Radioactive waste microbiology: predicting microbial survival and activity in changing extreme environments

The potential for microbial activity to occur within the engineered barrier system (EBS) of a geological disposal facility (GDF) for radioactive waste is acknowledged by waste management organizations as it could affect many aspects of the safety functions of a GDF. Microorganisms within an EBS will be exposed to changing temperature, pH, radiation, salinity, saturation, and availability of nutrient and energy sources, which can limit microbial survival and activity. Some of the limiting conditions are incorporated into GDF designs for safety reasons, including the high pH of cementitious repositories, the limited pore space of bentonite-based repositories, or the high salinity of GDFs in evaporitic geologies. Other environmental conditions such as elevated radiation, temperature, and desiccation, arise as a result of the presence of high heat generating waste (HHGW). Here, we present a comprehensive review of how environmental conditions in the EBS may limit microbial activity, covering HHGW and lower heat generating waste (LHGW) in a range of geological environments. We present data from the literature on the currently recognized limits to life for each of the environmental conditions described above, and nutrient availability to establish the potential for life in these environments. Using examples where each variable has been modelled for a particular GDF, we outline the times and locations when that variable can be expected to limit microbial activity. Finally, we show how this information for multiple variables can be used to improve our understanding of the potential for microbial activity to occur within the EBS of a GDF and, more broadly, to understand microbial life in changing environments exposed to multiple extreme conditions.

Subsurface Microbial Hydrogen Cycling: Natural Occurrence and Implications for Industry

Hydrogen is a key energy source for subsurface microbial processes, particularly in subsurface environments with limited alternative electron donors, and environments that are not well connected to the surface. In addition to consumption of hydrogen, microbial processes such as fermentation and nitrogen fixation produce hydrogen. Hydrogen is also produced by a number of abiotic processes including radiolysis, serpentinization, graphitization, and cataclasis of silicate minerals. Both biotic and abiotically generated hydrogen may become available for consumption by microorganisms, but biotic production and consumption are usually tightly coupled. Understanding the microbiology of hydrogen cycling is relevant to subsurface engineered environments where hydrogen-cycling microorganisms are implicated in gas consumption and production and corrosion in a number of industries including carbon capture and storage, energy gas storage, and radioactive waste disposal. The same hydrogen-cycling microorganisms and processes are important in natural sites with elevated hydrogen and can provide insights into early life on Earth and life on other planets. This review draws together what is known about microbiology in natural environments with elevated hydrogen, and highlights where similar microbial populations could be of relevance to subsurface industry.

Prevalence, outcome and risk factors for postoperative pyothorax in 232 dogs undergoing thoracic surgery

Objective

To determine the prevalence, outcome and risk factors for postoperative pyothorax in dogs undergoing thoracic surgery.

Methods

Case records were reviewed retrospectively to identify dogs with post thoracic surgery pyothorax, defined as septic neutrophilic inflammation within the pleural space based on cytology and/or a positive bacterial culture of pleural fluid. Those identified were reviewed for potential risk factors for postoperative pyothorax based on biological plausibility and previously published data. These potential risk factors were explored by multivariable logistic regression.

Results

Of 232 dogs undergoing thoracic surgery, 15 (6·5%) dogs developed pyothorax. Bacteria cultured included methicillin-resistant Staphylococcus aureus and multi-resistant Escherichia coli. Of these dogs, six died, four were euthanased and five were treated successfully. A diagnosis of idiopathic chylothorax [Odds Ratio (OR)=12·5, 95% Confidence Interval (CI)=2·7-58·5, P=0·001], preoperative intrathoracic biopsy (OR=14·3, 95% CI=1·7-118·7, P=0·014) and preoperative thoracocentesis (OR=11·2, 95% CI=1·6-78·2, P=0·015) were identified as independent risk factors for development of postoperative pyothorax.

Clinical Significance

Idiopathic chylothorax, intrathoracic biopsy and prior thoracocentesis are independent risk factors for postoperative pyothorax, which was associated with a 67% mortality rate.

Spontaneous gastroduodenal perforations in dogs: a retrospective study of 15 cases

The clinical findings and outcomes following surgical management of spontaneous gastroduodenal perforations in 15 dogs were reviewed in a retrospective study to identify related risk factors. Clinical and clinicopathological findings were diverse. Use of multiple diagnostic procedures yielded a strong index of suspicion for gastrointestinal perforation. There was a trend towards improved survival for animals with perforation of the gastric fundus/body compared to pyloric or duodenal perforation, although the difference was not statistically significant. Five dogs were euthanased at surgery; two dogs died within two days after surgery. Seven of the eight surviving dogs had a favourable long-term outcome. Previous administration of NSAIDs was the only identified predisposing factor in ten of 10 of the dogs.

Analysis of NOD1, NOD2, TLR1, TLR2, TLR4, TLR5, TLR6 and TLR9 genes in anal furunculosis of German shepherd dogs

Anal furunculosis (AF) primarily affects German shepherd dogs (GSD) and is characterised by inflammation and ulceration of the perianal tissues with development of cutaneous sinuses or rectocutaneous fistulae. Investigation of pattern recognition receptor (PRR) function has suggested that defective responses might occur in AF-affected GSD. The aim of the current study was to investigate whether canine PRR genes are involved in determining susceptibility to AF in this breed. Chromosomal location and coding sequences for NOD1, NOD2, TLR1, TLR2, TLR4, TLR5, TLR6 and TLR9 were determined and microsatellite markers identified for each gene. Microsatellite genotyping of 100 control GSD and 47 AF-affected GSD showed restricted allelic variation for AHT H91 (associated with TLR5) and REN216 NO5 (associated with both TLR1 and TLR6) compared with non-GSD dogs. Genotyping of single nucleotide polymorphisms identified in canine TLR1, TLR5, TLR6 and NOD2 genes failed to show any significant associations between PRR polymorphisms and AF. The highly restricted PRR genotypes seen in GSD are likely to have resulted from selective breeding and might influence innate immune responses in this breed.

Duplex gall bladder associated with choledocholithiasis, cholecystitis, gall bladder rupture and septic peritonitis in a cat

A 10-year-old cat was presented with a history of inappetence, pyrexia and weight loss. Clinical investigations showed anaemia, hyperbilirubinaemia, septic peritonitis and a double gall bladder with choleliths in an extrahepatic duct. Initial medical stabilisation was performed. At laparotomy, a duplex gall bladder with two separate cystic ducts was identified. The left gall bladder was thickened and had ruptured at the apex. Multiple choleliths were identified in the left cystic duct. The right gall bladder and cystic duct were grossly normal. The ruptured gall bladder was repaired, the gallstones were removed via a choledochotomy of the left cystic duct and a choledochoduodenostomy was created from the dilated left cystic duct. The cat remained depressed and anorexic, and it was euthanased 72 hours postoperatively at the owners' request. This is the first ante-mortem investigation of extrahepatic biliary disease associated with gall bladder duplication in the cat.

Solitary extramedullary plasmacytoma of the canine larynx

An 11-year-old, female, spayed cocker spaniel was presented with dysphonia caused by a solitary laryngeal mass. Excisional biopsy was performed, and a diagnosis of plasmacytoma was made on the basis of histological examination. Further investigations showed no signs of systemic involvement. Coarse fractionated radiation therapy failed to control the tumour. Therapy was successfully instituted with a conventional combination chemotherapy protocol over a period of 14 months. The dog remains disease free 30 months after diagnosis. Most solitary, extramedullary plasmacytomas in dogs arise in the gastrointestinal tract, with fewer reports in other sites. The larynx is an uncommon sight of involvement in any species, and to the authors' knowledge, this is the first report of this tumour type in the canine larynx. In contrast to the therapeutic benefits reported in humans, the combination of surgery and radiation therapy was unsuccessful in this case, although sustained remission was gained following chemotherapy.

Matrix metalloproteinase mRNA expression in canine anal furunculosis lesions

Although the aetiology of anal furunculosis (AF) in dogs is poorly understood, there is evidence for an underlying immune dysfunction. This is illustrated by the presence of a T helper type 1 cytokine mRNA profile in AF lesions and the clinical response to ciclosporin therapy. Expression of MMPs 2, 9 and 13 were evaluated in AF lesional biopsies by real-time quantitative RT-PCR. There was significantly increased expression of both MMP-9 and MMP-13 mRNA in AF biopsies compared to controls (p<0.001) but no significant difference in MMP-2 mRNA expression. Since MMP-9 and MMP-13 are primarily produced by macrophages, these data suggest that ulceration could be the result of aberrant activation of this cell type in the tissues. It is feasible that such pathological macrophage activity occurs in response to interferon-gamma secreted by T helper type 1 cells. This could explain why the lesions resolve following treatment with the immunosuppressive drug ciclosporin.

Cyclosporine treatment of anal furunculosis in 26 dogs

OBJECTIVES

To evaluate the effect of cyclosporine on anal furunculosis lesions in 26 dogs.

METHODS

Lesions were graded as mild in 11 dogs, moderate in eight and severe in seven. Each dog was treated with approximately 4 mg/kg cyclosporine orally every 12 hours until the lesions resolved or showed no further improvement. Residual lesions were resected surgically.

RESULTS

Eighteen dogs (69 per cent) experienced complete resolution, seven (27 per cent) improved but had residual lesions and one (4 per cent) showed no improvement. The mean duration of treatment until resolution or no further improvement was 8.8 weeks (range four to 24 weeks). Nine dogs (35 per cent) experienced recurrence. Six were from the group that had shown complete resolution and three were from the group that had surgery. Fifteen dogs (58 per cent) developed side effects to cyclosporine, although none required treatment to be discontinued. Mean duration of follow-up was 6.8 months (range one to 20 months).

CLINICAL SIGNIFICANCE

Cyclosporine was effective at resolving or reducing anal furunculosis lesions in 25 of 26 dogs (96 per cent). However, residual or recurrent lesions remain a potential problem, and surgical resection or long-term cyclosporine treatment may be necessary in some dogs.

Expression of cytokine mRNA in canine anal furunculosis lesions

The pattern of expression of cytokine mRNA in the lesions of anal furunculosis was evaluated in tissue biopsies from 15 dogs, and compared with the pattern in control skin samples from 24 dogs, by reverse-transcriptase PCR using canine cytokine-specific primers and a semi-quantitative multiplex PCR assay. Interleukin-2 (IL-2) was detected in 11 of the 15 affected dogs but in only one of the controls, and interferon-gamma was detected in 14 of the affected dogs but none of the controls. In contrast, IL-4 was detected only in one of the affected dogs. Increased expression of mRNA for IL-1beta, IL-6, tumour necrosis factor alpha, IL-8, IL-10 and transforming growth factor beta1 was detected in the biopsies from the lesions of anal furunculosis relative to the control tissues (P < 0.05).

Parotid duct dilation in two dogs

Two cases of parotid duct dilation are described; the clinical signs on initial examination were a tubular swelling over the lateral aspect of the face with an associated intraoral submucosal distension. Surgical exploration confirmed that the distended structure was the dilated parotid duct and intraoral marsupialisation resulted in no recurrence postsurgery.

Middle ear disease associated with congenital palatine defects in seven dogs and one cat

Medical records of eight dogs and one cat with congenital palatine defects were reviewed retrospectively. Five of the dogs had nasal discharge and seven had radiographic signs of middle ear disease, but no clinical signs of ear disease were identified in any of the dogs, nor were any reported by their owners during a one- to five-year follow-up period. One dog had an ipsilateral impairment of hearing detected by brainstem auditory evoked responses. The cat had clinical and radiographic signs of middle ear disease. These findings suggest that, as in humans, congenital palatine defects in dogs and cats may predispose to middle ear disease. Any associated deafness could cause problems for working dogs.

Suitability of the cranial portion of the vagina as a site for measurement of intra-abdominal pressure variations in dogs

OBJECTIVE

To determine whether the cranial portion of the vagina of dogs is a suitable site for measuring intra-abdominal pressure during cystometry.

ANIMALS

16 bitches (8 sexually intact and 8 spayed).

PROCEDURE

2 types of vaginal catheters were used to measure intra-abdominal pressure changes in anesthetized dogs. Catheters were inserted in the rectum and cranial portion of the vagina.

RESULTS

Intra-abdominal pressure variations were detected with greater magnitude in the rectum than the cranial portion of the vagina, regardless of type of catheter used and reproductive status (sexually intact vs spayed) of the dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

The rectum was the better site for measuring intra-abdominal pressure changes in female dogs. Measurement of intra-abdominal pressure with concomitant measurement of intravesical pressure to determine detrusor pressure during cystometry in female dogs is more reliably detected from the rectum than the cranial portion of the vagina.

Vaginal position and length in the bitch: relationship to spaying and urinary incontinence

A study was undertaken to determine if the vagina might be a suitable site for the measurement of intra-abdominal pressure during cystometry in the bitch. The position of the cranial vagina and vaginal length were measured radiographically and the effects of spaying and urinary incontinence on these variables were evaluated in 30 continent and 30 incontinent bitches. The study used retrograde vaginourethrograms which had been obtained from animals used in a previous study. The cranial vagina was intra-abdominal on 36 of the vaginourethrograms, being least commonly intra-abdominal in incontinent bitches (11/30). Vaginal position was related linearly to vaginal length and continence status (P < 0.01), while its length was related to bodyweight (P < 0.01). Allowing for bodyweight, neutered animals had significantly shorter vaginas than entire bitches (P < 0.01). Measurement of intra-abdominal pressure with concomitant measurement of intravesical pressure is essential if accurate assessment of detrusor pressure is to be determined during cystometry. The vagina is unlikely to be a useful location from which to measure intra-abdominal pressure since any pressure-measuring catheter inserted into it may fall outside the abdominal pressure zone. This is particularly true of neutered and/or incontinent bitches, the groups in which urodynamic investigations of urinary incontinence are most frequently indicated.

Ultrasonographic findings in 14 dogs with ectopic ureter

To evaluate ultrasonography as an alternative to contrast radiography for diagnosis of ectopic ureter in dogs, ultrasonography of the urinary tract was performed prospectively in a series of urinary incontinent dogs anesthetized for contrast radiography. Fourteen dogs had ectopic ureter based on surgical, necropsy or unequivocal contrast radiographic findings. There were eight females and six males of a variety of breeds; five were Labrador retrievers. Mean (range) age at the time of diagnosis was 1.2 (0.2-4) years for females and 3.5 (0.3-5) for males (p < 0.05). Ectopic ureters were unilateral in five dogs (2 left; 3 right) and bilateral in nine dogs. Both ultrasound images and contrast radiographs were positive for 21 (91%) ectopic ureters; the same two ectopic ureters were not detected using either modality. The termination of each of the five normal ureters was visible on ultrasound images; two (40%) were visible on radiographs. Other ultrasonographic findings included dilatation of the ectopic ureter and/or ipsilateral renal pelvis in ten (43%) instances, evidence of pyelonephritis in two dogs (with enlargement of the contralateral kidney in one dog), and urethral diverticuli in one dog. Ultrasonography is a practical diagnostic test for ectopic ureter in dogs. In this series there was close correlation between the ultrasonographic and contrast radiographic findings for each ectopic ureter, but ultrasonography enabled more accurate determination of normal ureteral anatomy.

Evaluation of the canine tympanic membrane by positive contrast ear canalography

Positive contrast ear canalography was described briefly in 1973 as a method for detecting rupture of the tympanic membrane in dogs with otitis media. The purpose of this study was to evaluate the sensitivity and usefulness of the technique. The ears of 10 normal canine cadavers and 31 dogs with clinical signs of ear disease were examined using otoscopy, radiography and contrast radiography after infusing 2 to 5 ml of positive contrast medium into the ear canals. These examinations were repeated in the cadavers after the tympanic membrane had been punctured with a Spreull needle. In the cadavers 14 of 19 (74 per cent) of the tympanic membranes were visible otoscopically; contrast medium did not enter the tympanic bulla of any of the ears before the tympanic membrane was ruptured, but was visible in the bulla in every ear after rupture. In the clinical study, 40 of 61 (66 per cent) of the tympanic membranes were visible otoscopically, and 12 appeared to be ruptured. Radiographic signs of otitis media (increased opacity and/or thickening of the tympanic bulla) were identified in seven ears. Canalography was positive for rupture of the tympanic membrane in 13 ears, including four in which it appeared to be intact otoscopically. In normal canine ears, canalography was a more accurate method for detecting iatrogenic tympanic membrane rupture than otoscopy. In dogs with ear disease, canalography may be more sensitive for otitis media than either otoscopy or survey radiography.

Immunohistochemical demonstration of Wilms tumour gene product WT1 in a canine "neuroepithelioma" providing evidence for its classification as an extrarenal nephroblastoma

An intradural extramedullary tumour, surgically removed from the spinal canal of a young dog with paraplegia, had the histological appearance of a nephroblastoma. Subsequent necropsy revealed no evidence of a renal primary tumour or of any other tumour. Similar tumours of the spinal canal have been described previously under a variety of names, in particular neuroepithelioma. With an antibody to the human Wilms tumour (nephroblastoma) gene product WT1, labelling of glomeruloid bodies, similar to glomerular podocytes in human fetal kidney, was demonstrated in the tumour. This finding strengthened the suggestion that it was a nephroblastoma.

Surgical treatment of urinary incontinence resulting from a complex congenital abnormality in two dogs

Two young dogs were presented for the investigation of urinary incontinence. Both were found to have complex urogenital anatomy including a micropenis and a midline vestibuloperineal fistula situated just below the anus. Both dogs were considered to be intersexes and had the karyotype 78XX. In both cases, incontinence was attributed to increased resistance to the passage of urine, with vaginal reflux and subsequent passive leakage. This report details the investigation of these dogs and their surgical treatment to resolve the urinary incontinence.

Vaginourethroplasty for treatment of urethral obstruction in the bitch

Vaginourethroplasty was performed in six bitches with infiltrative, obstructive urethral disease. The initial clinical signs included dysuria, hematuria, pollakiuria, and stranguria. Diagnosis was based on the clinical signs, plain radiography and contrast vagino-urethrogram examination, and urethral biopsy. Five dogs were diagnosed as having urethral neoplasia; the sixth dog had granulomatous urethritis. In all six dogs, up to 50% of the urethra and the urethral tubercle were resected to ensure adequate surgical margins. One dog was euthanatized 4 months after surgery for recurrence of a transitional cell carcinoma at the surgical site. Long-term resolution of the problem (minimum of 12 months) was achieved in the other five dogs. The frequency of serious complications, including urinary incontinence and ascending lower urinary tract infections, was low.

Ultrasound-guided catheter biopsy of the lower urinary tract: technique and results in 12 dogs

Ultrasound-guided catheter biopsy of lesions affecting the lower urinary tract was attempted in 12 dogs with mucosal lesions affecting the bladder (nine) or urethra (three). Histological biopsies were obtained by catheter biopsy in 10 dogs, enabling diagnosis of transitional cell carcinoma in five, papilloma in two, prostatic carcinoma in two and chronic cystitis in one. Cytological samples alone were obtained in two dogs, one of which enabled a diagnosis of transitional cell carcinoma; the other contained evidence of haemorrhage and inflammation, but squamous cell carcinoma was found in a subsequent excisional biopsy. Intravesicular haemorrhage after biopsy was observed ultrasonographically in two dogs. Ultrasound guidance enables accurate determination of biopsy catheter position. The size of biopsies obtained by this method may limit the accuracy of histological diagnosis.

Comparison of urethral pressure profilometry and contrast radiography in the diagnosis of incompetence of the urethral sphincter mechanism in bitches

Three diagnostic indicators of urethral sphincter mechanism incompetence were compared in 25 continent and 25 incontinent anaesthetised bitches: the resting urethral pressure profile, the stressed urethral pressure profile and the radiographic position of the bladder neck. Logistic regression indicated that the best predictor of continence status was the stressed urethral pressure profile as assessed by the percentage of negative peaks extending below the resting intravesical pressure; it classified 43 of the 50 dogs correctly. The radiographic position of the bladder neck was a better predictor of continence than either the measurement of functional profile length or the maximum urethral closure pressure from the resting urethral pressure profile, whether alone or in combination. By combining the percentage of negative peaks on the stressed profile with the position of the bladder neck, 46 of the 50 dogs were classified correctly. Cut-off values for the percentage of negative peaks on the stressed urethral pressure profile, and for the radiographic position of the bladder neck are suggested for use in evaluating incontinent bitches in clinical practice.

The immediate effect of colposuspension on resting and stressed urethral pressure profiles in anaesthetized incontinent bitches

The aim of this study was to document what changes in the resting and stressed urethral pressure profile occur in the incontinent bitch with urethral sphincter mechanism incompetence (SMI) immediately after colposuspension. Resting and stressed subtracted simultaneous urethral pressure profilometry was performed immediately pre- and postcolposuspension in 26 bitches diagnosed with SMI. All of the urethral pressure profiles were measured in anaesthetized bitches using a standard technique and two orientations of the catheter transducers (dorsal and left). Readable pre- and postoperative urethral pressure profiles were obtained in 20 of the 26 bitches. Subjective and objective evaluation of the profiles showed significant differences in the profiles pre- and postcolposuspension. Immediately postoperatively there were significant (P < .05) increases in functional profile length, maximum urethral closure pressure (MUCP), and distance between the bladder neck and the first negative respiratory peak and stressed spike. There was a significant (P < .001) decrease in the percentage of negative spikes extending below the resting intravesical pressure on the subtracted profile. The pressure transmission profiles were significantly (P < .001) altered by surgery. The findings presented support the hypothesis that colposuspension may restore continence by increasing pressure transmission to the proximal urethra and bladder neck. The results also suggest that immediately after surgery functional urethral length and urethral resistance are increased.

Developments in the understanding of the pathophysiology of urethral sphincter mechanism in competence in the bitch

Developments in understanding the pathophysiology of urinary incontinence caused by urethral sphincter mechanism incompetence (SMI) are reviewed. SMI is a multifactorial condition; affected bitches have shorter urethras, reduced urethral tone and more caudally positioned bladder necks than continent bitches. Other factors thought to be important in the aetiology of SMI include neutering, breed, body size, docking and obesity. Most of the recent developments in the understanding of SMI have resulted from radiographic and urodynamic investigations of normal and affected bitches. The urodynamic technique of urethral pressure profilometry is discussed and its contribution as an investigative tool reviewed.

Ultrasonography of the ureterovesicular junction in the dog: a preliminary report

Contrast radiography followed by ultrasonography of the urinary bladder was performed on 10 incontinent dogs. The ureterovesicular junctions and ureteral jets were identified by ultrasonography in all the dogs except one that had a caudally displaced bladder. An ectopic ureter in one dog was diagnosed by ultrasonography on the basis of the absence of a ureteral jet on the affected side, and the direct identification of the ureter passing caudal to the bladder neck. Ultrasonography appears to be a simple, repeatable test for identifying the distal ureters.

Comparison of stressed simultaneous urethral pressure profiles between anesthetized continent and incontinent bitches with urethral sphincter mechanism incompetence

The popular urodynamic technique of stressed urethral pressure profilometry used for investigation of genuine stress incontinence in women was adapted and applied to bitches. The aim was to assess the suitability and reproducibility of the technique in the canine species, and to determine whether differences seen in continent and incontinent women were found in bitches. Resting and stressed simultaneous urethral pressure profiles were obtained for 25 continent and 25 incontinent bitches, the latter diagnosed as having urethral sphincter mechanism incompetence. The stressed urethral pressure profiles were produced by ballottement of the abdomen during catheter withdrawal. The degree of stress induced was consistent and had got short-term reproducibility. Highly significant (P < 0.001) differences in the percentage of negative spikes extending below the resting intravesical pressure were found between continent and incontinent bitches. Significant differences were not observed in the pressure transmission profiles between continent and incontinent bitches; both groups had a gradual decrease in pressure transmission from the bladder neck to the external urethral orifice. The distance from the start of the urethral pressure profile to the first negative peak (attributable to respiration or ballottement) on the subtracted profile was compared with the radiographic distance that the bladder neck was positioned with respect to the cranial pubic brim, taking body weight and continence status into account. Body weight and continence status did not have significant effect on the relation in either instance.(ABSTRACT TRUNCATED AT 250 WORDS)

Urethral conformation and position in relation to urinary incontinence in the bitch

The conformation of the urethra, the position of the bladder neck and the distance between the external urethral orifice and the cranial pubic brim were compared in 30 continent and 30 incontinent bitches with incompetence of the urethral sphincter mechanism, using the measurements made from vagino-urethrograms. The bladder neck was significantly (P less than 0.001) further caudal in incontinent dogs than in continent dogs. Its position was not affected by neutering and could not be explained by the degree of urethral curvature. The distance from the external urethral orifice to the cranial pubic brim was correlated (P less than 0.001) with bodyweight but was not significantly different in the continent and incontinent bitches. In neutered animals, the distance between the cranial pubic brim and the external urethral orifice was significantly (P less than 0.05) shorter than in entire animals.

Effect of body position on intravesical pressure in the anaesthetised bitch

The position adopted by 50 recumbent dogs was recorded while they were sleeping or resting; the commonest orientation of their hindquarters was right lateral recumbency. The intravesical pressure in the urinary bladder of 24 anaesthetised bitches lying in right lateral recumbency was compared with the intravesical pressure recorded when the same bitches were supported in a standing position. The intravesical pressure was significantly higher when the bitches were in right lateral recumbency (P less than 0.001) and the difference was unaffected by whether they were continent or not, and had no significant correlation with bodyweight. These findings help to explain why bitches with an incompetent urethral sphincter mechanism tend to leak predominantly when they are recumbent.

Comparison of two catheter withdrawal speeds during simultaneous urethral pressure profilometry in anesthetized bitches

Maximal urethral closure pressure, functional profile length, and number of respiratory peaks on the resting urethral pressure profile, expressed as a percentage of those occurring on the bladder pressure recording, were compared at catheter withdrawal speeds of 1 and 3 mm/s in 30 anesthetized bitches. Significant (P less than 0.001) differences were found in maximal urethral closure pressure and percentage of transmission of respiratory peaks between the 2 speeds. Significant difference was not detected in functional profile length.

The generation of a single nick per plasmid molecule using restriction endonucleases with multiple recognition sites

Some restriction endonucleases generate a single-stranded nick at their recognition sequences in the presence of ethidium bromide (EtBr). This nick can then be extended to a single-stranded gap in which mutations can be introduced by a variety of techniques. To date, the templates used in these studies have largely contained a single recognition site for a given enzyme. Therefore, we have extended these studies to twelve enzymes for which multiple recognition sites exist in the template and show that, under appropriate conditions, one single-stranded nick is introduced per plasmid molecule.

A comparison of the promoter strengths of two eukaryotic genes in vitro reveals a region of DNA that can influence the rate of transcription in cis over long distances

We have compared the strength of a trout protamine gene promoter with that of the mouse beta major-globin gene by analysing the relative levels of run-off transcripts produced in a single mammalian in vitro transcription reaction. When the promoters are introduced on separate recombinant plasmids, the protamine transcripts are synthesised with much greater efficiency than those originating from the globin cap site. This enhanced transcription of the protamine gene is again observed when the promoters are applied as separate DNA fragments derived from the same recombinant plasmid. However, when the promoters are linked on a DNA fragment that includes 7 kb of DNA separating the initiation sites, then there is a marked reduction in the protamine signal relative to the globin. Deletion of a region of this fragment that contains the sequences flanking the globin gene at positions -335 to -1400 restores the enhanced protamine gene expression to the levels observed when the promoters are carried on separate DNA fragments.

The localisation of the 5'-termini of in vivo transcripts of a cloned rainbow trout protamine gene

The mRNA start site of a cloned rainbow trout protamine gene (TPG-3) has been localised using S1-nuclease mapping and primer extension of in vivo synthesised trout testis poly A+-RNA. The presumptive cap site occurs within an AT-rich region, only 14 nucleotides from the start of the protein-coding sequence. Transcription of this protamine gene in vitro, using the Hela whole-cell extract system, generates products initiated at the same nucleotide as that used in vivo. In vitro transcription is abolished by deletion of sequences between -20 and -48, within which is a canonical TATA-box having an llbp homology with the strong chick conalbumin and Adenovirus-2 major late promoters (CTATAAAAGGG).

A possible novel interaction between the 3'-end of 18 S ribosomal RNA and the 5'-leader sequence of many eukaryotic messenger RNAs

A novel interaction between the 5'-untranslated region of eukaryotic messenger RNAs and non-contiguous sequences in the 18 S ribosomal RNA is proposed. The small ribosomal RNA contains, at its 3'-terminus, a heavily conserved hairpin structure. It is suggested that mRNA 5'-leader sequence stabilises this structure by interacting with other conserved nucleotides which flank it. Sequences closely related to the required sequence (A-U-C-C-A-C-C) occur quite commonly in eukaryotic mRNAs and are often found immediately upstream from the AUG-codon. This interaction may have a role in the events which lead up to the initiation of protein synthesis.

Structural transitions of chromatin in isolated Xenopus erythrocyte nuclei. I. The effects of ions

Nuclei from Xenopus erythrocytes have been isolated under varying ionic conditions and their morphology studied by light and electron microscopy. The 200-A beaded chromatin fibre observed in vivo is maintained in media containing MgCl2 or CaCl2, but not in those containing Mn2+ as the sole divalent cation. In the absence of these alkaline-earth metal ions, 100-A filaments predominate. This suggests that the native 200-A fibre in isolated nuclei is also stabilized by specific divalent cations. Gross chromatin condensation within the nucleus occurs independently of whether the chromatin is in the form of 100-A or 200-A fibres, but requires the presence of divalent cations. Lower concentrations of MgCl2 or CaCl2 are necessary as compared with MnCl2. In the presence of sufficient divalent cations, decreasing KCl concentration causes peripheral condensation, the condensation of chromatin towards the nuclear membrane. Monovalent cation alone does not appear capable of inducing peripheral condensation. The transcriptional capacities of the different morphological types identified have been studied using E. coli RNA polymerase as a probe. Neither the degree of chromatin condensation nor the state of higher-order coiling have a significant effect on the rate of transcription of the DNA. These results are discussed with regard to further in vitro studies on eukaryotic gene activity.

Structural transitions of chromatin in isolated Xenopus erythrocyte nuclei. II. Computer-based image analysis

The morphology of isolated Xenopus erythrocyte nuclei is largely determined by the ionic constitution of the isolation medium. Electron microscopy of thin sections of nuclei isolated under varying ionic conditions has revealed four different morphological types with characteristic chromatin configurations. These nuclei have been used to study the condensation of chromatin within the confines of the nucleus. Electron micrographs of thin nuclear sections have been analysed by computer on the basis of their intensity of staining with lead citrate/uranyl acetate. The staining pattern (image analysis scan) is characteristic for each nuclear morphology and can be explained by a model which assumes that there are only four higher-order conformations that chromatin can adopt within the nucleus. These are present in varying amounts in the different nuclear types and an attempt has been made to equate the peaks identified by image analysis with previously-described chromatin structures. The results of this study serve to emphasize the potential of computer-based image analysis in the study of chromatin structure.

Transcriptional reactivation of isolated Xenopus erythrocyte nuclei: patterns of RNA synthesis

Nuclei isolated from Xenopus erythrocytes can be transcriptionally reactivated by exposure to certain cytoplasmic proteins. The types of RNA synthesized during this reactivation have been studied and compared with those present in, or synthesized by, isolated nuclei not so reactivated or in entire Xenopus erythrocytes. In all cases, the pattern of transcription indicates the synthesis of a broad range of low molecular weight RNAs. Competitive hybridization demonstrates that the reactivated nuclei synthesize some transcripts not normally produced by the isolated nuclei and we have shown that a proportion of these possess amino acid-accepting activity. The significance of these results is discussed in relation to the control of gene activity in these cells.