Specific enzymatic dephosphorylation of the retinoblastoma protein.

The retinoblastoma gene product (RB) undergoes cell cycle-dependent phosphorylation and dephosphorylation. Pulse-chase experiments revealed that the change in RB gel electrophoretic migration which occurs near mitosis is due to enzymatic dephosphorylation (J. W. Ludlow, J. Shon, J. M. Pipas, D. M. Livingston, and J. A. DeCaprio, Cell 60:387-396, 1990). To determine the precise timing of RB dephosphorylation and whether a specific phosphatase is active in this process, we have utilized a nocodazole block and release protocol which allows a large population of cells to progress synchronously through mitosis. In such experiments, RB dephosphorylation began during anaphase and continued until complete dephosphorylation was apparent in the ensuing G1 period. In addition, late mitotic cell extracts were capable of dephosphorylating RB in vitro. This RB-specific mitotic phosphatase activity was more active in anaphase extracts than in pro- or metaphase extracts, which is consistent with the results obtained in vivo. Okadaic acid and protein phosphatase inhibitors 1 and 2 inhibited this specific RB phosphatase activity. These results suggest a role for serine and threonine phosphoprotein phosphatase type 1 in the late mitotic dephosphorylation of RB.     

Village trial of bednets impregnated with wash-resistant permethrin compared with other pyrethroid formulations

Abstract. A village-scale field trial of pyrethroid-impregnated mosquito nets was undertaken in The Gambia, West Africa, in the Mandinka village of Saruja (13^o13'N, 14^o55'W) during July-November 1989. Nearly all the villagers possessed and used their own bednets. Anopheles gambiae is the main vector of human malaria in the area.
An experimental wash-resistant formulation of permethrin was compared with standard emulsifiable concentrate (EC) formulations of permethrin and lambda-cyhalothrin, versus placebo-treated bednets. Target concentrations of pyrethroids on bednets were permethrin 500mg/m² and lambda-cyhalothrin 25 mg/m². The experimental design involved random allocation of a treatment to one net per family. Whereas 68% of people questioned said they washed their nets fortnightly, observations during the 16-week trial period showed that only 4/130 (3%) of nets involved in the trial had been washed as frequently as once per month.
Early morning searches for mosquitoes under bednets (1 day/week for 16 weeks) found significantly more mosquitoes (60% An. gambiae ) in placebo-treated nets than in pyrethroid-treated nets. The numbers found with each of the three pyrethroid treatments did not differ significantly from each other. Insecticidal efficacy of the treatments was tested by bioassays using wild-caught unfed mosquitoes exposed to netting for 3min. Linear regression analysis of bioassay mortality against number of times that a net had been washed by villagers showed that nets impregnated with the wash-resistant permethrin retained their insecticidal properties better than nets impregnated with lambda-cyhalothrin or with the standard permethrin formulation.     

Chemotropism and branching as alternative responses of Achlya bisexualis to amino acids

Hyphae of Achlya bisexualis growing on lean media orient their extension towards a source of amino acids, and also put forth branches. Micropipettes were used to generate gradients of amino acids in the vicinity of individual hyphae. Phenylalanine and methionine were the most powerful attractants: 0.04 mM amino acid in the pipette produced reorientation, and higher concentrations made the hyphae curl around the pipette and grow into its tip. Hyphae detected gradients as low as 5% across their width. Methionine and phenylalanine appeared to bind to different receptors. Local application of these amino acids also elicited the emergence of single branches, next to the pipette and on the high side of the gradient; comparison of diverse amino acids and their analogues suggested that branching and chemotropism share common receptors. By contrast, cytochalasin A and various ionophores induced branches at random sites, without receptor involvement. We propose that binding of amino acids to their receptors determines the site of precursor vesicle exocytosis, and consider possible mechanisms.     

Relation between socioeconomic deprivation and pathological prognostic factors in women with breast cancer.

OBJECTIVE--To investigate the relation between socioeconomic deprivation and pathological prognostic factors in women with breast cancer as a possible explanation for socioeconomic differences in survival. DESIGN--Retrospective analysis of data from cancer registry and from pathology and biochemistry records. SETTING--Catchment areas of two large teaching hospitals in Glasgow. SUBJECTS--1361 women aged under 75 who had breast cancer diagnosed between 1980 and 1987. MAIN OUTCOME MEASURES--Tumour size, axillary lymph node status, histological grade, and oestrogen receptor concentration in relation to deprivation category of area of residence. RESULTS--There was no significant relation between socioeconomic deprivation and four pathological prognostic factors: 93 (32%) women in the most affluent group presented with tumours less than 20 mm in size compared with 91 (31%) women in the most deprived group; 152 (48%) of the most affluent group presented with negative nodes compared with 129 (46%) of the most deprived group; 23 (22%) of the most affluent group presented with grade I tumours compared with 12 (17%) of the most deprived group; and 142 (51%) of the most affluent group had a low oestrogen receptor concentration at presentation compared with 148 (52%) of the most deprived group. None of these differences was statistically significant. CONCLUSIONS--Differences in survival from breast cancer by socioeconomic deprivation category could not be accounted for by differences in tumour stage or biology. Other possible explanations, such as differences in treatment or in host response, should be investigated.     

Detection of Aldehydes and Their Conjugated Hydroperox Ydiene Precursors in Thermally-Stressed Culinary Oils and Fats: Investigations Using High Resolution Proton Nmr Spectroscopy

High field (400 and 600 MHz) proton NMR spectroscopy has been employed to investigate the thermally-induced autoxidation of glycerol-bound polyunsaturated fatty acids present in intact culinary frying oils and fats. Heating of these materials at 180°C for periods of 30, 60 and 90 min. generated a variety of peroxidation products, notably aldehydes (alkanals, trans-2-alkenals and alka-2, 4-dienals) and their conjugated hydroperoxydiene precursors. Since such aldehydes appear to be absorbed into the systemic circulation from the gut in vivo, the toxicological significance of their production during standard frying practices is discussed.     

Haemorrhagic disease of the newborn in the British Isles: two year prospective study.

OBJECTIVE--To determine the incidence of haemorrhagic disease of the newborn in the British Isles, study risk factors, and examine the effect of vitamin K prophylaxis. DESIGN--Prospective survey of all possible cases of haemorrhagic disease of the newborn as reported by consultant paediatricians using the monthly notification cards of the British Paediatric Surveillance Unit and a follow up questionnaire for each case to validate the diagnosis and accrue further data. SETTING--Britain (England, Scotland, and Wales) and Ireland (Northern Ireland and the Irish Republic) during December 1987 to March 1990. PATIENTS--27 infants classified as having confirmed (n = 25) or probable (n = 2) haemorrhagic disease of the newborn. RESULTS--24 of the 27 infants were solely breast fed. 10 suffered intracranial haemorrhage; two of these died and there was clinical concern about the remainder. 20 infants had received no vitamin K prophylaxis, and seven had received oral prophylaxis. Relative risk ratios for these groups compared with babies who had received intramuscular vitamin K were 81:1 and 13:1 respectively. Six infants had hepatitis (alpha 1 antitrypsin deficiency in four), unsuspected until presentation with haemorrhagic disease of the newborn, of whom four had received oral prophylaxis. One other baby had prolonged jaundice. One mother had taken phenytoin during pregnancy. CONCLUSIONS--All newborn infants should receive vitamin K prophylaxis. Intramuscular vitamin K is more effective than oral prophylactic regimens currently used in the British Isles.