Regulated vacuole fusion and fission in Schizosaccharomyces pombe: an osmotic response dependent on MAP kinases

BACKGROUND

The budding yeast Saccharomyces cerevisiae uses two mitogenactivated protein (MAP) kinase cascades, the Hog1p and the Mpk1p pathways, to signal responses to hypertonic and hypotonic stress, respectively. Mammalian cells and the fission yeast Schizosaccharomyces pombe have functional homologues of Hog1p - p38/RK/CSBP and Sty1 - which, unlike Hog1p, also mediate other responses. We have investigated the involvement of S. pombe MAP kinase pathways in signalling a newly described response to osmotic stress - that of vacuole fusion and fission.

RESULTS

When S. pombe is placed into water, its vacuoles rapidly fuse into larger structures enclosing a greater proportion of the cell's volume. Under some conditions, its vacuoles can slowly fragment in response to salt. Fission requires the Sty1 pathway and also Pmk1, the homologue of S. cerevisiae Mpk1p. Fusion requires Pmk1, Ypt7 - the homologue of a protein involved in S. cerevisiae vacuole fusion - and part of the Sty1 pathway, although Sty1 phosphorylation is unaffected by hypotonic conditions.

CONCLUSIONS

Vacuole fusion and fission appear to be homeostatic mechanisms that restore the concentration of the cytosol. Vacuole fusion, like stimulated secretion in higher eukaryotes, is a rapid and specific process of membrane fusion in response to an external stimulus. The Sty1 pathway, in addition to its role in responding to hypertonic stress, is required at a basal level for the expression of factors required to respond to hypotonic stress - a mechanism that may allow the cell to use a common pathway for different responses.

The influence of two types of meal on the pharmacokinetics of a modified-release formulation of nifedipine (Adalat Retard)

OBJECTIVE

The effect of two different types of meal on the absorption of a modified-release formulation of nifedipine (Adalat Retard) was studied.

RESULTS

A light breakfast produced a delay in gastric emptying (indicated by the rate of paracetamol absorption) compared with the fasting state but did not alter the tmax or Cmax for nifedipine significantly. After a cooked breakfast, there was less delay in gastric emptying and again no delay in tmax for nifedipine. However, the Cmax for nifedipine was significantly higher than in the fasting state. Neither meal influenced the bioavailability of nifedipine.

CONCLUSION

The results suggest that the nature of the meal has an important influence on the absorption profile of this formulation of nifedipine, probably by an effect on its dissolution. This study illustrates the importance of considering the effects of different types of meal before concluding that food does not affect the pattern of drug absorption.

Pollination by deceit in nutmeg (Myristica insipida, Myristicaceae): floral displays and beetle activity at male and female trees

Pollination by deceit in Myristica insipida, a beetle-pollinated nutmeg, was hypothesized to operate on intersexual differences in flower production and longevity, producing a daily fluctuation between floral display maxima and minima. Sticky traps were used to continuously monitor beetle activity. Flower production and naturally occurring intersexual differences in display were recorded. Male and female trees flowered in synchrony producing daily display maxima at 1800-0600 and display minima at 1400-1800. Rewarding male trees produced three times the number of flowers of female trees, but the greater longevity of female flowers reduced the intersexual difference in display maxima to a factor of two. There was no intersexual difference in display minima. Beetles were demonstrated to be sensitive to differences in both maximum and minimum displays on rewarding male trees, a necessary prerequisite for directional selection on display size. Beetle captures were significantly higher at male trees during floral display maxima, and no intersexual differences in capture rate occurred during floral display minima. However, capture rates at male trees did not decline as predicted, and the pattern of captures was consistent with crepuscular activity. Beetle captures at male and female trees were lower from 1800 to 0600 and 1000 to 1400, and higher from 0600 to 1000 and 1400 to 1800, but the differences were only significant at female trees. These data suggests that foraging errors are numerous, frequent, and the result of overall foraging activity.

A comparison of the effects of aspirin on bleeding time measured using the Simplate method and closure time measured using the PFA-100, in healthy volunteers

AIMS

The aim of this study was to compare the effects of aspirin on platelet function as measured by the 'classical' template bleeding time with a new ex vivo method measuring closure times using the PFA-100 machine. Platelet aggregation in response to arachidonic acid was also measured ex vivo.

METHODS

The trial was a randomized, double-blind, placebo-controlled crossover design, with each volunteer taking 750 mg aspirin (BP) or placebo, three times a day for 5 days, with an 18 day wash-out period between treatments. Bleeding times and closure times were measured before the first dose on the first day and 0.5 h after the last dose on the fifth day of each treatment period. They were also measured 2 weeks after the last day of the trial.

RESULTS

Baseline bleeding times (pre-placebo) were 415 s using the Simplate, whilst baseline closure times were 115 s using the PFA-100. Aspirin treatment caused an increase of both the template bleeding time (61%) and the closure time of the PFA-100 (79%) when compared with the effects of placebo. The platelet aggregatory response to arachidonic acid was completely inhibited following aspirin treatment and was unaffected following placebo. Two weeks after the end of the trial, all values had returned to pre-treatment levels. The template bleeding time was unaltered in 1 of the 12 volunteers during aspirin treatment and was significantly prolonged in 3 of the 12 volunteers during placebo treatment. The PFA-100 closure time was unaltered in 1 of the 12 volunteers during aspirin treatment and was prolonged in 1 subject during placebo treatment.

CONCLUSIONS

The change in closure time using the PFA-100 is as sensitive and reproducible to the effects of aspirin on platelet function as is the template bleeding time test. However, the PFA-100 produced less variable effects with fewer false positive results.

Promising survival with three-dimensional conformal radiation therapy for non-small cell lung cancer

PURPOSE

Local failure is a major obstacle to the cure of locally advanced non small-cell lung cancer. Three-dimensional conformal radiation therapy (3-DCRT) selects optimal treatment parameters to increase dose to tumor and reduce normal tissue dose, potentially representing an enhancement of the therapeutic ratio of radiation therapy for lung cancer. We performed this analysis of 45 non-small cell lung cancer patients treated with 3-DCRT alone, to evaluate the ability of computer derived lung dose volume histograms to predict serious pulmonary toxicity, to assess the feasibility of this approach, and to examine the resulting survival.

METHODS

There were 28 males (62%) and 17 females (38%). The median age was 65 (range: 38-82). Tumor stage was Stage I/II in 13%, IIIa in 42%, and IIIb in 44%. The histology was squamous in 44%, adenocarcinoma in 36%, and other non-small cell histologies in the others. Only 47% of patients. had combined favorable prognostic factors (i.e. KPS < or = 80, and < or = 5% wt. loss). The median dose of radiation to gross disease was 70.2 Gy (range: 52.2-72 Gy) delivered in fractions of 1.8 Gy, 5 days per week.

RESULTS

Seven patients did not complete 3-DCRT due to disease progression outside the port. Follow-up data are mature: the median follow up of the 6 survivors is 43.5 months (35-59). Thoracic progression occurred in 46%. Median survival (all 45 patients.) is 15.7 months and survival is 32% at 2 years and 12% at 59 months. Pulmonary toxicity > or = grade 3 occurred in 9% of patients. Dose volume histograms were available in 31 patients and showed a correlation between risk of pulmonary toxicity and indices of dose to lung parenchyma. Grade 3 or higher pulmonary toxicity occurred in 38% (3/8) of patients with > 30% of lung volume receiving > or = 25 Gy, versus 4% (1/23) of patients with < or = 30% lung receiving > or = 25 Gy (P = 0.04). Grade 3 or higher pulmonary toxicity occurred in 29% (4/14) of patients with a predicted pulmonary normal tissue complication probability of 12% or higher versus 0% (0/17) in patients with a predicted probability of less than 12% (P = 0.03).

CONCLUSIONS

Despite adverse prognostic criteria median survival is encouraging and may be higher than some combined modality approaches. Dose volume histogram parameters may be useful to determine the maximum dose for individual patients and thereby permit avoidance of toxicity.

Differential expression of c-fos in vitro by all anterior pituitary cell types during the estrous cycle: enhanced expression by luteinizing hormone but not by follicle-stimulating hormone cells

C-fos expression appears in some activated cell types. Because of dynamic changes in gonadotropes during the estrous cycle, this study was initiated to determine if fos might be expressed in gonadotropes before any period of activation. We detected c-fos and pituitary antigens in dissociated anterior pituitary cells by dual-labeling immunocytochemistry. The highest percentage of cells with fos protein were found in proestrous rat populations. In diestrous and proestrous populations, dual labeling showed that 6-9% of pituitary cells contained fos with adrenocorticotropin, thyroid-stimulating hormone, prolactin, or growth hormone antigens. In contrast, only 0.8-3% contained fos with luteinizing hormone (LH) or follicle-stimulating hormone (FSH) antigens. We then tested the hypothesis that gonadotropes might increase fos expression earlier in the cycle. In populations from metestrous rats, c-fos labeling was found in 45% of LH cells compared to only 23% of LH cells in the proestrous group. This suggests that proportionately more LH cells are being activated to produce fos early in the cycle. Perhaps fos is used in translation of LH beta antigens or gonadotropin-releasing hormone (GnRH) receptor mRNAs. In contrast, less than 1% of all pituitary cells expressed fos with FSH at all stages of the cycle (only 6-12% of FSH cells). This differential expression suggests one mechanism behind the regulation of non-parallel storage and release of gonadotropin antigens.

Plasma renin activity and angiotensin I and aldosterone concentrations in cats with hypertension associated with chronic renal disease

OBJECTIVE

To determine plasma renin activity (PRA), angiotensin I (Ang I), and aldosterone (ALDO) values in clinically normal cats and hypertensive cats with renal disease, and the relation of renin-angiotensin-aldosterone activation in response to treatment with beta-blockers or angiotensin-converting enzyme inhibitors.

ANIMALS

5 normotensive healthy control cats and 12 Untreated hypertensive cats with chronic renal disease.

PROCEDURE

Untreated hypertensive cats received either propanolol (n = 6) or enalapril (n = 6) as initial antihypertensive treatment. PRA and baseline plasma Ang I and ALDO concentrations were measured prior to treatment. The difference in Ang I values at 2 hours (Ang I generated) and at time 0 (baseline Ang I) was divided by 2 to give the PRA value. Values for PRA, Ang I, and ALDO were obtained from 5 clinically normal, normotensive cats, and compared with those of hypertensive cats.

RESULTS

Mean +/- SD PRA and baseline Ang I concentration were not significantly different between normotensive and hypertensive cats. Mean ALDO concentration was significantly (P = 0.0235) higher in hypertensive cats with renal disease (186.18 +/- 145.15 pg/ml), compared with that in normotensive controls (51.1 +/- 16.76 pg/ml). Eight hypertensive cats with ALDO concentration > 2 SD above the mean concentration in control cats had low (n = 3), normal (n = 4), or high (n = 1) PRA, suggesting variable activation of the renin-angiotensin-aldosterone axis in the hypertensive state. Overall, enalapril was effective long-term monotherapy in only 1 of 6 cats, and propranolol was ineffective as long-term monotherapy.

CLINICAL RELEVANCE

Evaluation of the renin-angiotensin-aldosterone system in cats with hypertension associated with renal disease may lead to greater understanding of the pathophysiologic mechanisms of this disorder. In addition, identification of biochemical markers in hypertensive cats may permit selection of appropriate antihypertensive drugs. Propranolol and enalapril were ineffective antihypertensive agents in most cats of this study.

Changes in expression of epidermal growth factor receptors by anterior pituitary cells during the estrous cycle: cyclic expression by gonadotropes

Epidermal growth factor (EGF) stimulates gonadotropin secretion, suggesting that it may regulate gonadotrope functions. These responses may be modulated by changes in expression of EGF receptors (EGFR), especially during the estrous cycle. To test this hypothesis, EGFR and pituitary hormones were detected by dual immunocytochemistry. Pituitary cells from metestrous rats contained 41 +/- 4% cells labeled for EGFR. This peak was followed by a decline to 17.6 +/- 2% of cells from proestrous rats. The percentages of metestrous pituitary cells with EGFR and each hormone were: PRL, 11.8 +/- 1; ACTH, 9.9 +/- 1.8%; GH, 8.2 +/- 0.6%; TSH, 6.3 +/- 0.8%; FSH, 4 +/- 0.6%; and LH, 2.6 +/- 0.6%. The relatively low percentages of gonadotropes may have reflected the low expression of LH or FSH antigens during metestrus. Dual labeling for EGFR and LHbeta or FSHbeta messenger RNAs (mRNAs) showed a significant increase in the percentages of pituitary cells with LHbeta mRNA and EGFR (to 5.7% of pituitary cells), but there were no increases in the EGF target cells bearing FSHbeta mRNA. When gonadotropin antigens were detected in EGF target cells during other stages of the cycle, there was an increase to reach a peak of 6.6-7% of pituitary cells by the morning of proestrus (or 40-50% of gonadotropes). To summarize, EGFR are seen in few gonadotropes during the metestrous peak, although more LH cells (but not FSH cells) can be identified by their content of LHbeta mRNA. This suggests that EGFR is expressed initially in monohormonal LH gonadotropes. The peak expression of EGFR by gonadotropes during diestrus and proestrus suggests that EGF may be involved in the development of the gonadotropes as they approach surge secretory activity. It also may help stimulate the transcription of new gonadotropin beta-subunit mRNA seen late in proestrus, early in estrus.

Rat basophilic leukaemia (RBL) cells overexpressing Rab3a have a reversible block in antigen-stimulated exocytosis

The rat basophilic leukaemia (RBL) cell line has been widely used as a convenient model system to study regulated secretion in mast cells. Activation of these cells through the high-affinity receptor for IgE (Fcepsilon-RI) results in degranulation and the extracellular release of mediators. There is good evidence of a role for GTPases in mast cell degranulation, and a number of studies with peptides derived from the Rab3a effector domain have suggested that Rab3a may function in this process. However, in neuroendocrine cells, overexpression of Rab3a can act as a negative regulator of stimulated exocytosis [Holz, Brondyk, Senter, Kuizon and Macara (1994) J. Biol. Chem. 269, 10229-10234; Johanes, Lledo, Roa, Vincent, Henry and Darchen (1994) EMBO J. 13, 2029-2037]. In order to study the function of Rab3a in RBL degranulation, we have generated clones of RBL cells stably expressing Rab3a, and show that in these haematopoietic cells Rab3a can also function as a negative regulator of exocytosis. Overexpression of a mutant form of Rab3a (Asn-135 to Ile), which is predicted to be predominantly GTP-bound, also inhibited degranulation. However, overexpression of a mutant form of Rab3a that was truncated at the C-terminus to remove the sites for geranylgeranylation failed to inhibit degranulation. The effect of Rab3a is specific to secretion, and we observe no effect of Rab3a on receptor-mediated endocytosis. The Rab3a-induced block in degranulation can be bypassed by stimulation of streptolysin-O-permeabilized cells with guanosine 5'-[gamma-thio]triphosphate. We conclude from these studies that Rab3a is implicated in an early stage of granule targeting, whereas fusion of granules with the plasma membrane is regulated by a distinct downstream GTP-binding protein or proteins.

Phragmites die-back: sulphide- and acetic acid-induced bud and root death, lignifications, and blockages within aeration and vascular systems

Phragmites rhizome cuttings, and plantlets raised from seed, were exposed to the phytotoxins acetic acid or dissolved sulphide in unstirred solution cultures to determine whether die-back symptoms found in field-grown plants, and attributed to phytotoxin damage, could be induced. Many of the die-back symptoms associated with field sites, namely stunted adventitious roots and laterals, bud death, callus blockages of the gas-pathways, and vascular blockages, were all reproduced, and were particularly acute at the higher concentrations of the phytotoxins: acetic acid (1.67 mm), sulphide (1.4 mm). The results accord with the hypothesis that phytotoxins may play a critical role in Phragmites australis die-back.

Therapeutic blood levels of sirolimus (rapamycin) in the allografted rat

A study was conducted to determine the relationship among oral dose, trough whole blood levels, graft survival, and side effects in sirolimus-treated allografted rats. The heterotopic heart allograft model using Brown Norway donors and Lewis rat recipients was used. Rats were dosed daily with sirolimus or vehicle until graft failure or up to a maximum of 28 days. Upon graft failure, rats were bled for measurement of trough blood levels of drug and tissues sent for histopathologic analysis. Sirolimus blood concentration correlated positively with dose and graft survival. Significant graft survival occurred at whole blood trough levels of 0.5 ng/ml achieved at the 0.3 mg/kg/day dose. Analysis of the concentration-effect data using a sigmoidal Emax model calculated a whole blood EC50 of 2.0 ng/ml for graft survival. With mean trough concentrations of 7 ng/ml and higher, grafts survived after cessation of drug treatment. At the 0.8 mg/kg/day dose, there was a significant decrease in body weight gain in the rats. Histopathologic examination of sirolimus-treated animals detected thymic and lymphoid atrophy, both considered pharmacologic extensions of sirolimus's immunosuppressive activity and focal myocardial degeneration, an exacerbation of a spontaneous occurring lesion. These results demonstrate that sirolimus prolongs graft survival in rat in a concentration dependent manner with therapeutic whole blood levels of about 10 ng/ml.

Florid oral manifestations in an atypical familial adenomatous polyposis family with late presentation of colorectal polyps

Early identification and prophylactic surgery are essential in preventing development of malignancy in colorectal polyps in familial adenomatous polyposis (FAP). Previous studies indicate a 100% cumulative risk of developing colonic polyps in individuals with FAP by the age of 34 yr. However, we have previously reported late-onset and non-penetrance of polyposis in four families. We describe here in detail one of these families with florid oral manifestations detectable on panoramic radiography of the jaws, which were instrumental in the diagnosis of FAP in the index patient and for ascertainment of her family for screening. The pathological adenomatous polyposis coli (APC) gene mutation in this family was shown to segregate with dento-osseous changes. Panoramic jaw radiography is a common examination carried out prior to dental or oral surgical procedures. This case illustrates the importance of appropriate investigations, including family history and colonoscopy, even in relatively older patients with radiological findings such as those described here and in members of their families at risk of FAP.

Interleukin-1 beta in coronary arteries of patients with ischemic heart disease

Interleukin-1 beta (IL-1 beta) is known to have a number of effects on the different cell types present within coronary arteries. In this study we identified the location and phenotype of cells containing IL-1 beta in human coronary artery specimens from patients suffering from either coronary atherosclerosis or cardiomyopathy and correlated the presence of IL-1 beta with disease severity. Luminal endothelial cells, adventitial vessel wall cells, and macrophages were double labeled immunohistochemically for IL-1 beta protein and a cell type-specific monoclonal antibody for either endothelial cells or macrophages. In situ hybridization was performed to locate the presence of IL-1 beta mRNA within the coronary artery wall. In this study IL-1 beta protein was found to be increased in the adventitial vessel walls of atherosclerotic coronary arteries compared with coronary arteries from nonischemic cardiomyopathic hearts. This increase was directly proportional to the severity of coronary atherosclerosis. IL-1 beta protein was also detected in luminal endothelium and macrophages of atherosclerotic coronary arteries and coronary arteries from nonischemic cardiomyopathic hearts. IL-1 beta mRNA was found in luminal endothelial cells, adventitial vessel endothelial cells, and macrophages. We conclude that IL-1 beta is produced by endothelial cells and macrophages in coronary arteries from ischemic hearts and to a lesser extent from nonischemic cardiomyopathic hearts.

Intensity resolution and subjective magnitude in psychophysical scaling

Several successful theories of psychophysical judgment imply that exponents of power functions in scaling tasks should covary with measures of intensity resolution such as d' in the same tasks, whereas the prevailing metatheory of ideal psychophysical scaling asserts the independence of the two. In a direct test of this relationship, three prominent psychophysical scaling paradigms were studied: category judgment without an identification function, absolute magnitude estimation, and cross-modality matching with light intensity as the response continuum. Separate groups of subjects for each scaling paradigm made repeated judgments of the loudnesses of the pure tones that constituted each of two stimulus ensembles. The narrow- and wide-range ensembles shared six identical stimulus intensities in the middle of each set. Intensity resolution, as measured by d'-like distances, of these physically identical stimuli was significantly worse for the wide-range set for all three methods. Exponents of power functions fitted to geometric mean responses, and in magnitude estimation and cross-modality matching the geometric mean responses themselves, were also significantly smaller in the wide-range condition. The variation of power function exponents, and of psychophysical scale values, for stimulus intensities that were identical in the two stimulus sets with the intensities of other members of the ensembles is inconsistent with the metatheory on which modern psychophysical scaling practice is based, although it is consistent with other useful approaches to measurement of psychological magnitudes.

Identification of a novel member of the Rab8 family from the rat basophilic leukaemia cell line, RBL.2H3

We describe the cloning of a cDNA from the rat basophilic leukaemia cell line (RBL.2H3) encoding a novel member of the Rab family of small GTP binding proteins. The novel clone, which we call Rab8b, is most highly related to the Rab8 family with substantial divergence in the variable C-terminal domain. Northern blot analysis reveals highest levels of expression of Rab8b in the spleen, testis and brain, which is in marked contrast to the tissue distribution of Rab8. The Rab8b cDNA was modified to introduce a c-myc epitope tag at the extreme N terminus of the protein, and transient transfection studies were performed to analyse the intracellular localization of Rab8b by confocal microscopy. Transient expression of the c-myc/Rab8b fusion protein in both PC12 and RBL.2H3 cells shows staining of both the plasma membrane and ill-defined vesicular structures, and in the case of RBL.2H3 cells appears to induce striking outgrowths of the plasma membrane.

STAT3beta, a splice variant of transcription factor STAT3, is a dominant negative regulator of transcription

The 89-kDa STAT3 protein is a latent transcription factor which is activated in response to cytokines (interleukin (IL)-5 and -6) and growth factors (epidermal growth factor). Binding of IL-5 to its specific receptor activates JAK2 which leads to the tyrosine phosphorylation of STAT3 proteins. Here we report the cloning of a cDNA encoding a variant of the transcription factor STAT3 (named STAT3beta) which was isolated by screening an eosinophil cDNA library. Compared to wild-type STAT3, STAT3beta lacks an internal domain of 50 base pairs located near the C terminus. This splice product is a naturally occurring isoform of STAT3 and encodes a 80-kDa protein. We found by reconstitution of the human IL-5R in COS cells that like STAT3, STAT3beta is phosphorylated on tyrosine and binds to the pIRE from the ICAM-1 promoter after IL-5 stimulation. However, STAT3beta fails to activate a pIRE containing promoter in transient transfection assays. Instead, co-expression of STAT3beta inhibits the transactivation potential of STAT3. These results suggests that STAT3beta functions as a negative regulator of transcription.

Neuroendocrine and cardiovascular effects of serotonin: selective role of brain angiotensin on vasopressin

Central serotonin (5-HT) and angiotensin (ANG II) stimulate arginine vasopressin (AVP), oxytocin (OT), and adrenocorticotropin (ACTH) secretion and increase blood pressure. Studies were conducted in conscious rats to determine whether neuroendocrine activation by 5-HT requires a brain angiotensinergic intermediate pathway. In the first study, ANG II formation was inhibited by the angiotensin-converting enzyme inhibitor enalapril before injection of the 5-HT releaser/uptake inhibitor d-fenfluramine. Fenfluramine (2 mg/kg ip) stimulated AVP, OT, corticosterone, and prolactin (PRL) secretion (P<0.01). Enalapril (60 mg/l in drinking water for 4 days and 10 mg/kg ip 2 h before the rats were killed) inhibited only the AVP response (P<0.01) to d-fenfluramine. In the second study, the effect of intracerebroventricular injection of the 5-HT2A/2C antagonist LY-53857 (10 microgram), or the ANG II AT1 antagonist DuP-753 (10 microgram), on intracerebroventricular 5-HT (10 microgram)-stimulated AVP, OT, ACTH, PRL, renin secretion, mean arterial pressure (MAP) and heart rate (HR) was tested. LY-53857 inhibited the AVP, OT, and ACTH responses to 5-HT (P<0.01), whereas DuP-753 inhibited only the AVP response (P<0.01). Intraventricular injection of 5-HT increased MAP and decreased HR. The MAP response was not affected by LY-53857 or DuP-753, and at no time did MAP decline below starting levels. The decreased HR was inhibited by LY-53857 but not by DuP-753. These results demonstrate that 5-HT-induced AVP secretion is mediated selectively via brain angiotensinergic mechanisms by way of the AT1 receptor.