Cyclic alternating pattern: a new marker of sleep alteration in patients with fibromyalgia?

OBJECTIVE

In the dynamic organization of sleep, cyclic alternating pattern (CAP) expresses a condition of instability of the level of vigilance that manifests the brain's fatigue in preserving and regulating the macrostructure of sleep. We evaluated the presence of CAP in patients with fibromyalgia (FM) compared to healthy controls.

METHODS

Forty-five patients with FM (42 women) were studied and compared with 38 healthy subjects (36 women) matched for age, sex, and body mass index. Entry criteria were diagnosis of FM according to 1990 American College of Rheumatology criteria; willingness to participate in the study; and having no other diagnosis of autoimmune, neoplastic, or other possible causes of secondary diffuse musculoskeletal pain. Patients in the study underwent polysomnography recordings and a sleep questionnaire. Hypersomnolence was evaluated according to the Epworth Sleepiness Scale.

RESULTS

FM patients had less sleep efficiency (sleep time/time in bed) than controls (79 +/- 10 vs 89 +/- 6; p < 0.01), a higher proportion of stage 1 non-rapid eye movement (non-REM) sleep (20 +/- 5 vs 12 +/- 5; p < 0.001), and twice as many arousals per hour of sleep (9.7 +/- 3.3 vs 4.1 +/- 1.9; p < 0.01). The CAP rate (total CAP time/non-REM sleep time) was significantly increased in FM patients compared to controls (68 +/- 6% vs 45 +/- 11%; p < 0.001). CAP rate seemed to correlate with the severity of clinical symptoms in FM patients (tender points index; p < 0.01) and with less efficiency of sleep (p < 0.01).

CONCLUSION

The increase of CAP rate indicates a worse quality of sleep in patients with FM. These data are strongly correlated to the severity of symptoms.

Surgery of Glomus Jugulare Tumors

The treatment of choice for glomus jugulare tumors is still controversial. High rates of morbidity, incomplete resection, and the aggressive behavior of these tumors are the main arguments for advocates of primary radiotherapy. However, constant refinements in skull base techniques have made complete resection of these lesions a realistic goal. The high probability of achieving local control of these tumors by surgery has convinced us to support this option strongly. Between 1993 and 2000 we diagnosed 52 glomus tumors of the temporal bone. Of these patients, only 42 had a class C lesion (glomus jugulare) and were included in this study; 37 of these patients underwent surgery, 10 of whom had intracranial extension of the disease. The overall resection rate was 96 %. Facial nerve function at 1 year was House-Brackmann grade I to II in 52 % of patients and grade III or better in 84 % of patients. Hospitalization was shorter than 14 days in 33 patients (89 %). All patients with pharyngolaryngeal palsy had sufficient compensation at discharge. Twelve vocal chord Teflon injections were performed after surgery to reduce hoarseness and aspiration. No patient died. No relapse was observed (mean follow-up, 4.9 years).

Two cases of cutaneous nodular dirofilariasis in the cat

Cutaneous nodular dirofilariasis is occasionally reported in dogs but is rare in cats. This report describes two cases of cutaneous nodular lesions due to Dirofilaria immitis adult parasites in domestic shorthaired cats living in an endemic area in northern Italy.

Posterior fossa vestibular neurotomy as primary surgical treatment of Menière's disease: a re-evaluation

Fifty-eight patients underwent vestibular neurotomy via the posterior fossa approach between September 1992 and December 1998 at the ENT department of Legnano. All patients presented a history of disabling unilateral Menière's disease and underwent complete neuro-otologic evaluation following the 1985 American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) guidelines. All patients underwent MRI imaging, ABR and electronystagmographic testing before surgery. Objective analysis of results is reported using the criteria published by the Committee on Hearing and Equilibrium of the AAO-HNS in 1985. According to the AAO formula, 52 patients obtained a score of 0, indicating complete control of major vertigo spells, while four were classified within the 'substantial control' group. Immediate hearing results indicated that 93 per cent of the patients maintained a level within 10 dB from the pre-operative level. Only one patient experienced a subtotal hearing loss yet retained measurable hearing. No major complications were reported. We conclude that a retrosigmoid approach to vestibular neurotomy can be considered a safe and effective procedure in relieving medically refractory vertigo in Menière's disease while preserving the hearing. Tinnitus and long-term hearing deterioration are not influenced by the procedure.

Nasal resistances are useful in identifying children with severe obstructive sleep apnea before polysomnography

OBJECTIVE

In this study, we would like to show that anterior rhinometry measurement of nasal resistance would be a simple and useful test to identify severe obstructive sleep apnea (OSA) in a population of children affected by adenotonsillar hypertrophy.

METHODS

Seventy-three consecutive children (44 males; mean age 5.4+/-1.2 years) with adenotonsillar hypertrophy, who complained sleep-disordered breathing, were studied. All the parents completed a questionnaire concerning the children's sleeping habits and sleep complaints before consultation; each child underwent a general paediatric examination and an evaluation of craniofacial features and upper airway patency. In all 73 children polysomnography was performed and anterior rhinometry nasal patency was measured.

RESULTS

The diagnosis of OSA was confirmed in 44/73 patients (60%). Total nasal resistance showed a significant direct correlation with apnea hypopnea index, arousal index, snoring time, percentage of sleep time spent at SaO(2)<90% and a significant inverse correlation with total sleep time, sleep efficiency and the mean of SaO(2)% during sleep. Total nasal resistance was significantly related to snoring, mouth breathing and daytime sleepiness. The receiver operator characteristics (ROC) curve indicates that in the range of age of our sample a nasal resistance value of 0.59 Pa/cm(3)/s has a sensitivity of 91% and specificity of 96% for identifying the children with adenotonsillar hypertrophy affected by OSA.

CONCLUSIONS

Our study shows that in children with adenotonsillar hypertrophy nasal resistance seems to be risk factor for OSA. The anterior rhinometry appears as a useful tool in routine evaluation of sleep-disordered breathing in these patients.

Activity of GH/IGF-I axis in trauma and septic patients during artificial nutrition: different behavior patterns?

The aim of this study was to compare several parameters of GH/IGF-I axis activity in septic and trauma patients during Intensive Care Unit (ICU) stay. To this goal, 13 patients with sepsis (SEP) and 16 with trauma (TRA) were studied. Thirty-three adult subjects (AS) were studied as controls. Serum IGF-I and -II, IGFBP-1, -2 and -3, GH and GHBP levels were studied on day 1, 3, 5 and 7 after ICU admission, during comparable artificial nutrition in SEP and TRA and basally in AS. In 5 patients with SEP and 6 with TRA, the GH response to GHRH was evaluated on day 3. On ICU day 1, IGF-I and -II and IGFBP-3 in SEP were lower (p<0.05) than in TRA which, in turn, were lower (p<0.01) than in AS. IGF-I increased (p<0.05) both in SEP and TRA, but, on ICU day 7, those in SEP persisted lower than in TRA, which became similar to those in AS. IGF-II levels increased (p<0.05) in SEP only, persisting lower (p<0.05) than in TRA. On ICU day 1, GH in SEP and TRA were similar and did not vary until day 7, overlapping those in AS. The GH response to GHRH in SEP and TRA was similar and lower (p<0.01) than in AS. These findings indicate that IGF-I activity is impaired more in septic than in trauma patients. Reduced IGF-I activity probably reflects peripheral GH resistance though basal and GHRH-induced GH levels were not increased in these conditions.

[Trans-labyrinthine approach for the resection large and giant acoustic nerve neuromas]

The standard translabyrinthine approach for acoustic neuromas removal was introduced by W. House in 1964. After several years of experience the original translabyrinthine approach has been progressively modified into the current "enlarged" approach by extending the area of bone removal. This increased surgical field has made the translabyrinthine approach suitable for the removal of tumours of all sizes. We present our serie of 71 large (52) and giant (19) neuromas of the VIIIth nerve removed through a translabyrinthine approach between 1993 and 1998 at the ENT Department of Legnano.

Hypersomnolence in fibromyalgia syndrome

OBJECTIVE

To evaluate hypersomnolence in patients affected by fibromyalgia syndrome.

METHODS

Thirty consecutive patients affected by fibromyalgia syndrome (FMS) (28 F) completed a sleep questionnaire and underwent the following evaluations: lung function tests; polysomnography; the Epworth sleepiness scale (ESS), which measures sleep complaints and daytime hypersomnolence; and the visual analogical scale (VAS) to detect subjective pain, fatigue, anxiety and depression.

RESULTS

The FMS patients were divided into two groups based on their ESS score. Patients complaining of daytime hypersomnolence had a higher number of tender points (15 +/- 2 vs. 12 +/- 1, p < 0.01), a higher subjective pain score (72 +/- 15 vs. 52 +/- 13, p < 0.05), and more fatigue (p < 0.05). The diffusing capacity of the lung (Tlco) was more impaired and the occurrence of periodic breathing was higher. FMS patients complaining of daytime somnolence had significantly less efficient sleep than the FMS patients with no daytime somnolence (p < 0.05), i.e. a lower proportion of stage 3 sleep (5 +/- 2% vs. 12 +/- 3%; p < 0.001), stage 4 sleep (1 +/- 0.5% vs. 4 +/- 1%; p < 0.001), and twice as many arousals per hour of sleep (p < 0.01). The respiratory pattern of FMS patients with hypersomnolence showed a higher occurrence of periodic breathing (p < 0.05). The short length of apneas and hypopnoeas did not affect the apnea/hypopnea index (5.1 +/- 3 vs. 7 +/- 4; ns), but FMS patients with daytime hypersomnolence had a greater number of desaturations per hour of sleep (11 +/- 6 vs. 6 +/- 5; p < 0.05). Pulmonary volumes did not differ between the two groups. The EES score was significantly correlated in FMS patients, and even more markedly in the FMS patients with hypersomnolence, TLco, A/I, and disease duration. The ESS score was correlated significantly with the number of tender points only in FMS patients with daytime hypersomnolence.

CONCLUSION

The occurrence of daytime hypersomnolence in FMS patients is linked to a greater severity of fibromyalgia symptoms and to more severe polysomnographic alterations.

Left ventricular changes in isolated office hypertension: a blood pressure-matched comparison with normotension and sustained hypertension

BACKGROUND

Isolated office (IO) hypertension is a benign condition according to some researchers, whereas others believe it is associated with cardiovascular abnormalities and increased cardiovascular risk. The aim of this study is to compare morphofunctional characteristics of the left ventricle (LV) in IO hypertensive subjects, normotensive subjects (hereafter, hypertensives and normotensives), and never-treated sustained hypertensives. The 3 groups were matched not only by age, sex, and body mass index but also by clinic blood pressure (BP) (IO hypertensives and sustained hypertensives) and daytime BP (IO hypertensives and normotensives).

METHODS

We enrolled 42 IO hypertensives (clinic BP > 140 and/or 90 mm Hg and daytime BP < or = 130/80 mm Hg), 42 sustained hypertensives (clinic BP > 140 and/or 90 mm Hg and daytime BP > or = 140 and/or 90 mm Hg) and 42 normotensives (clinic BP < 135 and/or 85 mm Hg and daytime BP < or = 130/80 mm Hg). Left ventricular morphologic features and function were assessed using digitized M-mode echocardiography.

RESULTS

Compared with normotensives, IO hypertensives had significantly thicker LV walls, increased LV mass, reduced diastolic function, increased prevalence of LV hypertrophy, and preclinical diastolic dysfunction. Sustained hypertensives, compared with IO hypertensives, had significantly thicker LV wall, higher LV mass, and lower diastolic function, whereas the prevalence of LV hypertrophy and preclinical diastolic dysfunction was greater than in IO hypertensives, but the difference did not reach statistical significance (P = .29).

CONCLUSIONS

Comparing matched BP groups, IO hypertensives have LV morphofunctional characteristics considerably different from normotensives and qualitatively similar to sustained hypertensives. Therefore, our results support the hypothesis that IO hypertension should not be considered as simply a benign condition.

Efficacy of itraconazole as a combined continuous/pulse therapy in feline dermatophytosis: preliminary results in nine cases

This study evaluated the efficacy of itraconazole as a combined continuous/pulse therapy for feline dermatophytosis. Nine cats with dermatophytosis caused by Microsporum canis were treated with itraconazole at 10 mg kg(-1) orally once daily for 28 days and then on an alternate week regimen (1 week off, 1 week on) at the same dosage. Cats were re-evaluated by physical examination and fungal culture at days 28, 42, 56 and 70 if necessary. Treatment was stopped when two consecutive negative fungal cultures were obtained. Eight cats were cured after 56 days, with two negative cultures obtained at days 28 and 42. In one case, a positive culture was obtained at day 28, but negative cultures were achieved at days 42 and 56. This protocol appears to be effective in the treatment of feline dermatophytosis, although these preliminary results should be confirmed by a controlled study.

[Petrous bone cholesteatoma: surgical strategy]

Petrous bone cholesteatoma is a rare pathology which grows slowly and is often asymptomatic. This work presents a series of 25 cases of Petrous bone cholesteatoma and discusses the diagnostic impact, the surgical approach, the results and the complications. Currently our surgical orientation favors translabyrinthine and transcochlear approaches which, better than other ones, allow both radical excision of the lesion and preservation of the main neuro-vascular structures. Out of the 25 patients undergoing surgery, 22 were treated with the translabyrinthine (6 cases) or transcochlear (16 cases) approaches, in 1 case an infratemporal type A approach was used while the remaining 2 were treated with a median cranial fossa approach. Paralysis of the facial nerve is the most dreaded complication, particularly when a deficit is already present prior to surgery. In just a few cases did the hearing justify an attempt at preservation but in no case should this compromise radical removal of the cholesteatoma.

Targeting of a tail-anchored protein to endoplasmic reticulum and mitochondrial outer membrane by independent but competing pathways

Many mitochondrial outer membrane (MOM) proteins have a transmembrane domain near the C terminus and an N-terminal cytosolic moiety. It is not clear how these tail-anchored (TA) proteins posttranslationally select their target, but C-terminal charged residues play an important role. To investigate how discrimination between MOM and endoplasmic reticulum (ER) occurs, we used mammalian cytochrome b(5), a TA protein existing in two, MOM or ER localized, versions. Substitution of the seven C-terminal residues of the ER isoform or of green fluorescent protein reporter constructs with one or two arginines resulted in MOM-targeted proteins, whereas a single C-terminal threonine caused promiscuous localization. To investigate whether targeting to MOM occurs from the cytosol or after transit through the ER, we tagged a MOM-directed construct with a C-terminal N-glycosylation sequence. Although in vitro this construct was efficiently glycosylated by microsomes, the protein expressed in vivo localized almost exclusively to MOM, and was nearly completely unglycosylated. The small fraction of glycosylated protein was in the ER and was not a precursor to the unglycosylated form. Thus, targeting occurs directly from the cytosol. Moreover, ER and MOM compete for the same polypeptide, explaining the dual localization of some TA proteins.

Orthostatic intolerance: different abnormalities in the neural sympathetic response to a gravitational stimulus

In this paper we shall focus on the different abnormalities in the neural sympathetic response to a gravitational stimulus, characterising syndromes with symptoms of orthostatic intolerance. In Vaso vagal Syncope, an increase or a reduction of cardiac and vascular sympathetic modulation have been described in occasional and habitual fainters, respectively. Pure Autonomic Failure (PAF) is characterized by a global cardiovascular denervation. Accordingly, the spectral markers of cardiac and vascular sympathetic modulation are absent or reduced. However, a concomitant vagal diminished activity is present. In Chronic Orthostatic Intolerance (COI), the most common form of dysautonomia in young female, an abnormal regional distribution of sympathetic discharge has been hypothesized during standing. Indeed, an overall increased sympathetic activity is present in recumbent position; during tilt a blunted vascular sympathetic discharge, with a concomitant exaggerated cardiac sympathetic modulation, is evident. Baroreflex Failure is a syndrome that may result from neck surgery or irradiation due to different forms of regional cancer. It is characterized by a volatility of blood pressure and heart rate, without habitual orthostatic hypotension. In the present paper, we describe a case of Baroreflex Failure with marked orthostatic hypotension in spite of a huge muscle sympathetic nerve activity (MSNA) and high levels of plasma cathecolamines. The most relevant finding was the absence of any coordinate rythmicity in blood pressure, heart rate and MSNA, both at rest and during tilt, particularly in the frequency band likely to be related with sympathetic modulation, i.e. at 0.1 Hz. We hypothesize that the absence of 0.1 Hz spontaneous fluctuations might play a role in sustaining orthostatic hypotension.

Microalbuminuria as a marker of preclinical diastolic dysfunction in never-treated essential hypertensives

Using 24-h ambulatory blood pressure (BP) monitoring and digitized M-mode echocardiography, we evaluated whether microalbuminuria is related to preclinical left ventricular (LV) diastolic dysfunction in hypertensive patients. We selected 87 never-treated hypertensive patients (mean 24-h BP > 140 and/or > 90 mm Hg); albuminuria was evaluated as mean value of 24-h urinary albumin excretion (UAE) from two 24-h urine collections. Microalbuminuria was found in 28 patients, classified as MA+ (UAE 30 to 300 mg/24 h); 59 patients had normal UAE (< 30 mg/24 h) and were classified as MA-. The MA+ and MA- groups did not differ with regard to age, sex, body mass index, or 24-h heart rate, whereas 24-h, daytime, and nighttime systolic and diastolic BP were significantly higher in MA+ than in MA-. The LV mass index was greater in MA+, as was the prevalence of LV hypertrophy; peak shortening rate of LV diameter, index of systolic function, was normal in all, but was lower in MA+. Peak lengthening rate of LV diameter and peak thinning rate of posterior wall, indices of diastolic function, were lower in MA+ and the prevalence of diastolic dysfunction was higher in MA+. UAE was inversely correlated with both indices of LV diastolic function, also after correction for age, 24-h heart rate, 24-h BP, and LV mass. In conclusion, in never-treated hypertensive patients, microalbuminuria is not only associated with greater myocardial mass, but is also related with preclinical impairment of LV diastolic function. This relation, independent from increased BP or LV mass, strengthens the role of microalbuminuria as an early and reliable marker of preclinical cardiac involvement.

Role of guanine nucleotides in the regulation of the Ras/cAMP pathway in Saccharomyces cerevisiae

The CDC25 gene product is a guanine nucleotide exchange factor for Ras proteins in yeast. Recently it has been suggested that the intracellular levels of guanine nucleotides may influence the exchange reaction. To test this hypothesis we measured the levels of nucleotides in yeast cells under different growth conditions and the relative amount of Ras2-GTP. The intracellular GTP/GDP ratio was found to be very sensitive to growth conditions: the ratio is high, close to that of ATP/ADP during exponential growth, but it decreases rapidly before the beginning of stationary phase, and it drops further under starvation conditions. The addition of glucose to glucose-starved cells causes a fast increase of the GTP/GDP ratio. The relative amount of Ras2-GTP changes in a parallel way suggesting that there is a correlation with the cytosolic GTP/GDP ratio. In addition 'in vitro' mixed-nucleotide exchange experiments done on purified Ras2 protein demonstrated that the GTP and GDP concentrations influence the extent of Ras2-GTP loading giving further support to their possible regulatory role.

The balance between proteinases and inhibitors in a murine model of proliferative retinopathy

PURPOSE

To examine the expression of matrix metalloproteinases (MMPs) and their inhibitors during the development of retinal neovascularization (NV) in a mouse model.

METHODS

A well-characterized murine model of retinal NV was used to study the expression of specific MMPs (MMP-2, MMP-9, and MT1-MMP) and tissue inhibitor of metalloproteinases (TIMPs types 1, 2, and 3). NV of the retina was induced in mice by exposure to 75% O(2) from postnatal day (P)7 to P12, followed by return to room air from P12 to P17. Expression of MMP mRNA was analyzed by reverse transcription-polymerase chain reaction (RT-PCR). In addition, retinal tissue removed from control (without NV) and experimental animals (with NV) was analyzed for the expression of TIMP-1, TIMP-2, and TIMP-3 mRNA and protein using RT-PCR and Western blot analysis.

RESULTS

During the angiogenic period from P13 to P17, MMP-2 and -9, and MT1-MMP message expression increased in experimental retinas compared with control samples. The TIMP-2 message and protein levels increased steadily in the retina of control animals until P17. This was in contrast to that seen in the retinas of the experimental animals in which TIMP-2 message and protein remained low and significantly less than in control samples. There were no significant changes in TIMP-3 message levels in retinal tissues, and TIMP-1 message and protein were undetectable.

CONCLUSIONS

Correlation was made at the mRNA and protein levels of TIMP expression compared with that of MMPs in a murine model of retinal NV, which suggests a temporal role for MMP-2 and -9, MT1-MMP, and TIMP-2 in new vessel formation in response to hypoxic stimulation.

A baker's yeast mutant (fil1) with a specific, partially inactivating mutation in adenylate cyclase maintains a high stress resistance during active fermentation and growth

The initiation of fermentation in the yeast Saccharomyces cerevisiae is associated with a rapid drop in stress resistance. This is disadvantageous for several biotechnological applications, e.g. the preparation of freeze doughs. We have isolated mutants in a laboratory strain which are deficient in fermentation-induced loss of stress resistance ('fil' mutants) using a heat shock selection protocol. We show that the fil1 mutant contains a mutation in the CYR1 gene which encodes adenylate cyclase. It causes a change at position 1682 of glutamate into lysine and results in a tenfold drop in adenylate cyclase activity. The fil1 mutant displays a reduction in the glucose-induced cAMP increase, trehalase activation and loss of heat resistance. Interestingly, the fil1 mutant shows the same growth and fermentation rate as the wild type strain, as opposed to other mutants with reduced activity of the cAMP pathway. Introduction of the fil1 mutation in the vigorous Y55 strain and cultivation of the mutant under pilot scale conditions resulted in a yeast that displayed a higher freeze and drought resistance during active fermentation compared to the wild type Y55 strain. These results show that high stress resistance and high fermentation activity are compatible biological properties. Isolation of fil-type mutations appears a promising avenue for development of industrial yeast strains with improved stress resistance during active fermentation.

[Evaluation of parameters for laboratory diagnosis of genital female infection by Chlamydia trachomatis]

In order to evaluate the occurrence of Chlamydia trachomatis, we have examined samples of cervical swabs from 189 women (166 of which were symptomatic and the remaining 23 were asymptomatic with regard to chlamydial infection. Two specimens from the endocervical channel were collected and examined by immunofluorescent assay (DIF) and Chlamydia isolation. Detection of IgG and IgA antibodies specific to C. trachomatis was also effected by indirect immunofluorescent assay (IIF), in a cervical secretion sample. We succeeded in isolating chlamydia in 14 (8.4%) symptomatic and 3 (13%) asymptomatic women. The observation that the 152 symptomatic patients with negative results from chlamydia culture presented similar symptoms of disease, indicating that there is no specific symptom for genital infection caused by Chlamydia (p > 0.05). All the 13 (76.5%) positive endocervical specimens, as determined by cell culture and DIF reaction, presented more than 5 epithelial cells in the smears. These cells may represent an interference factor to the positivity of cell culture (p < 0.001). Antibodies of the IgG and/or IgA classes were detected in 11 (64.7%) out of 17 women with positive chlamydia culture, considering as positive the IIF titre of > or = 8. Consequently, this method can not be used as an alternative means of diagnosis, particularly in the earlier stages of chlamydial genital infections, since the presence of the antibodies depends on the phase of the infection and on the individual humoral immune response.

[Retinoic acid syndrome. Severe respiratory insufficiency treated with CPAP]

Retinoic acid syndrome is a potentially life-threatening complication of therapy for acute promyelocytic leukemia (APL) with all-transretinoic acid (ATRA). The case of a 55-year old male patient admitted to the hospital because of a bleeding diathesis is reported. APL was diagnosed and he underwent treatment with idarubicin and ATRA (GIMEMA protocol); 24 hrs after ATRA treatment he developed retinoic acid syndrome and was admitted to the Intensive Care Unit because of severe respiratory insufficiency (dyspnoea, tachypnea and severe hypoxemia (SpO2 75%). Pulmonary insufficiency was treated non-invasively with CPAP and the patient recovered from pulmonary distress one week later.

Characterization of a new set of mutants deficient in fermentation-induced loss of stress resistance for use in frozen dough applications

In frozen dough applications a prefermentation period during the preparation of the dough is unavoidable and might also be important to obtain bread with a good texture. A major disadvantage of the prefermentation period is that it is associated with a rapid loss of the freeze resistance of the yeast cells. A major goal for the development of new baker's yeast strains for use in frozen dough applications is the availability of strains that maintain a better freeze resistance during the prefermentation period. We have isolated mutants that retain a better stress resistance during the initiation of fermentation. Some of these showed the same growth rate and fermentation capacity as the wild type cells. These mutants are called 'fil', for deficient infermentation induced loss of stress resistance. First we used laboratory strains and heat stress treatment, given shortly after the initiation of fermentation, as the selection protocol. The first two mutants isolated in this way were affected in the glucose-activation mechanism of the Ras-cAMP pathway. The fil1 mutant had a partially inactivating point mutation in CYR1, the gene encoding adenylate cyclase, while fil2 contained a nonsense mutation in GPR1. GPR1 encodes a member of the G-protein coupled receptor family which acts as a putative glucose receptor for activation of the Ras-cAMP pathway. In a next step we isolated fil mutants directly in industrial strains using repetitive freeze treatment of doughs as selection protocol. Surviving yeast strains were tested individually for maintenance of fermentation capacity after freeze treatment in laboratory conditions and also for the best performing strains in frozen doughs prepared with yeast cultivated on a pilot scale. The most promising mutant, AT25, displayed under all conditions a better maintenance of gassing power during freeze-storage. It was not affected in other commercially important properties and will now be characterised extensively at the biochemical and molecular level.

A specific mutation in Saccharomyces cerevisiae adenylate cyclase, Cyr1K176M, eliminates glucose- and acidification-induced cAMP signalling and delays glucose-induced loss of stress resistance

The cAMP-protein kinase A (PKA) pathway in the yeast Saccharomyces cerevisiae plays a major role in the control of metabolism, proliferation and stress resistance. Derepressed cells show a rapid increase in the cAMP level (within 1 min) after addition of glucose or after intracellular acidification. A specific mutation in adenylate cyclase, the enzyme that catalyzes the synthesis in cAMP, largely prevents both cAMP responses. The responsible mutation was originally called lcr1 (for lack of cAMP responses); lcr1 was later identified as allelic with CYR1/CDC35. The mutation was introduced into the CYR1 gene of a W303-1A wild type strain, which resulted in a large decrease in cAMP signalling. Furthermore, there was a strong reduction in GTP/Mg2+-stimulated but not in Mn2+-stimulated adenylate cyclase activity in isolated plasma membranes, which is consistent with the absence of signalling through adenylate cyclase in vivo. Glucose-induced activation of trehalase was reduced and mobilization of trehalose and glycogen and loss of stress resistance were delayed in the lcr1 mutant. Because of the absence of cAMP signalling during exponential growth on glucose, it was concluded that glucose-induced cAMP signalling is restricted to the transition from gluconeogenic/respiratory to fermentative growth. Activation of the PKA pathway is mediated by a G protein (either Ras1/Ras2 or Gpa2). Constitutive activation of the pathway by Ras2val19 or Gpa2val132 has a negative effect on glycogen and trehalose accumulation and heat shock survival. The lcr1 mutation partially suppresses this effect indicating that the target sites of the two G-proteins on adenylate cyclase might have at least a part in common.