Synthesis of poly(2-hydroxypropyl methacrylate) latex particles via aqueous dispersion polymerization.

Poly(2-hydroxypropyl methacrylate) latexes were prepared by aqueous dispersion polymerization at 60 °C using poly(-vinylpyrrolidone) [PNVP] as a steric stabilizer. The mean latex diameter can be controlled over a wide range by varying the synthesis parameters (initiator type, stabilizer concentration, addition of co-surfactant or comonomer), and narrow size distributions were observed in most cases. These sterically-stabilized latex particles were characterized by electron microscopy, dynamic light scattering, Malvern Mastersizer and FT-IR spectroscopy. The presence of the PNVP stabilizer at the surface of the latex particles was confirmed by X-ray photoelectron spectroscopy and the stabilizer content was assessed by H NMR spectroscopy and nitrogen microanalyses. Colloidally stable surfactant-stabilized poly(2-hydroxypropyl methacrylate) latexes could also be prepared in the absence of any PNVP stabilizer. Since 2-hydroxypropyl methacrylate contains a small amount of dimethacrylate impurity, these latexes are actually lightly cross-linked; their degree of swelling in DO, d-methanol and d-pyridine was investigated using dynamic light scattering and H NMR spectroscopy. Finally, three ionic water-soluble comonomers were successfully copolymerized with 2-hydroxypropyl methacrylate under aqueous dispersion conditions, as judged by aqueous electrophoresis studies.

Delivery of biological performance via micro-encapsulation formulation chemistry.

Lambda-cyhalothrin micro-capsules have been prepared by a novel in situ procedure. Manipulation of the chemistry has led to slow- and fast-release formulations. The latter has a biological performance comparable to commercial lambda-cyhalothrin emulsifiable concentrates, but exhibits a significantly improved toxicological profile over EC, WP and WG formulations. Micro-encapsulation technology satisfies many of the drivers towards the safer use of pesticides.

Routine radiographer screening for fetal abnormalities by ultrasound in an unselected low risk population.

A screening programme for fetal abnormalities began at The Hillingdon Hospital in July 1986. Second trimester ultrasound scans are performed by radiographers. A combined prospective and retrospective study of the ultrasound findings and outcome in all pregnancies delivered in 1989-1990 was undertaken. 6412 babies were born during this period, of whom 6183 (96%) were examined by ultrasound in the second trimester; 29 pregnancies were terminated for fetal abnormality. Of the 89 fetuses who were abnormal at birth or at induced termination of the pregnancy (1.4%), 84 were scanned in the second trimester. In 51 cases the abnormality was detected before 22 weeks gestation (sensitivity, 60.7%). 56 of these 84 abnormal fetuses scanned had potentially lethal or major handicapping abnormalities of which 41 were detected by ultrasound before 22 weeks gestation (sensitivity, 73%). There was one false positive diagnosis of abnormality which did not affect outcome. 6352 babies were normal at delivery or on discharge from hospital (specificity, 99.98%).

Is maternal alpha-fetoprotein screening still of value in a low-risk area for neural tube defects?

Estimation of maternal serum alpha-fetoprotein (AFP) was used as a screening method for the detection of neural tube defects (NTDs) in 6344 women over three years. Of 88 (1.4 per cent) who had one or more serum AFP levels equal to, or greater than, 2.5 multiples of the median (MoM) for the relevant gestational age, 43 (0.68 per cent) underwent amniocentesis. There were eight NTDs. Four of these were screened by serum AFP, and all cases of spina bifida had serum AFP levels greater than 3.0 MoM, including one small open defect which was not seen on ultrasound. The other four cases of NTD, which were not screened, were identified by ultrasound. Of 64 singleton pregnancies 32 (50 per cent) had serum AFP levels between 2.5 and 3.0 MoM, and low birthweight (less than or equal to 2500 g) occurred in 29 per cent. Because of improvements in ultrasound techniques and the apparent falling incidence of NTD, the role of serum AFP as the primary screening procedure should be regularly reviewed. Effective screening is dependent on mothers booking early.

Obstetric outcome and problems of mid-trimester fetal blood sampling for antenatal diagnosis.

Detailed follow-up is presented of 335 pregnancies in which mid-trimester fetal blood sampling was performed for the diagnosis of a haemoglobinopathy, mostly beta-thalassemia. There were three twin pregnancies. Thirty-eight fetuses were lost including four in whom a diagnosis of thalassemia major was made. Placentacentesis was particularly associated with fetal vessel trauma, exsanguination and early intrauterine fetal death, while late complications associated with fetoscopy or failed fetoscopy necessitating subsequent placentacentesis included spontaneous abortion, leakage of amniotic fluid and premature onset of labour.

Four years' experience of maternal alpha-fetoprotein screening and its effect on the pattern of antenatal care.

Estimation of alpha-fetoprotein (A.F.P.) in maternal serum was used as a screening method for the detection of fetal neural tube defect (N.T.D.) in 7315 women over a four year period. Of these, 5668 pregnancies were tested between 15 and 21 weeks. Action was advised in 129 patients (2.3 per cent). In 74 patients, the only action required was reviewing the notes, including the report of any ultrasound examination, and repeating the blood A.F.P. Detailed ultrasound including scanning the fetal spine was requested in 47 patients and amniocentesis was advised in 19 of these (0.33 per cent). In practice the incidence of amniocentesis was 0.28 per cent as three patients declined our advise. The programme gave detection rates between 15 and 21 weeks of 100 per cent and 75 per cent respectively for anencephaly and open spina bifida. A high fetal mortality was associated with persistently elevated blood A.F.P. levels whether amniocentesis was performed or not.

Ultrasound and amoebic liver abscess.

Eight of 12 patients referred to an ultrasound clinic were eventually found to have a liver abscess. All 8 abscesses were confirmed positively by ultrasonic examination. Using ultrasound, an amoebic abscess can be accurately located within the liver and the optimal site for needling suggested to the clinician. Ultrasound is an accurate, non-invasive, diagnostic aid in this condition.

Ultrasound and jaundice.

We have examined 26 consecutive jaundiced patients referred to the ultrasound clinic. A differentiation between extrahepatic and other causes of jaundice was possible in 23 of the 24 patients satisfactorily examined. The use of ultrasonic techniques in the jaundiced patient offers a high degree of accuracy to the clinician, and little or no discomfort to the patient.

Ultrasound and abdominal hydatid disease.

Twenty-two hydatid cysts have been accurately located in the abdomens of seven patients by ultrasound B-scanning. Lapartomy has confirmed the presence of 19 of these cysts. Grey-scale techniques do not appear to add appreciably to the ease of diagnosis in this condition. Ultrasound can give the clinician a good idea of the extent of the disease process and has the advantage of being completely non-invasive.

Androgen dynamics in vitro in the human prostate gland. Effect of cyproterone and cyproterone acetate.

Hyperplastic and adenocarcinomatous human prostatic tissue was superfused in vitro with radioactively labelled androst-4-ene-3,17-dione, testosterone and 5alpha-dihydrotestosterone (17beta-hydroxy-5alpha-androstan-3-one), with and without addition of the anti-androgens cyproterone and cyproterone acetate. Cyproterone competitively inhibited the entry of the androgens into the majority of the tissues, whereas cyproterone acetate increased this entry. These findings indicated that transport of androstenedione, testosterone and 5alpha-dihydrotestosterone into prostatic tissue is performed by a specific mechanism, possibly involving a carrier situated in the cell membrane. The extent of metabolism of the three androgens was also modified: formation of 5alpha-dihydrotestosterone from testosterone, and of the latter from androstenedione, was decreased by cyproterone and increased by the acetate. Acetate was more effective than cyproterone in decreasing the ;uptake' of the perfused androgens by the tissue; at the same time, it increased the androgen clearance from the tissue. As cyproterone acetate is the more potent of the two anti-androgens, the possibility that these findings in vitro are related to the different anti-androgenic potency exhibited by the two compounds in vivo is discussed. ;Uptake' of the two anti-androgens and the response to their action on androgen dynamics were similar in adenocarcinomatous and hyperplastic glands.

Androgen dynamics in vitro in the human prostate gland. Effect of oestradiol-17 .

Normal, hyperplastic and adenocarcinomatous human prostatic tissue was perfused in vitro with radioactively labelled androstenedione, testosterone and 5alpha-dihydrotestosterone with and without added oestradiol-17beta. Various parameters of tissue-steroid relationship were measured at the steady state. When oestradiol (0.11 or 0.22mumol/l) was added to the perfusing medium, the entry of the steroids into the tissue and their metabolism was increased in the majority of the glands studied. The ;uptake' of all the steroids varied, in response to the addition of oestradiol, in both normal and adenocarcinomatous glands in a way differing from the response of hyperplastic glands. As a consequence, the tissue clearance of the steroids, particularly of androstenedione and testosterone, increased in normal and adenocarcinomatous glands in the presence of oestradiol, and decreased in the hyperplastic tissues. At a concentration 0.33mumol/l, oestradiol decreased the entry of the steroids in all the tissues studied, while the clearance of steroids tended to decrease. The significance of these findings in terms of the regulation of androgen dynamics in vivo in the normal and diseased human prostate, with particular regard to the response to oestrogen treatment, is discussed.