Wnt ligands influence tumour initiation by controlling the number of intestinal stem cells

Many epithelial stem cell populations follow a pattern of stochastic stem cell divisions called 'neutral drift'. It is hypothesised that neutral competition between stem cells protects against the acquisition of deleterious mutations. Here we use a Porcupine inhibitor to reduce Wnt secretion at a dose where intestinal homoeostasis is maintained despite a reduction of Lgr5+ stem cells. Functionally, there is a marked acceleration in monoclonal conversion, so that crypts become rapidly derived from a single stem cell. Stem cells located further from the base are lost and the pool of competing stem cells is reduced. We tested whether this loss of stem cell competition would modify tumorigenesis. Reduction of Wnt ligand secretion accelerates fixation of Apc-deficient cells within the crypt leading to accelerated tumorigenesis. Therefore, ligand-based Wnt signalling influences the number of stem cells, fixation speed of Apc mutations and the speed and likelihood of adenoma formation.

Glasgow's community care programme: 10 year follow up of discharged patients with schizophrenia

In 1986, the rehabilitation of every long stay psychiatric patient in Glasgow was assessed with a view to reducing bed numbers and developing comprehensive community services. Ten years on, we have attempted to trace 91 patients with a diagnosis of schizophrenia assessed at Gartnavel Hospital, in order to repeat assessments of their psychopathology and levels of functioning. We believe this population represents a unique group in terms of their age, length of hospital stay and chronicity of symptoms. Only two patients were untraced but 36% of the original 91 patients were decreased. Discharge to the community and variations in standards of care appeared to have little impact on the symptomatic presentation of the survivors over ten years. The results provide useful information on the success or otherwise of a large scale discharge and community care programme which is continuing in Scotland.

Organizing posterior fossa hematomas simulating developmental cysts on prenatal imaging: report of 3 cases

OBJECTIVE

We encountered 3 organizing tentorial hematomas simulating posterior fossa lesions such as Dandy-Walker, dermoid, or arachnoid cysts. We sought to correlate the clinical and pathologic features that allow distinction of developmental cysts from hematomas in the posterior fossa on imaging. METHODS. Prenatal sonograms in all fetuses and fetal magnetic resonance scans in 2 of the 3 were reviewed. One case proceeding to term had serial imaging up to age 11 months. Two cases had complete neuropathologic evaluation after termination. Maternal records were reviewed.

RESULTS

In each case, the ultrasonographic findings were reminiscent of a developmental cyst but with echogenic debris, a rim, or both. Magnetic resonance imaging suggested tentorial hemorrhage in 2, 1 also with falcine hemorrhage. Serial prenatal and postnatal imaging showed resolution in the surviving case. Pathologically, 2 fetuses had organizing tentorial hematomas causing brain displacement. Calcifications, white matter damage, germinal matrix hemorrhage, and brain stem necrosis were also present. One mother had von Willebrand disease.

CONCLUSIONS

Tentorial hematomas, with or without maternal coagulopathy, should be considered in the prenatal ultrasonographic diagnosis of cystlike posterior fossa abnormalities containing echogenic material. Fetal magnetic resonance imaging can suggest blood products. Hypoxic-ischemic brain damage may be concurrent; however, resolution of the hematoma, with no apparent neurologic sequelae, can occur.

Forming, changing, and acting on attitude toward affirmative action programs in employment: a theory-driven approach

A model of attitude toward affirmative action programs (AAPs) was applied in 4 studies involving 1,622 participants. In Study 1, attributes people tacitly associate with AAPs were identified by open-ended elicitation. Using those attributes, an instrument was developed and administered in Studies 2, 3, and 4. In those studies, a multiplicative composite of beliefs and evaluations about the AAP attributes predicted AAP attitude, consistent with M. Fishbein and I. Ajzen's (1975) theory of reasoned action. Demographic effects on AAP attitude were partially mediated by this composite. In Studies 3 and 4, an experimental manipulation of AAP information was successful in changing AAP attitude, but in a way that polarized existing demographic differences. Study 4 also showed that AAP attitude and subjective norm jointly and uniquely predicted intentions to perform AAP-related behaviors. Intentions predicted the actual behavior of mailing postcards to political representatives reflecting participants' support for AAPs.

Nf1;Trp53 mutant mice develop glioblastoma with evidence of strain-specific effects

Astrocytomas are the leading cause of brain cancer in humans. Because these tumours are highly infiltrative, current treatments that rely on targeting the tumour mass are often ineffective. A mouse model for astrocytoma would be a powerful tool for dissecting tumour progression and testing therapeutics. Mouse models of astrocytoma have been designed to express oncogenic proteins in astrocytes, but have had limited success due to low tumour penetrance or limited tumour progression. We present here a mouse model of astrocytomas involving mutation of two tumour-suppressor genes, Nf1 and Trp53. Humans with mutations in NF1 develop neurofibromatosis type I (NF1) and have increased risk of optic gliomas, astrocytomas and glioblastomas. The TP53 tumour suppressor is often mutated in a subset of astrocytomas that develop at a young age and progress slowly to glioblastoma (termed secondary glioblastomas, in contrast to primary glioblastomas that develop rapidly de novo). This mouse model shows a range of astrocytoma stages, from low-grade astrocytoma to glioblastoma multiforme, and may accurately model human secondary glioblastoma involving TP53 loss. This is the first reported mouse model of astrocytoma initiated by loss of tumour suppressors, rather than overexpression of transgenic oncogenes.

Mouse models of tumor development in neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a prevalent familial cancer syndrome resulting from germ line mutations in the NF1 tumor suppressor gene. Hallmark features of the disease are the development of benign peripheral nerve sheath tumors (neurofibromas), which can progress to malignancy. Unlike humans, mice that are heterozygous for a mutation in Nf1 do not develop neurofibromas. However, as described here, chimeric mice composed in part of Nf1-/- cells do, which demonstrates that loss of the wild-type Nf1 allele is rate-limiting in tumor formation. In addition, mice that carry linked germ line mutations in Nf1 and p53 develop malignant peripheral nerve sheath tumors (MPNSTs), which supports a cooperative and causal role for p53 mutations in MPNST development. These two mouse models provide the means to address fundamental aspects of disease development and to test therapeutic strategies.

APC-mediated proteolysis of Ase1 and the morphogenesis of the mitotic spindle

The molecular mechanisms that link cell-cycle controls to the mitotic apparatus are poorly understood. A component of the Saccharomyces cerevisiae spindle, Ase1, was observed to undergo cell cycle-specific degradation mediated by the cyclosome, or anaphase promoting complex (APC). Ase1 was degraded when cells exited from mitosis and entered G1. Inappropriate expression of stable Ase1 during G1 produced a spindle defect that is sensed by the spindle assembly checkpoint. In addition, loss of ASE1 function destabilized telophase spindles, and expression of a nondegradable Ase1 mutant delayed spindle disassembly. APC-mediated proteolysis therefore appears to regulate both spindle assembly and disassembly.

Mutation spectrum of the gene encoding the beta subunit of rod phosphodiesterase among patients with autosomal recessive retinitis pigmentosa

Mutations in the gene encoding the beta subunit of rod cGMP phosphodiesterase are known causes of photoreceptor degeneration in two animal models of retinitis pigmentosa, the rd (retinal degeneration) mouse and the Irish setter dog with rod/cone dysplasia. Here we report a screen of 92 unrelated patients with autosomal recessive retinitis pigmentosa for defects in the human homologue of this gene. We identified seven different mutations that cosegregate with the disease. They were found among four patients with each patient heterozygously carrying two mutations. All of these mutations are predicted to affect the putative catalytic domain, probably leading to a decrease in phosphodiesterase activity and an increase in cGMP levels within rod photoreceptors. Mutations in the gene encoding the beta subunit of rod phosphodiesterase are the most common identified cause of autosomal recessive retinitis pigmentosa, accounting for approximately 4% of cases in North America.

The intraoperative administration of ketorolac tromethamine in evaluating length of stay in a same day surgery unit

This study was performed to determine if intraoperative administration of ketorolac tromethamine, a nonsteroidal anti-inflammatory drug, could shorten the length of stay in the same day surgery unit of a 535-bed medical center. Fifty laparoscopic patients were included in this study. Laparoscopic patients were chosen because they demonstrated an increased incidence of postoperative pain that delayed hospital discharge. The study population was divided into a test and control group. To eliminate procedural variability, the 50 subjects were chosen from a single group practice. Length of stay was recorded on a data retrieval form. Reasons for delay in discharge were identified. Subjects who received ketorolac tromethamine were discharged an average of 30 minutes earlier than those who did not receive it (94 minutes versus 124 minutes, respectively). A t-test revealed this difference to be statistically significant (P < or = .004). Intraoperative administration of ketorolac tromethamine should be considered for laparoscopy patients in same day surgery units, because criteria for discharge, such as stable vital signs, minimal nausea or vomiting, minimal pain, and oriented x 3 with a stable gait, are met sooner.

Recessive mutations in the gene encoding the beta-subunit of rod phosphodiesterase in patients with retinitis pigmentosa

We have found four mutations in the human gene encoding the beta-subunit of rod cGMP phosphodiesterase (PDE beta) that cosegregate with autosomal recessive retinitis pigmentosa, a degenerative disease of photoreceptors. In one family two affected siblings both carry allelic nonsense mutations at codons 298 and 531. Affected individuals have abnormal rod and cone electroretinograms. PDE beta is the second member of the phototransduction cascade besides rhodopsin that is absent or altered as a cause of retinitis pigmentosa, suggesting that other members of this pathway may be defective in other forms of this disease.

Cognitive processes in self-report responses: tests of item context effects in work attitude measures

Much applied research relies on multi-item, self-report instruments. Drawing from recent cognitive theories, it was hypothesized that the items preceding a self-report item, its item context, can generate cognitive carryover and prompt context-consistent responses. These hypotheses were tested in 2 investigations: a field experiment involving 431 employees of a nonprofit urban hospital and a laboratory replication involving 245 undergraduate business students who held full- or part-time jobs. In both studies, evaluatively neutral items were placed in specially arranged blocks of uniformly positive, uniformly negative, or randomly mixed items on 3 modified Job Descriptive Index scales. Responses to the neutral items differed across the 3 forms, but scale-level psychometric properties remained unchanged. The implications of these item- and scale-level results for a variety of self-report measures in organizations are discussed.

TATA-dependent and TATA-independent transcription at the HIS4 gene of yeast

Two systems of transcription factors stimulate expression of the HIS4 gene of Saccharomyces cerevisiae. High-level transcription induced by amino-acid starvation is mediated by Gcn4(ref.1) and basal transcription is mediated jointly by the factors Bas1 and Bas2 (Pho2). We now show that wild-type Gcn4 requires the TATA element for correct messenger RNA start-site selection, but Gcn4 derivatives with deletions in the activation domain activate HIS4 transcription at the correct mRNA start site (I) in the absence of the TATA element. Gcn4 derivatives that activate TATA-independent transcription show low levels of activation. Similarly, we find that low levels of transcription by Bas1/Bas2 are TATA-independent, whereas high levels are TATA-dependent. These results show that the HIS4 TATA element is required for mRNA start-site selection only under conditions of high-level transcription.

A quantitative in vitro assay of polymorphonuclear leukocyte migration through human amnion membrane utilizing 111in-oxine

A modified amnion chemotaxis assay is described for measurement of polymorphonuclear leukocyte(s) (PMNL) migration (random and directed) into a viable membrane. The primary modifications are the use of 111In-oxine-labelled PMNL and replacement of the nitrocellulose 'trap' filter with a type I collagen sponge. The modifications resulted in four important benefits: the quantification of PMNL migration was simplified; reader subjectivity was eliminated; the information gained of the migration process was enhanced; and the assay time was decreased. The amnion chemotaxis assay with the modifications reported should provide the means of evaluating several aspects of the inflammatory response of PMNL.

Proteolytic and metastatic activities of clones derived from a methylcholanthrene-induced murine fibrosarcoma

Eighteen clones of a methylcholanthrene-induced murine fibrosarcoma (3AM) which were heterogeneous with respect to metastatic potentials and in vivo growth rates were examined for five different protease activities: acid protease (cathepsin D), BANA hydrolase (cathepsin B), neutral protease, collagenase, and plasminogen activator. Homogenates of the solid tumors produced by the clones were heterogeneous with respect to the activities of the proteases; these activities were in all cases (except plasminogen activator) higher than those obtained for normal muscle tissue. There was, however, no correlation between any of these protease activities and the metastatic potential or in vivo growth rates. The cathepsin B activity has also been evaluated on the cultured cells of the various clones. Results similar to that of the in vivo study were obtained. Analysis of the enzyme activity of the cell culture and of organ culture media, however, revealed no cathepsin B activity. It is concluded that the measurement of any one biochemical parameter such as proteolysis may not be sufficient to establish a correlation with the overall process of metastasis; a more precise dissection of the individual steps culminating in metastasis may provide a more fruitful approach to this problem.

Immune responsiveness against the human placenta. I. Generation of cellular and humoral activity in experimental animals

Using a new adaptation of the 51Cr release assay, it was found that plasma membrane vesicles from the human placental microvillous surface were not only capable of eliciting both cellular and humoral immunity in mice, but were also susceptible to lysis by these immune components. The production of cytotoxic cells and circulating antibody in immunized animals was only observed in the presence of Freund's complete adjuvant. The cells exhibited reactivity only against vesicles from a limited range of placentae, while the antibodies showed reactions against vesicles from a wider range of placentae. These vesicles were also susceptible to lysis by antisera raised against placental alkaline phosphatase but were resistant to attack by antibodies raised against normal human serum and HLA (multispecific) determinants and by a cytotoxic monoclonal antibody against human beta 2-microglobulin. The cellular cytotoxicity in the spleens of immunized animals could be abrogated if the cells were pretreated with AKR anti-C3H antiserum and complement. Further, in the spleens of in immunized animals, a population of cells was detected that exhibited a 'natural' cytotoxicity against several of the membrane preparations. This cytotoxicity was heat-labile, being abrogated if the cells were preincubated at 37 degrees for 4 hr before the assay, but was resistant to attack by the anti-Thy 1 antiserum. The results indicate that the use of 51Cr-labelled placental microvillous vesicles is a useful way of searching for anti-trophoblast immunity which may now be applied to the search for immune responses in pregnancy.

Immune responsiveness against the human placenta. II. Response with xenogeneic lymphocytes in culture

Human placental plasma membrane vesicles were cultured for up to 5 days in the presence of spleen cells from (BALB/c X C57BL/6By) F1 hybrid mice. The membrane preparations either inhibited the uptake of [3H]-thymidine ([3H]-TdR) by destroying the viability of the T-cell population or stimulated weak lymphocyte division which was primarily an expansion of the T-cell population. This differential effect was dependent on the membrane concentration in culture and the length of time the membrane preparation had been stored. Membrane preparations that inhibited [3H]-TdR uptake could be converted into stimulatory-type membranes by preincubating them at 37 degrees for several days. This conversion coincided with a change in status concerning membrane susceptibility to disruption by cytotoxic non-T-cells present in the spleen of unimmunized animals. The conversion from stimulating-type membrane into inhibitory-type was never observed. Throughout these cultures the generation of cell-mediated cytolysis could not be detected.