Retention of prefabricated attachments for implant stabilized overdentures in the edentulous mandible: an in vitro study

STATEMENT OF PROBLEM

Bar and stud attachments are widely used to stabilize overdentures on implants in the mandible. There is strong evidence that retention of the attachment is an important factor for a patient's satisfaction.

PURPOSE

This study describes retentive forces and wear of commercially available attachments of 4 implant systems (31, IMZ, Nobel Biocare, ITI Straumann) and 2 magnets (Steco).

METHODS

Forces while removing the keyway portion of an attachment in its path of insertion were measured with a platform load cell. A total of 15,000 removals were performed to simulate fatigue.

RESULTS

Retentive forces ranged between 3 and 85 N. The fatigue test revealed an initial increase of forces with some attachments. After 15,000 cycles, most of the attachments showed little loss of retention compared with the initial retentive forces. It is suggested that conventional fatigue tests with application of axial loads do no simulate clinical fatigue adequately.

Biochemical characterization and histochemical localization of nitric oxide synthase in the nervous system of the snail, Helix pomatia

Nitric oxide synthase (NOS) in the snail Helix pomatia was characterized by biochemical and molecular biological techniques and localized by histochemical methods. Central ganglia contained particulate paraformaldehyde-sensitive and cytosolic paraformaldehyde-insensitive NADPH-diaphorase. The cytosolic NADPH-diaphorase activity coeluted with NOS activity. The activity of NOS was dependent on Ca2+ and NADPH and was inhibited by N(G)-nitro-L-arginine (L-NNA). Proteins purified by 2',5'-ADP affinity chromatography were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and migrated at 150, 60, 40, and 30 kDa. An antibody to mammalian NOS exclusively labeled the 60-kDa protein. Characterization of the cDNA of the corresponding 60-kDa NOS-immunoreactive protein revealed no sequence homology with any known NOS isoform. The recombinant protein exhibited Ca2+- and NADPH-dependent NOS activity, which was partially inhibited by EGTA and L-NNA. Histochemistry showed NADPH-diaphorase activity in discrete regions of the central and peripheral nervous system. About 60% of the NADPH-diaphorase-positive neurons colocalize with immunoreactive material detected by antibodies to mammalian NOS. Comparison of organs showed the highest NADPH-diaphorase activity in the nervous system, whereas moderate activity was present in muscle tissue, digestive tract, and gonads. Our study suggests the presence of NOS and a putative NOS-associated/regulating protein in mollusk nervous tissue.

Immunological and biological properties of Bet v 4, a novel birch pollen allergen with two EF-hand calcium-binding domains

We have isolated a cDNA clone coding for a birch pollen allergen, Bet v 4. The deduced amino acid sequence of Bet v 4 contained two typical EF-hand calcium-binding domains. Sequence similarities of Bet v 4 to calmodulin are primarily confined to the calcium-binding domains. However, significant sequence similarities extending outside the Ca2+-binding sites were found with a recently described group of pollen-specific allergens of Brassica and Bermuda grass. Both EF-hand domains of Bet v 4 are able to bind Ca2+, as demonstrated by 45Ca2+ blot overlay of wild type and calcium-binding deficient mutants of Bet v 4. Among pollen-allergic patients, protein-bound Ca2+ was not an absolute requirement for IgE recognition of Bet v 4. However, disruption of the carboxyl-terminal Ca2+-binding domain indicated that most IgE antibodies from allergic patients are directed against this site. IgE inhibition experiments suggested that Bet v 4 represents a highly cross-reactive pollen allergen. Pre-absorption of allergic sera with Bet v 4 drastically reduced IgE binding to proteins of similar molecular weight in pollen extracts from distantly related plant species (e.g. timothy grass, mugwort, lily) but not in extracts from plant-derived foodstuff. To test for a possible biological role in pollen germination and tube growth, we introduced recombinant Bet v 4 protein into growing lily pollen tubes by iontophoresis. As a result, cytoplasmic streaming stopped in the vicinity of the electrode tip, and a slight depolarization of the membrane voltage was measured. These effects were not observed with Ca2+-binding deficient mutants of Bet v 4. Thus, Bet v 4 and homologous proteins represent a new class of pollen-specific Ca2+-binding allergens that may have a physiological role as inhibitors of cytoplasmic streaming in outgrowing pollen tubes.

Human spasmolytic polypeptide decreases proton permeation through gastric mucus in vivo and in vitro

Exogenously administered trefoil peptides are gastroprotective in rat injury models. We hypothesized that trefoil-associated gastroprotection occurred by decreasing the rate of proton permeation through mucus. Gastric surface cell intracellular pH and mucus gel thickness were measured by in vivo microscopy. Gastric mucosal blood flow was measured by laser-Doppler flowmetry. The effect of human spasmolytic peptide (hSP) on H+ diffusion through 5% purified porcine mucin was measured using an Ussing chamber. Buffering action of mucin was measured by titration. In vivo, gastric mucosal blood flow and mucus gel thickness were not affected by any of the treatments. Topical hSP, but not intravenous hSP, decreased initial acidification rate and elevated the intracellular pH of gastric surface cells during luminal acid challenge. In in vitro studies, hSP dose dependently decreased the diffusion coefficient of H+ through 5% porcine mucin solution. hSP had no significant effect on the buffering action of mucin solutions. These data support our hypothesis that hSP interacts with gastric mucin in a manner that inhibits proton permeation through the mucus gel layer.

Imprinting is also a mechanism for immediate or delayed hemizygous expression of several uniparental haplotypes selected from the genome of each sex

A peculiar and interesting aspect of monoallelic or hemizygous expression, resulting from genomic imprinting, should be a likeness or resemblance for some phenotypic traits between relatives inheriting identical active genes or domains. Although the word "likon," a neologism, is reminiscent of the above implication, it is here proposed for use in a broader sense, namely, to designate a haplotype or part of a haplotype of an imprinted domain. As learned from earlier studies of imprinting and uniparental disomies, haplotypes at loci of such domains may be expressed (E) or unexpressed (U) in somatic cells; they may also be transmitted to be expressed or not in the next generation by germ cells "acting" (A) or marked to be "resting" (R) for such loci. Thus the soma/germinal status of "likons" might for each genitor be abbreviated as EA, UA, ER, and UR. In an evolutionary sense the assumption is that the same monoallelically expressed loci and domains when carried by two or more relatives should be the source of identical transcripts contributing to a closely similar phenotype. If so, the overall phenotype would be distinct if arising from some 10 to 20 imprinted genes or domains potentially gaining expression from the germ cells of either one or the other sex in humans. The result may have evolutionary implications by narrowing the scope of random individual variation and by strengthening assortative and associative values (physical, behavioral, and instinctual) in one's own lineage and species.

In vivo color stability of resin-veneered telescopic dentures: a double blind pilot study

STATEMENT OF PROBLEM

Discoloration is a major disadvantage of resin veneers on telescopic dentures. In vitro color measurements with large and flat samples of resin veneer composites have been published, but no in vivo data are available.

PURPOSE

This study describes the discoloration of resin veneers in vivo by use of spectrophotometry and the L*a*b* system of the Commission Internationale de L'Eclairage (CIE).

METHODS

In a clinical evaluation of this technique, two composite veneer materials were compared in 18 patients.

RESULTS

Both brands discolored significantly after 1 year. While L* and a* were not changed significantly, b* and the total color difference delta E increased by approximately 2 units each year. No statistically significant differences were found between the materials.

Uniparental disomy (UPD). Genomic imprinting and a case for new genetics (prenatal and clinical implications: the "Likon" concept)

Uniparental disomy (UPD) is often the result of an aneuploid event masquerading under the features of diploidy. As such, it may never be recognized, being at 2 opposite phenotypic poles, harmless to the bearer, or, if harmful, eventually responsible for uncharacteristic although perhaps serious conditions. UPD can also be associated with problems such as recessiveness or mosaicism. This article considers the chances of unmasking UPD, in the course of CVS or AC prenatal diagnosis, by reviewing the main cytogenetic signals and major familial or personal antecedents raising its suspicion. Once suspected, the lead toward UPD may or may not be followed through appropriate molecular studies. UPD for either maternal or paternal chromosomes 13, 21 and 22 may not have consistent, common deleterious effects, while other identified UPD's are too rare to call. Unconditionally, main, consistent or near consistent damages to the phenotype have been traced to specific chromosome pairs such as 15 mat (Prader-Willi syndrome), 15 pat (Angelman syndrome), 11 pat (Wiedemann-Beck with syndrome), 14 mat and pat (multiple cogenital and developmental anomalies [MCDA]-several rather constant) and 7 mat (Russel-Silver [RS] and Growth-failure [GF]). The above problems all stem from an alteration of the normal, developmentally important genomic imprinting processes and most of them may recognize several etiopathogenic paths, other than UPD, none of which abides by straight Mendelian rules. In this very area, therefore, a new, non-traditional type of inheritance is confronting genetic counselling. In this paper, for want of appropriate semantic language, the neologism "likon" (or "laïkon") is coined to make reference to the hemizygously expressed sequences of the genomic parts imprinted in the somatic tissues. Broadening the definition, the word is then applied to the 4 possible epigenotypes of imprinted domains, which depend on the parental sex-of-origin: germinally "resting" (R), or "acting" (A), to be made somatically silent, that is to say "unexpressed" (U), or transcribed and "expressed" (E), thus abbreviated as EA, ER, UA and UR. Entire pedigrees may then be analyzed accordingly in health and in disease. Examples are presented herewith.

Chronic recurrent multifocal osteomyelitis: an evolving clinical and radiological spectrum

OBJECTIVE

To describe unusual clinical and radiological features in patients with chronic recurrent multifocal osteomyelitis (CRMO).

DESIGN AND SUBJECTS

Based on radiographic and microscopic findings, three patients were prospectively diagnosed as having chronic recurrent multifocal osteomyelitis (CRMO). They form the basis of this report because of either the unusualness of the clinical presentation, hitherto undescribed associated diseases or the unusual age of presentation and sites of lesions.

RESULTS

One patient developed pyoderma gangrenosum at the site of one of the skeletal lesions and then went on to develop ulcerative proctitis. A second patient presented with a soft tissue mass, which on MRI mimicked a sarcoma. The final patient presented with lesions in the wrist and phalanges of the toes at the unusual age of 38. None of the patients was treated with steroids or antibiotics for the skeletal lesions. Steroids were administered to one patient for treatment of pyoderma gangrenosum.

CONCLUSIONS

The pattern and distribution of skeletal lesions in CRMO are well recognized in the pediatric age group. The unusual clinical and/or radiological features discussed herein suggests that this is a disease that continues to evolve with a broader spectrum of features than recognized.

Uniparental disomy and genome imprinting: an overview

The following paper is concerned with potential changes in the normal epigenetic process in a diploid individual, when a chromosome pair or segment is inherited from one parent only, instead of the expected biparental contribution. This aberrant mode of transmission arises from the high rate of gamete aneuploidy in humans. It has received the name uniparental disomy (UPD), and has emerged as an important factor in the new field of nontraditional inheritance, depicted in Table 1.

The following definitions may foster a better understanding of this discussion.

UPDis the inheritance ofbothcopies of a chromosome [or chromosomal segment(s)] from asingleparent, instead of the normal biparental transmission of the pair. Inisodisomy,the two uniparental copies areidentical, being derived from the same parental chromosome. Inheterodisomy, the two uniparental chromosomes aredifferent, being derived from the homologues of a pair.

Barrier function of the gastric mucus gel

The gastric epithelium is covered by a continuous layer of secreted mucus and bicarbonate. The function of this mucobicarbonate layer in terms of protecting the epithelial cells from luminal acid is controversial. Several studies conducted in vitro have shown that gastric mucus can slow proton diffusion and can enable the formation of a pH gradient across the mucobicarbonate layer. In our laboratory, simultaneous measurements of intracellular pH and the thickness of the mucus gel overlying gastric surface cells in vivo indicated that surface cell acidification rates and mucus gel thickness were inversely related. This suggests that the gastric mucobicarbonate layer delays proton permeation into gastric surface cells, enabling secreted bicarbonate to neutralize luminal acid. Several theoretical models, including the effects of mucus and bicarbonate secretion, convection, stirring, and lipids are offered as a possible explanation for the experimental observations. Lipid content and additional unstirred layers outside of the mucus gel are offered as possible explanations for the experimental observations. On the basis of the available data and theoretical considerations, we can conclude that all of these factors probably interact in an integrated manner to protect the gastric epithelial cells from damage due to luminal acid.

Treatment of edentulous patients with temporomandibular disorders with implant-supported overdentures

Treatment of edentulous patients who have temporomandibular disorders is difficult because of the poor stability of their conventional complete dentures. With an implant-supported bar and a clip-to-bar overdenture, mandibular dentures can be stabilized. The results of a prospective clinical study of 10 edentulous patients with temporomandibular disorders and treatment with implant-supported overdentures in mandibles are presented. Before and after 3 years of wearing the implant-supported overdentures, patients were interviewed and a clinical functional analysis was taken. Patients with displacement of the articular disc or bone destruction of the joints had a decrease in pain, an enhanced mobility of the mandible, and a decrease in temporomandibular joint sounds. Patients with pain of muscular genesis as a result of bruxism suffered after 3 years from the same pain and did not show an improvement of muscle or joint sensitivity.

Bicarbonate diffusion through mucus

The mucus layer overlying duodenal epithelium maintains a pH gradient against high luminal acid concentrations. Despite these adverse conditions, epithelial surface pH remains close to neutrality. The exact nature of the gradient-forming barrier remains unknown. The barrier consists of mucus into which HCO3- is secreted. Quantification of the ability of HCO3- to establish and maintain the gradient depends on accurate measurement of this ion's diffusion coefficient through mucus. We describe new experimental and mathematical methods for diffusion measurement and report diffusion coefficients for HCO3- diffusion through saline, 5% mucin solutions, and rat duodenal mucus. The diffusion coefficients were 20.2 +/- 0.10, 3.02 +/- 0.31, and 1.81 +/- 0.12 x 10(-6) cm2/s, respectively. Modeling of the mucobicarbonate layer with this latter value suggests that for conditions of high luminal acid strength the neutralization of acid by HCO3- occurs just above the epithelial surface. Under these conditions the model predicts that fluid convection toward the lumen could be important in maintaining the pH gradient. In support of this hypothesis we were able to demonstrate a net luminal fluid flux of 5 microliters.min-1.cm-2 after perfusion of 0.15 N HCl in the rat duodenum.

Uniparental disomy in humans: development of an imprinting map and its implications for prenatal diagnosis

Uniparental disomy (UPD) in humans is caused primarily by meiotic nondisjunction events, followed by trisomy or monosomy 'rescue'. The majority of cases appear to be associated with advanced maternal age, and may be initially detected as mosaic trisomies during routine prenatal diagnosis by chorionic villus sampling or amniocentesis. In addition, structural abnormalities including Robertsonian translocations, reciprocal translocations and supernumerary marker chromosomes appear to be associated with an increased risk of UPD. Predicting the phenotypic effects of UPD is complex, as three independent factors are involved: (i) effects of trisomy on the placenta or the fetus; (ii) autosomal recessive disease due to reduction to homozygosity; and (iii) imprinted gene effects for some chromosomes. To date, UPD in humans has been reported for 25 of the 47 possible uniparental types. Imprinting effects have been established with certainty for four human chromosomes that have homology to mouse chromosomes which have been shown to have significant phenotypic effects in uniparental animals. A normal phenotype has been reported for 14 other UPD types. Thus, collection of data on UPD cases in humans is providing an imprinting map analogous to the experimentally derived imprinting map in mouse. This human imprinting map has important clinical implications, particularly in the area of prenatal diagnosis.

Palliative therapy of melanoma patients with fotemustine. Inverse relationship between tumour load and treatment effectiveness. A multicentre phase II trial of the EORTC-Melanoma Cooperative Group (MCG)

Fotemustine (FM) is a new chloronitrosurea (CNU), chemically characterized by the graft of an aminophosphonic acid on the CNU radical, which makes it highly lipophilic. Following single-institution phase I and II studies with remarkably high response rates of some 40%, including brain metastases of 25% and more, the EORTC-MCG started a multicentre phase II trial to confirm these results according to EORTC guidelines. Treatment consisted of an induction cycle of FM (100 mg/m2 on days 1 + 8 + 15), followed by maintenance courses (q3w). Fifty-four patients were entered by 11 institutions. General interest in this promising new agent, however, led clinicians of six additional institutions to join the EORTC trial and 90 more patients were included in only 4 months. This rapidly rising accrual rate became inversely related to the physicians' adherence to the eligibility criteria: palliation of symptoms rather than clinical research was the dominant reason to start treatment. Clinical characteristics and results in the eligible vs non-eligible patient group (in parentheses) were as follows: male/female 29/26 (68/65), mean age 54 years (53), ECOG-PS 0-1 (0-4), CR 2 (0), PR 10 (2), NC 17 (5) and for brain metastases: PR 4 (1), NC 2 (1), for an ORR of 12% (5%). Median duration of response was 6 months (range 4-16). The clinically relevant toxicity was limited to the haematopoiesis with delayed platelet nadirs (30% grade III+IV), granulocyte (25% grade III + IV) and the gastrointestinal tract: nausea and vomiting (26% grade II, 18% III, 1% IV). This study confirms that FM is active in melanoma including brain metastases.(ABSTRACT TRUNCATED AT 250 WORDS)

Isoforms of Bet v 1, the major birch pollen allergen, analyzed by liquid chromatography, mass spectrometry, and cDNA cloning

Bet v 1, the major allergen of birch pollen, displays a considerable degree of heterogeneity. Several charge variants have been detected by two-dimensional IgE immunoblots and isoelectric focusing techniques. This heterogeneity has been attributed to glycosylation (or other post-translational modifications) or to isogenes coding for Bet v 1 isoforms and/or allelic variants. However, until now, only limited structural data for Bet v 1 have been published. Recently, we described the expression, purification, and immunological properties of recombinant Bet v 1 (rBet v 1) produced in Escherichia coli as a non-fusion protein (Ferreira, F. D., Hoffmann-Sommergruber, K., Breiteneder, H., Pettenburger, K., Ebner, C., Sommergruber, W., Steiner, R., Bohle, B., Sperr, W. R., Valent, P., Kungl, A. J., Breitenbach, M., Kraft, D., and Scheiner, O. (1993) J. Biol. Chem. 268, 19574-19580). Here, we present a more detailed structural characterization of Bet v 1 by both cDNA cloning and mass spectrometry. Thirteen different cDNA clones coding for Bet v 1 isoforms were obtained by polymerase chain reaction amplification of birch pollen cDNA with a sequence-specific 5'-terminal primer and a nonspecific 3'-terminal primer or by immunological screening of a birch pollen cDNA library. These isoforms are referred to as Bet v 1b to Bet v 1n, whereas the previously isolated Bet v 1 cDNA (Breiteneder, H., Pettenburger, K., Bito, A., Valenta, R., Kraft, D., Rumpold, H., Scheiner, O., and Breitenbach, M. (1989) EMBO J. 8, 1935-1938) is now referred to as Bet v 1a. High performance liquid chromatography and plasma desorption mass spectrometry of proteolytic fragments of purified natural Bet v 1 (nBet v 1) and rBet v 1a were used to (i) confirm the primary structure of all Bet v 1 isoforms and (ii) to investigate any possible postsynthetic modifications on rBet v 1a or on the natural mixture of isoallergens obtained from birch pollen. Except for the cleavage of initiating methionine, no postsynthetic modifications were found in either nBet v 1 or rBet v 1a.

Angelman syndrome due to paternal uniparental disomy of chromosome 15: a milder phenotype?

The Angelman syndrome (AS) is a neurological disorder characterized by severe mental retardation, absent speech, seizures, gait disturbances, and a typical age-dependent facial phenotype. Most cases are due to an interstitial deletion on the maternally inherited chromosome 15, in the critical region q11-q13. Rare cases also result from paternal uniparental disomy of chromosome 15. In a group of 14 patients with sporadic AS diagnosed in Switzerland, we found 2 unrelated females with paternal isodisomy for the entire chromosome 15. Their phenotypes were milder than usually seen in this syndrome: one girl did not show the typical AS facial changes; both patients had late-onset mild seizures; as they grew older, they had largely undisturbed gross motor functions, in particular no severe ataxia. Both girls were born to older fathers (45 and 43 years old, respectively). The apparent association of a relatively milder phenotype in AS with paternal uniparental disomy will have to be confirmed by detailed clinical descriptions of further patients.

Changes in chewing patterns after implantation in the edentulous mandible

Almost all edentulous patients with implant-supported prostheses in mandibles describe an improvement in their chewing function and quality of life. This was reason to believe that an implant prosthetic treatment actually influences mandibular border movements, as well as the chewing patterns. The present study compares border movements and chewing patterns in 15 patients recorded with the Sirognathograph. The first measurements were made with existing complete dentures. After implantation and rehabilitation with a Dolder-bar and clip-to-bar overdenture, the movements were recorded again. The measurements revealed an improved guidance of the mandibular movements and larger borderline patterns following stabilization of the complete denture with the bar. This leads to more harmonic shapes in the movements and better chewing efficiency.

Uniparental disomy revisited: the first twelve years

Uniparental disomy (UPD), the exceptional derivation of a pair of the offspring chromosomes from one parent only, may be compatible with normal or abnormal development and can result from gamete complementation, chromosome loss in trisomy, or duplication in monosomy (with or without residual mosaicism) and somatic recombination. In isodisomy, the uniparental pair is a duplicate of a same chromosome DNA template and causes an increased risk of recessive disorder by reduction to homozygosity. In heterodisomy, the pair remains heterozygous, made up of 2 non-recombinant homologous segments. But both iso- and heterodisomy may also cause disruption of the genomic imprints needed for differential expression of some maternal and paternal genes crucial to growth and development. Pure UPD preserves euploidy and, when harmful, is best regarded as a genomic qualitative imbalance by symmetrical excess and loss of parental homologous contribution affecting zygosity and imprint content. Instances of UPD reported till the spring 1992 are reviewed and their deleterious effects are described as they carried out lethality or morbidity by altering imprinting processes, mimicking deletions, generating recessive disorders, or prompting malignant cellular growth.

Effect of Toremifene in patients with metastatic melanoma: a phase II study of the EORTC Melanoma Cooperative Group

The EORTC Melanoma Cooperative Group conducted a phase II trial (study number 18891) to study the effect of Toremifene in 45 patients with advanced, metastatic melanoma. Male and female patients, median age 61 (range 23-88) years received a mean total dose of 11 g (4.3-62.6) orally for at least 6 weeks. No objective remissions were seen. Four patients (3 women and 1 man; 9%) experienced 3-6 months' disease stabilization. The toxicity of the drug, given at a dose of 240 mg daily, was negligible. Because of the minimal side-effects, Toremifene may be recommended for patients who have only a small number of slowly growing metastases, in particular to soft tissue and lung.

Mechanisms of ring chromosome formation in 11 cases of human ring chromosome 21

We studied the mechanism of ring chromosome 21 (r(21)) formation in 13 patients (11 unique r(21)s), consisting of 7 from five families with familial r(21) and 6 with de novo r(21). The copy number of chromosome 21 sequences in the rings of these patients was determined by quantitative dosage analyses for 13 loci on 21q. Nine of 11 r(21)s, including the 5 familial r(21)s, showed no evidence for duplication of 21q sequences but did show molecular evidence of partial deletion of 21q. These data were consistent with the breakage and reunion of short- and long-arm regions to form the r(21), resulting in deletion of varying amounts of 21q22.1 to 21qter. The data from one individual who had a Down syndrome phenotype were consistent with asymmetric breakage and reunion of 21q sequences from an intermediate isochromosome or Robertsonian translocation chromosome as reported by Wong et al. Another patient, who also exhibited Down syndrome, showed evidence of a third mechanism of ring formation. The likely initial event was breakage and reunion of the short and long arms, resulting in a small r(21), followed by a sister-chromatid exchange resulting in a double-sized and symmetrically dicentric r(21). The phenotype of patients correlated well with the extent of deletion or duplication of chromosome 21 sequences. These data demonstrate three mechanisms of r(21) formation and show that the phenotype of r(21) patients varies with the extent of chromosome 21 monosomy or trisomy.

Uniparental disomy, isodisomy, and imprinting: probable effects in man and strategies for their detection

The concept of uniparental disomy--the presence of a chromosome pair derived solely from one parent in a diploid offspring--was introduced in 1980 as a probable consequence of the high rate of germ cell aneuploidy in man, and has now been convincingly demonstrated through molecular analyses in several families. A most likely mechanism for the production of uniparental disomy is the chance reunion, and complementation, of 2 gametes aneuploid for the same chromosome member; uniparental disomy could also occur through other mechanisms including postzygotic non-segregation in a trisomic conceptus. Uniparental disomy may result in isodisomy, i.e., homozygosity of a series of contiguous alleles in a pair of homologues. The presence and degree of isodisomy in an offspring depend in turn on the occurrence, timing, and extent of the meiotic recombination that had occurred in the chromosome pair of the disomic gamete involved. Uniparental disomy with or without isodisomy can explain a number of unusual observations, such as the unexpected pattern of transmission of a genetic disorder. The two may be associated with an imprinting effect to produce pathological phenotypes, as has been observed in the mouse, and may be the basis for a number of syndromes of as yet unclear cause. The evidence for uniparental disomy, isodisomy, and imprinting in man is reviewed, and strategies for their detection presented.

[The future of medical genetics in a university hospital setting]

The author presents three potential ways of developing an university centre of medical genetics, to make most effective use of this fast-evolving discipline. The three possibilities discussed are: i) the attachment of genetics units to major departments; ii) the creation of a large autonomous genetics centre (be Department or Institute) fulfilling all the requirements of the hospital; and iii) an "ecumenical" approach, that is a main genetics centre with a very few associated, highly specialized, departmental satellite units. The author argues in favour of the last solution.

Genetic alterations of c-myc, c-erbB-2, and c-Ha-ras protooncogenes and clinical associations in human breast carcinomas

We have analyzed genomic DNA sequences from 125 prospectively collected single unilateral primary breast carcinoma samples for the presence of alterations of c-myc, c-erbB-1, c-erbB-2, c-Ki-ras and c-Ha-ras protooncogenes. Amplification of the c-myc gene was found in 18% of the samples, and in one sample a non-germ line c-myc related DNA fragment or rearrangement was detected. We have found a significant association (P = 0.0010) between amplified c-myc gene and inflammatory carcinoma, a particularly aggressive breast cancer. The c-erbB-2 gene was amplified in 22% of the tumor samples and a rearrangement was observed once. Alteration of the c-erbB-2 gene was significantly linked to histological grade III tumors (P = 0.005) and the absence of estrogen and progesterone receptors (P = 0.036). No amplifications were observed for c-erbB-1, c-Ki-ras, and c-Ha-ras genes. About 40% of breast carcinomas contain either amplified c-myc or c-erbB-2 protooncogenes, whereas simultaneous amplification of both was seen in only one sample, suggesting the involvement of two distinct molecular mechanisms in breast cancer. Comparison of DNA from peripheral blood and tumor samples indicated loss of one c-Ha-ras allele in 29% of patients heterozygous for this polymorphism. A significant correlation (P = 0.016) between c-Ha-ras locus (11p14) allele loss and patient survival was found. These data suggest that 11p14 allelic loss plays a role in the evolution of human breast cancer, amplification of c-erbB-2 gene is associated with increasing stage of malignancy, and alteration of the c-myc gene in inflammatory breast carcinoma may contribute to the rapid progression of this human tumor subtype.

Connatal Pelizaeus-Merzbacher disease

Type II connatal Pelizaeus-Merzbacher disease is a degenerative disease of the developing nervous system. Confirmation of diagnosis is only by histopathological examination at present. The authors describe an infant with several clinical features which are apparently unique to this disease. These features may allow a presumptive clinical diagnosis to be made in other cases, thereby allowing valuable genetic counselling to be given before the death of the affected infant enables confirmation by autopsy.

[Microencephalic nanism, severe retardation, hypertonia, obesity, and hypogonadism in two brothers: a new syndrome?]

Two brothers are described with a severe syndrome of postnatal growth and mental retardation which includes extreme microcephaly, obesity developing during infancy, microgonadismsm, and a characteristic amphora-shaped facies. The neurological exam is highly abnormal, with hypertonia and hyperreflexia, nystagmus, and an extremely irritable and agitated behavior. The first child, who died at 4/1/2 years, also presented neonatal hypoglycemia and chronic constipation. Although the etiology of this syndrome is unknown, it is tempting to consider an X-linked recessive gene, given the importance of the X chromosome in mental retardation. Among the over 70 syndromes of X-linked mental retardation already described, our patients resemble individuals with the Börjeson-Forssman-Lehmann (BFL) syndrome the most. However, the severity of their dwarfism and mental retardation is much greater than described in any BFL patient to date, and the neurological and dysmorphic features vary significantly from those described in the BFL. Although a particularly severe variant, perhaps allelic, is a possibility, an as yet undescribed disorder is also plausible, the etiology of which would probably be recessive, either autosomal or X-linked.