Microsatellite instability in yeast: dependence on repeat unit size and DNA mismatch repair genes

We examined the stability of microsatellites of different repeat unit lengths in Saccharomyces cerevisiae strains deficient in DNA mismatch repair. The msh2 and msh3 mutations destabilized microsatellites with repeat units of 1, 2, 4, 5, and 8 bp; a poly(G) tract of 18 bp was destabilized several thousand-fold by the msh2 mutation and about 100-fold by msh3. The msh6 mutations destabilized microsatellites with repeat units of 1 and 2 bp but had no effect on microsatellites with larger repeats. These results argue that coding sequences containing repetitive DNA tracts will be preferred target sites for mutations in human tumors with mismatch repair defects. We find that the DNA mismatch repair genes destabilize microsatellites with repeat units from 1 to 13 bp but have no effect on the stability of minisatellites with repeat units of 16 or 20 bp. Our data also suggest that displaced loops on the nascent strand, resulting from DNA polymerase slippage, are repaired differently than loops on the template strand.     

P2Y2 nucleotide receptors expressed heterologously in sympathetic neurons inhibit both N-type Ca2+ and M-type K+ currents

The P2Y2 receptor is a uridine/adenosine triphosphate (UTP/ATP)-sensitive G-protein-linked nucleotide receptor that previously has been reported to stimulate the phosphoinositide signaling pathway. Messenger RNA for this receptor has been detected in brain tissue. We have investigated the coupling of the molecularly defined rat P2Y2 receptor to neuronal N-type Ca2+ channels and to M-type K+ channels by heterologous expression in rat superior cervical sympathetic (SCG) neurons. After the injection of P2Y2 cRNA, UTP inhibited the currents carried by both types of ion channel. As previously reported [Filippov AK, Webb TE, Barnard EA, Brown DA (1997) Inhibition by heterologously expressed P2Y2 nuerones. Br J Pharmacol 121:849-851], UTP inhibited the Ca2+ current (ICa(N)) by up to 64%, with an IC50 of approximately 0.5 microM. We now find that UTP also inhibited the K+M current (IK(M)) by up to 61%, with an IC50 of approximately 1.5 microM. UTP had no effect on either current in neurons not injected with P2Y2 cRNA. Structure-activity relations for the inhibition of ICa(N) and IK(M) in P2Y2 cRNA-injected neurons were similar, with UTP >/= ATP > ITP > GTP,UDP. However, coupling to these two channels involved different G-proteins: pretreatment with Pertussis toxin (PTX) did not affect UTP-induced inhibition of IK(M) but reduced inhibition of ICa(N) by approximately 60% and abolished the voltage-dependent component of this inhibition. In unclamped neurons, UTP greatly facilitated depolarization-induced action potential discharges. Thus, the single P2Y2 receptor can couple to at least two G-proteins to inhibit both Ca2+N and K+M channels with near-equal facility. This implies that the P2Y2 receptor may induce a broad range of effector responses in the nervous system.     

Recovery of thermally-stressed Escherichia coli O157:H7 by media supplemented with pyruvate

Unheated and heat-stressed (57 degrees C, 50 min and 60 min) cells of Escherichia coli O157:H7, were enumerated using three media supplemented with 1% sodium pyruvate (NaPyr): plate count agar (PCA), tryptic soy agar (TSA) and phenol red sorbitol agar (PhRSA) using the spread plate method. The medium recovering the greatest numbers of severely heated E. coli O157:H7 was PCA with 1% NaPyr. Recovery of heat stressed E. coli O157:H7 on this medium was significantly higher (P < 0.05) than the two other media with pyruvate: 16.3% (50 min heating) and 0.55% (60 min heating) of the total population was recovered with TSA + 1% NaPyr when compared to those numbers found on PCA + 1% NaPyr. The ability of PhRSA + 1% NaPyr to recover heat-stressed E. coli O157:H7 was similar to that of TSA + 1% NaPyr. Using PhRSA + 1% NaPyr media. 12.9% (50 min heating) and 0.61% (60 min heating) of the total population were recovered when compared with the cells enumerated on PCA + 1% NaPyr. Recovery of the heat-stressed cells using the spread plate method was greater than using pour plate method. Recovery was significantly higher (P < 0.05) on the spread plates for highly stressed E. coli O157:H7(1.2 log) heated for 60 min than on the pour plates. Overall, the populations on the TSA spread and pour plates were low compared with the same heat-stressed cells recovered on media containing pyruvate. The     

A physical model of sound diffraction and reflections in the human concha

An approximated physical model of the frequency transfer function of the human concha is developed in this paper. This formulation includes diffraction, reflection, and interference phenomena in the concha cavity. The performance of the proposed diffraction/ reflection model is compared with that of the single-delay-and-add approximation by checking their predictions against the experimental transfer function of a metal spiral-shaped diffracting/reflecting system. Results show that the diffraction/reflection model performs considerably better at predicting both the absolute center frequency of spectral minima and the relative frequency spacing between them. The diffraction/reflection model is then applied to a realistic concha shape and its predictions are compared with experimental head-related transfer functions for azimuth- and elevation-varying sound sources. In this case, the model predicts the elevation-dependent spectral features related to the transverse dimensions of the concha. Additionally, the diffraction/reflection model predicts that, because of sound diffraction, similar spectral features must be generated in the concha for sources at all azimuths within the frontal part of the ipsilateral hemisphere. Experimental and theoretical evidence supporting this prediction is presented.     

Hormonal and gestational parameters in female rats submitted to the pilocarpine model of epilepsy

Endocrine and reproductive alterations are frequently reported to occur in women with temporal lobe epilepsy as well as in female rats in different experimental models of limbic seizures. As previously reported, women with epilepsy have lower fertility rates than women without epilepsy (Tanganelli, P., Regesta, G., 1992. Neurology (suppl.) 42 (5), 89-93; Cummings, L.N., Guidice, L., Morrel, M.J., 1995. Epilepsia 36, 355-359). In order to investigate the possible substrate of endocrine alterations in epilepsy, hormonal and gestational parameters were studied in female rats submitted to the pilocarpine model of epilepsy. The results demonstrated that the oestrus cycle is altered following pilocarpine-induced status epilepticus and such alteration lasted for several weeks. Progesterone, LH and FSH levels decreased and estradiol levels increased significantly during the period of spontaneous and recurrent seizures. The frequency of seizures during pregnancy and lactation decreased. These results document that significant changes in gonadal, hypophyseal and hypothalamic hormones, as well as in sexual behaviour, occur following status epilepticus induced by pilocarpine administration.     

A lea-class gene of tomato confers salt and freezing tolerance when expressed in Saccharomyces cerevisiae

Although less cytotoxic, the new platinum complex [meso-1,2-bis(2,6-difluoro-4-hydroxyphenyl)-ethylenediamine]sulfatopl atinum (II) (2) is equipotent to cisplatin (1) in the oestrogen-dependent MXT mammary tumour of the mouse. As this may be due to oestrogen level-lowering properties, we compared the effect of 1 and 2 on steroidogenesis in the rat. A single dose of 1 and 2 (20 mumol/kg s.c.) decreased plasma testosterone level in male rats by 90% (1, day 3) and 80% (2, day 7). Luteinizing hormone level remained unchanged in intact and in ovariectomized rats. The activities of the following testicular enzymes were decreased (day 7): cholesterol side-chain cleavage enzyme (1: 33%; 2: 36%), 3 beta-hydroxysteroid dehydrogenase/delta 4,delta 5-isomerase (1: 31%; 2: 48%) and 17 alpha-hydroxylase/17,20-lyase (1: 21%; 2: 15%). Testicular microsomal cytochrome P450 content was also diminished (1: 60%; 2: 49%, day 7). Corticosterone level in plasma and biosynthesis in adrenal explants was not affected, indicating the selectivity of action at the gonadal level. In vitro, neither 1 nor 2 (2 and 20 microM) influenced binding of human chorionic gonadotropin to testis interstitial cells during an observation period up to 21 h. These results suggest that 1 and 2 act at the gonadal level by inhibiting the expression of the steroidogenic enzymes. They do not, however, inactivate the luteinizing hormone receptor.     

Pregnancy outcomes among women with and without diabetic microvascular disease (White's classes B to FR) versus non-diabetic controls

The objective of this paper is to evaluate the impact of contemporary management on the maternal and neonatal outcomes of pregnancies complicated by diabetes in women with microvascular disease versus women without microvascular disease. The study population consisted of two hundred and eighty-eight (288) pregnant women with pregestational diabetes and one hundred and fifty (150) healthy pregnant controls. Diabetic women were grouped according to the presence (n = 103) or absence of diabetic microvascular disease (n = 185). Data were collected regarding diabetes management, level of glycemic control, and the development of antenatal complications. Maternal and neonatal outcomes were compared among the three groups. Women in the diabetes groups were stratified according to mean blood glucose levels and glycosylated hemoglobin during each trimester. There was no significant difference found between the two diabetes groups in terms of preterm labor, polyhydramnios, pyelonephritis, and growth restriction. The only maternal complications that occurred with increased incidence among women with microvascular disease were acute hypertensive complications (51.6 vs. 32.9%; p<0.05). However, when the diabetes groups were compared to healthy controls, a significant difference was seen in all maternal and neonatal complications. Preterm delivery, polyhydramnios, and large-for-gestational-age (LGA) infants were associated with poor third-trimester metabolic control as compared with others in satisfactory metabolic controls: 30.8 vs. 11.4% for preterm delivery; 17.3 vs. 5.1% for polyhydramnios; 51.9 vs. 33.9% for LGA; p<0.05. Congenital malformations were associated with poor first-trimester glucose control (5.8 vs. 1.3% anomalies in well-controlled women). Furthermore, major congenital malformations were also significantly increased in the offspring of women with diabetic microvascular disease 6.8%, as compared to 1.69% in diabetic women without microvascular disease; p<0.01. The incidence of hypertensive complications did not differ between the two diabetic groups. Pregestational diabetic women with and without microvascular disease can be counseled to anticipate comparably favorable pregnancy outcomes, although maternal and neonatal complications may exceed that experienced by pregnant women without diabetes mellitus.     

Computerized medication instruction for psychiatric inpatients admitted for acute care

We studied the efficacy and feasibility of using computer-based instruction to provide medication information to hospitalized patients with acute psychotic conditions. Patients were randomly assigned to receive computer-based (n = 21) or personal instruction (n = 21); for the final analyses the computer group was expanded to include 13 patients from a pilot study. Outcome measures were knowledge retention (indicated by changes in test scores) and compliance with medication regimens after discharge (indicated by telephone follow-up at one week, one month, and three months). The subjects reacted positively to the computer program. Knowledge retention and compliance were similar in the computer and control groups. We conclude that psychiatric inpatients admitted for acute care can participate in, and learn from, computerized medication instruction.