an attempt to define the normal appearance of developing periventricular white matter and to assess how pathologic conditions may modify this appearance. METHODS: Sixty-eight newborn infants, median postmenstrual age (PMA) 34 weeks (range, 24 to 42 weeks), were subdivided into two groups: group A (n = 33), which included those with normal clinical and sonographic examinations, and group B (n = 35), which contained those with evidence of neuroabnormality detected prior to the MR study, either clinically or by cerebral sonography. Images were acquired in two planes on a 1.5-T imager using turbo spin-echo pulse sequences. RESULTS: Symmetric periventricular bands of reduced signal intensity were noted in the frontal periventricular white matter on T2-weighted images in 98% of group A infants and in 97% of group B infants. The number of bands was inversely related to PMA. The reduction in number of bands with increasing PMA was delayed in group B infants. CONCLUSION: The uniform appearance of periventricular bands in a population of healthy infants and their relationship to the infants' maturity is consistent with the results of previous histologic studies. These studies demonstrate the presence of migrating glial cells within the periventricular white matter of infants beyond 20 weeks' gestation, when neuronal migration to the cortex is complete. We postulate that the bands seen on T2-weighted images represent groups of migrating glial cells, providing a further marker of cerebral maturation.

Brain↗

Mandibular fractures following third molar extraction. A retrospective clinical and radiological study.

Twelve patients with 13 mandibular fractures following third molar extraction were treated in our Department between 1980 and 1995. Clinical and radiographic data relating to these patients were analysed retrospectively to determine complication characteristics. Only one fracture occurred during surgery. The first week after the operation was found to be most critical for fracture occurrence. A "cracking" sound from the jaw while eating frequently indicated that a fracture had occurred, but repeated radiographic examination may be necessary for definitive diagnosis. Most teeth removed belonged to Groups II/III according to PELL & GREGORY's classification, indicating partial or total impaction of the tooth and a narrow space in the retromolar triangle. In all cases, tooth roots were superimposed on or adjacent to the inferior alveolar canal. Clinically, the age of the patient seemed to be a common predisposing factor, and patients older than 30 to 40 years were considered to be a risk group. Regardless of the degree of impaction and tooth position, the fracture type seen was uniform, i.e. preangular location and a typical course of the fracture line. After adequate fracture treatment, no further complications were noted.

Adult↗

Frontal-striatal cognitive deficits in patients with chronic schizophrenia.

Spatial working memory and planning abilities were assessed in 36 hospitalized patients with chronic schizophrenia, using the computerized Cambridge Neuropsychological Test Automated Battery (CANTAB), and compared with those of normal subjects and patients with neurological disorders (frontal lobe lesions; temporal lobe and amygdalohippocampal lesions; Parkinson's disease), matched for age, sex and National Adult Reading Test IQ. The patients in the group with temporal lobe lesions were unimpaired in their performance on these tasks. Patients with schizophrenia were impaired on visuo-spatial memory span compared with all the other groups, while severity of Parkinson's disease was correlated with the degree of impairment on this task. The patients with schizophrenia and those with frontal lobe lesions were impaired on a 'spatial working memory' task, with increased 'between-search errors'. Patients with Parkinson's disease performed this task poorly compared with the younger control subjects. Patients with schizophrenia were unable to develop a systematic strategy to complete this task, relying instead on a limited visuo-spatial memory span. Higher level planning ability was investigated using the CANTAB 'Tower of London'. All groups were equally able to complete the task. However, the groups of patients with schizophrenia and frontal lobe lesions made fewer perfect solutions and required more moves for completion. Movement times were significantly slower in the schizophrenia group, suggesting impairment in the sensorimotor requirements of the task. The patients with schizophrenia were not impaired in their 'initial thinking' (planning) latencies, but had significantly prolonged 'subsequent thinking' (execution) latencies. This pattern resembled that of the group with frontal lobe lesions and contrasted with the prolonged 'initial thinking' time seen in Parkinson's disease. The results of this study are indicative of an overall deficit of executive functioning in schizophrenia, even greater than that seen in patients with frontal lobe lesions. However, the pattern of results in schizophrenia resembled that seen in patients with lesions of the frontal lobe or with basal ganglia dysfunction, providing support for the notion of a disturbance of frontostriatal circuits in schizophrenia. Our findings also indicate that there is a loss of the normal relationships between different domains of executive function in schizophrenia, with implications for impaired functional connectivity between different regions of the neocortex.

Adolescent↗

Regional responsiveness of the tibia to intermittent administration of parathyroid hormone as affected by skeletal unloading.

To determine whether the acute inhibition of bone formation and deficit in bone mineral induced by skeletal unloading can be prevented, we studied the effects of intermittent parathyroid hormone (PTH) administration (8 micrograms/100 g/day) on growing rats submitted to 8 days of skeletal unloading. Loss of weight bearing decreased periosteal bone formation by 34 and 51% at the tibiofibular junction and tibial midshaft, respectively, and reduced the normal gain in tibial mass by 35%. Treatment with PTH of normally loaded and unloaded animals increased mRNA for osteocalcin (+58 and +148%, respectively), cancellous bone volume in the proximal tibia (+41 and +42%, respectively), and bone formation at the tibiofibular junction (+27 and +27%, respectively). Formation was also stimulated at the midshaft in unloaded (+47%, p < 0.05), but not loaded animals (-3%, NS). Although cancellous bone volume was preserved in PTH-treated, unloaded animals, PTH did not restore periosteal bone formation to normal nor prevent the deficit in overall tibial mass induced by unloading. We conclude that the effects of PTH on bone formation are region specific and load dependent. PTH can prevent the decrease in cancellous bone volume and reduce the decrement in cortical bone formation induced by loss of weight bearing.

Animals↗

A novel SR-related protein specifically interacts with the carboxy-terminal domain (CTD) of RNA polymerase II through a conserved interaction domain.

The largest subunit of the RNA polymerase II (pol II) contains at the carboxy-terminus a peculiar repetitive sequence that consists of 52 tandem repeats of the consensus motif Tyr-Ser-Pro-Thr-Ser-Pro-Ser, referred to as the C-terminal domain (CTD). Upon transcriptional initiation/promoter clearance, the CTD becomes extensively phosphorylated and apparently remains so during elongation. While the underphosphorylated CTD plays a role in transcriptional initiation, recent evidence couples the highly phosphorylated CTD to RNA processing, namely polyadenylation and splicing. Using a yeast two-hybrid screen, we have selected for human proteins that interact with the CTD of RNA polymerase II. The CTD-GAL fusion protein used as a bait is highly phosphorylated in yeast and, accordingly, we did not isolate proteins implicated in transcriptional regulation but rather proteins with possible roles in RNA splicing. One major cDNA clone isolated this way encodes SRrp129/CASP11, a protein that contains a conserved CTD-interaction domain at the C-terminus and an internal serine-arginine rich domain (SR domain). Proteins of the SR family have been implicated in RNA splicing, notably in the regulation of alternative splicing. Thus we consider it likely that SRrp129 is an auxiliary splice factor. We also improved our method to quickly map domains involved in protein-protein interaction (Stagljar et al., 1996, BioTechniques 21, 430-432). Instead of using sonication for the production of a random DNA fragment library, we took advantage of the fact that DNAse I in the presence of manganese (II) produces double strand rather than single strand DNA breaks. The DNA fragment library of the SRrp129 clone was then used in the yeast two-hybrid system to identify the 100-amino acid domain that interacts with the CTD of RNA polymerase II.

Alternative Splicing↗

Retrorsine in breast milk influences copper handling in suckling rat pups.

AIMS: To explore the hypothesis that a second xenobiotic agent is required with excess copper to produce Indian Childhood Cirrhosis, this study investigated the effect of the pyrrolizidine alkaloid retrorsine fed to the mother during the suckling period upon the serial changes in neonatal copper status. METHODS: Female Wistar rats with new-born litters were fed either a control or a retrorsine (50 mg/kg) diet. At 0, 4, 8, 11, 15, 18 and 21 days, pups from each litter were weighed, sacrificed and their livers removed for copper, DNA and metallothionein analysis. Serum samples were assayed for caeruloplasmin oxidase activity and albumin. RESULTS: 1) Higher than adult level of hepatic copper in normal rats which rose post-natally before declining from day 11 after birth, 2) raised hepatic copper concentrations and total copper in the retrorsine group from day 15; levels were higher than adult at birth, 3) reduced serum caeruloplasmin oxidase activity and albumin levels in retrorsine group, but both groups lower than adult, 4) lower hepatic metallothionein levels in retrorsine group, but both groups higher than adult, and 5) reduced liver DNA in the retrorsine group when expressed as total DNA and per gram of tissue. These changes were not secondary to under-nutrition as a small study on under-nourished rat neonates showed that copper handling is not significantly altered when compared to well-nourished rats. CONCLUSIONS: Retrorsine passing to rat neonates via breast milk causes: 1) the accumulation of hepatic copper, 2) impairment of the rise in serum caeruloplasmin, which could indicate a decline in synthesis or failure of copper incorporation into the apo-protein, 3) a decrease in hepatic metallothionein and serum albumin levels, again suggesting diminished protein synthesis, and 4) reduced hepatic DNA indicative of decreased cell number but increased cell size. Accumulation of liver copper but reduction of copper-binding proteins could result in free copper and explain the synergistic hepatotoxicity of copper and retrorsine.

Animals↗

Skeletal unloading induces selective resistance to the anabolic actions of growth hormone on bone.

Loss of skeletal weight bearing or physical unloading of bone in the growing animal inhibits bone formation and induces a bone mineral deficit. To determine whether the inhibition of bone formation induced by skeletal unloading in the growing animal is a consequence of diminished sensitivity to growth hormone (GH) we studied the effects of skeletal unloading in young hypophysectomized rats treated with GH (0, 50, 500 micrograms/100 g body weight/day). Skeletal unloading reduced serum osteocalcin, impaired uptake of 3H-proline into bone, decreased proximal tibial mass, and diminished periosteal bone formation at the tibiofibular junction. When compared with animals receiving excipient alone, GH administration increased bone mass in all animals. The responses in serum osteocalcin, uptake of 3H-proline and 45Ca into the proximal tibia, and proximal tibial mass in non-weight bearing animals were equal to those in weight bearing animals. The responses in trabecular bone volume in the proximal tibia and bone formation at the tibiofibular junction to GH, however, were reduced significantly by skeletal unloading. Bone unloading prevented completely the increase in metaphyseal trabecular bone normally induced by GH and severely dampened the stimulatory effect (158% vs. 313%, p < 0.002) of GH on periosteal bone formation. These results suggest that while GH can stimulate the overall accumulation of bone mineral in both weight bearing and non-weight bearing animals, skeletal unloading selectively impairs the response of trabecular bone and periosteal bone formation to the anabolic actions of GH.

Analysis of Variance↗

Experimental atrophy/hypertrophy complex (AHC) of the liver: portal vein, but not bile duct obstruction, is the main driving force for the development of AHC in the rat.

BACKGROUND/AIMS: Patients with lobar or segmental impairment of bile flow or of portal venous blood flow frequently develop considerable atrophy of the area involved, followed by compensatory hypertrophy/hyperplasia of the non-affected parts. This configuration is termed atrophy/hypertrophy complex of the liver. METHODS: In order to analyze the relative contributions of bile duct and portal vein obstruction in the pathogenesis of atrophy/hypertrophy complex, we developed a rat model with selective bile duct and/or portal vein ligation of the anterior liver lobes, representing about two thirds of the liver mass. Evolution of total body weights and weights of the different liver lobes were determined, and morphometry and functional scintigraphy (hepatoiodida scanning) were performed immediately after ligation and at 30 h, 4, 8 and 28 days postoperatively. RESULTS: The major findings were: 28 days after biliary and/or portal ligation there was no difference between the body weights of all animals, all ligated animals having compensated an initial body weight loss. Total liver weight remained constant during the whole observation period, while atrophy of the anterior and hypertrophy/hyperplasia of the posterior lobes occurred. A significant atrophy/hypertrophy complex developed only after selective portal ligation, but not after selective biliary ligation. Morphometrically analyzed histologic changes after selective biliary ligation were reversible, whereas in portally ligated liver lobes a progressive parenchymal destruction and involution with subsequent impairment of hepatic function of the concerned lobe were observed. CONCLUSIONS: The present findings indicate that impairment of portal venous flow is the major driving force for the development of lobar atrophy in the rat and that atrophy/hypertrophy complex can be produced in a rodent model.

Animals↗

Psychological effects of Hurricane Andrew on an elementary school population.

OBJECTIVE: To explore the prevalence and progression of posttraumatic symptomatology (PTS), using emotional and behavioral indices of psychopathology in school-age children in the pathway of Hurricane Andrew (HI-IMPACT) and in a comparison group north of Miami (LO-IMPACT). METHOD: Pynoos' Posttraumatic Stress Disorder Reaction Index and Achenbach's Teacher's Report Form (TRF) were administered 8 weeks and 32 weeks after the hurricane. In addition, 21 measures of disruptive behavior cataloged by Dade County Public Schools were aggregated and compared by grading period between pre- and posthurricane school years. RESULTS: There were no statistically significant differences between the two schools in PTS at 8 weeks after the hurricane, although the children in the HI-IMPACT school were more likely to have severe PTS. TRF findings at 8 weeks revealed that children in the HI-IMPACT school evidenced lower means on the eight TRF scales and on the broader Internalizing and Externalizing measures. Analysis of the disruptive behavior revealed a drop in the marking period immediately after the hurricane in the HI-IMPACT area, but an opposite effect was observed in the LO-IMPACT area. CONCLUSIONS: After the hurricane there was an initial increase in PTS and a concomitant decrease in other measures of behavior and psychopathology. PTS remained relatively high throughout the school year, but there was a rebound and subsequent normalization of the measures of disruptive behavior.

Child↗

The molecular response of bone to growth hormone during skeletal unloading: regional differences.

Hind limb elevation of the growing rat provides a good model for the skeletal changes that occur during space flight. In this model the bones of the forelimbs (normally loaded) are used as an internal control for the changes that occur in the unloaded bones of the hind limbs. Previous studies have shown that skeletal unloading of the hind limbs results in a transient reduction of bone formation in the tibia and femur, with no change in the humerus. This fall in bone formation is accompanied by a fall in serum osteocalcin (bone Gla protein, BGP) and bone BGP messenger RNA (mRNA) levels, but a rise in bone insulin-like growth factor-I (IGF-I) protein and mRNA levels and resistance to the skeletal growth-promoting actions of IGF-I. To determine whether skeletal unloading also induced resistance to GH, we evaluated the response of the femur and humerus of sham and hypophysectomized rats, control and hind limb elevated, to GH (two doses), measuring mRNA levels of IGF-I, BGP, rat bone alkaline phosphatase (RAP), and alpha 1(1)-procollagen (coll). Hypophysectomy (HPX) decreased the mRNA levels of IGF-I, BGP, and coll in the femur, but was either less effective or had the opposite effect in the humerus. GH at the higher dose (500 micrograms/day) restored these mRNA levels to or above the sham control values in the femur, but generally had little or no effect on the humerus. RAP mRNA levels were increased by HPX, especially in the femur. The lower dose of GH (50 micrograms/day) inhibited this rise in RAP, whereas the higher dose raised the mRNA levels and resulted in the appearance of additional transcripts not seen in controls. As for the other mRNAs, RAP mRNA in the humerus was less affected by HPX or GH than that in the femur. Hind limb elevation led to an increase in IGF-I, coll, and RAP mRNAs and a reduction in BGP mRNA in the femur and either had no effect or potentiated the response of these mRNAs to GH. We conclude that GH stimulates a number of markers of bone formation by raising their mRNA levels, and that skeletal unloading does not block this response, but the response varies substantially from bone to bone.

Analysis of Variance↗

Synergistic liver toxicity of copper and retrorsine in the rat.

To investigate the possible synergy between copper and retrorsine (a pyrrolizidine alkaloid) as a cause of Indian Childhood Cirrhosis, four groups of male Wistar rats were fed the following diets from weaning: A. Normal diet; B. Copper loaded (2 g CuSO4/kg diet); C. Retrorsine supplemented (Expt 1:25 mg/kg body weight/week by gavage, Expt 2:25 mg/kg food initially then 15 mg/kg food after 4 weeks); and D. Copper and retrorsine as above. Serial plasma samples were assayed for aminotransferases, albumin and bilirubin. Liver samples at biopsy and sacrifice provided samples for copper analysis and histology. Results showed that copper and retrorsine together significantly increased liver damage compared with feeding either alone as assessed by: 1. Increased mortality rate; 2. Decreased plasma albumin and increased plasma bilirubin (mainly conjugated) indicative of hepatocyte dysfunction; 3. Massive liver copper accumulation, and 4. Increased liver damage histologically. Thus retrorsine caused liver copper accumulation, and together copper and retrorsine led to severe hepatic dysfunction, characterised by hypoalbuminaemia and conjugated hyperbilirubinaemia. Plant alkaloids secreted in milk by grazing animals and copper from brass vessels may together produce Indian Childhood Cirrhosis.

Animals↗

[The significance of computerized tomography in the conservative treatment of liver injuries].

Increasing experience with early radiological evaluation by ultrasound (US) and computed tomography (CT) of patients with abdominal trauma is leading to more frequent use of conservative treatment in patients with severe liver injuries. In a retrospective study with predominant use of peritoneal lavage only 3 out of 100 patients with liver injuries were treated non-surgically. In a consecutive prospectively evaluated series of 75 patients with early use of US and CT, 30 patients in stable circulatory conditions were treated non-surgically. With increasing experience a higher percentage of patients, even with severe liver injuries, could be treated non-operatively. 17 patients with minor injuries (grade I and II, modified according to Moore) and 13 patients with severe injuries (grade III and IV) could be treated non-surgically. 2 patients with grade IV injury developed an arterial/portal-venous fistula and an arterial aneurysm which necessitated radiological embolizations. All conservatively treated patients have been followed up for a mean period of 18 months without complications. Although a precise anatomical classification of the liver injury degree seems difficult, the predictive value of computed tomography for non-surgical treatment was good. Use of i.v.-contrast is mandatory. We conclude that in experienced hands computed tomography allows precise evaluation of liver injuries for adequate treatment, provided careful follow-up (intensive care unit, CT, angiography) ensues to avoid complications.

Abdominal Injuries↗