The structure of the GTPase-activating domain from p50rhoGAP

Members of the Rho family of small G proteins transduce signals from plasma-membrane receptors and control cell adhesion, motility and shape by actin cytoskeleton formation. They also activate other kinase cascades. Like all other GTPases, Rho proteins act as molecular switches, with an active GTP-bound form and an inactive GDP-bound form. The active conformation is promoted by guanine-nucleotide exchange factors, and the inactive state by GTPase-activating proteins (GAPs) which stimulate the intrinsic GTPase activity of small G proteins. Rho-specific GAP domains are found in a wide variety of large, multi-functional proteins. Here we report the crystal structure of an active 242-residue C-terminal fragment of human p50rhoGAP. The structure is an unusual arrangement of nine alpha-helices, the core of which includes a four-helix bundle. Residues conserved across the rhoGAP family are largely confined to one face of this bundle, which may be an interaction site for target G proteins. In particular, we propose that Arg 85 and Asn 194 are involved in binding G proteins and enhancing GTPase activity.

[Emergency contraception with mifepristone and anordrin]

OBJECTIVE

To study the efficacy of mifepristone or with anordrin for emergency contraception.

METHODS

300 healthy women were recruited within 7.2 hours after unprotected intercourse or contraceptive failure and randomly allocated into 3 groups. Group 1 (n = 100), mifepristone 25 mg twice with 12 hours apart; group 2 (n = 99), single dose of mifepristone 25 mg; and group 3 (n = 101), mifepristone 25 mg and anordrine 7.5 mg given once.

RESULTS

No pregnancy occurred in group 1, while 1 pregnancy in each group 2 and 3. The contraceptive effectiveness were 100.0%, 83.8% and 86.1% for the 3 groups respectively. The overall menstruation disturbances and side effects were low.

CONCLUSIONS

Both mifepristone 50 or 25 mg were effective for emergency contraception and no synergetic effects of anordrin in combination with mifepristone was shown in this study.

Crystallization and preliminary X-ray analysis of maize ZBP14 protein, a member of a new family of zinc-binding proteins

A preliminary X-ray crystallographic study of a novel zinc-binding protein from maize is presented. Native and several heavy-atom derivative sets of data have been collected on synchrotron sources, to a resolution of 2.1 A. The space group was found to be orthorhombic, P2(1)2(1)2(1), with unit-cell dimensions of a = 92.64, b = 129.45 and c = 196.31 A.

Structure of a 14-3-3 protein and implications for coordination of multiple signalling pathways

A broad range of organisms and tissues contain 14-3-3 proteins, which have been associated with many diverse functions including critical roles in signal transduction pathways, exocytosis and cell cycle regulation. We report here the crystal structure of the human T-cell 14-3-3 isoform (tau) dimer at 2.6 A resolution. Each monomer (Mr 28K) is composed of an unusual arrangement of nine antiparallel alpha-helices organized as two structural domains. The dimer creates a large, negatively charged channel approximately 35 A broad, 35 A wide and 20 A deep. Overall, invariant residues line the interior of this channel whereas the more variable residues are distributed on the outer surface. At the base of this channel is a 16-residue segment of 14-3-3 which has been implicated in the binding of 14-3-3 to protein kinase C.

Effect of levonorgestrel-releasing intrauterine device on hormonal profile and menstrual pattern after long-term use

In the present study 14 women after 6 years' use of levonorgestrel-releasing IUD were investigated for the changes of LH, progesterone (P), estradiol (E2), prolactin (PRL) and serum binding globulin (SHBG) in relation to the levonorgestrel levels throughout a segment of 26-40 days with the aim of comparing the hormonal profiles with those during the first year of use of Lng-IUD. Ultrasound scanning was used to follow the development of follicles along with the RIA measurement of hormones. The results of serum LH, P and E2 showed ovulation in 11 cases with either normal menstrual cycles (5 cases), prolonged or irregular cycles (4 cases) or with amenorrhea for 2-3 years (2 cases). One case showed insufficiency of luteal function and 2 cases showed anovulation but with follicular hyperactivity. Higher percentages of ovulatory cycles (78.5%) were found after 6 years of use. No case of complete suppression of ovulation was found. Anovulatory cycles only constituted 14.3%. Clinically, the development of follicles followed by ultrasound scanning further confirmed the hormonal findings. The persistent enlargement of follicles coincided with high levels of E2. After 6 years of use, the serum levels of levonorgestrel were still maintained at mean levels of 314.26 pmol/L and 470.63 pmol/L in the ovulatory and anovulatory groups, respectively. It is concluded that over two-thirds of the cases have ovulatory cycles after long-term use of Lng-IUD; the contraceptive effect is mainly due to its local action on the endometrium, with much less effect on the ovarian function.

[Epidemiological studies on endemic fluorosis and arsenism in Xinjiang]

Epidemiological and clinical studies on the water of 102 wells containing high-level fluoride and arsenic and a population of 50,760 drinking the water in Kuitun Area, Xinjiang were conducted. Results indicated fluoride and arsenic contents in the well water were associated with geochemical environment, and drinking the water containing high-level fluoride and arsenic for a long-term was the cause of fluorosis and arsenism. Also, diagnostic criteria and major clinical manifestations for fluorosis and arsenism were put forward in the paper. Relationship between fluoride and arsenic contents in the well water and prevalence of fluorosis and arsenism in local residents was analyzed. It suggested fluorosis and arsenism was a systematic disorder and further studies on its potential hazard were merited.

Single dose pharmacokinetics of carbamazepine-10,11-epoxide in patients on lamotrigine monotherapy

The pharmacokinetics of a single oral dose of carbamazepine-10,11-epoxide (CBZ-E, 100 mg) were compared in 10 patients on chronic monotherapy with lamotrigine (LTG, 200-300 mg/day) and in 10 drug-free healthy control subjects. CBZ-E pharmacokinetic parameters in LTG-treated patients were found to be similar to those observed in controls (half-life: 7.2 +/- 1.6 vs 6.1 +/- 0.9 h; apparent oral clearance: 110.8 +/- 53.1 vs 120.5 +/- 29.9 ml/h/kg; apparent volume of distribution: 1.08 +/- 0.37 vs 1.04 +/- 0.25 l/kg respectively; means +/- s.d.). These data indicate that, contrary to previous suggestions, LTG has no effect on the metabolic disposition of CBZ-E.

Equivalent field of paraxial diffraction of a zone plate

A simplified way is proposed to compute the paraxial diffraction of a zone plate. The complicated diffraction field is approximated by an equivalent field, which is the diffraction field of a hole weighted by the area. Based on this equivalent expression of the diffraction field, a graphic method is applied to calculate the resolving power of a zone plate. The result is consistent with those reported in earlier publications [Am. J. Phys. 19, 359 (1951); J. Opt. Soc. Am. 57, 610 (1967)].

Effects of the antidepressant drug viloxazine on oxcarbazepine and its hydroxylated metabolites in patients with epilepsy

The effects of Viloxazine (VLX, 100 mg b.i.d. for 10 days) on the steady-state plasma concentrations of Oxcarbazepine (OXC), its active metabolite 10, 11-dihydro-10-hydroxy-carbazepine (MHD) and the corresponding diol (DHD) were studied in a randomized, double-blind cross-over placebo-controlled trial in 6 epileptic patients stabilized on a fixed dosage of OXC. Administration of VLX resulted in an 11% increase in the plasma concentration of MHD (p = 0.003) associated with a 31% fall in DHD levels (p = 0.0001). Plasma concentrations of unchanged OXC were unaffected by VLX. No changes in seizure frequency nor signs of drug toxicity were observed during the study. Although VLX may inhibit the conversion of MHD to the inactive diol, the interaction is unlikely to be of clinical significance.

Epitope analysis of human insulin and intact proinsulin

Residues belonging to epitopes on human insulin that were recognized by a panel of three monoclonal antibodies were located using mutated insulins and insulins from a number of different animal species. Epitopes on human proinsulin recognized by two monoclonal antibodies were also identified using partially processed proinsulin species. Epitopes were located on the C-A and B-C junctions of proinsulin and on the N-termini of the A- and B-chains and the central region of the B-chain of human insulin. Antibodies that bound proinsulin were found to induce conformational changes in the prohormone. The presence of a well-defined interaction between the C-peptide portion and the N-terminus of the A-chain of the insulin moiety of intact proinsulin has also been demonstrated. The relevance of these studies to the development of two-site assays for the measurement of partially processed proinsulin species in human sera is also discussed.

Role of B13 Glu in insulin assembly

The assembly of the insulin hexamer brings the six B13 glutamate side-chains at the centre into close proximity. Their mutual repulsion is unfavourable and zinc co-ordination to B10 histidine is necessary to stabilize the well known zinc-containing hexamers. Since B13 is always a carboxylic acid in all known sequences of hexamer forming insulins, it is likely to be important in the hormone's biology. The mutation of B13 Glu-->Gln leads to a stable zinc-free hexamer with somewhat reduced potency. The structures of the zinc-free B13 Gln hexamer and the 2Zn B13 insulin hexamer have been determined by X-ray analysis and refined with 2.5 A and 2.0 A diffraction data, respectively. Comparisons show that in 2Zn B13 Gln insulin, the hexamer structure (T6) is very like that of the native hormone. On the other hand, the zinc-free hexamer assumes a quaternary structure (T3/R3) seen in the native 4Zn insulin hexamer, and normally associated only with high chloride ion concentrations in the medium. The crystal structures show the B13 Gln side-chains only contact water in contrast to the B13 glutamate in 2Zn insulin. The solvation of the B13 Gln may be associated with this residue favouring helix at B1 to B8. The low potency of the B13 Gln insulin also suggests the residue influences the hormone's conformation.

[A clinicopathological study of neuronal ceroid lipofuscinosis]

4 unrelated patients with infantile type (one case), late infantile type (one case), juvenile type (two case) of neuronal ceroid-lipofuscinosis were reported. The pathological study by brain biopsy was carried out with light and electron microscopes as well as histochemical methods. Ultrastructurally, the infantile type showed deposits of lipofuscin bodies, fingerprint bodies, and the late infantile type showed a lot of curvilinear bodies and paracrystalline bodies. The ultrastructural configuration in the juvenile type is more heterogeneous and consisted of combination of lipofuscin bodies, fingerprint bodies and multilamellar structures. It was emphasized that fingerprint bodies were first discovered in infantile type, which might challenge the view that only lipofuscin bodies can be found in infantile type.

[Aluminum and fluorine in blood and bone of rats fed on diet mixed with various contents of aluminum, fluoride or their mixture]

Wistar rats were divided into 8 groups:control, 300 ppm F, 130 ppm F, 300 ppm Al, 1200 ppm Al, 130 ppm Al + 130 ppm F. 300 ppm Al + 300 ppm F and 1200 ppm Al + 300 ppm F. The chemicals were mixed into the standard diet. The animals were fed on the diets for 12 weeks. Contents of F, Al, Ca and P in the blood (or serum) and humerus were determined at the end of 12 weeks. The results showed that the level of F in the blood and bone in the unadulterated F group was increased, especially F in the bone reached a level more than 10 times that of the control. In the 3 mixture groups, blood F and bone F were lowered, while blood F was restored to normal level, but bone F was not nevertheless, the results showed that Al was in antagonism to the absorption of F. In the unadulterated Al groups, blood and bone Al did not parallel with the amount of Al administered. The level of Al in the median Al group was higher than that of the high Al group. Taking the level of blood and bone Al as a measure, when different doses of Al were administered with F, in the low and median dosage of Al, F was in antagonism to Al absorption, but in case of high dosage of Al, F was in potentiation to Al absorption. In all the experimental groups serum P was elevated, but serum Ca was not disturbed. Bone Ca and P were decreased only in the 3 groups with unadulterated F as well as unadulterated and adulterated high dosage of Al. Mechanism of the nonlinearity of Al absorption vs Al dosage, as well as the dual effect of F on the absorption of Al was proposed.

Hormonal profile of the menstrual cycle in Chinese women after tubal sterilization

Ten women after tubal sterilization were studied for the hormonal profile of the menstrual cycle. They had undergone sterilization procedures, on the average 5.3 years (range 1.5-10 years) earlier. The serum concentrations of LH, FSH, prolactin, estradiol and progesterone were measured by RIA in daily blood samples of a complete menstrual cycle. Another ten normal women were studied at the same time and were used as the control group. There were no significant differences in the hormonal patterns of the menstrual cycle between the two groups. There was a significantly lower LH level in the early luteal phase of the tubal ligation group compared to the control group. Also, a significantly lower E2 luteal peak compared to the preovulatory peak was observed in the tubal ligation group. The physiological significance of these minor changes is not clear. Only one out of ten women in the tubal ligation group, who had undergone sterilization 1.5 years prior, showed a deficiency in luteal function, but her ovulatory function and menstrual cycle appeared normal. This study indicates that normal hormonal profiles are retained after tubal sterilization.

[Effects of aluminum, fluorine and their mixtures on the enzyme activities of jejunal mucus membrane in the perfusion of small intestine of rats in vivo]

Buffer (control), F as NaF (100 mmol/L), Al as AlCl3 (32 and 170 mmol/L) and the two mixtures of Al and F (Al:F = 0.3:0.7 and 0.7:0.3) in Tris-buffered media of pH 7.0 were respectively perfused through the small intestine of rats over a period of 40 min. The jejunum was taken out from each animal immediately. Some of its parts were for HE staining; and the others for enzyme histochemical staining. Fifteen enzymes were observed. The results showed that (1) Fluorine chiefly inhibited the metal-enzymes and metal-activated enzymes; aluminum mainly depressed the activities of enzymes in relation to the cell energy metabolism, such as hydrogenases and oxidase. (2) The decreased activities of enzymes induced by Al or F increased significantly after mixing with each other, indicating that the simultaneous existence of Al and F decreased their ionic concentrations, so that strong antagonistic effects on the inhibition of enzymes were noticed since F or Al inhibited enzyme activities by their ions. (3) A high dose of Al intensively inhibited the enzymes related to the cell energy metabolism, which explained why less quantity of Al was absorbed in animals with high dose of Al than that of low dose Al seen in the absorption experiment. (4) The enzyme activities in the animals given high dose of Al mixed with F apparently were elevated in comparison with that in the animals given a pure high dose of Al which was the result of antagonistic effects of F on the inhibition of enzyme activities by Al, therefore the quantity of the absorbed Al was high.

Serum SHBG levels during normal menstrual cycle and after insertion of levonorgestrel-releasing IUD

Daily serum sex hormone binding globulin (SHBG) levels were measured during normal ovulatory menstrual cycles in ten women between the ages of 23 and 34 by the method of precipitation with ammonium sulfate. The results showed that the mean SHBG levels in a cycle were quite different among individuals, but that the SHBG levels were constant during a certain menstrual cycle. Neither SHBG peaks on day LH-0 (52.64 +/- 19.89 nmol/L) (x +/- SD) nor the mean SHBG levels between the follicular phase (57.10 +/- 17.64 nmol/L) and luteal phase (64.75 +/- 23.42 nmol/L) show any significant differences. The correlations between the mean SHBG levels and the mean concentrations of progesterone (P), estradiol (E2) and androstenedione during the menstrual cycles were insignificant, whereas the mean SHBG levels during the follicular and luteal phase and on LH-0 day were significantly correlated with the mean concentrations of testosterone (t = 0.474; p less than 0.05). In ten women between the ages of 25 and 34, serum SHBG, E2, P, and levonorgestrel (LNG) levels were measured once on day 20-21 of the pretreatment cycle and 3 times/week during the 1st, and 2 times/week during the 6th treatment cycle after insertion of a levonorgestrel-releasing IUD (LNG-IUD). The mean value of SHBG in the pretreatment blood samples (62.09 +/- 23.09 nmol/L) was higher than that after insertion of the LNG-IUD (41.82 +/- 20.50 nmol/L), though the difference was not significant (p greater than 0.05). The correlation between LNG and SHBG was highly significant (r = 0.89, p less than 0.01). The significance of this correlation and the degree of suppression of ovarian function are discussed.

[Aluminum and fluorine absorption in a perfusion system of rat small intestine in vivo]

Mixtures of aluminum an fluorine in two different ratios in tris-hydroxy-methyl-aminomethane buffered media of pH 7.0 were perfused respectively through the small intestine of the in vivo rat over a period of 40 min. The contents of aluminum and fluorine in the portal vein blood obtained from different perfusion periods were detected and determined simultaneously. The results showed that fluorine absorption was not significant in the mixtures. An obviously large amount of aluminum was absorbed in the mixture with a higher proportion of aluminum (4660 micrograms/ml Al + 200 micrograms/ml F/L), while in the mixture with a lower dose of aluminum (860 micrograms/ml Al + 200 micrograms F/L), a small quantity of aluminum was absorbed. It is evident that the mechanism by which aluminum inhibits fluorine toxicity is that aluminum decreases the intestinal fluorine absorption by the formation of aluminum fluoride complex.

[Autologous mixed lymphoma reaction in patients with malignant lymphoma]

Human T cells can be induced to proliferate in vitro when they are cocultured with autologous Non-T cells. This phenomenon has been termed the autologous mixed lymphocyte reaction, AMLR. In this study, AMLR was assessed in 14 untreated patients with lymphoma and 13 age-and-sex-matched healthy controls. This difference was significant (P less than 0.001), suggesting that patients with lymphoma may have impaired AMLR.

[Observation of enzyme histochemistry and ultrastructure of brain in kindling rats with epilepsy induced by intraperitoneal injection of coriaria lactone]

Kindling model of epilepsy induced by intraperitoneal injection of Coriaria lactone (CL) was used in the experiment. The dose of CL was 1.25 mg/kg. Thirty rats in various periods of kindling were killed and the materials of cerebral cortex, hippocampus and cerebellum were drawn. The enzyme activities of AchE, NADHD, CCO, LDH, SDH, AcP, ANAE and AkP of these areas were observed with enzyme histochemical techniques. In another three kindled rats, two blank control rats and two NS control rats, the ultrastructure of neurons in hippocampus were observed. The results of experiments showed an increased activity of enzymes related to saccharometabolism and energy metabolism, indicating that the metabolism of brain in rats was increased by repeated kindling seizures. The mechanism of kindling seizure induced by CL may be related to inhibitory effect of CL on AchE activity of brain. The degeneration damage of brain neurons in kindled rats may result from using CL for a long time.

[An acute experimental study on the combinations of aluminum and fluorine in various ratios]

The joint actions were assessed by four methods after male Wistar rats had been acutely intoxicated with nine proportional mixtures of Al and F. Strong antagonistic effects of Al on F were observed in the mixtures, in which the ratio of Al to F ranged from 0.8:0.2 to 0.1:0.9. The optimum ratio of Al to F for antagonism ranged from 0.3:0.7 to 0.1:0.9 without periorbital bleeding that was a regular finding in Al acute toxicity on the rat to be seen. When the amount of Al in the mixture was below 5% or above 90%, no antagonistic effect was shown. The kinetics on the absorption under the condition of Al and F existing simultaneously is still unknown, and warrants further investigation.

[The changes of beta-glucuronidase in rabbit model with calcium bilirubinate stone]

The aim of the present study is to determine the beta-glucuronidase changes in bile and hepatobiliary tissue of rabbit model having pigment gallstone by means of biochemical and enzymehistochemical assay methods. The result showed both of the bacterial and non-bacterial beta-glucuronidase take part in the course of pigment gallstone formation. The bacterial beta-glucuronidase level increased quickly before the formation of gallstone, then decreased with control of bacterial infection. Non-bacterial beta-glucuronidase increased slowly in pro-formation stage of gallstone, then kept high level for long period of time. The relationship between beta-glucuronidase and pigment gallstone formation is also discussed.

[Observation of morphological genesis and histochemistry of pulmonary adenocarcinoma in mice]

In the developing process of pulmonary adenocarcinoma in mice induced by N-methyl-N'-nitro-N-nitrosoguanidine, the observations of histological pathology, ultrastructure and the changes of enzyme activity of the lesions related to pulmonary adenocarcinoma were made by light microscopy, transmission electron microscopy and enzyme histochemistry, by sacrificing animals at intervals. The results indicated that there was a series of precancerous lesions before the initiation of adenocarcinoma; that adenoma was a kind of precancerous lesion which might develop into adenocarcinoma; and that adenoma with malignant change might be a focus of early adenocarcinoma. Based on the results of histological pathology, ultrastructure and enzyme histochemistry, a process of the morphological genesis of pulmonary adenocarcinoma in mice was proposed, and the metabolic changes related to various lesions were discussed.

Photoelastic analysis and comparison of force-transmission characteristics of intracoronal attachments with clasp distal-extension removable partial dentures

This investigation photoelastically compared the load-transfer characteristics of various bilateral distal-extension removable partial denture designs embodying intracoronal attachments and clasp assemblies. Six distal-extension designs that included the RPI clasp assembly, cast circumferential clasp, P.D. locking semiprecision, Thompson dowel nonlocking semiprecision, and McCollum and Stern G/L precision attachments were tested. Each prosthesis was subjected to various simulated occlusal loads. Evaluation of the load-transfer characteristics of the various designs was based on comparison of the recorded isochromatic fringe distributions. The RPI clasp assembly generated the most uniform stresses. In general, the four intracoronal retainer frameworks produced higher stresses than did the two clasp frameworks. The highest stresses were developed by the Stern G/L precision attachment.

Dynamic study of serum gonadotrophin and testosterone levels in gossypol-treated men. Long term follow-up study of 60 cases

The endocrine effects of gossypol were studied in 26 men for 52 months before, during and after treatment. A further 34 subjects were studied after cessation of gossypol treatment. A control group of 60 age-matched volunteers were monitored for 1 year. No significant changes in testosterone levels were observed during the course of study. Serum LH levels were, however, significantly higher (P less than 0.001) during earlier phases of gossypol treatment and returned to normal after cessation of treatment except in 14 men with persistent disruption of spermatogenesis. In the latter, serum levels of LH and testosterone were significantly higher (P less than 0.001) than those found in normal subjects and significantly lower (P less than 0.05) than in those subjects in which spermatogenesis had recovered. Serum FSH levels did not rise during the first 8-9 months of treatment with gossypol, although azoospermia generally occurred within 76 days of commencing treatment. After 9 months of treatment, serum FSH levels rose gradually and remained significantly elevated (P less than 0.001) after cessation of treatment in both the azoospermic/oligospermic group and in the group in which spermatogenesis recovered. In the latter group the serum levels of FSH were correlated significantly with the sperm concentration.