Clinicopathological features of familial Alzheimer's disease associated with the M139V mutation in the presenilin 1 gene. Pedigree but not mutation specific age at onset provides evidence for a further genetic factor

Sixteen affected individuals are described from two families with early onset autosomal dominant familial Alzheimer's disease. A mutation at codon 139 in the presenilin 1 gene on chromosome 14 results in a methionine to valine substitution which cosegregates with the disease in these families. Onset of dementia was before the age of 50 years in all individuals. The ages at onset within each family were tightly clustered but were significantly different between the families; this difference could not be accounted for by apolipoprotein E status and suggests the existence of a further genetic factor that modifies age at disease onset. The pattern of cognitive decline was similar in both families: early memory loss (initially selective for verbal memory in some individuals) was followed soon after by loss of arithmetic skills while naming and object perception skills were relatively preserved. A speech production deficit was observed in three members of one family but not in the other. Seizures were common and usually predated by myoclonic jerks by a number of years. Serial MRIs showed progressive cortical atrophy with periventricular white matter change appearing 3-4 years into the disease. PET revealed parieto-temporal hypometabolism in all individuals scanned. The diagnosis of Alzheimer's disease was confirmed with typical histopathology in one individual from each family.

Dynamic interfragmentary motion in fractures during routine patient activity

Natural interfragmentary motion was measured in tibial fractures during normal patient activity, and the results were interpreted using correlations from the literature to examine the influence of natural motion on healing. Ten patients were selected with reduced, diaphyseal tibial fractures stabilized with Orthofix external fixators. Three-dimensional motion was monitored with an instrumented spatial linkage during walking, standing, and muscle activities at 2 and 4 weeks postfixation. Fracture motion arising from dorsal to plantar flexion while supine produced peak cyclic displacements of the same order of magnitude as that seen during weightbearing activity. Thus, therapeutic exercise may be used to provide a stimulus to osteogenic repair processes in patients who are unable to bear weight. In 3 patients, maximum amplitudes of axial motion during walking were 1 mm or greater. This implied regular gap closure and high tissue strains within the 1 mm +/- 0.5 mm gaps. In 3 patients, axial motion was less than 0.25 mm. These 2 extremes may indicate a range of displacement relative to gap size that embraces inhibitive and stimulative influences on healing. Transverse shear displacements also varied greatly from between 0.6 and 0.75 mm in 3 patients to less than 0.2 mm in 5 patients.

Primary sellar haemorrhagic melanoma: case report and review of the literature

Primary melanoma of the sella turcica is very unusual with only four previous cases reported in the medical literature. This report describes a 47-year-old man whose headaches, endocrine dysfunction and neuro-imaging suggested a haemorrhagic pituitary macroadenoma. The histological examination showed a haemorrhagic melanoma. An extensive search for a primary source proved negative. The patient underwent three neurosurgical interventions and radiotherapy and died two years after presentation. Previous cases of primary melanoma in the pituitary region, as well as various hypotheses for this unusual site of origin are reviewed, followed by a discussion of the particular characteristics of melanin pigments on MRI. This case report illustrates that primary sellar melanoma may present as a haemorrhagic adenoma of the pituitary gland and have an unfavourable outcome despite repeated neurosurgical interventions and radiation therapy.

Presenilin-1 is processed into two major cleavage products in neuronal cell lines

Presenilin-1 (PS-1) has been identified as the protein encoded by the chromosome 14 locus that, when mutated, leads to familial Alzheimer's disease (FAD). Using PS-1 transfected SHSY5Y neuroblastoma cells, we have demonstrated by immunodetection, using polyclonal antibodies, that PS-1 is processed to give two fragments: an N-terminal 28 kDa fragment, and a C-terminal 18 kDa fragment. In a number of non-transfected cell types, most PS-1 is detected as the cleaved products. The molecular weights of the PS-1 cleavage products suggest that the cleavage point will most probably be within a region of the hydrophilic loop domain coded for by either exon 8 or 9 of the PS-1 gene. The clustering of FAD mutations within exon 8 strongly suggests that it encodes a key functional domain. It seems likely that the cleavage of PS-1 is crucial to some aspect of its functionality. An understanding of this process will give insights into the pathology of AD, and may offer new opportunities for therapeutic intervention.

Immunogenicity of a fusion protein linking the beta subunit carboxyl terminal peptide (CTP) of human chorionic gonadotropin to the B subunit of Escherichia coli heat-labile enterotoxin (LTB)

Human chorionic gonadotropin (hCG) is currently under investigation as an antigenic target in both anti-cancer and anti-fertility vaccines. Formulations studied to date show promise in clinical trials for both applications yet are expensive to produce and require frequented administration in order to maintain an effective antibody titer. We have engineered a fusion protein consisting of Escherichia coli heat-labile enterotoxin subunit B (LTB) genetically linked at its C terminus via a nine amino acid linker to the 37 amino acid carboxyl terminal peptide (CTP) of the hCG beta chain. This LTB-CTP fusion protein is stably expressed in bacteria and forms pentamers of full-length protein subunits. Purified LTB-CTP protein hCG-specific antibodies in mice without additional adjuvants.

Increased amyloid-beta42(43) in brains of mice expressing mutant presenilin 1

Mutations in the genes encoding amyloid-beta precursor protein (APP), presenilin 1 (PS1) and presenilin 2 (PS2) are known to cause early-onset, autosomal dominant Alzheimer's disease. Studies of plasma and fibroblasts from subjects with these mutations have established that they all alter amyloid beta-protein (beta APP) processing, which normally leads to the secretion of amyloid-beta protein (relative molecular mass 4,000; M(r) 4K; approximately 90% A beta1-40, approximately 10% A beta1-42(43)), so that the extracellular concentration of A beta42(43) is increased. This increase in A beta42(43) is believed to be the critical change that initiates Alzheimer's disease pathogenesis because A beta42(43) is deposited early and selectively in the senile plaques that are observed in the brains of patients with all forms of the disease. To establish that the presenilin mutations increase the amount of A beta42(43) in the brain and to test whether presenilin mutations act as true (gain of function) dominants, we have now constructed mice expressing wild-type and mutant presenilin genes. Analysis of these mice showed that overexpression of mutant, but not wild-type, PS1 selectively increases brain A beta42(43). These results indicate that the presenilin mutations probably cause Alzheimer's disease through a gain of deleterious function that increases the amount of A beta42(43) in the brain.

Alteration in brain presenilin 1 mRNA expression in early onset familial Alzheimer's disease

The expression of the presenilin 1 (PS-1) gene has been investigated by in situ hybridization in early onset familial Alzheimer's disease (FAD), late onset Alzheimer's disease (AD) and normal control brain. Mutations in this gene are responsible for chromosome 14-linked FAD. We have found that presenilin 1 mRNA is present throughout the human brain with a distribution consistent with both a glial and neuronal localization. The in situ hybridization pattern was similar for the controls, the early onset FAD cases and the late onset AD cases. However, one of the two forms of the mRNA for PS-1, the long form (which contains a sequence encoding a four amino acid (VRSQ) insert at its 5' end) was significantly reduced in early onset FAD brain compared with late onset AD. We suggest that this long transcript may alter the normal pathway for processing of amyloid precursor protein, the protein which appears to be central in the pathogenesis of AD.

A further presenilin 1 mutation in the exon 8 cluster in familial Alzheimer's disease

Recent studies suggest that mutations in the presenilin 1 gene, which encodes a polypeptide predicted to be a multispanning membrane protein, are responsible for the majority of cases of early onset, autosomal dominant Alzheimer's disease. Here we describe a further mutation in the presenilin 1 gene (R269G) in a family with early onset Alzheimer's disease. This mutation is in exon 8 which appears to be a favoured region for pathogenic mutations. In the presenilin protein the region coded for by this exon is likely to comprise a domain located on the membrane surface. We discuss the likely effects of the exon 8 mutations on the structure of the exon and in the pathogenesis of the disease.

Amyloid beta protein (Abeta) deposition in chromosome 14-linked Alzheimer's disease: predominance of Abeta42(43)

Amyloid beta protein (Abeta) deposition was investigated in the frontal cortex of 8 cases of (genetically confirmed) chromosome 14-linked Alzheimer's disease (AD) using the end-specific monoclonal antibodies BA27 and BC05 to detect the presence of Abeta40 and Abeta42(43), respectively. In all patients, Abeta42(43) was the predominant peptide species present. The total amount of Abeta40 and Abeta42(43) deposited was more than twice the amount deposited in cases of sporadic AD of similar disease duration, although the ratio between the extent of Abeta40 and Abeta42(43) deposition was unaltered, compared with sporadic AD. Therefore, (one of) the effects of the mutations in the presenilin 1:PS-1 (S182) gene may be to cause or at least promote an early and excessive deposition of Abeta42(43) within the brain, a property shared with other inherited forms of AD, such as those due to amyloid precursor protein mutations, and Down's syndrome (trisomy 21).

Surgical outcome after repeated transsphenoidal surgery in acromegaly

Transsphenoidal selective adenomectomy is the most efficient primary treatment for acromegaly. However, management of persistent or recurrent disease remains controversial. The objective of the present study was to evaluate the early and long-term efficacy and safety of a second transsphenoidal surgery performed in those cases. The results of a retrospective study of 16 patients undergoing reoperation by the senior author (J.H.) between 1970 and 1991 are reported. Reoperation was performed for persistent or progressive acromegaly in 11 patients, visual impairment in four, and disease recurrence in one. Normalization of growth hormone (GH) was defined as a basal GH level of less than 5 micrograms/L and suppression to less than 2 micrograms/L during the oral glucose tolerance test. Long-term follow-up data were available in 15 patients. The second transsphenoidal surgery induced a greater than 50% decrease of GH level in 11 patients. Three (19%) of 16 patients were cured according to the authors' criteria and remained so after 2, 7, and 20 years. Two more patients had a postoperative basal GH level of less than 5 micrograms/L but incomplete suppression during the oral glucose tolerance test. Thus, a total of five patients (31%) achieved a basal GH of less than 5 micrograms/L. One other patient who had no initial improvement after the second transphenoidal surgery had spontaneous normalization of his GH level after 13 years. The following complications of the second surgery occurred in three patients: one subarachnoid hemorrhage, two new visual field defects, one cranial nerve palsy, and one meningitis. Moreover, 10 patients (62.5%) developed one or more new pituitary hormone deficiencies. In conclusion, reoperation for persistent or recurrent acromegaly has low success and high complication rates. According to the authors' experience, this procedure should be reserved for patients unresponsive to other forms of therapy or with progressive visual impairment despite medical therapy.

Secreted amyloid beta-protein similar to that in the senile plaques of Alzheimer's disease is increased in vivo by the presenilin 1 and 2 and APP mutations linked to familial Alzheimer's disease

To determine whether the presenilin 1 (PS1), presenilin 2 (PS2) and amyloid beta-protein precursor (APP) mutations linked to familial Alzheimer's disease (FAD) increase the extracellular concentration of amyloid beta-protein (A beta) ending at A beta 42(43) in vivo, we performed a blinded comparison of plasma A beta levels in carriers of these mutations and controls. A beta 1-42(43) was elevated in plasma from subjects with FAD-linked PS1 (P < 0.0001), PS2N1411 (P = 0.009), APPK670N,M671L (P < 0.0001), and APPV7171 (one subject) mutations. A beta ending at A beta 42(43) was also significantly elevated in fibroblast media from subjects with PS1 (P < 0.0001) or PS2 (P = 0.03) mutations. These findings indicate that the FAD-linked mutations may all cause Alzhelmer's disease by increasing the extracellular concentration of A beta 42(43), thereby fostering cerebral deposition of this highly amyloidogenic peptide.

Structure and alternative splicing of the presenilin-2 gene

Missense mutations in the presenilin-1 (PS-1) and presenilin-2 (PS-2) genes have been shown to be causes of autosomal dominant Alzheimer's disease (the AD3 and AD4 loci, respectively). Alternative splicing has previously been reported in the PS-1 gene. In this study, elucidation of intron/exon boundary sequences revealed that PS-2 is encoded by 10 coding exons. In addition, PS-2 cDNA cloning and RT-PCR using RNA from a variety of normal tissues revealed the presence of alternatively spliced products. These products included species with in frame omissions of exon 8 and simultaneous omissions of exons 3 and 4.

Endoproteolysis of presenilin 1 and accumulation of processed derivatives in vivo

The majority of early-onset cases of familial Alzheimer's disease (FAD) are linked to mutations in two related genes, PS1 and PS2, located on chromosome 14 and 1, respectively. Using two highly specific antibodies against nonoverlapping epitopes of the PS1-encoded polypeptide, termed presenilin 1 (PS1), we document that the preponderant PS1-related species that accumulate in cultured mammalian cells, and in the brains of rodents, primates, and humans are approximately 27-28 kDa N-terminal and approximately 16-17 kDa C-terminal derivatives. Notably, a FAD-linked PS1 variant that lacks exon 9 is not subject to endoproteolytic cleavage. In brains of transgenic mice expressing human PS1, approximately 17 kDa and approximately 27 kDa PS1 derivatives accumulate to saturable levels, and at approximately 1:1 stoichiometry, independent of transgene-derived mRNA. We conclude that PS1 is subject to endoproteolytic processing in vivo.

New insights into the genetics of Alzheimer's disease

In early 1993, the genetic data implicating the amyloid precursor protein as one of the loci leading to early onset Alzheimer's disease were reviewed (Hardy and Duff, Annals of Medicine, 25: 437-440), together with the evidence implicating abnormal deposition of beta-amyloid as the initiating point of the process leading to the disease. Since that time, three other genetic loci have been directly implicated in the aetiology of the disease: the apolipoprotein E locus on chromosome 19, the presenilin 1 gene on chromosome 14 and the presenilin 2 gene on chromosome 1. In this article, I review the progress over the last three years and attempt to assess whether the evidence for the amyloid cascade hypothesis still stands scrutiny.

Molecular genetics of Alzheimer's disease

Four genes have thus far been implicated in the etiology of Alzheimer's disease (AD). A series of mutations in the amyloid precursor protein (APP) gene on chromosome 21, which cause disease with a typical onset of 55 years of age, have been described. These include mutations at APP670/671, APP692, and APP717. The epsilon 4 allele of the apolipoprotein E (ApoE) gene on chromosome 19 is positively associated with disease, whereas the epsilon 2 allele is usually negatively associated with disease. Mutations in the S182 gene on chromosome 14 seem to cause disease with an onset age of < 50 years and mutations in a gene on chromosome 1 (S182 Like Protein: S182LP) cause disease with variable onset. These genetic findings are reviewed within the framework of the amyloid cascade hypothesis of AD etiology and pathogenesis. The occurrence and effects of the mutations in APP and the fact that the epsilon 4 allele of ApoE are genetic risk factors point to the hypothesis that the extracellular deposition of beta-amyloid is the key initiating event in the pathogenesis of AD.

Transsphenoidal adenomectomy for microprolactinomas: 10 to 20 years of follow-up

BACKGROUND

Transsphenoidal adenomectomy is an effective treatment fo r microprolactinomas. However, postoperative recurrence of hyperprolactinemia is not rare. This study was designed to evaluate the long-term outcome of women with microprolactinomas operated on by transsphenoidal approach.

METHODS

We retrospectively studied 64 women with microprolactinomas who underwent transsphenoidal adenomectomy and were followed for 10 to 20 years.

RESULTS

Postoperatively, 58 women (90%) had normal plasma prolactin concentrations (<20 microg/L). After a mean of 3.3 years, during which the women were asymptomatic with normoprolactinemia, 25 (43%) had a relapse of hyperprolactinemia (> or = 20 microg/L). However, their evolution varied. Fifteen women had symptomatic hyperprolactinemia. Computed tomography (CT) scans showed recurrent microadenomas in 2 women. The other 10 women had only hyperprolactinemia. Of these women, 5 had transient hyperprolactinemia (29 +/- 4 microg/L) for 5 years, after which prolactin declined to normal 13 +/- 3 microg/L). The remaining five patients had elevated prolactin (31 +/- 3 microg/L) throughout the follow-up period (10 to 20 years). CT scan did not show recurrent adenomas in these women. Thirty-three women remained normoprolactinemic and asymptomatic for a mean period of 12 years (range, 10 to 20 years).

CONCLUSIONS

In conclusion, most of the patients with late relapse of hyperprolactinemia have slight functional hyperprolactinemia and remain asymptomatic with no evidence of tumor recurrence.

Joint pressure influences synovial tissue blood flow as determined by colored microspheres

We measured regional blood flow in synovial tissue of the antebrachiocarpal, midcarpal, and metacarpophalangeal joints of six normal adult anesthetized horses by using 15-microns-diameter polystyrene colored microspheres. The midcarpal fibrous capsule and synovial membrane blood flows (SMBF) were compared, and the effect of increased intra-articular pressure (30 and 60 mmHg) on midcarpal SMBF was investigated. Dorsal, medial palmar, and lateral palmar midcarpal SMBF measured 108 +/- 36, 61 +/- 12, and 50 +/- 11 microliters.min-1.g-1, respectively. Antebrachiocarpal, dorsal, and palmar metacarpophalangeal SMBF measured 103 +/- 8, 17 +/- 3, and 26 +/- 5 microliters.min-1.g-1, respectively. Midcarpal fibrous joint capsule blood flow was significantly lower than that of the synovial membrane. An increase in midcarpal intra-articular pressure to 30 or 60 mmHg resulted in an 84% decrease in SMBF. Colored microspheres provided a useful technique to determine sequential SMBF. Increased intra-articular pressure significantly altered SMBF, suggesting a role of the regional circulation in the pathogenesis of joint disease.

Colonic luminal pressure in horses with strangulating and nonstrangulating obstruction of the large colon

Colonic luminal pressure (median, range) measured during ventral midline celiotomy in 69 horses with strangulating obstruction (SO) of the large colon (SO; > or = 270 degrees large colon volvulus; 27 cm H2O: 2 to 80 cm H2O) was greater (P = .0023) than that measured in 37 horses with nonstrangulating obstruction (NSO) of the large colon (NSO; < or = 180 degrees volvulus or a nonstrangulating displacement; 18 cm H2O; 6 to 46 cm H2O). Sixty-five percent (45 of 69) of horses with SO and all horses with NSO survived. Survival analysis was restricted to 59 horses with large-colon SO that survived to hospital discharge or met the criteria specified for classification as nonsurvivors. Colonic luminal pressure in nonsurvivors (48.5 cm H2O; 34 to 80 cm H2O) was higher (P =.0001) than that measured in survivors (18 cm H2O; 2 to 50 cm H2O) of SO. From response operating characteristic curves, a luminal pressure of 38 cm H2O optimized the distribution of horses with SO into survivor and nonsurvivor groups. Sensitivity, specificity, and positive and negative predictive values for a colonic luminal pressure greater than 38 cm H2O in predicting nonsurvival were 0.89, 0.91, 0.72 and 0.97, respectively. Measurement of colonic luminal pressure may be useful for predicting survival in horses with colonic volvulus.

Polymorphism in AACT gene may lower age of onset of Alzheimer's disease

The ApoE-epsilon 4 allele is a predisposing factor for late onset Alzheimer's disease (AD), however it is neither necessary nor sufficient to cause the disease. A candidate for explaining part of the remaining genetic component is alpha 1-antichymotrypsin (AACT). In a case-control study we genotyped a polymorphism within the AACT gene to test for association with the disease. No allele of this gene showed an increased incidence among the population with AD compared with controls, even when taking ApoE genotype into account. This contrasts with the results of a recently published report. The mean age of onset was apparently lowered by the presence of the AACT AA genotype among ApoE-epsilon 4 bearers. If AACT genotype has an effect on risk for AD it may be predominantly amongst individuals with early onset AD.