Mutations in the TSC2 gene: analysis of the complete coding sequence using the protein truncation test (PTT)

Mutations in the TSC2 gene on chromosome 16p13.3 are responsible for approximately 50% of familial tuberous sclerosis (TSC). The gene has 41 small exons spanning 45 kb of genomic DNA and encoding a 5.5 kb mRNA. Large germline deletions of TSC2 occur in <5% of cases, and a number of small intragenic mutations have been described. We analysed mRNA from 18 unrelated cases of TSC for TSC2 mutations using the protein truncation test (PTT). Three cases were predicted to be TSC2 mutations on the basis of linkage analysis or because a hamartoma from the patient showed loss of heterozygosity for 16p13.3 markers. Three overlapping PCR products, covering the complete coding sequence of mRNA, were generated from lymphoblastoid cell lines, translated into 35S-methionine labelled protein, and analysed by SDS-PAGE. PCR products showing PTT shifts were directly sequenced, and mutations confirmed by restriction enzyme digestion where possible. Six PTT shifts were identified. Five of these were caused by mutations predicted to produce a truncated protein: (i) a sporadic case showed a 32 bp deletion in exon 11, and a mutant mRNA without exon 11 was produced; the normal exon 10 was also spliced out; (ii) a sporadic case had a 1 bp deletion in exon 12 (1634delT); (iii) a TSC2-linked mother and daughter pair had a G-->T transversion in exon 23 (G2715T) introducing a cryptic splice site causing a 29 bp truncation of mRNA from exon 23; (iv) a sporadic case showed a 2 bp deletion in exon 36; (v) a sporadic case showed a 1 bp insertion disrupting the donor splice site of exon 37 (5007+2insA), resulting in the use of an upstream exonic cryptic splice site to cause a 29 bp truncation of mRNA from exon 37. In one case, the PTT shift was explained by in-frame splicing out of exon 10, in the presence of a normal exon 10 genomic sequence. Alternative splicing of exon 10 of the TSC2 gene may be a normal variant. Three 3rd base substitution polymorphisms were also detected during direct sequencing of PCR products. Confirmed mutations were identified in 28% of the families studied and on the assumption that half of the sporadic cases should have TSC2 mutations, a crude estimate of the detection rate would be 60%. This compares favourably with other screening methods used for TSC2, notably SSCP, and since PTT involves much less work it may be the method of choice.      

Detecting pre-ovulatory luteinizing hormone surges in urine

The study objectives were to determine (i) if pre-ovulatory luteinizing hormone (LH) surges, undetected in urine by two immunoradiometric assays (IRMA), were detectable by an ultrasensitive immunofluorometric assay (IFMA) and (ii) the influence of creatinine adjustment on the detection and timing of the urinary LH surges. Daily urine specimens were contributed by healthy 25-36 year old volunteers during 14 ovulatory menstrual cycles for an epidemiological study conducted in 1983-1985. Specimens were selected as having been previously assayed by two IRMA without consistently detecting LH surges. These urine specimens were remeasured using an IFMA and adjusted for creatinine concentration. IFMA measurements revealed unambiguous LH surges in all cycles. Adjusting IRMA urinary LH values for creatinine concentrations revealed previously undetected LH surges in four of eight cycles. Creatinine adjustment also altered the timing of IRMA and IFMA LH surges by 1-5 days. These results demonstrate an IFMA that detects pre- ovulatory LH surges in unpreserved, frozen urine from cycles where such surges were previously undetectable. Further, creatinine adjustment can markedly affect detection and timing of the onset and peak of the urinary LH surge. While our analysis suggests that this adjustment improves the validity of the LH measure, this requires further investigation.      

Tourniquet inflation after intra-articular morphine and bupivacaine administration following knee arthroscopy

We performed a randomized doubled-blind study to evaluate whether there was a benefit in delay in tourniquet deflation with intra-articular administration of morphine and bupivacaine following operative arthroscopic surgery. In 34 patients the tourniquet was deflated immediately and in 38 patients the tourniquet remained inflated for 10 min following injection. The analgesic efficacy was assessed using pain scores and the amount of supplementary analgesia required. The results demonstrate no benefit in delay in tourniquet deflation.     

An on-line system for acquisition and processing of cerebral blood flow data

Regional cerebral blood flow is measured by monitoring the clearance from the brain of the gamma emitting radioisotope ¹³³Xe following an intracarotid artery bolus injection. On-line data analysis, which is performed on a PDP $\text{12}\text{30}$ digital computer, involves exponential stripping to isolate grey and white matter flows and integration of the clearance curves to infinity to enable the mean flow to be calculated. The data is displayed in real time and stored on the PDP 12 Linc tapes as a permanent record.     

Endocardial infiltrates in human heart transplants: a serial biopsy analysis comparing four immunosuppression protocols

Endocardial mononuclear cell infiltrates were studied in 2,350 consecutive biopsies from 172 patients over a period ranging from 4 to 16 months post cardiac transplantation. The patients, otherwise unselected, were equally subdivided into four groups based upon the specific type of maintenance immunosuppression used. This was to allow for comparison of the effects of four separate commonly used recipient immunosuppression protocols, which could potentially influence the characteristics of the infiltrates. With azathiaprine-corticosteroid immunosuppression, endocardial infiltrates in otherwise normal biopsies were exceedingly rare, very minor, and invariably unifocal. Mild and moderate rejection were associated with a highly significant stepwise increase in incidence, prominence, and multifocality of endocardial infiltrates. In contrast, with each of the three cyclosporine-based recipient immunosuppression protocols which were evaluated, approximately 15% of biopsies with no evidence of rejection were associated with endocardial infiltrates. There was a wide range of variation in the prominence of the endocardial infiltrates present. Multifocal infiltrates were frequently encountered, the incidence of which was exclusively dependent upon the specific cyclosporine-based immunosuppression protocol used. With mild and with moderate rejection there was a significant stepwise increase in overall biopsy incidence of all endocardial infiltrates in each of the three groups, although there was no variation in relative prominence of the infiltrates, or in incidence of multifocality when biopsies without rejection were compared. The presence of conspicuous vascular spaces within endocardial infiltrates and significant extension of the infiltrates into the adjacent myocardium, with or without associated myofiber necrosis, were characteristic features of the most prominent endocardial infiltrates in all three cyclosporine-based immunosuppression groups. This constellation of changes has sometimes been referred to as "Quilty" effect. The relative incidence with which these particular features were encountered in association with endocardial infiltrates did not vary with rejection category of the biopsies. This study has shown that the presence of all forms of endocardial infiltrates, in the absence of concomitant rejection, is a characteristic manifestation of cyclosporine-based recipient immunosuppression, regardless of the specific protocol and cyclosporine dosage schedule. Under azathiaprine-based immunosuppression, endocardial infiltrates are almost invariably associated with rejection. It is postulated that cyclosporine-related endocardial mononuclear cell infiltration, in the absence of overt rejection, may result from a low level alloimmune response secondary to fluctuations in cyclosporine drug levels or related factors, and that the incidence with these infiltrates occur can be augmented during acute rejection episodes when the strength of the recipient immune response is magnified.     

Effects of environmental temperature, relative humidity and vaccination on Pasteurella haemolytica in lungs of mice

Groups of mice were kept in four combinations of environmental temperature (8 and 20 degrees C) and humidity [50 per cent and 90 per cent relative humidity (RH)]. The mice were anaesthetized and inoculated intranasally with Pasteurella haemolytica growing logarithmically. Groups of 11 mice were killed at 0.5 h intervals for 6 h after inoculation and the number of colony-forming-units (CFU) of Pasteurella haemolytica in the lungs was determined. The CFU in the lungs of mice were affected by a significant interaction of temperature, relative humidity and time after inoculation (P less than 0.01). From 0.05 to 5.0 h after inoculation, fewer CFU were found in the lungs of mice kept in 8 degrees C 50 per cent RH than in mice kept in 8 degrees C 90 per cent RH, 20 degrees C 50 per cent RH and 20 degrees C 90 per cent RH. In each environment, CFU in the lungs of mice increased from inoculation to approximately 3.5 h after inoculation and then decreased (P less than 0.01). In a similar experiment in an environment of approximately 20 degrees C and 50 per cent RH, there were significantly fewer CFU in the lungs of mice vaccinated intranasally 21 days earlier with live P. haemolytica than in the lungs of mice either vaccinated intranasally with formalized P. haemolytica or not vaccinated with P. haemolytica (P less than 0.01).     

The Wnt pathway, epithelial-stromal interactions, and malignant progression in phyllodes tumours

In a previous study of phyllodes tumours, it has been shown that both the stroma and the epithelium can exhibit distinct molecular changes, suggesting that both are part of the neoplastic process. In view of this finding, it was decided to study stromal-epithelial interactions in these tumours by examining the Wnt-APC-beta-catenin pathway. Beta-catenin and cyclin D1 immunohistochemistry was performed on 119 phyllodes tumours. Eighty-six (72%) showed stromal nuclear beta-catenin localization and in 57% the staining was moderate or strong; however, of the eight malignant tumours in the series, seven showed absent or weak nuclear staining (p<0.025). In no tumour was nuclear beta-catenin staining seen in the epithelial component. Moderate or strong stromal cyclin D1 staining correlated with nuclear stromal beta-catenin staining (p<0.05). Forty-five of the tumours, including two malignant lesions, were screened for beta-catenin exon 3 mutations using SSCP and sequencing, but none was found. Loss of heterozygosity (LOH) of the marker D5S346 was used to infer APC mutation, but only one (benign) tumour showed LOH. Wnt2 and Wnt5a mRNA was localized by in situ hybridization in 13 cases (three malignant) chosen to reflect the different beta-catenin staining patterns. There was an association between strong nuclear beta-catenin staining of stromal cells and epithelial Wnt5a expression (p<0.0015). These data suggest that stromal proliferation in benign phyllodes tumours relies on abnormalities in the Wnt pathway which result not from mutation, but from Wnt5a expression in the epithelium. In the progression to malignancy, the stromal proliferation appears to become independent of the Wnt pathway and, presumably, of the epithelial component of these tumours.