Evidence for genetic linkage of Alzheimer's disease to chromosome 10q.

Recent studies suggest that insulin-degrading enzyme (IDE) in neurons and microglia degrades Abeta, the principal component of beta-amyloid and one of the neuropathological hallmarks of Alzheimer's disease (AD). We performed parametric and nonparametric linkage analyses of seven genetic markers on chromosome 10q, six of which map near the IDE gene, in 435 multiplex AD families. These analyses revealed significant evidence of linkage for adjacent markers (D10S1671, D10S583, D10S1710, and D10S566), which was most pronounced in late-onset families. Furthermore, we found evidence for allele-specific association between the putative disease locus and marker D10S583, which has recently been located within 195 kilobases of the IDE gene.

Presenilin-mediated modulation of capacitative calcium entry.

We studied a novel function of the presenilins (PS1 and PS2) in governing capacitative calcium entry (CCE), a refilling mechanism for depleted intracellular calcium stores. Abrogation of functional PS1, by either knocking out PS1 or expressing inactive PS1, markedly potentiated CCE, suggesting a role for PS1 in the modulation of CCE. In contrast, familial Alzheimer's disease (FAD)-linked mutant PS1 or PS2 significantly attenuated CCE and store depletion-activated currents. While inhibition of CCE selectively increased the amyloidogenic amyloid beta peptide (Abeta42), increased accumulation of the peptide had no effect on CCE. Thus, reduced CCE is most likely an early cellular event leading to increased Abeta42 generation associated with FAD mutant presenilins. Our data indicate that the CCE pathway is a novel therapeutic target for Alzheimer's disease.

Partially formed native tertiary interactions in the A-state of cytochrome c.

Considerable insight into protein structure, stability, and folding has been obtained from studies of non-native states. We have studied the extent of native tertiary contacts in one such molecule, the A-state of yeast iso-1-ferricytochrome c. Previously, we showed that the interface between the N and C-terminal helices is completely formed in the A-state. Here, we focus on interactions essential for forming the heme pocket of eukaryotic cytochromes c. To determine the extent of these interactions, we used saturation mutagenesis at the evolutionarily invariant residue leucine 68, and measured the free energy of denaturation for the native states and the A-states of functional variants. We show that, unlike the interaction between the terminal helices, the native interactions between the 60s helix and the rest of the protein are not completely formed in the A-state.

Probing weakly polar interactions in cytochrome c.

Theoretical, statistical, and model studies suggest that proteins are stabilized by weakly polar attractions between sulfur atoms and properly oriented aromatic rings. The two sulfur-containing amino acids, methionine and cysteine, occur frequently among functional alleles in random mutant libraries of Saccharomyces cerevisiae iso-1-cytochrome c genes at positions that form a weakly polar aromatic-aromatic interaction, the wild-type protein. To determine if a weakly polar sulfur-aromatic interaction replaced the aromatic-aromatic interaction, the structure and stability of two variants were examined. Phenylalanine 10, which interacts with tyrosine 97, was replaced by methionine and cysteine. The cysteine was modified to form the methionine and cysteine analog, S-methyl cysteine (CysSMe). Proton NMR studies indicate that changing Phe 10 to Met or CysSMe affects only local structure and that the structures of sulfur-containing variants are nearly identical. Analysis of chemical shifts and nuclear Overhauser effect data indicates that both sulfur-containing side chains are in position to form a weakly polar interaction with Tyr 97. The F10M and F10CSMe variants are 2-3 kcal mol-1 less stable than iso-1-cytochrome c at 300 K. Comparison of the stabilities of the F10M and F10CSMe variants allows evaluation of the potential weakly polar interaction between the additional sulfur atom of F10CSMe and the aromatic moiety of Tyr 97. The F10CSMe;C102T variant is 0.7 +/- 0.3 kcal mol-1 more stable than the F10M;C102T protein. The increased stability is explained by the difference in hydrophobicity of the sulfur-containing side chains. We conclude that any weakly polar interaction between the additional sulfur and the aromatic ring is too weak to detect or is masked by destabilizing contributions to the free energy of denaturation.

The incidence of transient renal medullary hyperechogenicity in neonatal ultrasound examination.

A prospective ultrasound study of the urinary tracts of 85 neonates (64 term, 21 preterm) was performed to assess the incidence of transient renal medullary hyperechogenicity (RMH) in the first week of life. None of the neonates examined had evidence of renal dysfunction. Echogenic material was observed in the renal papillae/calyces, ureter, or bladder of 33 of the 64 term babies, but in the bladder of only one pre-term infant. The distribution of the echogenicity differs from that seen in medullary hyperechogenicity due to crystal deposition, suggesting that calyceal involvement is a common feature. Follow-up ultrasound scans at 10-14 days were possible in eight of the term neonates and demonstrated complete resolution of the RMH. The aetiology of transient neonatal RMH is unclear, although it may be related to protein cast deposition in the renal tubules. RMH may rarely be associated with transient renal dysfunction, but in healthy neonates should be recognized as a normal variant.

The ultrasound appearances of neonatal renal vein thrombosis.

Renal vein thrombosis (RVT) is the most frequently occurring vascular condition in the new-born kidney. The predisposing factors include dehydration, sepsis, birth asphyxia, maternal diabetes, polycythaemia and the presence of an indwelling umbilical venous catheter. (RVT) may present clinically with a flank mass, haematuria, hypertension or renal failure. Many imaging modalities have been employed, but ultrasound is the technique most commonly used in the evaluation of neonates with suspected RVT. Thrombosis commences in the small renal veins and subsequently propagates via larger interlobar veins to the main renal vein and inferior vena cava (IVC). The ultrasound appearances depend upon the stage at which the examination is performed and extent of the thrombus. Initially, the interlobular and interlobar thrombus appears as highly echogenic streaks. These streaks commence in a peripheral, focal segment of the involved kidney and only persist for a few days. In the first week the affected kidney swells and becomes echogenic with prominent echopoor medullary pyramids. Later, the swelling increases and the kidney becomes heterogenous with loss of corticomedullary differentiation. Grey scale ultrasound readily demonstrates thrombus within the renal vein and IVC. Adrenal haemorrhage is a recognized association and may be identified ultrasonically. Colour Doppler scanning provides additional information. In the early stages of RVT, colour Doppler may demonstrate absent intrarenal and renal venous flow. Ultimately, the kidney may recover, show focal scarring or become atrophic. Thus, ultrasound provides an accessible and reliable tool in the assessment of suspected neonatal RVT.

Ultrasound examination of neonate's hip joints.

In a mass screening project, 872 neonates were examined clinically and by ultrasound. Hip joint stability was assessed in the ultrasound stress test showing a normal or physiologic instability, in the range of 0 to 2 mm. Along with the dynamic examination, a modified Graf's method was used. All obtained sonograms were submitted to careful assessment by one of authors, including regular measurement of alpha and beta angles. This relatively small group in the low-risk population served as a model of normality. White newborns compared with an black Caribbean group did not show the presence of apparent primary acetabular dysplasia. Both methods--dynamic ultrasound test and Graf's scanning--seemed to us to be valuable.

Role of common and rare APP DNA sequence variants in Alzheimer disease.

OBJECTIVES: More than 30 different rare mutations, including copy number variants (CNVs), in the amyloid precursor protein gene (APP) cause early-onset familial Alzheimer disease (EOFAD), whereas the contribution of common APP variants to disease risk remains controversial. In this study we systematically assessed the role of both rare and common APP DNA variants in Alzheimer disease (AD) families. METHODS: Families with EOFAD genetically linked to the APP region were screened for missense mutations and locus duplications of APP. Further, using genome-wide DNA microarray data, we examined the APP locus for CNVs in a total of 797 additional early- and late-onset AD pedigrees. Finally, 423 single nucleotide polymorphisms (SNPs) in the APP locus, including 2 promoter polymorphisms previously associated with AD risk, were tested in up to 4,200 individuals from multiplex AD families. RESULTS: Analyses of 8 21q21-linked families revealed one family carrying a nonsynonymous mutation in exon 17 (Val717Leu) and another family with a partially penetrant 3.5-Mb locus duplication encompassing APP. CNV analysis in the APP locus revealed an additional family carrying a fully penetrant 380-kb duplication, merely spanning APP. Last, contrary to previous reports, association analyses of more than 400 different SNPs in or near APP failed to show significant effects on AD risk. CONCLUSION: Our study shows that APP mutations and locus duplications are a very rare cause of EOFAD and that the contribution of common APP variants to AD susceptibility is insignificant. Furthermore, duplications of APP may not be fully penetrant, possibly indicating the existence of hitherto unknown protective genetic factors.

Spontaneously hypertensive, Wistar Kyoto and Sprague-Dawley rats differ in their use of place and response strategies in the water radial arm maze.

This study further characterises the use of mnemonic systems in the spontaneously hypertensive rat (SHR), which is frequently used as a rodent model of attention deficit hyperactivity disorder. The objective of this study was to assess the preference of male SHR, Wistar-Kyoto (WKY) and Sprague-Dawley (SD) rats for a place or response strategy when trained on an ambiguous T-maze task, and also to examine whether all strains acquired information about both strategies during ambiguous training, regardless of their preferred strategy. In the first experiment, SHR and WKY showed a preference for a response strategy on the ambiguous T-maze task; in contrast, SD displayed a preference for a place strategy. In the second experiment, all strains demonstrated that they learned information about both the response and place strategies during ambiguous training. However, on a conditioned place preference test SHR did not display as strong a preference for the place arm as WKY and SD. This finding supports previous research in a conditioned cue preference test, in which SHR did not display a preference for the cue associated with the platform. These observations that the strains differ with respect to behavioural strategy in a learning task suggest that they differ in the underlying neural circuitry that serves goal-directed behaviour, and are consistent with SHR having deficits associated with the nucleus accumbens.

Functional morphology of the piper Hyporhamphus ihi with reference to the role of the lateral line in feeding.

As a basis for understanding the function of the halfbeak of the piper Hyporhamphus ihi (Phillips), details of the structure and dimensions of the anterior lateral line on the head and lower jaw of the piper are described. The anterior lateral line is composed of a series of cranial canals; the supraorbital-postorbital canal; the suborbital canal; and the preopercular-mandibular canal which extends along the lower jaw. Each canal opens to the surface by a series of pores, and individual neuromasts exist in specialized regions of the canals between each of the pores. Piper are nocturnal plankivores and they possess the feeding structures and digestive tract suited to this diet. The hypothesis is proposed that they use the anterior lateral line system in prey detection, and this paper shows that the piper's elongate body form, swimming behaviour, and lack of a specialized visual system are all consistent with this hypothesis.

Field and laboratory studies of the feeding behaviour of the piper Hyporhamphus ihi with reference to the role of the lateral line in feeding.

Piper school in large groups close to the water surface during daylight hours, whereas at night the schools break up and individual fish can be observed swimming slowly through the water. Analysis of gut contents indicates that during the day piper feed primarily on copepods, and terrestrial insects trapped on the water surface; after dark the demersal zooplankton which enter the water column form the major dietary component. Prey selectivity is evident in that certain groups present in the plankton are not found in the stomach contents of piper, and that the size of prey taken is biased towards the larger size classes of plankton. Laboratory experiments establish that piper are capable of locating prey in total darkness, and that under these conditions live prey are consumed in a higher proportion, and much more quickly than dead prey. These results strengthen the hypothesis that piper use their anterior lateral line to feed on zooplankton at night.

Case report: ultrasonographic demonstration of portal vein thrombosis in the acute abdomen.

Ultrasonography demonstrated thrombus within the portal venous system in a child who presented with abdominal pain and a fever. This helped lead to a diagnosis of appendicitis complicated by ascending septic thrombophlebitis. Ultrasound of the portal vein may be of value when investigating such children with atyptical abdominal pain.

Cystic kidney disease presenting in infancy.

AIM: The clinical, histological and imaging findings of 12 children with ultrasound features of severe renal cystic disease presenting in the first year of life were reviewed. METHODS AND RESULTS: Two children had cystic dysplasia and four had autosomal dominant polycystic disease. Two had a malformation syndrome, one a variant of Meckel syndrome and the other Bardet Biedl syndrome. One had autosomal recessive polycystic disease and in three there was no final diagnosis. Intravenous urography gave non-specific information. In six cases clinical findings combined with imaging established a diagnosis. Diagnosis was established by biopsy in two and gave supportive evidence in one. Outlook for renal function is variable. One child has had a transplant and one is on dialysis awaiting a transplant. Three have a degree of renal failure and one has died. Six have normal renal function. Renal cystic disease is the common pathway for a heterogeneous group of disorders as shown in these children. CONCLUSION: It is emphasized that a specific diagnosis could not be made from the renal sonographic appearances alone, nor could any prognostic implications for renal function be made. Contrast retention on intravenous urography was also insufficiently specific to be of value. Ultrasound of the parents was the most useful imaging procedure and should be done in all cases.

Midgut malrotation diagnosed by ultrasound.

Ultrasound was used to demonstrate the abnormal orientation of the mesenteric vessels in six cases of midgut malrotation. Five of these patients were known to have an abnormality of rotation before the ultrasound scan. In one patient malrotation was predicted from the ultrasound scan and confirmed by a barium study and at operation.