The presence, morphology and clinical significance of vertebral body malformations in an Australian population of French Bulldogs and Pugs

OBJECTIVE

To describe the incidence, morphology and clinical significance of congenital vertebral malformations (CVM) in two breeds of brachycephalic dogs presenting to a referral veterinary hospital.

DESIGN

Prospective cohort study series.

MATERIALS AND METHODS

Forty-nine French Bulldogs and Pugs were prospectively evaluated and placed in one of two groups based on whether or not they presented for neurological signs referable to spinal cord disease. A computed tomography (CT) of their entire spine was obtained and the presence and classification of CVM along with the degree of spinal kyphosis recorded for all dogs. Statistical analysis was performed to identify clinical associations between these factors (P < 0.05).

RESULTS

CVM were prevalent across both breeds with the French Bulldog having more malformations than the Pug (Kruskal-Wallis nonparametric analysis of variance, P < 0.0001). Breed associated vertebral malformation subtypes included butterfly subtype in French Bulldogs (Chi-square, P = 0.0002), and transitional subtype in Pugs (odds ratio, 22.7; P = 0.000). A new subtype, dorsal wedge, was observed in 12 cases. The presence, number and subtype of vertebral malformation were not reliable for predicting the development of neurological signs across both breeds (Chi-square, P > 0.05). However, spinal kyphosis >35° calculated via Cobb angle was associated with Pugs that had neurological deficits (Chi-square, P = 0.028).

CONCLUSIONS

Congenital vertebral malformations largely appear to be incidental findings in this population of French Bulldogs but are of more significance in the Pug breed when spinal kyphosis is >35°. French Bulldogs that have spinal cord disease and CVM are more likely to have pathology distant to CVM with intervertebral disc herniation most common.

Retrospective analysis of 736 cases of canine gastric dilatation volvulus

OBJECTIVE

To identify factors influencing the survival of confirmed gastric dilatation volvulus (GDV) cases presented to a specialist referral and emergency hospital.

METHODS

Clinical records of confirmed GDV cases admitted to two specialist referral and emergency centres in Sydney (Animal Referral Hospital (ARH) Homebush and ARH Baulkham Hills) between July 1999 and July 2019 were searched.

RESULTS

A total of 736 GDV cases were reviewed, of which 460 dogs were surgically treated and 276 dogs were humanely killed. The survival rates of patients operated on by general surgeons and specialists were 81.7% and 88.7%, respectively. Both incisional gastropexy and belt-loop gastropexy were clinically effective in treating GDV, with no significant difference in survival rates. Intraoperative mortality rates for general surgeons and specialists were 7.0% and 2.9%, respectively. The odds of mortality in dogs operated on by general surgeons were 2.03 times those operated on by specialist surgeons. The odds of mortality in dogs presented between 3:00 and 9:00 am were 3.57 times those of dogs presented between 9:00 am and 9:00 pm. The odds of mortality in dogs where the duration from presentation to completion of surgery was more than 3 h were 2.53 times those of dogs where time lapsed was equal or less than 3 h.

CONCLUSION

The results suggested that admission time was statistically significantly related to the survival rate. Dogs operated on by specialist surgeons had a significantly higher survival rate compared to those operated on by general surgeons. Clinicians should aim to stabilise and complete surgical correction of GDV as soon as possible to decrease the mortality.

Use of osteogenic protein-1 in the management of a nonunion radial fracture in a Squirrel Monkey (Saimiri boliviensis)*

A Squirrel Monkey (Saimiri boliviensis) presented with comminuted, proximal diaphyseal fractures of the left radius and ulna which were repaired with a type II acrylic external fixateur and intramedullary pin, respectively. The external fixateur was removed six weeks postoperatively as the antebrachium was stable despite radiographic evidence that the radial fracture had failed to completely heal. Eight months postoperatively, radiographic examination revealed a nonunion fracture of the proximal radial diaphysis. The nonunion fracture was stabilised with a miniplate and screws, and osteogenic protein-1 (OP-1) (bone morphogenetic protein-7) was inserted to augment bony union. Radiographic evidence of fracture healing was present four weeks postoperatively. Bone morphogenetic proteins, in particular OP-1, can be used as a substitute for autogenous cancellous bone if there is an insufficient quantity of cancellous bone or harvesting will result in unacceptable morbidity.

Osteogenic protein-1 (OP-1 or bone morphogenetic protein 7) was used in the management of a nonunion fracture of the radius in a Squirrel Monkey (Saimiri boliviensis). Osteogenic protein-1 was used in preference to autogenous cancellous bone as the small size of the monkey would have limited the quantity of cancellous bone and predisposed to morbidity at the harvest site. This is the first report of the clinical use of OP-1 in veterinary surgery.

Long-term control of olfactory neuroblastoma in a dog treated with surgery and radiation therapy

BACKGROUND

Olfactory neuroblastoma is a rare malignancy of the nasal cavity in dogs that is thought to arise from specialised sensory neuroendocrine olfactory cells derived from the neural crest.

CASE REPORT

An 8-year-old dog was presented for reclusiveness and pacing. On CT and MRI, a contract-enhancing mass was disclosed within the rostral fossa, extending caudally from the cribriform plate into the left nasal sinus. Surgical excision was performed and the diagnosis was histological grade III (Hyams grading scheme) olfactory neuroblastoma. Based on human CT criteria this was high stage (modified Kadish stage C). Surgical excision was incomplete and was followed by curative-intent radiation therapy using a linear accelerator to a total dose of 48 Gy.

CONCLUSION

The dog survived 20 months after diagnosis. Although olfactory neuroblastoma is a rare tumour in dogs, aggressive local therapy may allow for prolonged survival, even when the tumour is advanced.

Population-based cohort study of variation in the use of emergency cholecystectomy for benign gallbladder diseases

Background

The aims of this prospective population-based cohort study were to identify the patient and hospital characteristics associated with emergency cholecystectomy, and the influences of these in determining variations between hospitals.

Methods

Data were collected for consecutive patients undergoing cholecystectomy in acute UK and Irish hospitals between 1 March and 1 May 2014. Potential explanatory variables influencing the performance of emergency cholecystectomy were analysed by means of multilevel, multivariable logistic regression modelling using a two-level hierarchical structure with patients (level 1) nested within hospitals (level 2).

Results

Data were collected on 4744 cholecystectomies from 165 hospitals. Increasing age, lower ASA fitness grade, biliary colic, the need for further imaging (magnetic retrograde cholangiopancreatography), endoscopic interventions (endoscopic retrograde cholangiopancreatography) and admission to a non-biliary centre significantly reduced the likelihood of an emergency cholecystectomy being performed. The multilevel model was used to calculate the probability of receiving an emergency cholecystectomy for a woman aged 40 years or over with an ASA grade of I or II and a BMI of at least 25·0 kg/m2, who presented with acute cholecystitis with an ultrasound scan showing a thick-walled gallbladder and a normal common bile duct. The mean predicted probability of receiving an emergency cholecystectomy was 0·52 (95 per cent c.i. 0·45 to 0·57). The predicted probabilities ranged from 0·02 to 0·95 across the 165 hospitals, demonstrating significant variation between hospitals.

Conclusion

Patients with similar characteristics presenting to different hospitals with acute gallbladder pathology do not receive comparable care.

Polyethylene wear of mobile-bearing unicompartmental knee replacement at 20 years

The Oxford unicompartmental knee replacement (UKR) was designed to minimise wear utilising a fully-congruent, mobile, polyethylene bearing. Wear of polyethylene is a significant cause of revision surgery in UKR in the first decade, and the incidence increases in the second decade. Our study used model-based radiostereometric analysis to measure the combined wear of the upper and lower bearing surfaces in 13 medial-compartment Oxford UKRs at a mean of 20.9 years (17.2 to 25.9) post-operatively. The mean linear penetration of the polyethylene bearing was 1.04 mm (0.307 to 2.15), with a mean annual wear rate of 0.045 mm/year (0.016 to 0.099). The annual wear rate of the phase-2 bearings (mean 0.022 mm/year) was significantly less (p = 0.01) than that of phase-1 bearings (mean 0.07 mm/year). The linear wear rate of the Oxford UKR remains very low into the third decade. We believe that phase-2 bearings had lower wear rates than phase-1 implants because of the improved bearing design and surgical technique which decreased the incidence of impingement. We conclude that the design of the Oxford UKR gives low rates of wear in the long term.

Load transfer in the proximal tibia following implantation with a unicompartmental knee replacement

Unicompartmental knee replacement (UKR) is an appealing alternative to total knee replacement when the patient has isolated medial compartment osteoarthritis. A common observation post-operatively is radiolucency between the tibial tray wall and the bone. In addition, some patients complain of persistent pain over the proximal tibia antero-medially; this may be related to elevated bone strains in the tibia. Currently, there is no intentionally made mechanical bond between the vertical wall of an Oxford UKR and the adjacent bone; whether one exists or not will influence the load transmission in the proximal tibia and may affect the elevated tibia strain. The aim of this study was to investigate how introducing a mechanical tie between the tibial tray wall and the adjacent bone might alter the load carried into the tibia for both cemented and cementless UKRs. Strain energy density in the region of bone adjacent to the tray wall was considerably increased when a mechanical tie was introduced; this has the potential of reducing the likelihood of a radiolucency occurring in that region. Moreover, a mechanical tie had the effect of reducing proximal tibia strain, which may decrease the incidence of pain following implantation with a UKR.

A first-principles study of the dielectric properties of TiO₂ polymorphs

We present an analysis of the dielectric properties of the three polymorphs of TiO₂ (rutile, anatase and brookite phases), using ab initio time-dependent density functional perturbation theory based on the Vignale-Kohn functional. We implement this functional, which incorporates many-body effects, using the periodic program BAND. The improved result for the density of states spectra for brookite is suggestive of increased titanium ion Jahn-Teller effects for this phase. The imaginary and real components of the frequency-dependent dielectric functions show notable dielectric anisotropies, with implications for excitonic interactions, for all three common phases of TiO₂. Comparison of the electron energy-loss spectrum for undoped and doped rutile and anatase reveals the critical role of collective charge excitations in photocatalytic mechanisms. The correlation between plasmon peaks present at lower energies and decreased photocatalytic activity due to substitutional aluminum doping in combination with oxygen vacancies in rutile and anatase is highlighted. Moreover, there is clear correlation between dielectric properties and the microstructure of the TiO₂ polymorphs as suggested via the framework of the Born effective charge and Hirshfeld charge distribution schemes.

The migration patterns of two versions of the Furlong cementless femoral stem: a randomised, controlled trial using radiostereometric analysis

We have evaluated the difference in the migration patterns over two years of two cementless stems in a randomised, controlled trial using radiostereophotogrammetric analysis (RSA). The implants studied were the Furlong HAC stem, which has good long-term results and the Furlong Active stem, which is a modified version of the former designed to minimise stress concentrations between the implant and bone, and thus to improve fixation. A total of 23 Furlong HAC and 20 Furlong Active stems were implanted in 43 patients. RSA examinations were carried out immediately post-operatively and at six, 12 and 24 months post-operatively. The subsidence during the first year in the Furlong HAC stem, was approximately one-third that of the Furlong Active stem, the measured mean subsidence of the femoral head at six months being 0.27 mm (95% confidence interval (CI) 0.03 to 0.51) and 0.99 mm (95% CI 0.38 to 1.60), respectively (p = 0.03). One Active stem continued to subside during the second year. All hips, regardless of the type of stem were clinically successful as judged by the Oxford hip score and a derived pain score without any distinction between the two types of stem. The initial stability of the Furlong Active stem was not as good as the established stem which might compromise osseo-integration to the detriment of long-term success. The changes in the geometry of the stem, to minimise stress have affected the attainment of initial stability.

Development of a Model-Based Roentgen Stereophotogrammetric Analysis System to Measure Polyethylene Wear in Unicompartmental Arthroplasty

One of the most important causes of failure in unicompartmental knee replacement (UKR) is polyethylene wear. The aim of this study was to develop and assess a novel Roentgen stereophotogrammetric analysis (RSA)-based method for the measurement of linear wear suitable for UKR.

Model-based RSA was used to estimate the linear wear of polyethylene bearings in UKR. A phantom was used to validate the method using in vitro measured bearing thicknesses and the linear wear of ten control bearings was estimated in vivo. Computer aided design (CAD) models for the UKRs were used in the model-based RSA system.

There was no statistically significant difference between the estimated and measured bearing thicknesses using the CAD models ( p = 0.386). The precision of the linear wear measurement, expressed as the standard deviation of the difference between the estimated and measured bearing thickness was 0.163 mm. The bias (mean difference) was 0.030 mm.

The use of RSA to measure in vivo wear in a UKR has been shown to be accurate in a phantom, and has been verified with in vivo measured controls. The technique does not require surgical implantation of marker balls and can be used retrospectively.

Analysis of wear of retrieved metal-on-metal hip resurfacing implants revised due to pseudotumours

The presence of pseudotumours, which are soft-tissue masses relating to the hip, after metal-on-metal hip resurfacing arthroplasty has been associated with elevated levels of metal ions in serum, suggesting that pseudotumours occur when there is increased wear. We aimed to quantify the wear in vivo of implants revised for pseudotumours (eight) and of a control group of implants (22) revised for other reasons of failure. We found that the implant group with pseudotumours had a significantly higher rate of median linear wear of the femoral component at 8.1 microm/year (2.75 to 25.4) than the 1.79 microm/year (0.82 to 4.15; p = 0.002) of the non-pseudotumour group. For the acetabular component a significantly higher rate of median linear wear of 7.36 microm/year (1.61 to 24.9) was observed in the pseudotumour group compared with 1.28 microm/year (0.81 to 3.33, p = 0.001) in the other group. Wear of the acetabular component in the pseudotumour group always involved the edge of the implant, indicating that edge-loading had occurred. Our findings are the first direct evidence that pseudotumour is associated with increased wear at the metal-on-metal articulation. Furthermore, edge-loading with the loss of fluid-film lubrication may be an important mechanism of generation of wear in patients with a pseudotumour.

Case report: Spinal dermoid sinus in a Burmese cat with paraparesis

A 2-year-old, male, Burmese cat was evaluated for chronic progressive hindlimb weakness, ataxia and urinary incontinence. Radiographic examination, myelography and magnetic resonance imaging defined congenital vertebral anomalies and a space-occupying intradural, extramedullary mass. A dermoid sinus was subsequently identified dorsal to the affected spine. Surgical excision of the tract necessitated a dorsal laminectomy and removal of a 1-cm diameter intradural dermoid sinus 'cyst' that contained hair and sebaceous debris. The cat recovered hindlimb function after surgery and remains asymptomatic 50 months after surgery except for a persistent inability to urinate voluntarily.

Acquired arachnoid cyst in a cat

A 5-year-old Birman cat presented with paraparesis associated with a fracture of the third thoracic vertebra and was managed conservatively. Voluntary function was regained over the next 6 months, but the cat was referred 4 years after the trauma because of recurrence of hindlimb paresis and ataxia. Magnetic resonance imaging (MRI) showed a spinal arachnoid cyst at the level of the fourth thoracic vertebra, which was treated surgically by dorsal laminectomy and durectomy, and hindlimb function subsequently recovered. The cat re-presented 4 years later for recurrent hindlimb paresis. Myelography and computed tomography-myelography (CT-M) showed dorsolateral pooling of cerebrospinal fluid (CSF) at the previous laminectomy site. The neurological signs after the second surgery improved, but not as much as after the first surgery and the cat remained ataxic with moderate paresis. Seven months later repeat CT-M revealed an atrophic spinal cord, but negligible pooling of CSF at the previous site of the arachnoid cyst. The cat could walk, but was being treated for self-induced trauma of the left hindlimb that was thought to be related to paraesthesia. The neurological signs gradually deteriorated over 3 months and the cat was euthanased.

Influence of component alignment on outcome for unicompartmental knee replacement

This study's aim was to assess the effect of component mal-alignment on outcome of Oxford Unicompartmental Knee Replacement (UKR). Two hundred and eleven knees implanted with a medial UKR, using a minimally invasive approach, were followed up at a minimum of 4 years. Sagittal and frontal plane femoral and tibial component alignments were determined from antero-posterior and lateral radiographs. The cohort was divided into alignment groups which represented consecutive 2.5 degrees intervals over the range of measured values for femoral varus/valgus, femoral flexion/extension, tibial varus/valgus and tibial tilt. The Oxford Knee Score (OKS) and incidence of radiolucency (RL) were compared between alignment groups for each alignment parameter. In 98% of cases the femoral components were positioned between 10 degrees varus and 10 degrees valgus; all femoral components were within +/-10 degrees flexion. In 92% of cases the tibial components were positioned between +/-5 degrees varus/valgus and superior/inferior tilt (neutral tilt being 7 degrees). Within these ranges there were no significant differences in OKS or RL between the alignment groups; nor were there any differences between those at the extremes of component alignment compared to those in the inner ranges of alignment. We conclude that, because of the spherical femoral component, the Oxford UKR is tolerant to femoral mal-alignment of 10 degrees and tibial mal-alignment of 5 degrees.

Finite element analysis of intramedullary devices: The effect of the gap between the implant and the bone

This paper examines the interaction interface between the implant and the bone for an intramedullary femoral nailing system using a finite element (FE) model and specifically considers the hypothesis that the local geometry at the interface is significant to the resulting localized contact stress between the medial and lateral aspect of nail and endosteum. Contact mechanics algorithms are used in the FE modelling technique that can be developed to deal with any form of intramedullary device for which contact at the bone—implant interface is important.

Global stiffness data from the FE model are compared with available data from an experiment carried out on a construct of the bone and the device that uses intramedullary femoral nails. Acceptable agreement is obtained.

The results demonstrate that the mechanical interface between the implant and the bone is significantly affected by the gap geometry and magnitude. In particular, larger gaps lead to greater concentrations of stress on the medial side, while the distribution of stress is more uniform at the lateral contacts. Furthermore, the results show that the gap can have a marked effect on the stresses that occur on the fracture plane.

Surgical management of a recurrent spinal meningioma in a cat

A 13-year-old male neutered Persian crossbred cat was evaluated for hindlimb paresis, ataxia and urinary incontinence that had been progressing over the previous 3 months. Neurologically, the cat had thoracolumbar spinal cord deficits and a myelogram detected the presence of a mass compressing the thoracic spinal cord. A hemilaminectomy was performed to excise the soft tissue mass, subsequently identified histologically as a psammomatous meningioma. The cat regained ambulatory function and continence following surgery until a recurrence of paresis and ataxia 36 months later. A second myelogram suggested local recurrence of the tumour, which was confirmed by histological examination of the tumour after its removal at a second laminectomy. The cat again regained normal neurological function, until a further recurrence 16 months after the second surgery. The meningioma was surgically debulked a third time and the cat regained ambulation and continence postoperatively. This case demonstrates the successful use of repeated surgical resection in the management of a recurrent spinal meningioma in a cat. The cat was ambulatory and continent at a follow-up examination 63 months after the initial presentation.

Paraneoplastic limbic encephalitis

Paraneoplastic limbic encephalitis (PLE) is a rare neurological consequence of a variety of cancers, most commonly originating from lung, breast and testis. The aetiology is believed to be immune-mediated, caused by tumour-induced autoimmunity launching an attack against one's own central nervous system. The patient may present with amnesia, depression, anxiety, seizures and/or personality changes. The onset of these symptoms may precede the diagnosis of malignancy by a period of up to 2 years. The malignancy may be occult and unless the syndrome is recognised, it may fail to be detected. The diagnosis of PLE is suggested by the clinical picture, MRI evidence of mesial temporal lobe abnormality and CSF abnormalities such as the presence of oligoclonal bands. It may be further supported by the presence of paraneoplastic antibodies in the serum. Immunosuppression has been tried in some cases but memory impairment is often irreversible. There are several case reports in the literature of paraneoplastic limbic encephalitis but few emphasise the resulting impact that this may have on the patient's quality of life and their carers. The accompanying amnesia is often far more distressing to the carers, who are aware of the limitations of treatment of the underlying malignancy. Hospices offer the appropriate palliative environment for such patients as well as physical and psychological respite to the carers.

Genome-wide amplification and allelotyping of sporadic pituitary adenomas identify novel regions of genetic loss

Through the use of a candidate gene approach, several previous studies have identified loss of heterozygosity (LOH) at putative tumor-suppressor gene (TSG) loci in sporadic pituitary tumors. This study reports a genome-wide allelotyping by use of 122 microsatellite markers in a large cohort of tumors, consisting of somatotrophinomas and non-functioning adenomas. Samples were first subject to prior whole genome amplification by primer extension pre-amplification (PEP) to circumvent limitations imposed by insufficient DNA for whole-genome analysis with this number of microsatellite markers. The overall mean frequency of loss in invasive tumors was significantly higher than that in their non-invasive counterparts (7 vs. 3% somatotrophinomas; 6 vs. 3% non-functioning adenomas, respectively). Analysis of the mean frequency of LOH, across all markers to individual chromosomal arms, identified 13 chromosomal arms in somatotrophinomas and 10 in non-functioning tumors, with LOH greater than the 99% upper confidence interval calculated for the rate of overall random allelic loss. In the majority of cases, these losses were more frequent in invasive tumors than in their non-invasive counterparts, suggesting these to be markers of tumor progression. Other regions showed similar frequencies of LOH in both invasive and non-invasive tumors, implying these to be early changes in pituitary tumorigenesis. This genome-wide study also revealed chromosomal regions where losses were frequently associated with an individual marker, for example, chromosome arm 1q (LOH > 30%). In some cases, these losses were subtype-specific and were found at a higher frequency in invasive tumors than in their non-invasive counterparts. Identification of these regions of loss provides the first preliminary evidence for the location of novel putative TSGs involved in pituitary tumorigenesis that are, in some cases, subtype-specific. This investigation provides an unbiased estimate of global aberrations in sporadic pituitary tumors as assessed by LOH analysis. The identification of multiple "hotspots" throughout the genome may be a reflection of an unstable chromatin structure that is susceptible to a deletion or epigenetic-mediated gene-silencing events.

Pituitary tumours are multiclonal from the outset: evidence from a case with dural metastases

In 1992 a 54-year-old man underwent transsphenoidal adenomectomy to remove a clinically nonfunctioning pituitary adenoma during which there was a transient cerebrospinal fluid (CSF) leak. He received radiotherapy to a small residual remnant. Follow-up magnetic resonance imaging (MRI) scan in 1997 showed an increase in the tumour in the pituitary stalk region and an additional intradural lesion at C1 level. In the absence of neurological symptoms and signs, an observational policy was followed. By 1999 the cervical dural lesion had enlarged and laminectomy was performed, during which three intradural lesions were removed. Histology and immunohistochemistry of the metastases were identical to those of the initial pituitary adenoma. Follow-up MRI scan showed extension of the pituitary remnant above the chiasma, requiring transfrontal surgery. Operation was complicated by secondary brain haemorrhage from which the patient died. Autopsy revealed a small amount of residual tumour at the top of the stalk and several small intradural tumour nodules at the level of the foramen magnum. Genetic analysis of the initial pituitary tumour identified significant allelic losses in keeping with its invasive nature, while that of the metastases indicated a separate clone as shown by retention of alleles lost in the primary tumour. The regrown pituitary tumour also appeared to be of a different clone to the initial tumour and the same as two of three of the first metastases (C1 level). The foramen magnum metastasis showed the same loss of heterozygosity (LOH) pattern as one of the original C1 metastases and the pituitary tumour tissue obtained at autopsy. We speculate that at the initial pituitary surgery, cells seeded into the CSF and grew in the dura. These cells were from a different clone, implying that the original pituitary tumour contained at least two clones, possibly three, providing evidence for the contemporaneous oligoclonality of the original pituitary tumour.

Preferential loss of Death Associated Protein kinase expression in invasive pituitary tumours is associated with either CpG island methylation or homozygous deletion

Death Associated Protein kinase (DAP kinase) a novel calmodulin-dependent serine/threonine kinase was first identified as a positive mediator of programmed cell death. Loss of DAP kinase expression was first demonstrated in highly metastatic cells, whilst re-expression of the protein resulted in delayed local tumour growth and a decreased incidence of metastasis. Although loss of DAP kinase expression has been reported in several cell lines derived from human malignancies the mechanisms responsible have not been defined. In this study we have examined 32 sporadic pituitary tumours for expression of the DAP kinase protein and transcript. In addition, we examined the methylation and deletion status of the DAP kinase CpG island as possible mechanisms for the inactivation of the DAP kinase gene. Eleven of 32 (34%) tumours had undetectable DAP kinase expression, by Western blot and/or RT-PCR analysis. Loss of DAP kinase expression was significantly (P=0.004) associated with invasive tumours (10 of 17; 59%) compared to their non-invasive (1 of 15; 7%) counterparts. Of 11 tumours that failed to express DAP kinase, five (45%) showed de novo methylation of the CpG island contained within the promoter region, while four (36%) had evidence of homozygous deletion of this region. Statistical analysis showed that loss of DAP kinase expression was significantly (P=<0.001) associated with methylation or deletion of the DAP kinase CpG island. With two exceptions, none of the remaining tumours or five histologically normal post-mortem pituitaries examined had evidence of methylation or deletion within this region. To our knowledge this is the first report that describes two mutually exclusive mechanisms associated with loss of DAP kinase gene expression. In addition, we also show that loss of the DAP kinase protein and associated genetic aberrations preferentially segregates with tumours that show an invasive phenotype.

Identification and molecular characterisation of hordoindolines from barley grain

Grain texture in barley is an important quality character as soft-textured cultivars have better malting quality. In wheat, texture is considered to be determined by the puroindolines, a group of basic hydrophobic proteins present on the surface of the starch granule. Hard wheats have been proposed to lack puroindoline a or to have mutant forms of puroindoline b which do not bind to the granule surface. Analysis of six barley cultivars (three soft-textured and three hard) showed that all contained proteins homologous to wheat puroindoline b, but PCR analysis failed to show any differences in amino acid sequences similar to those which have been proposed to determine textural differences in wheat. Southern blot analysis showed two hordoindoline b genes which were isolated and shown to encode proteins with 94% sequence identity. Expression of hordoindoline b mRNA occurred in the starchy endosperm and aleurone layer of the developing seed, but not in the embryo. Analysis of seven soft- and six hard-textured barley varieties showed that all contained hordoindoline a except two hard varieties (Sundance, Hart) which were subsequently shown to both lack hordoindoline a mRNA. It was therefore concluded that there is not a clear relationship between the presence of hordoindoline a and grain texture in barley.

Cyclin D1 (CCND1) genotype is associated with tumour grade in sporadic pituitary adenomas

The cyclin D1 (CCND1) gene contains a frequent A/G polymorphism within the splice donor region of exon 4/intron 4. CCND1 genotype is associated with clinical outcome in a number of malignancies although prognostic significance varies with tumour type. We examined CCND1 allele frequencies and genotype distribution in 294 patients with sporadic pituitary adenomas of various histologies. CCND1 allele frequencies and distribution of genotypes were similar in the 294 cases compared with previously reported control populations. Analysis according to tumour subtype showed no statistical difference in allele frequencies compared with controls. However, CCND1 genotype distribution in the somatotrophinomas showed a significant difference compared with normal controls (P = 0.008). We next examined CCND1 allele frequencies and genotype distribution across the tumour grades. Within the total tumour cohort the CCND1 allele frequencies showed a significant inverse relationship across the tumour grades (P = 0.005). The CCND1 A allele progressively increased from grade 1 (0.37) through to grade 4 (0.62) tumours, whilst the CCND1 G allele frequency progressively decreased from grade 1 (0.63) through to grade 4 (0.38) tumours. Trend analysis of CCND1 genotypes showed a significant progressive increase in AA frequency from grade 1 (15%) through to grade 4 (46%) tumours (P = 0.005). The CCND1 GG genotype progressively decreased from grade 1 (41%) through to grade 4 (23%) tumours (P = 0.204). No statistical significance was observed between CCND1 AG genotype and tumour grades. While the functional significance of the observed segregation of the CCND1 A/G polymorphism and tumour grade is unclear, our data suggest that CCND1 allele frequencies and genotype distributions show significant differences between tumour grades in sporadic pituitary adenomas. Since CCND1 genotype may be determined by analysis of peripheral blood samples it may provide a useful predictive marker for those tumours likely to show invasive behaviour. This may be clinically useful in indicating which tumours should receive adjunctive treatment (e.g. radiotherapy) immediately after surgical resection.

Aberrant expression of G(1)/S regulators is a frequent event in sporadic pituitary adenomas

Components of the pRb/p16/cyclin D1/CDK4 pathway are frequent targets in numerous tumour types, including those of pituitary origin. However, previous studies of pituitary tumours have examined individual components of this pathway. Therefore, to determine their overall contribution we have simultaneously examined the immunohistochemical status of pRb, p16 and cyclin D1 and analysed the CDK4 gene for a characterized activating mutation. Of the total pituitary tumour cohort (29 clinically non-functioning adenomas and 16 somatotrophinomas) abnormal expression of either pRb, p16 or cyclin D1 was observed in 36 of 45 (80%) tumours and was significantly (P = 0.005) associated with non-functioning tumours (27/29; 93%) compared with somatotrophinomas (9/16, 56%). Loss of either pRb or p16 expression was mutually exclusive in 23 of 45 (51%) tumours, whilst concomitant loss of pRb and p16 expression was observed in five tumours. Cyclin D1 overexpression was observed in 22 of 45 (49%) tumours, however, there was no significant association between overexpression of cyclin D1 and the expression status of either pRb or p16. In addition, no activating mutations within codon 24 of the CDK4 gene were detected. This study provides evidence for the first time that components of the pRb/p16/cyclin D1/CDK4 pathway, either alone or in combination, are frequently deregulated in human pituitary tumours, suggesting that this pathway may be a useful target in drug or gene therapeutic approaches.

Decreased proliferation and cell cycle arrest in neoplastic rat pituitary cells is associated with transforming growth factor-beta1-induced expression of p15/INK4B

Transforming growth factor beta (TGF-beta) is a member of a family of cytokines that regulate differentiation and proliferation in a wide variety of tissues including the pituitary gland. In both the normal pituitary and tumorous cell lines TGF-beta1 has anti-proliferative activity, however the intracellular mechanisms responsible have not been defined. In the pituitary derived cell line GH(3), p27(Kip1), a key regulator of G(1)/S transition is not expressed, suggesting that this protein is not an effector of the anti-proliferative response following TGF-beta1 treatment. Among other TGF-beta responsive cell cycle regulators p15(Ink4b) has been shown to have anti-proliferative effects associated with cell cycle arrest in other cell types. We therefore examined p15(Ink4b) expression in response to TGFbeta-1 to determine if this cyclin dependent kinase inhibitor was responsible for anti-proliferative activity in GH(3) cells. Treatment of GH(3) cells with TGF-beta1 (0.5-30 ng/ml) showed significant dose dependent growth inhibition (P<0.001) as assessed by viable cell counts. Maximum growth inhibition (66%) was observed following treatment with 2 ng/ml TGF-beta1. FACS analysis carried out in parallel with the growth studies showed treatment was associated with a decrease in the proportion of cells in S-phase (22-9%) and a significant increase in the G(1) fraction from 58 to 75% relative to controls (P<0.001). The absence of a sub G(1) fraction and reversibility of the G(1) arrest over three cycles showed that these changes were not due to either an apoptotic response or cytoxicity, respectively. Semi-quantitative RT-PCR and Western blot analysis showed no change in the expression level of cyclin dependent kinase 4 (CDK4), p16(Ink4a) or p21(Cip1). However, p15(Ink4b) mRNA and protein levels showed a 10 and 8 -fold induction, respectively. Increased levels of p15(Ink4b) were accompanied by a shift in the phosphorylation status of pRb toward its active hypophosphorylated form. Furthermore, studies of the kinetics of p15(Ink4b) induction showed that arrest of cells in G(1) is preceded by induction of p15(Ink4b) mRNA and protein. These investigations would suggest that p15(Ink4b) is a functional effector of TGF-beta1 mediated cell cycle arrest in GH(3) cells. However, our present studies cannot determine if it is the sole mediator. Identification of intracellular target(s) that mediate responses to anti-proliferative signals will increase our understanding of these pathways and aberrations responsible for their dysfunction in tumorigenesis.

The ricinosomes of senescing plant tissue bud from the endoplasmic reticulum

The ricinosome (synonym, precursor protease vesicle) is a novel organelle, found so far exclusively in plant cells. Electron microscopic studies suggest that it buds off from the endoplasmic reticulum in senescing tissues. Biochemical support for this unusual origin now comes from the composition of the purified organelle, which contains large amounts of a 45-kDa cysteine endoprotease precursor with a C-terminal KDEL motif and the endoplasmic reticulum lumen residents BiP (binding protein) and protein disulfide isomerase. Western blot analysis, peptide sequencing, and mass spectrometry demonstrate retention of KDEL in the protease proform. Acidification of isolated ricinosomes causes castor bean cysteine endopeptidase activation, with cleavage of the N-terminal propeptide and the C-terminal KDEL motif. We propose that ricinosomes accumulate during senescence by programmed cell death and are activated by release of protons from acidic vacuoles.

Intraoperative hemorrhage during patent ductus arteriosus ligation in dogs

OBJECTIVE

To determine the prevalence of intraoperative hemorrhage in a consecutive series of dogs undergoing patent ductus arteriosus (PDA) ligation at a veterinary teaching hospital, and to describe strategies to reduce the risk of ductus perforation and deal with hemorrhage when it occurs.

STUDY DESIGN

Retrospective clinical study.

ANIMALS

Sixty-four dogs.

METHODS

The records of all dogs undergoing PDA ligation at the University Veterinary Center, Sydney between May 1989 and February 1998 were reviewed and the prevalence and nature of complications identified.

RESULTS

Serious hemorrhage occurred in 4 of 64 dogs (6.25%) that underwent PDA ligation. In all cases, hemorrhage resulted from perforation of the craniomedial aspect of the ductus while attempting to expose the tips of the dissecting forceps. Hemorrhage was controlled in 3 dogs by clamping the main pulmonary artery, digital compression of the descending aorta, and completion of ductus ligation during an approximately 5-minute period of circulatory arrest. The remaining dog exsanguinated during an unsuccessful attempt to locate, clamp, and ligate the bleeding point. The mortality rate for PDA ligation was I of 64 dogs (1.6 %).

CONCLUSIONS

The technique described in this report permits simple ligation of a range of different ductus morphologies in dogs of varying breeds, weights, and ages. In the event of serious hemorrhage, prompt ventricular outflow occlusion and ductus ligation followed by rapid whole blood transfusion is life saving in most cases.

Down-regulation of the PSI-F subunit of photosystem I (PSI) in Arabidopsis thaliana. The PSI-F subunit is essential for photoautotrophic growth and contributes to antenna function

The PSI-F subunit of photosystem I is a transmembrane protein with a large lumenal domain. The role of PSI-F was investigated in Arabidopsis plants transformed with an antisense construct of the psaF cDNA. Several plant lines with reduced amounts of the PSI-F subunit were generated. Many of the transgenic plants died, apparently because they were unable to survive without the PSI-F subunit. Plants with 5% of PSI-F were capable of photoautotrophic growth but were much smaller than wild-type plants. The plants suffered severely under normal growth conditions but recovered somewhat in the dark indicating chronic photoinhibition. Photosystem I lacking PSI-F was less stable, and the stromal subunits PSI-C, PSI-D, and PSI-E were present in lower amounts than in wild type. The lack of PSI-F resulted in an inability of light-harvesting complex I-730 to transfer energy to the P700 reaction center. In thylakoids deficient in PSI-F, the steady state NADP(+) reduction rate was only 10% of the wild-type levels indicating a lower efficiency in oxidation of plastocyanin. Surprisingly, the lack of PSI-F also gave rise to disorganization of the thylakoids. The strict arrangement in grana and stroma lamellae was lost, and instead a network of elongated and distorted grana was observed.

Loss of pRb expression in pituitary adenomas is associated with methylation of the RB1 CpG island

We recently showed loss of pRb in a proportion of pituitary tumors that was not associated with loss of heterozygosity of an RB1 intragenic marker. To further define the mechanism responsible for loss of retinoblastoma protein (pRb) expression, we have investigated the methylation status of the CpG island contained within the promoter region of the RB1 gene, together with sequence analysis of the essential promoter region and exons coding for the protein-binding pocket domain. Methylation of the CpG island within the RB1 promoter region was detected in 6 of 10 tumors that failed to express pRb. In contrast, 18 of 20 tumors and all six histologically normal postmortem pituitaries that expressed pRb were unmethylated. No inactivating mutations were found within the RB1 promoter region in the four unmethylated tumors that failed to express pRB. However, one or more exons comprising the coding region for the protein-binding pocket domain were shown to be homozygously deleted in three of four tumors available for analysis. This study describes an additional tumor type, in addition to retinoblastoma, in which methylation of the RB1 promoter is associated with loss of pRb expression. Furthermore, we show that in addition to methylation of the RB1 promoter region, deletion within the protein-binding pocket domain is associated with a loss of detectable pRb expression. The reactivation of tumor suppressor genes, silenced through methylation, represents a promising therapeutic target in sporadic pituitary adenomas.

Purification and characterization of barley dipeptidyl peptidase IV

Barley (Hordeum vulgare L.) storage proteins, which have a high content of proline (Pro) and glutamine, are cleaved by cysteine endoproteases to yield peptides with a Pro next to the N-terminal and/or C-terminal amino acid residues. A peptidase cleaving after Xaa-Pro- at the N terminus of peptides was purified from green barley malt. It was identified as a serine-type dipeptidyl peptidase (DPP), based on inhibitor studies, and the nature of the cleavage product. It is a monomeric glycoprotein with an apparent molecular mass of 105 kD (85 kD after deglycosylation), with a pI of 3.55 and a pH optimum at 7.2. Substrate specificity was determined with a series of fluorogenic peptide substrates with the general formula Xaa-Pro-AMC, where Xaa is an unspecified amino acid and AMC is 7-amino-4-methylcoumarin. The best substrates were Xaa = lysine and arginine, while the poorest were Xaa = aspartic acid, phenylalanine, and glutamic acid. The K(m) values ranged from 0.071 to 8.9 microM, compared with values of 9 to 130 microM reported for mammalian DPP IVs. We discuss the possible role of DPP IV in the degradation of small Pro-containing peptides transported from the endosperm to the embryo of the germinating barley grain.

Prediction of protein cleavage sites by the barley cysteine endoproteases EP-A and EP-B based on the kinetics of synthetic peptide hydrolysis

Hordeins, the natural substrates of barley (Hordeum vulgare) cysteine endoproteases (EPs), were isolated as protein bodies and degraded by purified EP-B from green barley malt. Cleavage specificity was determined by synthesizing internally quenched, fluorogenic tetrapeptide substrates of the general formula 2-aminobenzoyl-P(2)-P(1)-P(1)'-P(2)' 1-tyrosine(NO(2))-aspartate. The barley EPs preferred neutral amino acids with large aliphatic and nonpolar (leucine, valine, isoleucine, and methionine) or aromatic (phenylalanine, tyrosine, and tryptophan) side chains at P(2), and showed less specificity at P(1), although asparagine, aspartate, valine, and isoleucine were particularly unfavorable. Peptides with proline at P(1) or P(1)' were extremely poor substrates. Cleavage sites with EP-A and EP-B preferred substrate sequences are found in hordeins, their natural substrates. The substrate specificity of EP-B with synthetic peptides was used successfully to predict the cleavage sites in the C-terminal extension of barley beta-amylase. When all of the primary cleavage sites in C hordein, which occur mainly in the N- and C-terminal domains, were removed by site-directed mutagenesis, the resulting protein was degraded 112 times more slowly than wild-type C hordein. We suggest that removal of the C hordein terminal domains is necessary for unfolding of the beta-reverse turn helix of the central repeat domain, which then becomes more susceptible to proteolytic attack by EP-B.

Methylation mechanisms in pituitary tumorigenesis

Methylation is essential for embryonic development, however aberrant methylation of CpG islands associated with the tumour suppressor genes (TSGs) and leading to gene silencing is found in numerous tumour types. The TSG p16/CDKN2A is involved in the genesis of many tumour types and frequent methylation of the CpG island of the p16/CDKN2A gene is associated with loss of protein expression in pituitary tumours. In addition, CpG sites are mutational hotspots and abnormal methylation patterns have been shown to lead to genetic instability, predisposing to, and preceding allelic loss. Although several studies of pituitary tumours have shown loss of genetic material at known and putative TSGs loci, studies of the retained alleles have revealed infrequent mutation. Equally, for several other TSGs no mechanisms have been described for their reduced expression. Methylation may represent a unifying theme, responsible in some cases for an absence or reduced expression and in other cases predisposing to allelic loss that may or may not encompass a TSG. In several tumour types treatment of tumours or their cognate cell lines with demethylating agents induces expression of previously methylated genes. Using the mouse corticotroph cell line AtT20 as a model system, transfection studies showed restoration of growth control through induction of ectopically expressed p16/CDKN2A. These effects were reversed by prior in vitro methylation of the constructs' CpG sites within the coding region of this gene. Methylation of an otherwise unmethylated CpG island renders a gene transcriptionally incompetent and clinically these genes represent attractive therapeutic targets since the gene is neither lost nor mutated, but may be reactivated. Future studies will no doubt describe more efficacious pharmacological interventions and identify the mechanisms responsible for the abnormal methylation patterns seen in tumours including those of pituitary origin.

Transfection of an inducible p16/CDKN2A construct mediates reversible growth inhibition and G1 arrest in the AtT20 pituitary tumor cell line

Recent studies have shown that methylation of the CpG island within the p16/CDKN2A gene is associated with an absence of p16 protein in human pituitary tumors. However, the effect of restoration of p16 protein expression in this tumor type has not been investigated. In the absence of an available human pituitary cell line we first assessed the suitability of the mouse corticotroph cell line AtT20 as a model system. Initial experiments showed that the p16/CDKN2A gene was not expressed, whereas a transcript for RB1 was detected as assessed by RT-PCR. Further studies showed the p16/CDKN2A gene to be homozygously deleted. The absence of p16/CDKN2A and presence of RB1, the down-stream effector of p16-mediated cell cycle arrest confirmed the suitability of the AtT20 cell line as a model system. Stable transfectants were generated in which p16/CDKN2A is regulated by an inducible promoter. The regulatory effects of p16/CDKN2A expression on cell proliferation were assessed and complemented by fluorescence-activated cell sorting (FACS) analysis of cell cycle profile. Induced expression of p16/CDKN2A resulted in a profound inhibition of cell growth and G1 arrest (80-82%). Western blot analysis showed concomitant expression of p16 protein in arrested cells and a shift in the phosphorylation status of pRB toward its hypophosphorylated form. To further confirm that expression of p16/CDKN2A mimicked its in vivo role, reversibility was assessed using alternate cycles in the presence and absence of inducer (isopropyl-1-thio-beta-D-galactopyranoside). Over three cycles the absence of induced expression of p16/CDKN2A resulted in release from G1 arrest. These results show that, in a pituitary cell line model, restoration of p16 expression is indeed sufficient to arrest cells in G1 and inhibit cell proliferation and is reversible. Thus restoration of p16 expression through novel strategies, including gene therapy or demethylating agents, may offer successful therapeutic intervention in human forms of this disease.

Surgical removal of an ependymoma from the third ventricle of a cat

A 10-year-old spayed domestic shorthaired cat was presented for behavioural changes, signs suggestive of visual deficits and aimless circling. Neuro-ophthalmological examination suggested the cat had central blindness. CT scans following administration of iohexol demonstrated a contrast-enhancing mass in the vicinity of the third ventricle resulting in obstructive hydrocephalus. Following rostral tentorial craniotomy and incision through the cerebral cortex, the third ventricle was approached via the dilated left lateral ventricle. An ependymoma was seen through a dorsocaudolateral incision into the third ventricle, and removed by gentle manipulation and suction. The cat recovered unremarkably, regaining normal vision and behaviour.

Analysis of cyclin D1 (CCND1) allelic imbalance and overexpression in sporadic human pituitary tumors

Cyclin D1 plays an important role in the regulation of cell progression through G1 of the cell cycle and has been demonstrated to have oncogenic properties. Using RFLP-PCR, an A/G polymorphism within the cyclin D1 (CCND1) gene was analyzed in 151 sporadic human pituitary tumors, of which 60 were informative at this locus. Further analysis showed that in 15 of 60 (25%) tumors, there was evidence of allelic imbalance, which is indicative of gene amplification. Allelic imbalance was observed more frequently in invasive tumors (11 of 29 tumors; 38%) than in their noninvasive counterparts (4 of 31 tumors; 13%; P = 0.02). Forty-six of the tumors informative for the polymorphism were available for immunohistochemical analysis. Cyclin D1 expression (nuclear and/or cytoplasmic) was detected in 25 of 46 (54%) tumors. Of these cases, expression of nuclear cyclin D1 was detected in 9 of 46 (20%) tumors, whereas 16 of 46 (35%) tumors showed cyclin D1 staining exclusively confined to the cytoplasm. Neither nuclear staining nor cytoplasmic staining was observed in any of the normal pituitaries or in the negative control. Expression of cyclin D1 was observed in significantly more nonfunctional tumors (18 of 27 tumors; 67%) than in somatotrophinomas (7 of 19 tumors; 37%; P = 0.046). Nuclear cyclin D1 expression was observed more frequently in nonfunctional tumors (8 of 27 tumors; 30%) than in somatotrophinomas (1 of 19 tumors; 5%; P = 0.04). There was no correlation between cyclin D1 expression and tumor grade or between allelic imbalance of CCND1 and cyclin D1 expression. We conclude that amplification of CCND1 occurs in pituitary tumors and that the overexpression of cyclin D1 may be an early event in tumorigenesis. Cyclin D1 overexpression occurring in the absence of CCND1 allelic imbalance suggests that additional mechanisms responsible for deregulated cyclin D1 expression are involved in human pituitary tumorigenesis.

Hypermethylation of the p16/CDKN2A/MTSI gene and loss of protein expression is associated with nonfunctional pituitary adenomas but not somatotrophinomas

The cyclin-dependent kinase inhibitor 2A/multiple tumor suppressor gene 1 (CDKN2A/MTS//p16) plays an important role in the control of progression from G to S-phase of the cell cycle through the inhibition of CDK4-mediated RBI phosphorylation. In this study we investigated 46 nonfunctional pituitary tumors and 21 somatotrophinomas for aberrant methylation of the CpG island contained within the CDKN2A gene as an alternative mechanism of gene silencing. We demonstrate methylation in 32/46 (70%) of nonfunctioning tumors, in contrast to 2/21 (9.5%) somatotrophinomas and 0/15 histologically normal postmortem pituitaries. Methylation in noninvasive and invasive nonfunctional tumors was approximately equal at 15/20 (75%) and 17/26 (65%), respectively. Immunohistochemical analysis showed an absence of CDKN2A protein in 25/32 (78%) methylated nonfunctioning tumors, demonstrating a highly significant overall correlation (P = 0.00007) between hypermethylation of the gene and absence of the p 16 protein. The association between hypermethylation and absence of CDKN2A protein remained when the cohort of nonfunctional tumors was further subdivided into noninvasive 12/15 (80%; P = 0.004) and invasive 13/17 (76%; P = 0.01), suggesting this to be an early event in pituitary tumorigenesis. In contrast, a single invasive methylated somatotrophinoma failed to express the CDKN2A protein. These data show that hypermethylation of the CpG island within exon 1, but not exon 2, of the CDKN2A gene is frequently associated with loss of protein expression in nonfunctional pituitary tumors, but not somatotrophinomas, suggesting different tumorigenic pathways.

Benign masses in the pericardium of two dogs

Two miniature Schnauzer dogs were treated for pericardial masses. In one dog the mass consisted of necrotic fat that was attached to the apex of the pericardium by a pedicle. No obvious communication with the abdomen was present. The second dog had a peritoneopericardial hernia associated with a chronic cystic haematoma. In each case the mass was presumed to have arisen following congenital displacement of the omentum into the pericardium. The pericardial mass was removed and subtotal pericardectomy performed in both dogs. Recovery was complete in each case.

Chromosome 13q deletion mapping in pituitary tumors: infrequent loss of the retinoblastoma susceptibility gene (RB1) locus despite loss of RB1 protein product in somatotrophinomas

Two recent studies have described allelic loss of an RB1 intragenic marker on chromosome 13q in aggressive and metastatic pituitary tumors that did not correlate with loss of pRB. The second report also showed that losses were more frequently associated with a more centromeric marker. Because both of these studies suggest the presence of another or other tumor suppressor genes (TSGs) on 13q, we carried out an allelotype analysis encompassing known and recently described TSG loci on 13q, together with immunohistochemical analysis of pRB. We analyzed 82 nonfunctional tumors and 53 somatotrophinomas subdivided into invasive and noninvasive cohorts. A significantly higher frequency of loss, at one or more of 13 markers, was evident in the invasive nonfunctional tumors (54%, 26 of 48) than in their noninvasive counterparts (29%, 10 of 34). An approximately equal frequency of loss was apparent in invasive (28%, 5 of 18) and noninvasive (31%, 11 of 35) somatotrophinomas at one or more markers. In those tumors harboring deletion, loss at two or more markers was more frequent in invasive nonfunctional tumors 65% (17 of 26) compared with 36% (4 of 11) of their noninvasive counterparts. In somatotrophinomas, 40% (2 of 5) of invasive tumors as compared with 64% (7 of 11) of noninvasive tumors had evidence of two or more deletions. In tumors showing loss at two or more loci, the majority showed large deletions; however, loss of the RB1 intragenic marker D13S153 was infrequent. In most cases, loss at individual markers was more frequent in invasive tumors than their noninvasive counterparts. A marker 3 cM telomeric to RB1 (D13S1319) showed the highest frequency of deletion in both invasive cohorts (29% of somatotrophinomas and 24% of nonfunctional tumors). Immunohistochemical analysis of pRB showed frequent loss in somatotrophinomas (27%, 9 of 33) in comparison with 4% (2 of 53) of non-functional tumors. Although loss of pRB did not correlate with loss of an intragenic marker or tumor grade, it was significantly associated with the somatotrophinoma subtype (P = 0.002). These data suggest that chromosome 13q is a frequent target for allelic deletion in pituitary tumors and point to another or other TSG loci in these regions.

Sequence analysis and transcript expression of the MEN1 gene in sporadic pituitary tumours

The majority of pituitary tumours are monoclonal in origin and arise sporadically or occasionally as part of multiple endocrine neoplasia type 1 (MEN1). Whilst a multi-step aetiology involving both oncogenes and tumour suppressor genes has been proposed for their development, the target(s) of these changes are less clearly defined. Both familial and sporadic pituitary tumours have been shown to harbour allelic deletion on 11q13, which is the location of the recently cloned MEN1 gene. We investigated 23 sporadic pituitary tumours previously shown to harbour allelic deletion on 11q13 with the marker PYGM centromeric and within 50 kb of the MEN1 locus. In addition, the use of intragenic polymorphisms in exon 9 and at D11S4946, and of telomeric loci at D11S4940 and D11S4936, revealed that five of 20 tumours had loss of heterozygosity (LOH) telomeric to the menin gene. However, the overall pattern of loss in informative cases was indicative of non-contiguous deletion that brackets the menin gene. Sequence analysis of all MEN1 coding exons and flanking intronic sequence, in tumours and matched patient leucocyte DNA, did not reveal mutation(s) in any of the 23 tumours studied. A benign polymorphism in exon 9 was encountered at the expected frequency, and in seven patients heterozygous for the polymorphism the tumour showed retention of both copies of the menin gene. Reverse transcription polymerase chain reaction analysis of ten evaluable tumours and four normal pituitaries revealed the presence of the menin transcript. Whilst these findings suggest that gene silencing is unlikely to be mechanistic in sporadic pituitary tumorigenesis, they do not exclude changes in the level or stability of the transcript or translation to mature protein. Our study would support and extend very recent reports of a limited role for mutations in the MEN1 gene in sporadic pituitary tumours. Alternatively, these findings may point to an, as yet, unidentified tumour suppressor gene in this region.

Substrate specificity of barley cysteine endoproteases EP-A and EP-B

The cysteine endoproteases (EP)-A and EP-B were purified from green barley (Hordeum vulgare L.) malt, and their identity was confirmed by N-terminal amino acid sequencing. EP-B cleavage sites in recombinant type-C hordein were determined by N-terminal amino acid sequencing of the cleavage products, and were used to design internally quenched, fluorogenic peptide substrates. Tetrapeptide substrates of the general formula 2-aminobenzoyl-P2-P1-P1'-P2'-tyrosine(NO2)-aspartic acid, in which cleavage occurs between P1 and P1', showed that the cysteine EPs preferred phenylalanine, leucine, or valine at P2. Arginine was preferred to glutamine at P1, whereas proline at P2, P1, or P1' greatly reduced substrate kinetic specificity. Enzyme cleavage of C hordein was mainly determined by the primary sequence at the cleavage site, because elongation of substrates, based on the C hordein sequence, did not make them more suitable substrates. Site-directed mutagenesis of C hordein, in which serine or proline replaced leucine, destroyed primary cleavage sites. EP-A and EP-B were both more active than papain, mostly because of their much lower Km values.