Coherent Optical Signatures of Electron Microbunching in Laser-Driven Plasma Accelerators

We report observations of coherent optical transition radiation interferometry (COTRI) patterns generated by microbunched ∼200-MeV electrons as they emerge from a laser-driven plasma accelerator. The divergence of the microbunched portion of electrons, deduced by comparison to a COTRI model, is ∼9× smaller than the ∼3  mrad ensemble beam divergence, while the radius of the microbunched beam, obtained from COTR images on the same shot, is <3  μm. The combined results show that the microbunched distribution has estimated transverse normalized emittance ∼0.4  mm mrad.

Developing personal sense of risk: a grounded theory in men with hypertension

BACKGROUND

For older men with hypertension living in rural areas, non-adherence to treatment is a common phenomenon. The experience on risk perception of individuals with their condition is recognized as playing a critical role in promoting treatment adherence. However, the experience on risk perception in a cohort of older men with hypertension seems unclear.

AIM

To develop a theory concerning risk perception experience in a cohort of older men with hypertension from a rural area of Thailand.

METHODS

A grounded theory approach was used. Semi-structured, face-to-face interviews with 29 hypertensive older men were conducted in Thailand using purposive and theoretical sampling methods. The grounded theory analytical method that included initial and focused coding, and constant comparison was used to analyse the data.

FINDINGS

'Developing a personal sense of risk' emerged as a core category, which incorporated the related four subprocesses: comparing healthcare provider information with stories of people with hypertension, comparing one's own situation with stories of people with hypertension, changing personal sense of risk and changing risk-related behaviour. Older men selected to focus on one particular outcome, using the selected outcome to monitor their risk.

CONCLUSION

This investigation provides a theory for healthcare providers to understand older men's perceptions of personal risk for complications of hypertension. A personal sense of risk influences risk-related behaviour change.

IMPLICATIONS FOR NURSING AND HEALTH POLICY

The findings can be used in assessing a personal sense of risk and promoting treatment adherence in older men with hypertension. Effective storytelling intervention, a standard tool for assessment personal sense of risk in older men with hypertension, should be developed. Hypertension care policy needs to be developed for individualized approaches.

Planning and decision making about the future care of older group home residents and transition to residential aged care

BACKGROUND

Planning for future care after the death of parental caregivers and adapting disability support systems to achieve the best possible quality of life for people with intellectual disability as they age have been important issues for more than two decades. This study examined perceptions held by family members, group home staff and organisational managers about the future of older residents and the decisions made that a move to residential aged care was necessary.

METHODS

Grounded Dimensional Analysis was used to guide data collection and analysis by an interdisciplinary research team. Three sets of interviews over a period of 18 months were conducted with a family member, house supervisor and the programme manager for each of seventeen older group home residents in Victoria. For the eight people for whom it was decided a move was necessary and the six who eventually moved focussed questions were asked about the decision-making process.

RESULTS

While plans for lifelong accommodation in a group home proved unfounded, key person succession plans were effective. However, decisions to move to a residential aged care facility where necessary were made in haste and seen as a fait accompli by involved family members.

CONCLUSIONS

Although family members take seriously their mandate to oversee well-being of their older relative, they have little knowledge about their rights or avenues to safeguard untimely or inappropriate decisions being made by professionals.

Transport of Neurohormones from the Corpora Cardiaca in Insects

Evidence from electron microscope studies of aphid and cockroach nerves, and from the bioassay of extracts of the aortal nerves of cockroaches indicates that some neurohormones are distributed from the corpora cardiaca along nerve axons to their target organs.

A survey of people with intellectual disabilities living in residential aged care facilities in Victoria

BACKGROUND

Australia's national ageing policy recognises that people ageing with intellectual disability (ID) require particular attention, yet there is no policy framework concerning this population. This study describes the distribution and characteristics of people with ID in residential aged care in Victoria, provides insights into the pathways they take into aged care, and gives some indications of how facilities adapt to their needs.

METHOD

A postal survey was sent to 826 residential aged care facilities in Victoria, seeking information from directors about their residents with ID. Facilities that responded were fairly representative of all facilities in Victoria.

FINDINGS

Residents with ID were younger, had entered at an earlier age and remained longer than other residents. Their reported dependency profile was similar to the general aged care population, although the incidence of dementia was lower. Primary areas of concern identified by providers were: inability to fit into the resident community, lack of participation in activities and lack of meaningful relationships.

CONCLUSION

This study provides a first glimpse into how older people with ID find their way into aged care and how others view their experiences once there. It suggests that further investigation is required into the accuracy of assessment undertaken prior to entry to more clearly understand whether residents with ID are inappropriately placed in residential aged as a result of a shortage of disability accommodation and inadequate resources to support aging in place for those in such accommodation.

Pre-operative intra-aortic balloon counterpulsation in stable patients with left main coronary disease

OBJECTIVE

To determine whether prophylactic, pre-operative, intra-aortic balloon counterpulsation (IABC) improves clinical outcome in stable patients with severe left main coronary artery disease.

METHODS

A post-hoc analysis of 457 prospectively tracked, non-randomized patients undergoing coronary artery bypass graft surgery (CABG) for left main stenoses 50% and multivessel coronary disease, but without any hemodynamic compromise or ongoing angina, was conducted. Patients with heart failure, shock, ongoing ischemia or previous CABG were excluded. In 287 patients, pre-operative IABC was not used (Group 1), while IABC was initiated in 170 patients for "prophylaxis" (Group 2).

RESULTS

Groups 1 and 2 were similar in age (67 +/- 10 years versus 67 +/- 11 years, respectively), sex (72% male versus 71% male, respectively), and body mass index (28 +/- 5.5 versus 27 +/- 5.1, respectively). However, more Group 1 patients had peripheral vascular disease (PVD) (25% versus 11%), but more Group 2 patients had diabetes (37% versus 29%), and a lower left ventricular ejection fraction. The unadjusted 30-day mortality was significantly higher in Group 1 [16 (5.6%) versus 2 (1.2%); p = 0.02]. Cardiopulmonary bypass time and post-operative length of stay did not differ between the two groups. After adjusting for PVD in the multivariate analysis, the p-value for the no IABP versus IABP comparison in the presence of PVD was 0.10, even though 0/18 patients with PVD and IABC died.

CONCLUSION

While unadjusted mortality appears lower with prophylactic IABC, confounding variables such as PVD mandate a larger, randomized clinical trial in order to establish the role of IABC in stable patients with left main disease.

Cutaneous basal cell carcinomas: distinct host factors are associated with the development of tumors on the trunk and on the head and neck

BACKGROUND

Patients with basal cell carcinoma (BCC) demonstrate marked variation in clinical phenotype, suggesting the presence of distinct subgroups. Patients with truncal lesions comprise an interesting subgroup, because, although the pathogenesis of these tumors is unclear, there is evidence to suggest that their development is mediated by different mechanisms than the mechanisms that mediate the development of BCC on other sites. The authors now speculate that some patients inherit a predisposition to truncal BCC and develop disproportionately more BCC on this site than other patients.

METHODS

The authors studied 100 patients who, at the time of initial presentation, had a truncal BCC lesion and 493 patients who had a lesion on the head and neck. The 493 patients with head and neck lesions included 36 patients who subsequently developed a truncal BCC and 457 patients who do not.

RESULTS

Initial presentation with a truncal tumor was associated with significantly more subsequent BCC lesions on this site compared with patients who presented initially with a head and neck lesion. The mean truncal tumor accrual after initial presentation in patients who presented with an initial truncal BCC lesion was 0.13 BCC lesions per year compared with 0.03 BCC lesions per year in patients who presented with an initial head and neck lesion (P < 0.001). Patients with truncal lesions were significantly younger at the time of initial presentation and developed more clusters of BCC lesions (2--10 new tumors at any presentation) compared with patients who did not develop tumors on the trunk.

CONCLUSIONS

These data suggest that the development of a truncal BCC is not random but, rather, is associated with a predisposition. In contrast, the accrual of nontruncal BCC lesions was similar in patients with and without initial truncal lesions, suggesting that different mechanisms determine the development of truncal BCC and nontruncal BCC.

Direct DNA binding by Brca1

The tumor suppressor Brca1 plays an important role in protecting mammalian cells against genomic instability, but little is known about its modes of action. In this work we demonstrate that recombinant human Brca1 protein binds strongly to DNA, an activity conferred by a domain in the center of the Brca1 polypeptide. As a result of this binding, Brca1 inhibits the nucleolytic activities of the Mre11/Rad50/Nbs1 complex, an enzyme implicated in numerous aspects of double-strand break repair. Brca1 displays a preference for branched DNA structures and forms protein-DNA complexes cooperatively between multiple DNA strands, but without DNA sequence specificity. This fundamental property of Brca1 may be an important part of its role in DNA repair and transcription.

Basal cell carcinomas: association of allelic variants with a high-risk subgroup of patients with the multiple presentation phenotype

Previous studies have shown that patients who present at first or a later presentation with a cluster of new basal cell carcinoma (BCC) comprise a subgroup, termed multiple presentation phenotype (MPP), that is at increased risk of developing further lesions. In this study, we examined the hypothesis that patients who develop multiple clusters are a high-risk subgroup. We found, in a total group of 926 BCC patients, 32 patients with 2-5 BCC clusters (multiple cluster MPP) and 113 cases with only one cluster (single cluster MPP). Multiple cluster MPP cases had mean of 11.3 BCC compared with 3.7 in single cluster MPP cases during similar follow-up. Ultraviolet (UV) exposure in these groups was similar. We determined whether the multiple cluster MPP was associated with characteristics associated with sensitivity to UV or glutathione S-transferase (GST) GSTT1, GSTM1, cytochrome P450 (CYP) CYP2D6, tumour necrosis factor (TNF)-alpha and vitamin D receptor (VDR) genotypes previously associated with BCC presentational phenotypes. While the frequencies of blue eyes and male gender were greater in multiple cluster than single cluster cases, these differences were not significant. In multiple cluster cases, mean age at first presentation with single tumours occurred earlier and the frequencies of CYP2D6 extensive metabolizer (EM) (94.4%) and GSTT1 null (41.2%) were significantly greater (P = 0.028 and P = 0.004) than in single cluster cases (67.1% and 14.3%, respectively). The odds ratios for the individual associations of CYP2D6 EM and GSTT1 null with the multiple cluster MPP were relatively larger; 15.5 and 7.39, respectively. TNF-alpha and VDR genotypes were not associated with multiple cluster MPP. We propose that the MPP is not the consequence of excessive UV exposure but rather reflects the presence of a distinct BCC subgroup which is defined by combinations of risk genes.

Basal cell carcinoma

BACKGROUND

Basal cell carcinoma (BCC) is characterized by marked interpatient variation in tumor accrual. The authors previously reported that presentation with a cluster of BCC is associated with an inherited predisposition to develop many additional lesions suggesting clustering is a critical event. A cluster is defined as the presence of two or more new, primary BCCs, at initial or later presentation.

METHODS

The authors recruited 927 cases and determined whether 1) clustering was an early or late event and 2) tumor accrual was altered after clustering.

RESULTS

In the cases, 669 patients developed only 1 lesion, 112 patients presented more than once but with single lesions (single presentation phenotype[SPP]-more), 94 cases had a cluster at first presentation (multiple presentation phenotype [MPP]-cluster initial), and 52 cases first presented with 1 lesion but later had a cluster (MPP-cluster later). The authors found that 1) clustering occurred relatively late. The mean ages at first presentation with 1 BCC of the SPP-more (61.5 years) and MPP-cluster later patients (60.4 years) were similar although presentations with clusters in the MPP-cluster initial (67.6 years, P = 0.0002) and -cluster later cases (68.1 years, P = 0.002) occurred significantly later. 2) Clustering was associated with increased accrual. Thus, 26 patients (MPP-cluster later/a) in the MPP-cluster later group had a additional BCC postcluster. Mean accrual post-cluster (1.99 BCC/year) in these cases was significantly increased (P = 0.0001) compared with precluster accrual (0.39 BCC/year).

CONCLUSIONS

The authors found that the formation of BCC clusters represents a critical event such that after a cluster presentation, tumor accrual is significantly increased. Cluster presentation is a relatively late event suggesting reduced effectiveness in immune surveillance.

Glutathione S-transferase GSTP1 and cyclin D1 genotypes: association with numbers of basal cell carcinomas in a patient subgroup at high-risk of multiple tumours

We previously described associations between basal cell carcinoma (BCC) numbers and allelic variants at loci that mediate host response to ultraviolet radiation (UV). These associations were largely exerted in cases with the multiple presentation phenotype (MPP). This phenotype describes patients who present at their first or a later presentation with a cluster of BCC (2-10 new BCC). Remaining BCC cases have the single presentation phenotype (SPP) and may develop more than one BCC but only have single new lesions at any presentation. We proposed that the MPP cases comprise a high-risk group as they suffer significantly more lesions than SPP cases. We are attempting to determine, in the total BCC case group and subgroups, how many genes influence BCC numbers and their relative importance. In this study, we assessed the influence of two further candidates, glutathione S-transferase GSTP1 and cyclin D1 (CCND1), on tumour numbers in a total group of 457 patients comprising MPP and SPP cases. The relative importance of these genes in comparison with occupational UV exposure and host response (skin type) was also considered. We found that the frequencies of GSTP1 genotypes based on the Ile105 and Val105-expressing alleles and CCND1 AA, AG, GG genotypes were similar in MPP and SPP cases and that there were no significant associations between GSTP1 or CCND1 genotypes and BCC numbers in the total or SPP groups. However, in the MPP cases, GSTP1 Val105/Val105 was associated with more tumours (P = 0.05, reference GSTP1 Ile105/Ile105). Inclusion of skin type and indoor/outdoor occupation in the negative binomial regression models did not alter the associations of these genotypes with tumour numbers. DNA from 258 cases was analysed to identify GSTP1*A (Ile105-Ala114), GSTP1*B (Val105-Ala114), GSTP1*C (Val105-Val114) and GSTP1*D (Ile105-Val114). In SPP cases, there was no association between BCC numbers and GSTP1 BB, though the association with GSTP1 BC approached significance (P = 0.09). In MPP cases, GSTP1 BC was associated with BCC numbers (P = 0.03). We also found that the interaction term, GSTP1 Val105/Val105 with CCND1 AA, was associated with BCC numbers in the total (P = 0.001) and MPP (P = 0.006) but not SPP (P = 0.68) groups. In a stepwise model including GSTP1 Val105/Val105, CCND1 AA and their interaction terms as well as GSTM1, GSTT1 and CYP2D6 genotypes, skin type 1 and gender, the combination of genotypes was the best predictor of BCC numbers. These data suggest that study of further genes involved in cell-cycle control and protection from oxidative stress will be useful, particularly in high-risk subgroups.

Treatment of ras-induced cancers by the F-actin-bundling drug MKT-077

A rhodacyanine dye called MKT-077 has shown a highly selective toxicity toward several distinct human malignant cell lines, including bladder carcinoma EJ, and has been subjected to clinical trials for cancer therapy. In the pancreatic carcinoma cell line CRL-1420, but not in normal African green monkey kidney cell line CV-1, it is selectively accumulated in mitochondria. However, both the specific oncogenes responsible for its selective toxicity toward cancer cells, and its target proteins in these cancer cells, still remain to be determined. This study was conducted using normal and ras-transformed NIH 3T3 fibroblasts to determine whether oncogenic ras mutants such as v-Ha-ras are responsible for the selective toxicity of MKT-077 and also to identify its targets, using its derivative called "compound 1" as a specific ligand. We have found that v-Ha-ras is responsible for the selective toxicity of MKT-077 in both in vitro and in vivo. Furthermore, we have identified and affinity purified at least two distinct proteins of 45 kD (p45) and 75 kD (p75), which bind MKT-077 in v-Ha-ras-transformed cells but not in parental normal cells. Microsequencing analysis has revealed that the p45 is a mixture of beta- and gamma-actin, whereas the p75 is HSC70, a constitutive member of the Hsp70 heat shock adenosine triphosphatase family, which inactivates the tumor suppressor p53. MKT-077 binds actin directly, bundles actin filaments by cross-linking, and blocks membrane ruffling. Like a few F-actin-bundling proteins such as HS1, alpha-actinin, and vinculin as well as F-actin cappers such as tensin and chaetoglobosin K (CK), the F-actin-bundling drug MKT-077 suppresses ras transformation by blocking membrane ruffling. These findings suggest that other selective F-actin-bundling/capping compounds are also potentially useful for the chemotherapy of ras-associated cancers.

Effect of ADP and ionic strength on the kinetic and motile properties of recombinant mouse myosin V

Mouse myosin V is a two-headed unconventional myosin with an extended neck that binds six calmodulins. Double-headed (heavy meromyosin-like) and single-headed (subfragment 1-like) fragments of mouse myosin V were expressed in Sf9 cells, and intact myosin V was purified from mouse brain. The actin-activated MgATPase of the tissue-purified myosin V, and its expressed fragments had a high V(max) and a low K(ATPase). Calcium regulated the MgATPase of intact myosin V but not of the fragments. Both the MgATPase activity and the in vitro motility were remarkably insensitive to ionic strength. Myosin V and its fragments translocated actin at very low myosin surface densities. ADP markedly inhibited the actin-activated MgATPase activity and the in vitro motility. ADP dissociated from myosin V subfragment 1 at a rate of about 11.5 s(-1) under conditions where the V(max) was 3.3 s(-1), indicating that, although not totally rate-limiting, ADP dissociation was close to the rate-limiting step. The high affinity for actin and the slow rate of ADP release helps the myosin head to remain attached to actin for a large fraction of each ATPase cycle and allows actin filaments to be moved by only a few myosin V molecules in vitro.

Association of NAD(P)H:quinone oxidoreductase (NQO1) null with numbers of basal cell carcinomas: use of a multivariate model to rank the relative importance of this polymorphism and those at other relevant loci

Glutathione S-transferase GSTM1 B and GSTT1 null, and cytochrome P450 CYP2D6 EM have been associated with cutaneous basal cell carcinoma (BCC) numbers, although their quantitative effects show that predisposition to many BCC is determined by an unknown number of further loci. We speculate that other loci that determine response to oxidative stress, such as NAD(H):quinone oxidoreductase (NQO1) are candidates. Accordingly, we assessed the association between NQO1 null and BCC numbers primarily to rank NQO1 null in a model that included genotypes already associated with BCC numbers. We found that only 14 out of 457 cases (3.1%) were NQO1 null. This frequency did not increase in cases with characteristics linked with BCC numbers including gender, skin type, a truncal lesion or more than one new BCC at any presentation (MPP). However, the mean number of BCC in NQO1*0 homozygotes was greater than in wild-type allele homozygotes and heterozygotes, although the difference was not quite significant (P = 0.06). These data reflect the link between NQO1 null and BCC numbers in the 42 MPP cases rather than the whole case group. We identified an interaction between NQO1 null and GSTT1 null that was associated with more BCC (P = 0.04), although only four cases had this combination. The relative influence of NQO1 null was studied in a multivariate model that included: (i) 241 patients in whom GSTM1 B, GSTT1 null and CYP2D6 EM genotype data were available, and (ii) 101 patients in whom these genotypes, as well as data on GSTM3, CYP1A1 and melanocyte-stimulating hormone receptor (MC1R) genotypes were available. NQO1 null (P = 0.001) and MC1R asp294/asp294 (P = 0.03) were linked with BCC numbers, and the association with CYP2D6 EM approached significance (P = 0.08). In a stepwise regression model only these genotypes were significantly associated with BCC numbers with NQO1 null being the most powerful predictor.

Cytochrome P450 CYP2D6 genotypes: association with hair colour, Breslow thickness and melanocyte stimulating hormone receptor alleles in patients with malignant melanoma

We previously identified associations between polymorphism in the cytochrome P450 CYP2D6 gene and outcome in several cancers. We have now examined the hypothesis that homozygosity for the mutant alleles, CYP2D6*4 and CYP2D6*3, is associated with susceptibility and outcome in malignant melanoma. Outcome was assessed by Breslow thickness. We first confirmed previous reports that these mutant alleles are associated with increased susceptibility to malignant melanoma. For example, the frequency of homozygosity for CYP2D6*4 was significantly greater (P = 0.006, chi-squared 1 d.f. = 7.4, odds ratio 2.2, 95% confidence interval 1.2, 3.9) in cases (9.1%) than in control individuals (4.3%). The frequency of homozygosity for the mutant alleles was next examined in the malignant melanoma cases grouped on the basis of characteristics associated with malignant melanoma risk. Homozygosity was significantly more common (P = 0.038) in cases with red/blonde hair than in those with brown/black hair. We found no associations between the CYP2D6 genotype and sex, skin type or eye colour. The possible association of CYP2D6 with outcome was assessed by comparing genotype frequencies in patients with tumours of Breslow thickness < 1.5 mm with those whose tumours were > or = 1.5 mm. In patients with red/blonde, but not brown or black hair, homozygosity for CYP2D6*4 was significantly associated with thicker lesions in a multivariate model (P = 0.036). We further examined the association of CYP2D6*4 homozygosity with red/blonde hair by classifying patients on the basis of homo- or heterozygosity for wild-type or val92met, asp294his or asp84glu melanocyte stimulating hormone receptor (MC1R) alleles. None of the nine patients with brown/black hair with the asp294his allele were homozygotes for CYP2D6*4. By contrast, in the patients with red/blonde hair, three of five cases with asp294his were homozygotes for the mutant CYP2D6 allele. The difference in the frequency of CYP2D6*4 homozygotes in the red/blonde cases with wild-type MC1R alleles compared with those with asp294his was significant (exact P = 0.029). No associations between val92his or asp84glu and CYP2D6 alleles were identified.

Flexibility of Acanthamoeba myosin rod minifilaments

Previous electric birefringence experiments have shown that the actin-activated Mg2+-ATPase activity of Acanthamoeba myosin II correlates with the ability of minifilaments to cycle between flexible and stiff conformations. The cooperative transition between conformations was shown to depend on Mg2+ concentration, on ATP binding, and on the state of phosphorylation of three serines in the C-terminal end of the heavy chains. Since the junction between the heavy meromyosin (HMM) and light meromyosin (LMM) regions is expected to disrupt the alpha-helical coiled-coil structure of the rod, this region was anticipated to be the flexible site. We have now cloned and expressed the wild-type rod (residues 849-1509 of the full-length heavy chain) and rods mutated within the junction in order to test this. The sedimentation and electric birefringence properties of minifilaments formed by rods and by native myosin II are strikingly similar. In particular, the Mg2+-dependent flexible-to-stiff transitions of native myosin II and wild-type rod minifilaments are virtually superimposable. Mutations within the junction between the HMM and LMM regions of the rod modulate the ability of Mg2+ to stabilize the stiff conformation. Less Mg2+ is required to induce minifilament stiffening if proline-1244 is replaced with alanine. Deleting the entire junction region (25 amino acids) results in a even greater decrease in the Mg2+ concentration necessary for the transition. The HMM-LMM junction does indeed seem to act as a Mg2+-dependent flexible hinge.

The melanocyte stimulating hormone receptor polymorphism: association of the V92M and A294H alleles with basal cell carcinoma

Allelic variants in the melanocyte stimulating hormone receptor (MC1R) gene are susceptibility/outcome candidates for cutaneous basal cell carcinoma (BCC). We identified the val92met (V92M) and asp294his (A294H) alleles in 311 cases and 190 controls. The cases included four homo- and 53 heterozygotes for V92M and 12 heterozygotes for A294H and two compound heterozygotes (V92M/A294H). Allele frequencies were similar in controls. In the cases, we found no association between the alleles and skin type though A294H was more common in those with red hair (4/19) than with other hair colours (6/163) (P = 0.012). V92M was not associated with BCC numbers. Cases with A294H had fewer BCC in comparison with those without the allele though the difference was not significant. After inclusion of red hair in the model, A294H was significantly associated with fewer tumours. While MCIR alleles are attractive candidates for BCC, the variants studied did not influence susceptibility. The association with outcome was relatively weak. The large number of MC1R alleles and their low frequency, make assessment of the importance of this gene in the pathogenesis of skin cancers difficult.

Presentation with multiple cutaneous basal cell carcinomas: association of glutathione S-transferase and cytochrome P450 genotypes with clinical phenotype

We previously reported associations between numbers of basal cell carcinomas (BCCs) and glutathione S-transferase (GSTM1 and GSTT1) and cytochrome P450 (CYP2D6) genotypes. Thus, although GSTM1 AB is protective, GSTM1 null, GSTT1 null, and CYP2D6 EM are associated with increased numbers of lesions. Here, we examine the hypothesis that these genotypes are associated with high-risk subgroups. The subgroup studied comprised 119 patients with more than one previously unidentified BCC at first or later presentations [multiple presentation phenotype (MPP)]. These patients were part of a group of 773 BCC patients that also included 567 patients with one BCC and 87 patients with only one lesion at each presentation [single presentation phenotype (SPP)] but who developed multiple BCCs. The number of tumors in the MPP was significantly greater than that in the SPP groups. In the MPP but not SPP patients, GSTM1 AB, GSTT1 null, and CYP2D6 EM were significantly associated with BCC numbers, suggesting that previously observed associations reflect the influence of these genes only in the MPP cases. There was no evidence that MPP patients had received more UV exposure. We also determined whether the increased numbers of BCC in the MPP cases reflects an association with the truncal tumor phenotype. The values of the rate ratios indicated that the MPP is a marker for the risk of many BCCs, although the combination of MPP and a truncal tumor is a higher-risk phenotype. The data demonstrate the heterogeneity in BCC patients, which reflects differences in genetic factors that determine skin response to UV.

Visualization of melanosome dynamics within wild-type and dilute melanocytes suggests a paradigm for myosin V function In vivo

Unlike wild-type mouse melanocytes, where melanosomes are concentrated in dendrites and dendritic tips, melanosomes in dilute (myosin Va-) melanocytes are concentrated in the cell center. Here we sought to define the role that myosin Va plays in melanosome transport and distribution. Actin filaments that comprise a cortical shell running the length of the dendrite were found to exhibit a random orientation, suggesting that myosin Va could drive the outward spreading of melanosomes by catalyzing random walks. In contrast to this mechanism, time lapse video microscopy revealed that melanosomes undergo rapid ( approximately 1.5 microm/s) microtubule-dependent movements to the periphery and back again. This bidirectional traffic occurs in both wild-type and dilute melanocytes, but it is more obvious in dilute melanocytes because the only melanosomes in their periphery are those undergoing this movement. While providing an efficient means to transport melanosomes to the periphery, this component does not by itself result in their net accumulation there. These observations, together with previous studies showing extensive colocalization of myosin Va and melanosomes in the actin-rich periphery, suggest a mechanism in which a myosin Va-dependent interaction of melanosomes with F-actin in the periphery prevents these organelles from returning on microtubules to the cell center, causing their distal accumulation. This "capture" model is supported by the demonstration that (a) expression of the myosin Va tail domain within wild-type cells creates a dilute-like phenotype via a process involving initial colocalization of tail domains with melanosomes in the periphery, followed by an approximately 120-min, microtubule-based redistribution of melanosomes to the cell center; (b) microtubule-dependent melanosome movement appears to be damped by myosin Va; (c) intermittent, microtubule-independent, approximately 0.14 microm/s melanosome movements are seen only in wild-type melanocytes; and (d) these movements do not drive obvious spreading of melanosomes over 90 min. We conclude that long-range, bidirectional, microtubule-dependent melanosome movements, coupled with actomyosin Va-dependent capture of melanosomes in the periphery, is the predominant mechanism responsible for the centrifugal transport and peripheral accumulation of melanosomes in mouse melanocytes. This mechanism represents an alternative to straightforward transport models when interpreting other myosin V mutant phenotypes.

Cytotoxicity of substituted alkyl-3,4-bis(4-methoxyphenyl)pyrrole-2-carboxylates in L1210 lymphoid leukemia cells

Two alkyl-3,4-bis(4-methoxyphenyl)pyrrole-2-carboxylates proved to be potent cytotoxic agents in the murine L1210 lymphoid leukemia screen. DNA synthesis was preferentially inhibited with the major target of the agents being de novo purine biosynthesis at the regulatory enzyme sites of PRPP-amido transferase and IMP dehydrogenase. Other enzymatic activities which were suppressed by the drugs were DNA polymerase alpha, RNA polymerases, ribonucleoside reductase and dihydrofolate reductase. The d[NTP] pools, nucleoside kinase and the pyrimidine pathway were not affected by the presence of drugs. The DNA molecule itself was not the target of the agents, i.e. no alkylation of nucleotide bases, intercalation between bases or cross-linking of DNA strands occurred. The agents did cause L1210 DNA fragmentation after 24 h incubation at 100 microM.

Susceptibility to melanoma: influence of skin type and polymorphism in the melanocyte stimulating hormone receptor gene

Allelic variation at the melanocyte stimulating hormone receptor (MC1R) gene has been linked with sun-sensitive skin types, suggesting it is a susceptibility candidate for melanoma. We determined the frequency of the val92met, asp294his, and asp84glu MC1R alleles in 190 Caucasian controls and 306 melanoma cases and studied their association with skin type and hair color. The percentage of controls with at least one val92met, asp294his, or asp84glu allele was 17.3%, 6.8%, and 3.5%, respectively. Individually, frequencies of the val92met, asp294his, or asp84glu alleles in the controls with skin types 3 and 4 were similar to those with skin types 1 and 2. Trend analysis, however, did identify an association (exact p = 0.048, two-sided test) between skin type and MC1R variants in the group comprising all controls with any one or more of these alleles. There was no association between MC1R alleles and hair color. Allele frequencies were not different in melanoma cases and controls. There were no associations between skin types and the proportion of cases with the asp294his or asp84glu alleles, though the association between skin type and the val92met allele approached significance (exact p = 0.09, two-sided test). Unexpectedly, in the group comprising all cases with one or more variant alleles, the proportion of subjects with variant alleles increased with skin types associated with tanning rather than burning, although trend analysis showed that this association did not quite reach statistical significance (exact p = 0.08, two-sided test). Asp84glu (but not val92met or asp294his) variant alleles were more common in subjects with blonde hair, although the relationship between the asp84glu allele and hair color did not achieve statistical significance (chi(2)3 = 6.16, exact p = 0.10). We interpret the data presented as indicating that polymorphism at MC1R does not appear a major determinant of skin type, at least in terms of these allelic variants. Furthermore, considered alone, these alleles are not susceptibility candidates for malignant melanoma.

Truncal site and detoxifying enzyme polymorphisms significantly reduce time to presentation of further primary cutaneous basal cell carcinoma

Basal cell carcinoma (BCC) is the commonest cancer in Caucasians. Its incidence is rising and many patients develop multiple primary tumours at separate sites. Factors determining time between first primary tumour presentation and the next new primary lesion are unclear. We used Cox's proportional hazards model to study, in 856 Caucasians, the influence of tumour site, individual characteristics and polymorphism in glutathione S-transferase (GSTM1, GSTT1) and cytochrome P450 (CYP2D6, CYP1A1) loci on time to next primary tumour presentation. More than one tumour at first presentation (P <0.0001, hazard ratio 2.72) and GSTT1 null (P = 0.028, hazard ratio 1.74) were associated with decreased time to next primary tumour presentation. Significant two-factor interactions, corrected for number of tumours at presentation, were identified between a truncal tumour at first presentation and each of male gender, GSTM1 null and CYP2D6 EM (P <0.003, hazard ratios 3.09-3.82). In each of these cases, all patients with the risk combination demonstrated further separate tumours within 5 years of first presentation. Thus, patients with a truncal tumour at first presentation, especially males and those presenting with more than one lesion have a significantly decreased time to presentation of further tumours and should receive more meticulous follow-up. Polymorphism in GSTM1 and CYP2D6 also influences the rate of new primary tumour accrual giving insights into the link between ultraviolet exposure and multiple tumour development.

Truncal tumor site is associated with high risk of multiple basal cell carcinoma and is influenced by glutathione S-transferase, GSTT1, and cytochrome P450, CYP1A1 genotypes, and their interaction

Basal cell carcinoma (BCC) places increasing burdens on clinicians; incidence is rising and patients may develop multiple primary tumors. Although UV exposure is critical, many patients develop tumors at less-exposed sites, such as the trunk, suggesting a genetic predisposition. We previously showed that polymorphism in loci encoding the detoxifying enzymes, glutathione S-transferase (GSTM1, GSTM3, GSTT1) and cytochrome P450 (CYP2D6, CYP1A1) influences susceptibility to BCC. We now describe a case-control approach in 345 patients with BCC that examines the role of these polymorphisms and patient characteristics (age, gender, skin type, hair color, eye color, smoking, occupation) in determining susceptibility to truncal tumors. GST and CYP genotypes were identified using polymerase chain reaction-based methods. Patients with one or more truncal tumors were significantly younger (p = 0.0170) than those with no truncal tumors. Male gender also appeared more common in the truncal tumor group, although this did not achieve significance (p = 0.0925). Patients whose first tumor was truncal had significantly more tumors (p = 0.0297). GSTT1 null (p = 0.0245, odds ratio 2.24) and CYP1A1 Ile/Ile (p = 0.0386, odds ratio 2.86) were associated with truncal site after correction for age and gender. The combination, GSTT1 null and CYP1A1 Ile/Ile, was particularly significant (p = 0.0059, odds ratio = 2.95). These effects were present after correction for tumor numbers. These data show first, patients with truncal tumors constitute a high-risk group for BCC, second, a significant genetic influence on BCC site, and third, a significant interaction between GSTT1 and CYP1A1 genotypes.

Myosin V associates with melanosomes in mouse melanocytes: evidence that myosin V is an organelle motor

Mice with mutations at the dilute locus exhibit a ‘washed out’ or ‘diluted’ coat color. The pigments that are responsible for the coloration of mammalian hair are produced by melanocytes within a specialized organelle, the melanosome. Each melanocyte is responsible for delivering melanosomes via its extensive dendritic arbor to numerous keratinocytes, which go on to form the pigmented hair shaft. In this study, we show by light immunofluorescence microscopy and immunoelectron microscopy that the myosin V isoform encoded by the dilute locus associates with melanosomes. This association, which was seen in all mouse melanocyte cell lines examined and with two independent myosin V antibodies, was evident not only within completely melanized cells, but also within cells undergoing the process of melanosome biogenesis, where coordinate changes in the distributions of a melanosome marker and myosin V were seen. To determine where myosin V, a known actin-based motor, might play a role in melanosome transport, we also examined the cellular distribution of F-actin. The only region where myosin V and F-actin were both concentrated was in dendrites and dendritic tips, which represent the sole destination for melanosomes and where they accumulate in cultured melanocytes. These results support the idea that myosin V serves as the motor for the outward movement of melanosomes within dendritic extensions, and, together with the available information regarding the phenotype of mutant melanocytes in vitro, argue that coat color dilution is caused by the absense of this myosin V-dependent melanosome transport system.

Multiple cutaneous basal cell carcinomas: glutathione S-transferase (GSTM1, GSTT1) and cytochrome P450 (CYP2D6, CYP1A1) polymorphisms influence tumour numbers and accrual

The genetic factors that mediate the pathogenesis of multiple primary cutaneous basal cell carcinomas (BCC) are largely unclear. Thus, some patients suffer many BCC (>30) and/or rapid accrual (number of tumours/year from first presentation) of further lesions. We have studied, in 827 English Caucasians, the influence of polymorphism in carcinogen-metabolizing enzymes on susceptibility to this cancer. Accordingly, we describe, first, a cross-sectional analysis of the influence of GSTM1, GSTT1, CYP2D6 and CYP1A1 genotypes on tumour numbers, and secondly, a longitudinal analysis, in 169 of these cases, of the effect of these genes on tumour accrual. We have confirmed the expected importance of age and number of lesions at presentation, and male gender and skin type as risk factors. Furthermore, the cross-sectional analysis showed CYP1A1 m1m1 (P = 0.004; rate ratio 1.242) and CYP2D6 EM (P < 0.001, rate ratio 1.266) are associated with increased numbers of BCC. The longitudinal study showed, after adjustment for age and tumour number at presentation, that GSTT1 null (P < 0.001, rate ratio 2.677) and CYP2D6 EM (P < 0.001, rate ratio 2.154) were significant determinants of accrual while CYP1A1 Ile/Ile was associated with slower accrual than the Ile/Val and Val/Val genotypes (P = 0.008, rate ratio 0.690). We believe these are the first genetic factors to be associated with tumour accrual. No significant interactions between genotypes were identified, though the combinations GSTM1 null/skin type 1 (P < 0.001, rate ratio 2.702), CYP2D6 EM/male gender (P = 0.049, rate ratio 1.279) and CYP2D6 EM/blue+green eyes (P = 0.046, rate ratio 1.388) influenced tumour numbers. Previous studies indicate the importance of effective repair of UV-damaged DNA in the pathogenesis of multiple BCC; indeed the influence of GSTM1 may result from its ability to utilize 5'-hydroxymethyluracil. However, the finding that CYP2D6 and CYP1A1 influence tumour numbers and accrual indicates detoxification of unknown molecules is important and supports the view that factors other than UV are important in the pathogenesis BCC.

Polymorphism at the glutathione S-transferase locus GSTM3: interactions with cytochrome P450 and glutathione S-transferase genotypes as risk factors for multiple cutaneous basal cell carcinoma

The influence of polymorphism in the glutathione S-transferase, GSTM3 gene on susceptibility to cutaneous basal cell carcinoma (BCC) has been investigated. We have reported previously two GSTM3 alleles, GSTM3*A and GSTM3*B, distinguished by a recognition motif for the YY1 transcription factor in GSTM3*B. In this study, immunohistochemistry was used to identify GSTM3 expression in the epidermis of skin samples from 11 controls and 9 patients with BCC. A PCR method was used to identify GSTM3*A and GSTM3*B and thereby the GSTM3 AA, GSTM3 AB, and GSTM3 BB genotypes in 300 controls and 286 Caucasians with 1-35 primary BCCs. Genotypes at GSTM1, GSTT1, and the cytochrome P450 CYP1A1 and CYP2D6 loci were also determined. Frequencies of GSTM3, GSTM1, GSTT1, CYP2D6, and CYP1A1 genotypes in the cases and controls were not different. Dividing the BCC cases into groups of 92 patients with 1 lesion and 194 patients with 2-35 lesions showed that the frequencies of GSTM3 BB (2.6%) and GSTM1 A/B (1.3%) in the group with 2-35 tumors were almost significantly lower than in the group with 1 lesion (7.6%, exact P = 0.0601, chi 2(1) = 3.390; 6.5%, exact P = 0.055, chi 2(1) = 4.946, respectively). Within the cases with 2-35 tumors, a Poisson regression model was used to identify genotypes, characteristics such as skin type, and interactions between genotypes and characteristics associated with increasing numbers of tumors. This showed, after correction for male gender and age, that GSTM3 AA was not associated with risk of increased numbers of tumors, although in combination with skin type 1, GSTM1 null, and CYP1A1 m1m1, the genotype did confer increased risk (P < 0.001, rate ratio, 2.058; P < 0.001, rate ratio, 1.606; P < 0.001, rate ratio, 1.470 respectively). The data suggest that, like other allelic GST, GSTM3 influences cancer risk. As GSTM3 AA was associated with increased tumor numbers, it appears that YY1 acts as an activator of the recognition motif in GSTM3*B.

Susceptibility to multiple cutaneous basal cell carcinomas: significant interactions between glutathione S-transferase GSTM1 genotypes, skin type and male gender

The factors that determine development of single and multiple primary cutaneous basal cell carcinomas (BCCs) are unclear. We describe a case-control study firstly, to examine the influence of allelism at the glutathione S-transferase GSTM1 and GSTT1 and cytochrome P450 CYP2D6 loci on susceptibility to these tumours and, secondly, to identify interactions between genotypes and relevant individual characteristics, such as skin type and gender. Frequency distributions for GSTM1 genotypes in cases and controls were not different, although the frequency of GSTM1 A/B was significantly lower (P = 0.048) in the multiple BCCs than in controls. We found no significant differences in the frequencies of GSTT1 and CYP2D6 genotypes in cases and controls. Interactions between genotypes were studied by comparing multinomial frequency distributions in mutually exclusive groups. These identified no differences between cases and controls for combinations of the putatively high risk GSTM1 null, GSTT1 null, CYP2D6 EM genotypes. Interactions between GSTM1 A/B and the CYP2D6 PM and GSTT1-positive genotypes were also not different. Frequency distributions of GSTM1 A/B with CYP2D6 EM in controls and multiple BCCs were significantly different (P = 0.033). The proportion of males in the multiple BCC group (61.3%) was greater than in controls (47.0%) and single BCC (52.2%), and the frequency of the combination GSTM1 null/male gender was significantly greater in patients with multiple tumours (P = 0.002). Frequency distributions of GSTM1 null/skin type 1 were also significantly different (P = 0.029) and the proportion of subjects who were GSTM1 null with skin type 1 was greater (P = 0.009) in the multiple BCC group. We examined the data for interactions between GSTM1 null/skin type 1/male gender by comparing frequency distributions of these factors in the single and multiple BCC groups. The distributions were almost significantly different (exact P = 0.051). No significant interactions between GSTT1 null or CYP2D6 EM and skin type 1 were identified. Comparisons of frequency distributions of smoking with the GSTM1 null, GSTT1 null and CYP2D6 EM genotypes identified no differences between patients with single and multiple tumours.

Identification of a novel Giardia lamblia cyst wall protein with leucine-rich repeats. Implications for secretory granule formation and protein assembly into the cyst wall

Giardia lamblia trophozoites, like most intestinal parasitic protozoa, undergo fundamental biological changes to survive outside the intestine of their mammalian host by differentiating into infective cysts. This complex process entails the coordinated production, processing, and transport of cyst wall constituents for assembly into a protective cyst wall. Yet, little is known about this process and the identity of cyst wall constituents. We previously identified a 26-kDa cyst wall protein, CWP1. In the present work, using monoclonal antibodies to cyst wall antigens, we cloned the gene that encodes a novel 39-kDa cyst wall protein, CWP2. Expression of CWP1 and CWP2 was induced during encystation with identical kinetics. Soon after synthesis, these two proteins combine to form a stable complex, which is concentrated within the encystation-specific secretory granules before incorporation into the cyst wall. Both proteins contain five tandem copies of a 24-residue leucine-rich repeat, a motif implicated in protein-protein interactions. Unlike CWP1, CWP2 has an extremely basic 121-residue COOH-terminal extension that might be involved in the sorting of these proteins to the secretory granules.

Isolation of N-acetyl-beta-hexosaminidase from Acanthamoeba castellanii

The lysosomal enzyme N-acetyl-beta-hexosaminidase (beta hex) has been purified from Acanthamoeba castellanii growth medium by a three step procedure. The enzyme was precipitated with ammonium sulfate, partially purified on a DE52 column and purified to homogeneity on an affinity column. The purified beta hex appeared to be a monomer with a molecular mass of 58 kDa and a pI of approximately 5.8. The enzyme activity in growth medium at RT was stable for several months. The purified beta hex was enzymatically deglycosylated and injected into two rabbits to make polyclonal antibodies. One antiserum was specific for beta hex, but the other stained many bands on immunoblots of whole cell preparations. Using fluorescently labelled secondary antibodies we have determined that both antisera stain digestive vacuoles in the Acanthamoeba cytoplasm, and do not stain the contractile vacuole. The multi-specific antiserum had high avidity for beta hex, but also stained the carbohydrate portion of other molecules. These other molecules may be lysosomal enzymes as well, since the activity of several other lysosomal enzymes was partially immunoprecipitable with the antiserum. We plan to use these antibodies to study traffic patterns among the variety of vacuolar structures in Acanthamoeba cytoplasm.

Developmentally regulated expression of a Giardia lamblia cyst wall protein gene

The protozoan Giardia lamblia is an obligate parasite of the mammalian small intestine. We studied the expression of a gene that encodes a protein component of the cyst wall, a complex structure assembled during the differentiation of trophozoites to cysts and which is critical to survival of the parasite outside its mammalian host. Transcripts from the cyst wall protein gene increase more than 100-fold during encystation, reaching a maximum between 5 and 24 hours after induction. Cyst wall protein expression also increases dramatically during encystation, and, prior to its incorporation into the nascent cyst wall, the protein is contained within the encystation-specific vesicles of encysting trophozoites. The sequence of the cloned gene predicts an acidic, leucine-rich polypeptide of M(r) 26,000 that contains 5.3 tandemly arranged copies of a degenerate 24-amino-acid repeat. A hydrophobic amino-terminal peptide probably serves as the initial signal that targets this protein to a secretory pathway involving vesicular localization during encystation and, ultimately, secretion to form the cyst wall.

Glutathione S-transferase GSTM1 phenotypes and protection against cutaneous tumours

Multiple allelism at loci encoding detoxicating enzymes is associated with cancer risk. We have studied genetic variation at the glutathione S-transferase GSTM1 locus to see whether phenotypes confer altered susceptibility to basal cell carcinoma (BCC), squamous cell carcinoma (SCC), malignant melanoma (MM), or multiple skin tumours of different histological types. The frequency of GSTM1 null in cases and controls (52%) was similar, except for patients with two or more tumours of different types (71%, p = 0.033). GSTM1 A/B was reduced in frequency (p < 0.05) in patients with single or multiple BCC. Thus GSTM1 A/B may be protective, and effectiveness of detoxication may be a factor determining susceptibility to skin cancer.

Dissecting the protein kinase C/MAP kinase signalling pathway of Saccharomyces cerevisiae

The PKC1 gene of the budding yeast Saccharomyces cerevisiae encodes a homolog of the alpha, beta, and gamma isoforms of mammalian PKC that is essential for cell growth. Loss of PKC1 function results in a cell lysis defect that is suppressed by osmotic stabilizing agents, suggesting a defect in cell wall integrity. In this study, we show that Pkc1p-depleted cells develop holes in their cell walls positioned at their bud tips, the site to which growth is focused during polarized cell growth. This result suggests that pkc1 mutants are deficient in the process of cell wall remodeling during growth. In further support of this model, cells bearing a pkc1 delta mutation, allowed to proliferate in the presence of osmotic stabilizing agents, possessed cell walls that were only 60% as thick as wild-type cell walls. This diminution in cell wall material affected both the beta-glucan layer and the mannoprotein layer. We have exploited the cell lysis defect of pkc1 mutants to identify genes that function within the same signalling pathway at points downstream of PKC1. These genes comprise a protein kinase cascade that culminates in the activation of the MAP kinase homolog Mpk1p. The proposed order of protein kinase function, based on genetic experiments, is Pkc1p to Bck1p to Mkk1/2p to Mpk1p. Consistent with the proposed model, Pkc1p selectively phosphorylates Bck1p in vitro and Mpk1p protein kinase activity requires a functional BCK1 gene.

Hydrolase compartmentalization limits rate of digestion in Acanthamoeba

The kinetics of lysosomal enzyme acquisition by newly formed phagosomes was studied by following the rate of digestion of radiolabeled yeast fed to Acanthamoeba. The distribution of hydrolases among phagosomes was assessed by electron microscopic acid phosphatase cytochemistry and by measurement of three glycosidases in isolated early and late phagosomes. The results show that compartmentalization of hydrolases limit the digestion of large phagocytic loads. The hydrolases appear to be sequestered into the early phagosomes and not to be distributed either by small vesicle transport or phagosome-phagosome fusion to those formed later. We infer from these results that newly internalized surface membrane in phagosomes is not rapidly randomized with internal pools, but is recycled to the surface as a function of the digestive process.

Developing Analytic Thinking Skills in Early Undergraduate Education

This article describes how a required prenursing health issues course was substantially restructured to increase the opportunities for students to develop analytic skills and for faculty to gain greater insight into how the students processed course content. Using writing-to-learn (WTL) strategies based on theories of adult cognitive development (Kinneavy, McCleary, & Nakadate, 1985; Kohlberg, 1978; Perry 1978), course readings, writing assignments, and exam questions were revised continuously over five semesters. This article describes the purpose and process of redesigning the course and some reflections on the outcome.

Phase II trial of trimetrexate for unresectable or metastatic non-small cell bronchogenic carcinoma

We treated 34 chemotherapy-naive patients with stage IIIb or IV non-small cell lung cancer with trimetrexate 150-200 mg/m2 intravenously over 30 minutes every two weeks. Six of 31 evaluable patients (19%) achieved a partial response. The major toxic effects from this regimen were myelosuppression, nausea/vomiting, and skin rash. We conclude that this well-tolerated schedule of trimetrexate has significant activity as a single agent against non-small cell lung cancer.

Nurse's aides in nursing homes: the relationship between organization and quality

This study examines the work of the nurse's aide through a combination of participant observation and in-depth interviews with 30 nurse's aides. Data were analyzed using the grounded theory method of constant comparative dimensional analysis. Findings suggest that strategies developed by individual nurse's aides to organize their work are important determinants of both the quality of care and worker turnover. Quality of care may be better explained by Litwak's theory about the difficult juxtaposition between primary and formal groups than by the nurse's aides' lack of knowledge.

The function of chitin synthases 2 and 3 in the Saccharomyces cerevisiae cell cycle

The morphology of three Saccharomyces cerevisiae strains, all lacking chitin synthase 1 (Chs1) and two of them deficient in either Chs3 (calR1 mutation) or Chs2 was observed by light and electron microscopy. Cells deficient in Chs2 showed clumpy growth and aberrant shape and size. Their septa were very thick; the primary septum was absent. Staining with WGA-gold complexes revealed a diffuse distribution of chitin in the septum, whereas chitin was normally located at the neck between mother cell and bud and in the wall of mother cells. Strains deficient in Chs3 exhibited minor abnormalities in budding pattern and shape. Their septa were thin and trilaminar. Staining for chitin revealed a thin line of the polysaccharide along the primary septum; no chitin was present elsewhere in the wall. Therefore, Chs2 is specific for primary septum formation, whereas Chs3 is responsible for chitin in the ring at bud emergence and in the cell wall. Chs3 is also required for chitin synthesized in the presence of alpha-pheromone or deposited in the cell wall of cdc mutants at nonpermissive temperature, and for chitosan in spore walls. Genetic evidence indicated that a mutant lacking all three chitin synthases was inviable; this was confirmed by constructing a triple mutant rescued by a plasmid carrying a CHS2 gene under control of a GAL1 promoter. Transfer of the mutant from galactose to glucose resulted in cell division arrest followed by cell death. We conclude that some chitin synthesis is essential for viability of yeast cells.

Sequence and structure of Clp P, the proteolytic component of the ATP-dependent Clp protease of Escherichia coli

The ATP-dependent Clp protease of Escherichia coli contains two dissimilar components: the Clp A regulatory polypeptide, with two ATP binding sites and intrinsic ATPase activity, and the Clp P subunit, which contains the proteolytic active site. The DNA sequence of the clpP gene predicts a protein of 207 amino acids (Mr 21,679), which is in close agreement with the size determined by sodium dodecyl sulfate-gel electrophoresis of purified Clp P. Clp P has a native Mr of approximately 240,000, and electron micrographs of the protein show superimposed disk-like structures with a central cavity, similar in appearance to purified proteasomes from eukaryotic cells. Clp P is synthesized with a 14-amino acid leader which is rapidly cleaved in vivo to yield the 193-amino acid protein which has activity in vitro. The clpP gene is at 10 min on the E. coli map, close to that for the ATP-dependent Lon protease of E. coli and far from the gene for clpA. Primer extension experiments indicate that transcription initiates immediately upstream of the coding region for Clp P, with a major transcription start at 120 bases in front of the start of translation. Insertion mutations in clpP have been isolated and transferred to the chromosome; strains devoid of Clp P are viable in the presence or absence of Lon protease. Mutations in clpP stabilize the same Clp A-beta-galactosidase fusion protein specifically stabilized by clpA mutations, providing the first genetic evidence that Clp A and Clp P act together in vivo.