Alzheimer's disease: correlation of the suppression of beta-amyloid peptide secretion from cultured cells with inhibition of the chymotrypsin-like activity of the proteasome

Peptide aldehyde inhibitors of the chymotrypsin-like activity of the proteasome (CLIP) such as N-acetyl-Leu-Leu-Nle-H (or ALLN) have been shown previously to inhibit the secretion of beta-amyloid peptide (A beta) from cells. To evaluate more fully the role of the proteasome in this process, we have tested the effects on A beta formation of a much wider range of peptide-based inhibitors of CLIP than published previously. The inhibitors tested included several peptide boronates, some of which proved to be the most potent peptide-based inhibitors of beta-amyloid production reported so far. We found that the ability of the peptide aldehyde and boronate inhibitors to suppress A beta formation from cells correlated extremely well with their potency as CLIP inhibitors. Thus, we conclude that the proteasome may be involved either directly or indirectly in A beta formation.

pH and concentration of bilirubin in feeding tube aspirates as predictors of tube placement

BACKGROUND

Currently available bedside methods for determining feeding tube placement often provide inconclusive results. Therefore, additional data are needed to assist nurses in making decisions regarding tube location.

OBJECTIVES

To describe the usual concentration of bilirubin in aspirates from newly inserted feeding tubes and to determine the extent to which these measures can contribute to pH alone in correctly predicting feeding tube location.

METHODS

Gastrointestinal samples for concurrent pH and bilirubin testing were obtained from adult, acutely ill patients with newly inserted small-bore feeding tubes (nasogastric, n = 209; nasointestinal, n = 228) within 5 minutes of radiographs taken to determine tube location. Respiratory samples were tested (tracheobronchial, n = 126; pleural, n = 24). pH was measured with a pH meter, and bilirubin content was assayed spectrophotometrically. Results from the pH and bilirubin tests were compared with tube location as determined by radiography.

RESULTS

Mean pH levels in the lung (7.73) and intestine (7.35) were significantly higher than the mean pH level in the stomach (3.90; p < .001 for each comparison). Mean bilirubin levels in the lung (.08 mg/dl) and stomach (1.28 mg/dl) were significantly lower than the mean bilirubin level in the intestine (12.73 mg/dl; p < .001 for each). By visually inspecting distribution overlap and mean differences by tube site, results were dichotomized so that a combination of pH and bilirubin values could be used to develop a predictive algorithm. A pH of >5 and a bilirubin value of <5 mg/dl correctly identified all respiratory cases, whereas a pH >5 coupled with a bilirubin level of > or =5 mg/dl correctly identified three fourths of the intestinal cases. A pH of < or =5 coupled with a bilirubin value of <5 correctly identified more than two thirds of the gastric cases.

CONCLUSIONS

Preliminary laboratory-based data indicate that appropriate use of the proposed algorithm could significantly reduce the number of x-rays needed to exclude respiratory placement and to distinguish between gastric and intestinal placement.

Adventitia-dependent relaxations of canine basilar arteries transduced with recombinant eNOS gene

We recently reported that expression of recombinant endothelial nitric oxide (NO) synthase (eNOS) gene in adventitial fibroblasts restores NO formation in canine cerebral arteries without endothelium in response to bradykinin ex vivo and in vivo. The present study was designed to further characterize the stimuli that can activate recombinant eNOS enzyme expressed in the adventitia of cerebral arteries. To stimulate recombinant eNOS, we used serum (0. 1-10%), substance P (10(-11)-3 x 10(-9) M), and ANG II (10(-7)-10(-5) M) because they increase intracellular calcium concentrations in fibroblasts. Endothelium-denuded segments of canine basilar arteries were incubated with an adenoviral vector encoding beta-galactosidase gene or eNOS gene for 30 min at 37 degrees C. After 24 h, vasomotor activity and cGMP formation in eNOS or beta-galactosidase arteries were examined by isometric force recording and by radioimmunoassay, respectively. In control arteries and beta-galactosidase gene-transduced arteries, serum caused concentration-dependent contractions, whereas in recombinant eNOS gene-transduced arteries, serum produced concentration-dependent relaxations. Substance P and ANG II had no effect on vascular tone in control and beta-galactosidase arteries but caused concentration-dependent relaxations as well as a significant increase in cGMP levels in eNOS arteries. These relaxations were blocked by the NOS inhibitor NG-nitro-L-arginine methyl ester. Chemical treatment or mechanical inactivation of adventitial function significantly attenuated substance P-induced relaxations and ANG II-induced relaxations. These findings demonstrate that serum, substance P, and ANG II cause adventitia-dependent relaxations in cerebral arteries expressing the recombinant eNOS gene. This mechanism of vasodilatation may have beneficial effects in the prevention and treatment of vascular disorders characterized by the diminished bioavailability of NO, such as cerebral vasospasm.

Multiple signals mediate proliferation, differentiation, and survival from the granulocyte colony-stimulating factor receptor in myeloid 32D cells

Granulocyte colony-stimulating factor (G-CSF) regulates neutrophil production through activation of its cognate receptor, the G-CSF-R. Previous studies with deletion mutants have shown that the membrane-proximal cytoplasmic domain of the receptor is sufficient for mitogenic signaling, whereas the membrane-distal domain is required for differentiation signaling. However, the function of the four cytoplasmic tyrosines of the G-CSF-R in the control of proliferation, differentiation, and survival has remained unclear. Here we investigated the role of these tyrosines by expressing a tyrosine "null" mutant and single tyrosine "add back" mutants in maturation-competent myeloid 32D cells. Clones expressing the null mutant showed only minimal proliferation and differentiation, with survival also reduced at low G-CSF concentrations. Analysis of clones expressing the add-back mutants revealed that multiple tyrosines contribute to proliferation, differentiation, and survival signals from the G-CSF-R. Analysis of signaling pathways downstream of these tyrosines suggested a positive role for STAT3 activation in both differentiation and survival signaling, whereas SHP-2, Grb2 and Shc appear important for proliferation signaling. In addition, we show that a tyrosine-independent "differentiation domain" in the membrane-distal region of the G-CSF-R appears necessary but not sufficient for mediating neutrophilic differentiation in these cells.

Pig kidney legumain: an asparaginyl endopeptidase with restricted specificity

Legumain was recently discovered as a lysosomal endopeptidase in mammals [Chen, Dando, Rawlings, Brown, Young, Stevens, Hewitt, Watts and Barrett (1997) J. Biol. Chem. 272, 8090-8098], having been known previously only from plants and invertebrates. It has been shown to play a key role in processing of the C fragment of tetanus toxin for presentation by the MHC class-II system [Manoury, Hewitt, Morrice, Dando, Barrett and Watts (1998) Nature (London) 396, 695-699]. We examine here the specificity of the enzyme from pig kidney by use of protein, oligopeptide and synthetic arylamide substrates, all determinations being made at pH 5.8. In proteins, only about one in ten of the asparaginyl bonds were hydrolysed, and these were mostly predicted to be located at turns on the protein surface. Bonds that were not cleaved in tetanus toxin were cleaved when presented in oligopeptides, sometimes faster than an equivalent oligopeptide based on a bond that was cleaved in the protein. Legumain cleaved the bait region of rat alpha1-macroglobulin and was 'trapped' by the macroglobulin, as most other endopeptidases are, but did not interact with human alpha2-macroglobulin, which contains no asparagine residue in its bait region. Glycosylation of asparagine totally prevented hydrolysis by legumain. Specificity for arylamide substrates was evaluated with reference to benzyloxycarbonyl-Ala-Ala-Asn-aminomethylcoumarin, and the preference for the P3-position amino acid was Ala>Tyr(tertiary butyl)>Val>Pro>Phe=Tyr>Leu=Gly. There was no hydrolysis of substrate analogues containing mono- or di-N-methylasparagines, l-2-amino-3-ureidopropionic acid or citrulline in the P1 position. We conclude that mammalian legumain appears to be totally restricted to the hydrolysis of asparaginyl bonds in substrates of all kinds. There seem to be no strong preferences for particular amino acids in other subsites, and yet there are still unidentified factors that prevent hydrolysis of many asparaginyl bonds in proteins.

Phase I and pharmacologic study of the tyrosine kinase inhibitor SU101 in patients with advanced solid tumors

PURPOSE

To evaluate the clinical feasibility and pharmacologic behavior of the platelet-derived growth factor (PDGF) tyrosine kinase inhibitor SU101, administered on a prolonged, intermittent dosing schedule to patients with advanced solid malignancies.

PATIENTS AND METHODS

Twenty-six patients were treated with SU101 doses ranging from 15 to 443 mg/m(2) as a 24-hour continuous intravenous (IV) infusion weekly for 4 weeks, repeated every 6 weeks. Pharmacokinetic studies were performed to characterize the disposition of SU101 and its major active metabolite, SU0020. Immunohistochemical staining of PDGF-alpha and -beta receptors was performed on malignant tumor specimens obtained at diagnosis.

RESULTS

Twenty-six patients were treated with 52 courses (187 infusions) of SU101. The most common toxicities were mild to moderate nausea, vomiting, and fever. Two patients experienced one episode each of grade 3 neutropenia at the 333 and 443 mg/m(2) dose levels. Dose escalation of SU101 above 443 mg/m(2)/wk was precluded by the total volume of infusate required, 2.5 to 3.0 L. Individual plasma SU101 and SU0020 concentrations were described by a one-compartment model that incorporates both first-order formation and elimination of SU0020. SU101 was rapidly converted to SU0020, which exhibited a long elimination half-life averaging 19 +/- 12 days. At the 443 mg/m(2)/wk dose level, trough plasma SU0020 concentrations during weeks 2 and 4 ranged from 54 to 522 micromol/L. Immunohistochemical studies revealed PDGF-alpha and -beta receptor staining in the majority (15 of 19) of malignant neoplasms.

CONCLUSION

SU101 was well tolerated as a 24-hour continuous IV infusion at doses of up to 443 mg/m(2)/wk for 4 consecutive weeks every 6 weeks. Although further dose escalation was precluded by infusate volume constraints, this SU101 dose schedule resulted in the achievement and maintenance of substantial plasma concentrations of the major metabolite, SU0020, for the entire treatment period.

Liver disease in children with cystic fibrosis: US-biochemical comparison in 195 patients

PURPOSE

To determine if abnormal liver architecture at ultrasonography (US) is related to abnormal function in children with cystic fibrosis (CF).

MATERIALS AND METHODS

For 1 year, all 195 children (112 boys, 83 girls; mean age, 8.5 years) attending a CF clinic underwent abdominal US and a standard set of liver function tests. Aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyltransferase levels were analyzed. US signs were interpreted as follows: hypoechogenicity with prominent portal tracks as edema, hyperechogenicity as steatosis, and increased attenuation and nodules within or at the edge of the liver as cirrhosis. Signs of portal hypertension also were sought. US signs were compared with liver function test results.

RESULTS

Liver sonograms were abnormal in 38 children (19%); of these, 24 (63%) had abnormal test results. The 157 children with normal liver architecture had a much lower prevalence of biochemical abnormality (33 patients [21%]; P < or = .001). All eight children with signs of portal hypertension had abnormal test results. Fourteen (82%) of 17 children with signs of cirrhosis had abnormal liver function. Eight (57%) of 14 patients with signs of steatosis had abnormal function. Diffuse hypoechogenicity of the liver with prominent portal tracks in 16 patients was associated with abnormal function in only five patients.

CONCLUSION

The relation between abnormal liver architecture at US and results of three liver function tests in children with CF was significant. The most specific US abnormalities related to abnormal function are signs suggestive of portal hypertension and cirrhosis.

Embryonic stem cells can be used to construct hybrid cell lines containing a single, selectable murine chromosome

Microcell-mediated chromosome transfer is a useful technique for the study of gene function, gene regulation, gene mapping, and functional cloning in mammalian cells. Complete panels of donor cell lines, each containing a different human chromosome, have been developed. These donor cell lines contain a single human chromosome marked with a dominant selectable gene in a rodent cell background. However, a similar panel does not exist for murine chromosomes. To produce mouse monochromosomal donor hybrids, we have utilized embryonic stem (ES) cells with targeted gene disruptions of known chromosomal location as starting material. ES cells with mutations in aprt, fyn, and myc were utilized to generate monochromosomal hybrids with neomycin phosphotransferase-marked murine Chr 8, 10, or 15 respectively in a hamster or rat background. This same methodology can be used to generate a complete panel of marked mouse chromosomes for somatic cell genetic experimentaion.

Analysis of radiographic measurements as prognostic indicators of treatment success in patients with developmental dysplasia of the hip

Measurements were taken and statistically analyzed from the initial radiographs, the 1-year follow-up radiographs, and the most recent radiographs of 81 patients (103 hips) to determine which measurements could predict the success of treatment. The average follow-up was 49 months (range, 12-139 months), and the average age of the patients at the last follow-up was 65 months (range, 15-190 months). Analysis of the data showed that the measurement with statistically significant predictive value was the Tonnis grade of dislocation determined from the initial radiograph. A single unit increase in the Tonnis grade was associated with a doubling of the odds of failure in patients treated with a Pavlik harness (P < 0.04, odds ratio = 2.2) or a closed reduction (odds ratio = 2.0).

Engagement in breast cancer screening behaviors

PURPOSE/OBJECTIVES

To distinguish women who engaged in recommended breast cancer screening from those who did not.

DESIGN

Descriptive design, with quantitative measures.

SETTING

Urban, county hospital serving many low-income clients.

SAMPLE

119 women, age 51 to 80, who had not had mammograms in the last 13 months.

METHOD

Nurse-conducted telephone interviews that incorporated a modified Profile of Mood States, Attitudes Towards Mammography Scale, Barriers Scale, and reports of engagement in mammography and clinical breast exam (CBE) in the last 13 months and breast self-exam (BSE) practice in the last 3 months.

MAIN RESEARCH VARIABLES

Affect, beliefs, facilitators, and knowledge regarding screening; engagement in mammography, CBE, and BSE.

FINDINGS

In discriminant analyses of engagement in mammography and CBE, affect, barriers, prior history of breast problems, and race were significant variables. In discriminant analysis of BSE, history of breast biopsy, family history of breast cancer, beliefs about screening and cancer, prior instruction in BSE, and being single were significant variables.

CONCLUSIONS

Variables that discriminated between use and non-use of professional screening were different from those that discriminated between use and non-use of BSE.

IMPLICATIONS FOR NURSING PRACTICE

Nurses can promote professional breast screening by addressing women's negative affect, prior breast concerns, and barriers, especially among Caucasians. Nurses can promote monthly BSE by supporting realistic beliefs about screening and cancer as well as by demonstrating BSE, especially among married women.

Distribution of rest days in 12 hour shift systems: impacts on health, wellbeing, and on shift alertness

OBJECTIVES

To investigate of the effects of distribution of rest days in 12 hour shift systems. Although several studies have examined the effects of compressing work schedules by comparing 8 and 12 hour shift systems, there is little published research examining the various forms of 12 hour shift system.

METHODS

An abridged version of the standard shiftwork index which included retrospective alertness ratings was completed by a large sample of industrial shiftworkers. The respondents worked 12 hour shift systems that either did or did not incorporate breaks of > 24 hours between the blocks of day and night shifts. For the purposes of the analysis, each of these two groups were further subdivided into those who started their morning shift at 0600 and those who started at 0700.

RESULTS

Systems which incorporated rest days between the day and night shifts were associated with slightly higher levels of on shift alertness, slightly lower levels of chronic fatigue, along with longer sleep durations when working night shifts and between rest days. Early changeovers were associated with shorter night sleeps between successive day shifts, but longer and less disturbed day sleeps between night shifts. These effects of changeover time were broadly in agreement with previous research findings.

CONCLUSIONS

The distribution of rest days in 12 hour shift systems had only limited effects on the outcome measures, although the few modest differences that were found favoured systems which incorporated rest days between the day and night shifts. It is conceded that the design of the study may have obscured some subtle differences between the shift systems. Nevertheless, it is concluded that the impact of distribution of rest days seems to be minor relative to previously found effects of other features of shift systems--for example, shift duration.

Cross-sectional and longitudinal analysis of age-associated changes in body composition of male Brown Norway rats: association of serum leptin levels with peripheral adiposity

Aging-associated alterations in body composition are accompanied by changes in the endocrine system. We evaluated, in male Brown Norway rats, the effects of aging on body composition and the association with serum levels of leptin, insulin, and testosterone. Body composition was assessed cross-sectionally in male rats (3, 8, 17, and 29 months) by a combination of dual energy x-ray absorptiometry (DEXA) and dissection of specific muscles and adipose depots. Longitudinal changes in body composition were quantified by DEXA before and after 3 months of ad-libitum feeding. Body weight, lean mass, absolute and percentage fat increased with age, whereas percentage of lean mass decreased. Leptin and insulin levels increased with age in proportion to adiposity; the increase in leptin with age was related to increased total and peripheral, but not visceral, fat. Testosterone decreased with age, and was associated with decreased lean and skeletal muscle mass. These findings suggest that alterations in body composition with age may be due to decreased trophic and increased lipogenic hormones. Relative to other rodent models, Brown Norway rats undergo shifts in body composition and in the hormonal milieu that are consistent with changes seen in aging humans.

Progressive juvenile-onset punctate cataracts caused by mutation of the gammaD-crystallin gene

Cataracts are a significant public health problem. Here, we describe the genetic alteration responsible for a progressive form of cataract, segregating as an autosomal dominant trait in a three-generation pedigree. Unlike most autosomal dominant cataracts, these are not clinically apparent at birth but are initially observed in the first year or two of life. The opacification evolves relatively slowly, generally necessitating removal of the lens in childhood or early adolescence. A genome-wide search in our kindred revealed linkage at 2q33-35 where the gamma-crystallin gene cluster resides. A single base alteration resulting in an Arg- 14 --> Cys (R14C) substitution in gammaD-crystallin was subsequently identified. Protein modeling suggests that the effect of this mutation is a subtle one, affecting the surface properties of the crystallin molecule rather than its tertiary structure, consistent with the fact that the patients' lenses are normal at birth. This is the first gene defect shown to be responsible for a noncongenital progressive cataract, and studying the defective protein should teach us more about the mechanisms underlying cataract formation.