A role for the Pkc1 MAP kinase pathway of Saccharomyces cerevisiae in bud emergence and identification of a putative upstream regulator

The protein kinase C of Saccharomyces cerevisiae, Pkc1, regulates a MAP kinase, Mpk1, whose activity is stimulated at the G1-S transition of the cell cycle and by perturbations to the cell surface, e.g. induced by heat shock. The activity of the Pkc1 pathway is partially dependent on Cdc28 activity. Swi4 activates transcription of many genes at the G1-S transition, including CLN1 and CLN2. We find that swi4 mutants are defective specifically in bud emergence. The growth and budding defects of swi4 mutants are suppressed by overexpression of PKC1. This suppression requires CLN1 and CLN2. Inhibition of the Pkc1 pathway exacerbates the growth and bud emergence defects of swi4 mutants. We find that another dose-dependent suppressor of swi4 mutants, the novel gene HCS77, encodes a putative integral membrane protein. Hcs77 may regulate the Pkc1 pathway; hcs77 mutants exhibit phenotypes like those of mpk1 mutants, are partially suppressed by overexpression of PKC1 and are defective in heat shock induction of Mpk1 activity. We propose that the Pkc1 pathway promotes bud emergence and organized surface growth and is activated by Cdc28-Cln1/Cln2 at the G1-S transition and by Hcs77 upon heat shock. Hcs77 may monitor the state of the cell surface.

Normal rectal mucosa. Should we biopsy?

BACKGROUND/AIMS

To determine the practice of routine rectal biopsy in the United Kingdom, and assess the diagnostic yield and complications of rectal biopsy in patients presenting with diarrhea.

MATERIALS AND METHODS

A postal questionnaire was sent to consultant members of the British Society of Gastroenterology. An audit of the diagnostic yield and complications resulting from routine biopsy of normal looking rectal mucosa in patients presenting with diarrhea was performed.

RESULTS

Ninety five (35%) consultants "nearly always" biopsy normal looking mucosa, with a further 56 (20%) taking a biopsy in more than fifty percent of cases. Fifty five (20%) almost never biopsy if the mucosa looks normal, with 68 (20%) taking a biopsy less than fifty percent of the time. Biopsies were taken from 50 patients referred with diarrhea whose rectal mucosa looked normal. Abnormal histology was reported in 11 (22%) cases. The rectal biopsy led to a positive diagnosis and change in management in 4 (8%) cases. The remaining biopsies showed minor inflammatory changes that were not considered clinically important. One significant complication occurred due to rectal biopsy.

CONCLUSIONS

Clinicians disagree on the value of routine rectal biopsy in the investigation of diarrhea. In patients presenting with diarrhea, the diagnostic yield from biopsy of normal looking rectal mucosa is low. Life threatening complications can occur and in unselected patients routine biopsy should not be performed.

A study of the combined effects of shelf ageing following irradiation in air and counterface roughness on the wear of UHMWPE

Damage to polished femoral heads in vivo can cause increased wear of acetabular cups. Oxidation and ageing after sterilisation by gamma irradiation in air, can also change the mechanical properties and wear resistance of ultra high molecular weight polyethylene (UHMWPE). This study investigated the combined effect of these changes in material properties on the wear of UHMWPE for different counterface roughnesses, representative of new femoral heads and those damaged in vivo. Wear rates were studied on a tri-pin-on-disc tribometer in a protein-containing solution. A comparison was made of the wear, using three different counterface roughnesses, of specimens that were manufactured from polyethylene acetabular cups of different shelf ages (3-120 months) after gamma irradiation in air but never implanted. These were compared to the wear of control specimens that were manufactured from cups that had not been sterilised. The wear surfaces were tested 1 mm below the initial articulating surface of the cup, the position of high degradation. The wear rate of UHMWPE which had been sterilised by gamma irradiation in air was shown to increase significantly with ageing time on the shelf for all counterface conditions. The wear rate of all materials increased markedly as the counterface roughness increased, but to different extents depending on the age of the material. The combined effect of ageing and increase in counterface roughness had a dramatic effect (as high as 2000 fold increase) on the wear rate. Both ageing of the polymer and damage to the femoral head have been cited as causing increased wear in vivo. The results of this study demonstrate that these variables can act synergistically to markedly effect UHMWPE wear rate.

Three-dimensional tongue surface shapes of English consonants and vowels

This paper presents three-dimensional tongue surfaces reconstructed from multiple coronal cross-sectional slices of the tongue. Surfaces were reconstructed for sustained vocalizations of the American English sounds [symbol: see text]. Electropalatography (EPG) data were also collected for the sounds to compare tongue surface shapes with tongue-palate contact patterns. The study was interested also in whether 3-D surface shapes of the tongue were different for consonants and vowels. Previous research and speculation had found that there were differences in production, acoustics, and linguistic usage between the two groups. The present study found that four classes of tongue shape were adequate to categorize all the sounds measured. These classes were front raising, complete groove, back raising, and two-point displacement. The first and third classes have been documented before in the midsagittal plane [cf. R. Harshman, P. Ladefoged, and L. Goldstein, J. Acoust. Soc. Am. 62, 693-707 (1976)]. The first three classes contained both vowels and consonants, the last only consonants. Electropalatographic patterns of the sounds indicated three categories of tongue-palate contact: bilateral, cross-sectional, and combination of the two. Vowels used only the first pattern, consonants used all three. The EPG data provided an observable distinction in contact pattern between consonants and vowels. The ultrasound tongue surface data did not. The conclusion was that the tongue actually has a limited repertoire of shapes and positions them against the palate in different ways for consonants versus vowels to create narrow channels, divert airflow, and produce sound.

Ultra-high molecular weight polyethylene wear debris generated in vivo and in laboratory tests; the influence of counterface roughness

The objective of this study was to investigate the effect of counterface roughness and lubricant on the morphology of ultra-high molecular weight polyethylene (UHMWPE) wear debris generated in laboratory wear tests, and to compare this with debris isolated from explanted tissue. Laboratory tests used UHMWPE pins sliding against stainless steel counterfaces. Both water and serum lubricants were used in conjunction with rough and smooth counterfaces. The lubricants and tissue from revision hip surgery were processed to digest the proteins and permit filtration. This involved denaturing the proteins with potassium hydroxide (KOH), sedimentation of any remaining proteins, and further digestion of these proteins with chromic acid. All fractions were then passed through a 0.2 micron membrane, and the debris examined using scanning electron microscopy. The laboratory studies showed that the major variable influencing debris morphology was counterface roughness. The rougher counterfaces produced larger numbers of smaller particles, with a size range extending below 1 micron. For smooth counterfaces there were fewer of these small particles, and evidence of larger platelets, greater than 10 microns in diameter. Analysis of the debris from explanted tissues showed a wide variation in the particle size distribution, ranging from below 1 micron up to several millimetres in size. Of major clinical significance in relation to osteolysis and loosening is roughening of the femoral components, which may lead to greater numbers of the sub-micron-sized particles.

Sigmoidoscopy and rectal biopsy: a survey of current UK practice

OBJECTIVE

To establish the pattern of practice of sigmoidoscopy and rectal biopsy in the UK, and to estimate the rate of occurrence of important complications.

DESIGN

Postal questionnaire enquiring about practice in the previous 2 years.

SUBJECTS

Consultant members of the British Society of Gastroenterology.

MAIN OUTCOME MEASURES

Bleeding or perforation following sigmoidoscopy and rectal biopsy.

RESULTS

Completed replies were received from 277 consultants, giving a response rate of 84%. Of the sigmoidoscopies performed, 71% were rigid and the remainder fibreoptic flexible sigmoidoscopy (FOS). The complication rate after sigmoidoscopy and rectal biopsy was 0.01%. Perforation was significantly more common in FOS than in rigid sigmoidoscopy (eight in 134,482 sigmoidoscopies versus five in 328,815, chi2 = 5.18, P < 0.05). The distance from anal margin and wall of biopsy did not influence perforation rates. Significant bleeding was similar with both techniques (eight in 134,482 versus 35 in 328,815, chi2 = 2.27, NS).

CONCLUSION

Rigid sigmoidoscopy is still more widely used than FOS in the UK, and is probably safer. Complications resulting from rectal biopsy are uncommon but perforation occurs more frequently with FOS than with rigid sigmoidoscopy. The site of biopsy appears to be unimportant.

Bisphosphonates and the treatment of bone disease in the elderly

Recognition of the way in which naturally occurring pyrophosphate affects bone metabolism has stimulated the development of a whole series of related compounds, the bisphosphonates. Although the precise mechanism of action of these compounds remains incompletely understood, they have been proven profoundly effective in clinical practice and already constitute a major advance in the therapy of conditions characterised by excessive bone resorption. Serious adverse effects are rare; however, mineralisation problems are a concern, particularly with etidronate. The reduction in bone turnover during prolonged treatment for osteoporosis is also a concern but as yet of uncertain clinical importance. The wide variation in potency of different bisphosphonates in inhibiting the resorption, mineralisation and turnover of bone will increasingly determine which agents are used in various clinical situations. Bisphosphonates are the treatment of choice in Paget's disease and hypercalcaemia of malignancy. They also appear to have potential to alter the course of metastatic bony disease, although the magnitude and clinical importance of any such effect remains unclear. Bisphosphonates show promise in the prevention and treatment of osteoporosis and increase bone mass in postmenopausal and steroid-induced osteoporosis. The effects of these drugs in other situations are less clear and the effects on fracture rates are not yet fully characterised. Optimal regimens have yet to be established but the long half-lives of these agents makes intermittent treatment a rational and convenient approach.

A new application for electropalatography: swallowing

Electropalatography (EPG) has been applied to linguistic research and speech pathology. This study evaluated whether EPG could provide useful information on swallow-related tongue action. Specifically, the investigation focused on the quantification of tongue-palate contact patterns for swallowing and on the effects of bolus volume and consistency. Five normal subjects were tested during swallows of 5 and 30 ml of water, 5 and 30 ml of gelatin, and saliva. By segmenting the EPG time-motion sequences into four stages (prepropulsion, propulsion, full contact, withdrawal) and compartmentalizing the palate into six bins (front, central, back, lateral, medial, midline), temporal and spatial characteristics of deglutitive tongue-palate contact were revealed. Significant differences (p < 0.01) were found in contact timing across bolus sizes and consistencies for the propulsion and full contact stages. Water was propelled faster than gelatin. and 30-ml gelatin faster than 5-ml gelatin. Dry swallows had a longer full contact stage than water. Contact patterns, though not statistically analyzed at this time, appeared to vary little as a function of bolus properties. Our findings suggest potential value in using EPG to investigate the timing and patterning of abnormal tongue movements associated with disordered swallowing.

Distribution of lead, copper and zinc in size-fractionated river bed sediment in two agricultural catchments of southern Ontario, Canada

Metal (Pb, Cu and Zn) partitioning in six separated sediment size fractions (<8, 8-12, 12-19, 19-31, 31-42, 42-60 microm) of river bed sediment have been analyzed by sequential extraction. The concentrations of some major elements (Si, Al, Ca, Mg, K, Na, Fe, Mn and P), and organic and inorganic C were determined to correlate the elemental composition of the sediment with metal speciation and grain size. Results show that Zn and Pb concentrations increase with decreasing grain size. For Big Creek and Big Otter Creek, respectively, the highest concentrations of Zn (326 and 230 mg kg(-1)) and Pb (158 and 67 mg kg(-1)) were found in the smallest (<8 microm) fraction, whereas the Cu levels (619 and 1281 mg kg(-1)) were most abundant in the second smallest (8-12 microm) fraction. The major accumulative phases for Cu, Zn and Pb were carbonates, Fe/Mn oxides and organic matter, but the relative importance of each phase varied for individual metals and grain sizes. The extraction data show increasing potential bioavailability of metals with decreasing grain size. Estimates of metal yields in the study catchments suggest that over 80% of the metal yield in sediment smaller than 63 microm is associated with solids smaller than 31 microm.

Experimental and theoretical study of the contact mechanics of five total knee joint replacements

The tibio-femoral contact area in five current popular total knee joint replacements has been measured using pressure-sensitive film under a normal load of 2.5 kN and at several angles of flexion. The corresponding maximum contact pressure has been estimated from the measured contact areas and found to exceed the point at which plastic deformation is expected in the ultra-high molecular weight polyethylene (UHMWPE) component, particularly at flexion angles near 90 degrees. The measured contact area and the estimated maximum contact stress have been found to be similar in magnitude for all of the five knee joint replacements tested. A significant difference, however, has been found in maximum contact pressure predicted from linear elasticity analysis for the different knee joints. This indicates that varying amounts of plastic deformation occurred in the polyethylene component in the different knee designs. It is important to know the extent of damage as knees with large amounts of plastic deformation are more likely to suffer low cycle fatigue failure. It is therefore concluded that the measurement of contact areas alone can be misleading in the design of and deformation in total knee joint replacements. It is important to modify geometries to reduce the maximum contact stress as predicted from the linear elasticity analysis, to below the linear elastic limit of the plastic component.

A head and transducer support system for making ultrasound images of tongue/jaw movement

A head and transducer support system (HATS) was developed for use in ultrasound imaging of tongue movement. Ultrasound is an imaging technique that captures tongue motion during speech and thus has great appeal as a tool for speech research. However, because ultrasound systems are designed for clinical use, the transducer is hand-held and it is almost impossible to hold it completely steady under the chin when collecting tongue data. A system was needed to fix the head and support the transducer under the chin in a known position without disturbing speech. The HATS system was designed, constructed, and modified to provide valid, reliable tongue movement data by (1) immobilizing the head and (2) positioning the ultrasound transducer in a known relationship to the head.

Preliminary study of the effect of aging following irradiation on the wear of ultrahigh-molecular-weight polyethylene

Several studies have indicated that degradation of ultrahigh-molecular-weight polyethylene following gamma irradiation in air adversely affects the mechanical properties of the material; however, it is not known how this subsequently affects its wear rate. Wear studies have therefore been performed on three groups of ultrahigh-molecular-weight polyethylene; unirradiated material, recently irradiated material (aged for 2 months), and aged irradiated material (aged for 5 years). The aging took place in sterile packaging on the shelf. The wear studies were carried out on a tri-pin-on-disk wear tester, with a pin from each type of material being studied in each test. In each test the wear rate of the nonirradiated material was slightly lower than the 2-month-aged, irradiated material. The 5-year-aged, irradiated material had the highest wear rate, and this was significantly greater than that of the unirradiated material (P < .05).

Neoadjuvant chemotherapy and orthotopic liver transplantation for hepatocellular carcinoma

From 1987 to 1992, 27 patients with unresectable hepatocellular carcinoma were included in a neoadjuvant chemotherapy study prior to undergoing orthotopic liver transplantation. The results are reported. Other studies of patients involving orthotopic liver transplantation are reviewed.