Two-Level factorial screening of new plasmid/strain combinations for prodution of recombinant-DNA products

This article treats the basic problem of selection of experimental conditions for microbiological experiments for evaluation of newly isolated bacterial strains, mutants, or plasmid/strain combinations. For this purpose shake flask experiments in a 2(10-4)confounded factorial design at resolution IV with four blocks of 16 flasks were used. The design was used for testing of two new strain/plasmid combinations (E. coli MT 102/403-SD2 and W 3110/403-SD2) i.e., both strains with the same plasmid 403-SD2. Both strains were integrated in the design, so both strains were tested with nine factors (temperature, aeration, glucose, initial pH, pH regulation, reduced aeration, chloramphenicol, acetate, and glycerol). With both strains the interaction between initial pH and reduced aeration had a significant influence on the yield of the recombinant-DNA product nuclease. There was more than a factor of 10 between lowest and highest yield of product. In this interactive system the strains reacted differently. MT 102/403-SD2 had highest yields at high initial pH (8.4) and no reduction in aeration, whereas W 3110/403-SD2 had highest yields of nuclease at low initial pH (7.4) and reduced aeration (rubber stopper inserted after cultivation for 12 h). These data (and previous work) clearly demonstrate that it is impossible to suggest a simple set of experimental conditions for testing of new plasmid/strain combinations. It is clear that the exclusive application of a standardized growth technique e.g., LB-medium at 37 degrees C at an unspecified and uncontrolled aeration level, may lead to wrong conclusions on properties and potentials of now plasmid/strain combinations and may lead to rejection of useful strains or plasmids.

Phases and phase transitions of hexagonal cobalt oxide films on Ir(100)-(1 × 1)

Cobalt oxides on the unreconstructed Ir(100) surface were prepared by reactive deposition of Co established by simultaneous oxygen flux at about 50 °C and subsequent annealing. The films were investigated by low-energy electron diffraction (LEED), scanning tunnelling microscopy (STM) and thermal desorption spectroscopy (TDS). We show that in spite of the quadratic unit mesh of the substrate, oxide films of (111) orientation develop. As long as oxygen-rich conditions are maintained they are of spinel-type Co(3)O(4)(111). They are non-pseudomorphic and transform to rocksalt-type CoO(111) when oxygen loss is induced by annealing at elevated temperatures. Thin films of CoO(111) are commensurate, and so, in order to realize that, they exhibit a slightly distorted unit cell when below a thickness equivalent to about seven cobalt monolayers. With increasing film thickness the uniaxial strain accompanied by the commensurability is gradually relieved by the insertion of dislocations so that eventually the film assumes ideal hexagonality. All CoO(111)-type surfaces are reconstructed at low sample temperatures equivalent to a [Formula: see text] superstructure. They reversibly transform into a (1 × 1) phase at about 50 °C.

Coexistence of rocksalt and wurtzite structure in nanosized CoO films

Cobalt oxide (CoO) films epitaxially grown on Ir(100) in (111) orientation were investigated by means of quantitative low-energy electron diffraction and scanning tunneling microscopy. We find with high crystallographic precision that in the bulk of the films the rocksalt structure prevails while near the surface there is a switch towards the wurtzite structure. As a consequence, nanosized CoO cannot be considered as a single structural phase. The film surfaces prove to be metallic, apparently connected with polarity compensation.

Surface structure of polar Co(3)O(4)(111) films grown epitaxially on Ir(100)-(1 × 1)

Cobalt oxide films were prepared by oxidation of different amounts of cobalt deposited on Ir(100)-(1 × 1), where oxygen rich conditions were applied during deposition. The resulting oxide films with thicknesses of up to about 40 Å were investigated as regards their crystallographic structure and morphology, applying quantitative low energy electron diffraction (LEED) and scanning tunnelling microscopy (STM). It can be unequivocally shown that the spinel-type Co(3)O(4) phase develops, for which an excellent fit between measured and calculated LEED intensity spectra is achieved (Pendry R-factor R = 0.124). In spite of the quadratic unit cell of the substrate the oxide films are in the polar (111) orientation. Also, the native lattice parameter of the material is assumed, i.e. there is no pseudomorphic relation to the substrate. However, by means of orientational epitaxy, one of the unit-mesh vectors of the oxide and one of those of the substrate layer are aligned, leading to two mutually orthogonal domains in the oxide. The oxide is terminated by a sublayer of cobalt ions which in the bulk were tetrahedrally coordinated Co(2+) ions. There are drastic relaxations of layer spacings at and near the surface. As a consequence, the bond length between the surface terminating cobalt ions and oxygen ions below is considerably reduced, indicative of a substantial change of the ionicity of the cobalt and/or oxygen ions. This is interpreted as accounting for polarity compensation of the film, as surface reconstruction, oxygen vacancies and species adsorbed can be ruled out.

Crystal Structure of the Orf Virus NZ2 Variant of Vascular Endothelial Growth Factor-E

Mammalian vascular endothelial growth factors constitute a family of polypeptides, vascular endothelial growth factor (VEGF)-A, -B, -C, -D and placenta growth factor (PlGF), that regulate blood and lymphatic vessel development. VEGFs bind to three types of receptor tyrosine kinases, VEGF receptors 1, 2, and 3, that are predominantly expressed on endothelial and some hematopoietic cells. Pox viruses of the Orf family encode highly related proteins called VEGF-E that show only 25-35% amino acid identity with VEGF-A but bind with comparable affinity to VEGFR-2. The crystal structure of VEGF-E NZ2 described here reveals high similarity to the known structural homologs VEGF-A, PlGF, and the snake venoms Vammin and VR-1, which are all homodimers and contain the characteristic cysteine knot motif. Distinct conformational differences are observed in loop L1 and particularly in L3, which contains a highly flexible GS-rich motif that differs from all other structural homologs. Based on our structure, we created chimeric proteins by exchanging selected segments in L1 and L3 with the corresponding sequences from PlGF. Single loop mutants did not bind to either receptor, whereas a VEGF-E mutant in which both L1 and L3 were replaced gained affinity for VEGFR-1, illustrating the possibility to engineer receptor-specific chimeric VEGF molecules. In addition, changing arginine 46 to isoleucine in L1 significantly increased the affinity of VEGF-E for both VEGF receptors.

[Sodium concentration and pre-eclampsia: is salt restriction of value?]

The significance of sodium metabolism with respect to preeclampsia is discussed in the literature with a wide range of diverging opinions. The presented work analyses the influence of a low salt diet on the symptoms of preeclampsia and the consequences for the newborn.

MATERIAL AND METHODS

160 patients with preeclampsia between 1989 and 1993 were retrospectively studied. Serum sodium values (at hospital admission, lowest prepartal level, immediate and 3-8 days postpartum) were compared with the corresponding gestosis symptoms.

RESULTS

The mean sodium serum concentration at admission was 135.6 mmol/l (lower norm: 136 mmol/l). This was significantly different from the mean lowest prepartal value of 134.9 mmol/l (p < 0.0001). Postpartum the mean fell again significantly to 134.0 mmol/l (p < 0.0001). None of the parameters for gestosis symptoms, which were investigated (diastolic blood pressure, edema, proteinuria, serum protein levels and hyperreflexia) showed any statistically significant association with the serum sodium concentration. Five patients had very low serum natrium values, 130 mmol/l, either at admission or during hospitalisation. Three of the five infants of these patients had hyponatremia; two needed sodium supplementation.

CONCLUSION

There seems to be no reason supporting a low salt diet as therapy for preeclampsia, since it does not affect the symptoms and might lead to hyponatremia in the newborn.

Prevention of vertical HIV transmission: additive protective effect of elective Cesarean section and zidovudine prophylaxis. Swiss Neonatal HIV Study Group

OBJECTIVE

To study the effect of elective Cesarean section and zidovudine prophylaxis on vertical HIV transmission.

DESIGN

Prospective study.

SETTING

Obstetric and paediatric clinics in Switzerland.

PARTICIPANTS

Children of mothers with HIV infection identified before or at delivery.

INTERVENTIONS

Routine use of elective Cesarean section for HIV-infected parturients by some Swiss centres since 1985. National recommendation for zidovudine prophylaxis in mid-1994.

MAIN OUTCOME MEASURE

HIV infection status of children.

RESULTS

In a cohort of 494 children born at least 6 months before the analysis date, 67 out of 414 children with known infection status were found to be infected, giving an overall transmission rate of 16.2% [95% confidence interval (CI), 13.0-18.51. Elective Cesarean section with intact membranes and without previous labour was associated with a lower transmission rate of 6% [odds ratio (OR), 0.29; 95% CI, 0.12-0.70; P = 0.006 versus other delivery modes]. Transmission rate was intermediate after spontaneous delivery or non-elective Cesarean section (18%), and higher after obstetric interventions (27%; test for trend, P < 0.001). Since mid-1994, 78% of all women with registered pregnancies have received some form of zidovudine prophylaxis. Transmission rate was reduced from 17 to 7% after any zidovudine exposure (OR, 0.4; 95% CI, 0.11-1.41). Combined use of elective Cesarean section and zidovudine resulted in a 0% transmission rate (none out of 31), compared with 8% (seven out of 86) after elective Cesarean section without zidovudine, 17% (four out of 24) after zidovudine alone, and 20% (55 out of 271) after no intervention.

CONCLUSIONS

Elective Cesarean section and zidovudine prophylaxis appear to have an additive effect in the prevention of vertical HIV transmission.

The use of antibodies for characterization and quantification of a recombinant protein

In this study, we characterized proteinase A secreted by recombinant Saccharomyces cerevisiae bearing a multicopy plasmid containing the encoding gene (PEP4). Polyclonal and monoclonal antibodies were raised to study the product heterogeneity. Characterization of proteinase A was performed by immunoelectrophoresis and immunoblotting techniques. None of the monoclonal antibodies raised against proteinase A was found to react with the glycosyl side chains; thus cross-reaction with other glycosylated proteins (e.g. carboxypeptidase Y) was very low. This study allowed us to develop an ELISA method for the quantification of proteinase A in culture supernatants as well as the evaluation of monoclonal antibodies for their use in immunoaffinity chromatography.

Mathematical modeling of proteinase A overproduction by Saccharomyces cerevisiae

A simple, structured model was developed to describe the growth and product formation behavior of two recombinant strains of Saccharomyces cerevisiae (JG176 and JG180), both overproducing extracellular proteinase A. The model parameters were estimated to data from continuous fermentations obtained at steady-state conditions. Model predictions show good agreement with experimental data obtained by batch fermentations. The two concerned organisms are distinguished from each other by the type of promoter on the plasmids controlling the proteinase A expression. The proteinase A transcription is controlled by the natural proteinase A promoter in JG176 and by a tpi promoter in JG180. By means of experiments and simulations, the extracellular product formation from the two strains with different promoter systems was compared in batch and continuous fermentations. The results showed that the proteinase A formation kinetic from JG176 was a combination of growth and nongrowth associated (production in the stationary growth phase), whereas the proteinase A formation from JG180 was truly growth associated (production in the exponential growth phase). In both batch and continuous cultivations JG176 gave the highest product concentrations and volumetric productivities.

Lysozyme binds to elastin and protects elastin from elastase-mediated degradation

Lysozyme has been shown to be associated with damaged elastic fibers in many tissues and organs. To better characterize this interaction, binding of lysozyme to elastin was studied using solution-based binding assays. Under physiologic conditions, radio-labeled lysozyme bound specifically to elastin in a time- and concentration-dependent manner. Binding was reversible and was inhibited by unlabeled human and hen lysozyme but not by other proteins. Lysozyme had no elastolytic activity as assessed by a standard tritium-release assay, but, importantly, prevented the proteolytic degradation of elastin by human leukocyte elastase, pancreatic elastase, thermolysin, and Pseudomonas elastase. A striking feature of lysozyme's anti-elastase activity was that it did not function in the classical sense of inhibiting directly the enzymatic activity of the protease. Instead, by binding to elastin, lysozyme prevented the protease from interacting with the elastin substrate in ways that normally favor proteolysis. These results show that lysozyme binds to the elastin component of elastic fibers and that this interaction has important biological consequences for elastic fiber degradation. By preventing degradation of elastin, lysozyme can function as an important natural inhibitor that exerts a protective effect on elastic fibers at sites of tissue injury.

Production of proteinase A by Saccharomyces cerevisiae in a cell-recycling fermentation system: experiments and computer simulations

Overproduction of proteinase A by recombinant Saccharomyces cerevisiae was investigated by cultivations in a cell-recycling bioreactor. Membrane filtration was used to separate cells from the broth. Recycling ratios and dilution rates were varied and the effect on enzyme production was studied both experimentally and by computer simulations. Experiments and simulations showed that cell mass and product concentration were enhanced by high ratios of recycling. Additional simulations showed that the proteinase A concentration decreased drastically at high dilution rates and the optimal volumetric productivities were at high dilution rates just below washout and at high ratios of recycling. Cell-recycling fermentation gave much higher volumetric productivities and stable product concentrations in contrast to simple continuous fermentation.

Sleep and the sleep electroencephalogram across the menstrual cycle in young healthy women

Cyclic changes in hormones, body temperature, and metabolic rate characterize the menstrual cycle. To investigate whether these changes are associated with changes in sleep and the sleep electroencephalogram (EEG), a total of 138 sleep episodes from 9 women with no premenstrual syndrome symptoms were recorded every second night throughout one ovulatory menstrual cycle and analyzed in relation to menstrual phase. Ovulation and menstrual cycle stage were confirmed by measurements of temperature, urinary LH, and midluteal plasma levels of estrogen and progesterone. No significant variation across the menstrual cycle was observed for subjective ratings of sleep quality and mood as well as for objective measures of total sleep time, sleep efficiency, sleep latency, rapid eye movement sleep latency, and slow wave sleep. In nonrapid eye movement sleep, EEG power density in the 14.25-15.0 hertz band, which corresponds to the upper frequency range of the sleep spindles, exhibited a large variation across the menstrual cycle, with a maximum in the luteal phase. The data show that in healthy young women, sleep spindle frequency activity varies in parallel with core body temperature, whereas homeostatic sleep regulatory mechanisms, as indexed by the time course of EEG slow wave activity are not substantially affected by the menstrual cycle.

[HIV and pregnancy]

Since 1990 216 HIV-infected pregnant women have been enrolled in an ongoing nationwide study named "HIV and Pregnancy" financed by the Swiss Federal Office of Health (No. 90-7007 and 93-7131). Of a total of 228 recorded pregnancies 154 continued to parturition. Until now it has been definitively established whether or not 89 offsprings have been infected with HIV by their mothers. According to clinical and immunological findings most of the pregnant women are still in early, stable stages of HIV-infection (stages II and III of the CDC classification system in 94% of the subjects; mean CD4-cell count around 600/microliters). HIV infection was the consequence of an intravenous substance abuse in two thirds of the women. Detailed interviews revealed an alarming negligence with regard to compliance with safer sex recommendations and contraception. Advisory services of specialized AIDS information centers have very rarely been called on. In our group, the vertical transmission rate shows a statistically significant correlation with low maternal anti-HIV-p24 antibody titers, high serum neopterin- and IgA-concentrations, and also with the use of forceps and vacuum in vaginal delivery. Maternal substance abuse but not HIV infection itself resulted in an incidence of preterm deliveries roughly twice as high as in the normal Swiss population.

Uremic small-artery disease with medial calcification and intimal hyperplasia (so-called calciphylaxis): a complication of chronic renal failure and benefit from parathyroidectomy

BACKGROUND

Uremic small-artery disease with medial calcification and intimal hyperplasia can lead to life-threatening skin necrosis or acral gangrene. It is a distinct complication of chronic renal failure that must be differentiated from soft-tissue calcification. An increased calcium-phosphate product and secondary hyperparathyroidism are the main underlying conditions. The benefit of parathyroidectomy is controversial.

OBJECTIVE

This article is based on a literature search to determine prognostic factors and, in particular, the benefit of parathyroidectomy.

METHODS

The literature on uremic small-artery disease (so-called calciphylaxis) was reviewed (full data set: 104 cases, including five of our own). The therapeutic benefit of parathyroidectomy and the relation between prognostic predictors (localization, dialysis, and transplant) and outcome were analyzed. The relation between diabetes and acral gangrene was also examined. Further epidemiologic data on the reviewed group of patients were established.

RESULTS

Thirty-eight of 58 patients who underwent parathyroidectomy survived compared with 13 of 37 patients who did not undergo parathyroidectomy (p = 0.007, n = 95). Forty of 53 patients with distal localization of necrosis survived compared with 11 of 42 patients with proximal pattern (p < 0.00001; n = 95). Dialysis and kidney transplantation followed by immunosuppression showed no relation to disease outcome. No association was found between diabetes and acral gangrene (p = 0.50).

CONCLUSION

Uremic small-artery disease is a distinct complication of chronic renal failure. Its recognition and early diagnosis should allow more effective treatment. In our retrospective study parathyroidectomy was significantly related to survival. Only a randomized, controlled, prospective trial (parathyroidectomy vs conservative treatment of secondary hyperparathyroidism) can establish the value of parathyroidectomy in uremic small-artery disease.

[Pregnancies in HIV infected women in Switzerland]

In a national multicentre study, 229 pregnancies in 219 HIV-positive women were prospectively followed up between January 1, 1990, and October 30, 1993. 69.8% were infected by intravenous drug abuse and 91.5% were asymptomatic (CDC classes II and III) in early pregnancy. 48 (21.0%) were first discovered to be HIV-infected during the index pregnancy: 46 of these had risk factors. The present epidemiologic development does not seem to warrant a general HIV-screening in pregnancy at this time. 71 pregnancies (31%) were terminated; 158 children were born, 17 (23.3%) of the 73 definitely classified are HIV-infected. An asymptomatic HIV infection with a sufficiently high (> 200/microliters) CD4 cell count has no proven influence on the pregnancy. Otherwise, however, maternal infectious diseases can lead to prematurity. For mothers with i.v. drug abuse, there is a significantly higher incidence of prematurity and fetal growth retardation. The maternal HIV infection can be transmitted to the child either during pregnancy or at delivery. The incidence of vertical transmission in our study was 23.3%; the most predictive parameter for a prenatal HIV transmission is a low anti-p24 antibody titre. The risk of intrapartum transmission seems to be somewhat, but not significantly, reduced for primary Caesarean sections. Recently, prophylaxis with Zidovudin during pregnancy, beginning after the 14th GW, was found to reduce vertical HIV-transmission by 66%. Since the virus can also be transmitted through mothers' milk, HIV-positive mothers should not nurse their babies. Maternal infections are significantly more frequent in HIV-positive women, and are a risk factor for prematurity.(ABSTRACT TRUNCATED AT 250 WORDS)

[Characteristics of isoforms of Serratia marcescens from electrospray mass spectrometry]

Electrospray mass spectrometry was used to determine the molecular masses of nuclease isoforms isolated and purified from the cultural fluid of Serratia marcescens B10M1. The primary structure of each of the isoforms isolated from the nuclease preparations was established by comparing their masses with the known amino acid sequence encoded by the nuc-gene. The structure of some of these isoforms was verified by N-terminal sequencing, that of nearly all isoforms-by isoelectric focusing. All nuclease isoforms were found to be variants of native nuclease split at the molecular N-termini.

[Nuclease isoforms of natural and recombinant strains of Serratia marcescens. Comparative characteristics of plasma desorption mass spectrometry]

The primary structure of isoforms of natural nuclease secreted by Serratia marcescens as well as of recombinant nuclease produced by Escherichia coli has been characterized by plasma desorption mass spectrometry. The isoforms were isolated from the purified nuclease on a DEAE-cellulose anion-exchange column and digested with endoproteinase Lys-C. The peptides generated were isolated by reversed phase IIPLC and their molecular masses determined by plasma desorption mass spectrometry. Among the nuclease isoforms secreted by parent cells, a new isoform, Sm3, was found. Comparison of the peptides yielded by nuclease Sm2 and two isoenzymes, Sm1 and Sm3, demonstrated their distinction only in the N-termini; three amino acids are lacking in Sm1 and one residue in Sm3. Identity was demonstrated between nucleases Sm1 and Sm2 produced by S. marcescens and the isoforms rSm1 and rSm2 secreted by the recombinant E. coli strain.

[Premature labor in HIV infected women. Swiss "HIV and Pregnancy" Study Group]

In the Swiss Study "HIV and pregnancy" we observed 153 singleton pregnancies of HIV-positive women. 23 (15%) of those ended with a premature delivery. For drug addicts (n = 100), the incidence of prematurity, 20%, significantly higher than in those free of drugs (n = 53) with 5.6%. The most frequent cause of prematurity was premature labor or rupture of the membranes (n = 13), followed by maternal illness (n = 8) and fetal complications (n = 2). Women with premature delivery tended to have lower CD4 cell counts than those with term delivery (29.4% vs 12.0% with < 200 CD4 cells/microliters). Low CD4 cell counts and drug consumption are two independent but cumulative risks for severe infections. 16 of the 153 women (12 with, 4 without drug consumption) had severe infections during pregnancy; in 4 cases (25%), this led to prematurity. The most common infection was pneumonia (14/16), further one case of pyelonephritis and one of cerebral toxoplasmosis. Two of these 16 infants (12.5%) were HIV-positive. We could not confirm a relationship between prematurity and vertical HIV transmission. Of the HIV-classified children, 3/18 (16.7%) premature infants and 16/74 (21.6%) term infants were infected.

Pregnancy, immunosuppression and reactivation of latent toxoplasmosis

Toxoplasmosis is a chronic, latent infection which can be reactivated in the presence of immunosuppression. The critical question in obstetrics is whether toxoplasmosis may be reactivated in the presence of the physiological "immunosuppression" of pregnancy. Standard in vitro tests, done in 24 healthy pregnant women and compared with the literature, show no significant changes in humoral and cellular immunity during pregnancy. However, the fact that some infections occur more frequently and more severely than in non-pregnant women (e.g. those due to cytomegalovirus (CMV) and human papilloma virus (HPV) points to a degree of pregnancy-associated immunosuppression. Non-rejection of the semiallogenic fetus is achieved in presence of maternal immunocompetence and is explained mainly by local changes in immune function, mediated by inhibitors of decidual, placental and fetal origin, and by the absence of class II histocompatibility antigens at the fetomaternal interface. Immune status allowing reactivation of toxoplasmosis was studied in a selected group of (predominantly male) AIDS patients from the Swiss HIV Cohort study. Shortly before (cerebral) reactivation of toxoplasmosis, 92% of these patients had very low CD4 lymphocyte counts (mean 50 cells/microliters, i.e. lower than ever recorded in a normal uncomplicated pregnancy). In a larger population of 48 women receiving immunosuppressive therapy after organ transplantation, not a single case of cerebral toxoplasmosis was observed during pregnancy, while in the 105 HIV-positive women in the Swiss HIV and Pregnancy study, there was only one case of cerebral toxoplasmosis during pregnancy and the puerperium (20 CD4/microliters), even though some 17% of those sampled (18/105) had CD4 levels below 200 cells/microliters on at least one occasion during pregnancy. These findings explain why latent toxoplasmosis is not reactivated in normal pregnancy, and why it is only likely in an immunosuppressed mother when her CD4 lymphocyte count is very low (< 200 cells/microliters). In such cases, a prophylactic treatment to prevent maternal reactivation and vertical transmission of toxoplasmosis may be useful.

Do neuroactive steroids cause fatigue in pregnancy?

To elucidate factors causing widespread fatigue in pregnancy we studied plasma samples from 23 healthy pregnant volunteers, measuring endogenous neuroactive steroids, endozepines and benzodiazepines by receptor binding assays. The samples were taken at different gestational ages and the women were asked about their feeling of fatigue at the time of sample collection. We found a significant correlation between fatigue in pregnancy and presence of neuroactive steroid-like activity, but could not detect endogenous benzodiazepine-like factors. These results suggest that neuroactive steroids may be involved in fatigue during pregnancy. Their site of synthesis and their biological role remain unclear.

Changes in sleep and sleep electroencephalogram during pregnancy

The impairment of sleep quality is a common complaint during pregnancy. To investigate the changes in sleep in the course of pregnancy, the sleep electroencephalogram (EEG) was recorded and analyzed in nine healthy women on 2 consecutive nights during each trimester of pregnancy. Waking after sleep onset increased from the second (TR2) to the third (TR3) trimester, whereas rapid eye movement (REM) sleep decreased from the first trimester (TR1) to TR2. Spectral analysis of the EEG in nonrapid eye movement (NREM) sleep revealed a progressive reduction of power density in the course of pregnancy. In comparison to TR1, the values in TR2 were significantly lower in the 10.25-11.0-Hz and 14.25-17.0-Hz bands. In TR3, the significant reduction extended over the ranges of 1.25-12.0 Hz and 13.25-16.0 Hz. The largest decrease (30%) occurred in the 14.25-15.0-Hz band. In REM sleep, the spindle frequency range was not affected, and a minor reduction of power density in some frequency bins below 12 Hz was present only in TR3. The study documents major alterations of the sleep EEG that are not evident from the sleep scores and that may be associated with the characteristic hormonal changes occurring during pregnancy.

Quantitative anti-p24 determinations can predict the risk of vertical transmission. Swiss HIV and Pregnancy Collaborative Study Group

Quantitative serum antibody to p24 was evaluated as a predictor of risk of vertical transmission of human immunodeficiency virus type 1 (HIV-1) infection. HIV-positive mothers, 13 with HIV-infected children and 24 with noninfected children were investigated during pregnancy and at the time of delivery. A statistically significant difference in anti-p24 titers was found between the mothers with infected and those with noninfected children independent of whether antibodies were measured during pregnancy or at the time of delivery. High anti-p24 levels correlated with a low risk of vertical transmission, whereas low anti-p24 titers were associated with an increased risk of vertical transmission. Although the number of CD4+ T-cells was lower and neopterin and beta-2 microglobulin values were higher in the group of mothers with infected children than in the noninfected group, no statistical significance was achieved due to the small sample size.

Relevance of the miscarriage-new pregnancy interval

There is a wide divergence of opinion concerning the interval a woman should wait after a miscarriage before attempting a new pregnancy ("pregnancy interval"). Many authors recommend waiting 3-4 months in order to reduce the risk of another miscarriage [3, 6, 17, 21]. This retrospective study investigated whether a longer pregnancy interval lowers the risk of repeat miscarriage (R-risk) and/or prematurity. The association between parity and R-risk was also analyzed. Results showed that there are no proven reasons to recommend a waiting period between a miscarriage and a subsequent pregnancy, because the R-risk was around 20% irrespective of interval duration. Prematurity too is not influenced by a waiting period after miscarriage. There was, however, an association between parity and R-risk and risk of prematurity: nulliparae were more likely to have a repeat miscarriage (p < 0.05) or a preterm delivery in the next pregnancy (p < 0.05) than women who had already given birth to a child.

Characterization of natural and recombinant nuclease isoforms by electrospray mass spectrometry

Isoforms of natural and recombinant nuclease have been characterized on the basis of their M(r) as determined by electrospray m.s.. The natural nuclease was isolated and purified from Serratia marcescens B10M1 and the recombinant nuclease from Escherichia coli MT102 carrying the plasmid p403-SD2. The primary structure of each of the isoforms isolated from the nuclease preparations was established by comparing their mass with the known amino acid sequence derived from the nucleotide sequence of the nuc gene. All the preparations were found to be contaminated with the same N-terminal split variants of native nuclease, although the natural nuclease contained much larger amounts of these isoforms than did the recombinant nuclease. The structure of some of the isoforms could be verified by N-terminal sequencing, and nearly all of them by isoelectric focusing.

Characterization of proteinase A glycoforms from recombinant Saccharomyces cerevisiae

Proteinase A produced by Saccharomyces cerevisiae carrying the gene PEP4 (which encodes the prepro-proteinase A on multicopy plasmids) was isolated and characterized by means of SDS/PAGE, laser desorption m.s. (l.d.m.s.) and high-performance capillary electrophoresis. Although proteinase A is normally located in the yeast vacuole, overexpression resulted in it being secreted. SDS/PAGE revealed that the product isolated from the culture medium comprised an approx, 7:3 mixture of two different forms of proteinase A, the apparent molecular masses of which were 42 and 40 kDa respectively. The exact mass of each form, measured by l.d.m.s., was 40,755 and 38,132 Da respectively. Further analysis employing N-glycosidase F digestion and CNBr cleavage revealed that the larger molecule was native proteinase A bearing carbohydrate moieties at Asn68 and Asn269, whereas the smaller molecule was a proteinase A variant glycoform lacking the carbohydrate moiety at Asn269. Capillary electrophoresis of both the normal and underglycosylated proteinase A glycoforms revealed charge heterogeneities attributable to differences in the phosphorylation level of the carbohydrate moiety at Asn68.

Isolation and characterization of the outer membrane proteins of Serratia marcescens W225

The study addressed the general problem of fractionating cell envelopes in order to isolate the outer membranes of gram-negative bacteria. Whereas the cells are normally transformed into spheroplasts prior to disintegration and membrane separation, Serratia marcescens was found to be resistant to spheroplast formation using the procedures available, which were originally developed for Escherichia coli. An efficient technique for spheroplasting S. marcescens was therefore developed; this comprised combining osmotic shock and lysozyme-EDTA treatment of sucrose-conditioned cells. Spheroplasting efficiency and the amount of outer membrane protein recovered were highly dependent on the spheroplasting technique used. Separation of the outer and inner membranes was performed by two methods, isopyenic centrifugation and selective detergent solubilization with Sarkosyl. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and the analysis of specific inner membrane marker enzymes revealed that the protein obtained by detergent solubilization was much purer than that obtained by isopycnic centrifugation. The outer membrane isolated accounted for 60% of the envelope proteins and had a buoyant density of 1.2502 g/cm3. The protein profile of the outer membrane determined by SDS-PAGE resolved into 12 distinct protein bands, 3 of which represented major proteins.

Characterization of Serratia marcescens nuclease isoforms by plasma desorption mass spectrometry

Isoforms of Serratia marcescens nuclease found in the natural nuclease produced by S. marcescens and in recombinant nuclease produced by Escherichia coli were structurally characterized by peptide mapping using plasma desorption mass spectrometry. The nuclease isoforms produced and secreted from S. marcescens B10M1, which are present in much greater amounts than in S. marcescens W225 nuclease produced by E. coli, were characterized completely and the information used to facilitate characterization of the recombinant nuclease isoforms. After purification of the nuclease the isoforms were separated on a DEAE-cellulose anion-exchange column and then digested with endoproteinase Lys-C. The peptides generated were isolated by reverse-phase HPLC and their molecular masses determined by plasma desorption mass spectrometry. Comparison of the peptides from the native nuclease, Sm2, and the two isoforms, Sm1 and Sm3, revealed that they differed only in the N-terminus, the latter being found to lack three amino acids in Sm1 and one amino acid in Sm3. No interior post-translational changes were found in either of the three isoforms. Using this information we were able to confirm that Sm1, the isoform lacking three amino acids, was also present in very small amounts in recombinant S. marcescens W225 nuclease produced and excreted by E. coli.

Separation of isoforms of Serratia marcescens nuclease by capillary electrophoresis

Three S. marcescens nuclease isoforms differing mainly in charge (native nuclease with pI 6.8 and two minor isoforms with pI 7.3 and 7.4) were separated using several different modes of high-performance capillary electrophoresis. Separation of the isoforms by free solution capillary electrophoresis was unsatisfactory. Separation by micellar electrokinetic capillary chromatography was therefore investigated in detail and the method optimized with respect to pH and sodium dodecyl sulphate concentration; in addition, the effect of adding various substances to control dispersion and avoid analyte adsorption at the capillary wall was examined. Under optimal conditions there was almost complete baseline separation of the two isoforms with basic pI whereas there was only partial separation of the native form and the isoform with pI 7.4. With capillary isoelectric focusing there was complete baseline separation of the native nuclease and the other two isoforms.

[Early recognition of fetal abnormalities by transvaginal ultrasonography]

Three case reports illustrate situations where transvaginal sonography (TVS) can be important for detecting foetal malformation. In each of these cases a reliable diagnosis was not possible by abdominal ultrasound either because the part of the foetus to be examined lay too low in the pelvis or because it could not be imaged clearly enough due to lack of amniotic fluid. As we would recommend in such cases, diagnosis was then made by TVS. Since the area which can be imaged by TVS is limited mechanically by the anatomical situation, however, it should not be used as the primary method for prenatal screening, whereas in certain selected cases it can provide information not obtainable otherwise.

Case report 693: Schneckenbecken dysplasia

Three siblings with SBD from consangineous parents are reported. The prenatal diagnosis of a short-limbed form of dwarfism was made by ultrasonography and the final diagnosis in the index case by radiography, demonstrating a short-limbed, platyspondylic dwarf with a snail-like configuration of the ilium and vertebral bodies, flat on AP and round on lateral view. The histological examination showed a generalized, severe disturbance of cartilage formation with marked hypercellularity of proliferating and resting zones, reduction of intercellular matrix, and shortening of the irregular columns of proliferating cartilage. The ultramicroscopic findings were nonspecific. This is the first report of SBD after the original description, bringing the total to 14 cases in 5 families. The correct radiological diagnosis and the differential diagnosis, in particular thanatophoric dysplasia, are essential for genetic counselling and obstetrical guidance of families affected with this autosomal recessive dysplasia.

Quantitative binding studies of a monoclonal antibody to immobilized protein-A

Binding constants and column capacities are important factors for evaluating an affinity chromatography system. Scatchard plots based on classical equilibrium binding have been used to demonstrate how association constants and column capacities can be computed from simple binding experiments and a commercial computer program. The analysis has been demonstrated on a monoclonal antibody type IgG-1 Kappa against Serratia marcescens nuclease and a commercial protein-A column, Prosep-A. Additional analyses were performed with the same antibody and other protein-A affinity systems and the different binding constants and column capacities obtained confirmed the value of the analysis for evaluating an affinity system.

Fermentation studies of the secretion of Serratia marcescens nuclease by Escherichia coli

The secretion of a Serratia marcescens nuclease was followed by fermentation with Escherichia coli. A plasmid, p403-SD2, carrying a 1.3-kilobase-pair insert with a 0.4-kilobase-pair region upstream of the nuclease gene caused a growth-phase-regulated expression of nuclease in E. coli in the same way as that seen in S. marcescens. Deletion of the regulatory gene generating plasmid p403-Rsa1 resulted in a constitutive expression of the nuclease. Anaerobiosis stimulated the expression from p403-SD2 in stationary growth phase by a factor of 10 compared with expression stimulated by cultivation in aerobic conditions; no such effect was found for plasmid p403-Rsa1. Different nutritional factors caused the expression level and the amount of extracellular nuclease to vary more when nuclease was expressed from plasmid p403-SD2 than when it was expressed from plasmid p403-Rsa1. A correlation between the regulatory gene and the extracellular secretion of nuclease is proposed.

Purification and characterization of a Serratia marcescens nuclease produced by Escherichia coli

The primary structure and physical chemical properties were determined of a nuclease expressed and secreted by Escherichia coli. The plasmid p403-SD2 carried a DNA sequence isolated from Serratia marcescens encoding the enzyme. During cultivation of the E. coli cells, 85% of the enzyme was released to the growth medium. The enzyme was purified and exhibited a single band with a molecular weight about 30,600 daltons on SDS-PAGE similar to nuclease isolated from S. marcescens. The amino acid composition and the amino acid sequence determined directly confirmed the primary structure of 245 amino acids predicted from the DNA sequence, and, in addition, the two disulfide bridges were assigned. Several physical chemical properties were examined. The ability of the enzyme to cross the outer membrane is proposed to depend upon the formation of the proper structures during the folding process.