Diazinon resistance, fluctuating asymmetry and fitness in the Australian sheep blowfly, lucilia cuprina

Genetic evidence suggests that the evolution of resistance to the insecticide diazinon in Lucilia cuprina initially produced an increase in asymmetry. At that time resistant flies were presumed to be at a selective disadvantage in the absence of diazinon. Subsequent evolution in natural populations selected modifiers to ameliorate these effects. The fitness and fluctuating asymmetry levels of resistant flies are currently similar to those of susceptibles. Previous genetic analyses have shown the fitness modifier to co-segregate with the region of chromosome III marked by the white eyes, w, locus, unlinked to the diazinon resistance locus, Rop-1, on chromosome IV. This study maps the asymmetry modifier to the same region, shows, as in the case of the fitness modifier, its effect to be dominant and presents data consistent with the fitness/asymmetry modifier being the same gene (gene complex). These results suggest changes in fluctuating asymmetry reflect changes in fitness.     

Platelet-activating factor induces the expression of early pregnancy factor activity in female mice

When synthetic platelet-activating factor (PAF, 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) was injected into mature female mice during dioestrus, pro-oestrus or oestrus, it induced the expression of early pregnancy factor (EPF) activity in the sera of these animals within 1 h of injection. The sera of similarly injected males, metoestrous or immature females did not display any EPF activity. The results suggest that embryo-derived PAF may be the ovum factor responsible for triggering the generation of serum EPF activity during the preimplantation stages of pregnancy.     

Uptake and metabolism of lactosylceramide on low density lipoproteins in cultured proximal tubular cells from normal and familial hypercholesterolemic homozygotes

The metabolism of low density lipoproteins (LDL), and LDL modified by reductive methylation (M-LDL) of lysine residues, was studied in proximal tubular (PT) cells both from normal human kidney and from urine of patients with homozygous (LDL receptor-negative) familial hypercholesterolemia (FH). LDL and M-LDL was labeled either in the protein moiety with 125I or in the lactosylceramide moiety with 3H. The binding and degradation of 125I-LDL in normal cells was saturable and displaced by unlabeled LDL but not by M-LDL. The uptake of [3H]lactosylceramide (LacCer) low density lipoprotein in normal renal cells was saturable, and time and temperature-dependent. Exogenously derived [3H]LacCer on LDL was rapidly taken up and catabolized to monoglycosylceramide, or it was utilized for the endogenous synthesis of globotriaosylceramide (trihexosylceramide) and globotetraosylceramide (tetraglycosylceramide). [3H]LacCer M-LDL was taken up less avidly and metabolized less extensively than [3H]LacCer-LDL in normal cells. In homozygous FH renal cells the binding of 125I-LDL was not saturable and not displaced by unlabeled LDL. 125I-LDL degradation did not occur in FH cells. The homozygous FH PT cells took up a 2-fold greater amount of exogenously derived [3H]LacCer on LDL than normal cells. Yet, most of the [3H]LacCer taken up by FH PT cells accumulated as LacCer, and only small amounts were metabolized to monoglycosylceramide, globotriaosylceramide (trihexosylceramide), or globotetraosylceramide (tetraglycosylceramide). When normal and FH PT cells were preincubated with LDL (0-100 micrograms/ml medium), there was a 5-fold increase in cellular LacCer levels in FH cells at saturating levels of LDL, whereas there was about a 50% decrease in LacCer levels in normal cells. While the high affinity binding of LDL was not essential for the delivery of LacCer to cells, the data support the conclusion that LDL binding to the LDL receptor facilitates further LacCer processing and metabolism in normal renal cells. We speculate that [3H] LacCer is taken up by FH homozygous cells via a LDL receptor-independent mechanism and accumulates in the cells without significant metabolism. LacCer taken up by this mechanism contributes to the storage of LacCer in FH PT cells.     

Seasonal changes in LH secretion in normal ewes and ewes which grazed oestrogenic clover

Plasma luteinizing hormone (LH) concentrations were measured in normal (control) Corriedale X Merino (comeback) ewes and in clover-infertile comeback ewes which had grazed oestrogenic Yarloop clover (Trifolium subterraneum L. cv. Yarloop) for more than 4 years. Plasma LH concentrations were measured in samples taken at 20-min intervals for 6 h during the dioestrous stage of the oestrous cycle in the breeding season (BS) and during the anoestrous season (AS). In the control ewes during BS, transitory elevation in plasma LH concentration (pulses) occurred, reflecting secretory episodes, with a frequency of one per 5.2 h. This frequency fell to one per 16.5 h during the anoestrous season. In clover-infertile ewes, LH pulses occurred with a frequency of one per 4.5 h during BS and one per 4.9 h during AS (difference not significant). In the controls, plasma LH levels were higher (P less than 0.05) during BS (mean +/- s.d. = 1.2 +/- 0.4 ng/ml, n = 9) than in AS (0.7 +/- 0.3 ng/ml, n = 5). In the clover-infertile ewes, plasma LH levels in BS (1.3 +/- 0.6 ng/ml, n = 12) were similar to those of controls. During AS, plasma LH levels in the clover-infertile ewes (1.0 +/- 0.6 ng/ml, n = 10) remained similar to their BS levels, being significantly (P less than 0.05) higher than LH levels in the controls at this time. These studies indicate that the higher plasma concentrations of LH which have been reported in clover-infertile ewes arise from more frequent LH pulses. Furthermore, in contrast to normal ewes, average plasma LH, reflecting pulse frequency, is not reduced in AS. This supports the view that ingestion of phytooestrogens affects neural centres involved in regulating LH secretion.     

Depression of plasma luteinizing hormone concentration in quail by the anticholinesterase insecticide parathion

To examine the effects of parathion on basal plasma luteinizing hormone (LH) concentration, male Japanese quail (Coturnix japonica) were orally intubated with 0, 5 or 10 mg/kg parathion and sacrificed after 4, 8 and 24 hr. At the 5 mg/kg dose, plasma LH levels were reduced at 4 and 8 hr, but returned to control values by 24 hr. Brain acetylcholinesterase activity was substantially reduced by 10 mg/kg parathion (52, 75 and 37% inhibition at 4, 8 and 24 hr, respectively) and plasma LH concentration remained depressed through the 24-hr period. These findings suggest that the organophosphorus insecticide parathion may alter plasma LH concentration in a manner which might impair reproductive activity, and provide indirect evidence for a cholinergic component in the regulation of LH secretion in quail.     

Kinetic and Physical Studies of Cell Death Induced By Chemotherapeutic Agents Or Hyperthermia

The kinetics of three physical parameters: cell density, relative cytoplasmic viscosity and DNA stability to denaturation have been measured during the period preceding cell death induced by hyperthermia, methylprednisolone and a series of cancer chemotherapeutic agents. This series of measurements employed cultured human lymphoblastoid cells as an experimental system to establish the changes that can be observed in the early stages of cell death, prior to applying such measurements to tissue biopsies from solid human tumours. Cell death, induced by hyperthermia up to 43°C, methylprednisolone, vincristine, 5-fluorouracil, BCNU and melphalan, showed essentially identical and reproducible changes corresponding to those which characterize programmed cell death (apoptosis). Such changes could also be observed following hyperthermia above 43°C, but reproducibility was poor and increasing damage to the cell membranes was evident. In cells treated with adriamycin or methotrexate, cell sub-populations showing an increase in cell density were not detected. Measurements of DNA stability were readily performed by flow cytofluorometry thus allowing rapid quantitation of the fraction of cells in the early stages of cell death. Modified flow cytometric instrumentation would further allow measurement of cytoplastic viscosity as an additional parameter to indicate entry into programmed cell death. This suggests that these measurements could readily be applied to cell suspensions derived from tumour tissue biopsies for a more accurate assessment of tumour growth rate, and to allow monitoring of response to therapy in sequential tumour biopsies.     

An enzymatic assay for acetate in spent bacterial culture supernatants

A method is presented for the rapid enzymatic determination of acetate in spent bacterial culture supernatants. The assay is based on a previously published assay for acetate kinase [Bergmeyer et al. (1974) in Methods of Enzymatic Analysis (Bergmeyer, H. V., ed.), Vol. 1, pp. 425-426, Verlag Chemie-Academic Press, New York/London], and is sufficiently sensitive to detect acetate levels of 50 microM. The assay is cheaper than commercially available assays and is particularly useful for occasional use by laboratories not equipped for routine acetate analysis using gas chromatography. The application of the assay to the measurement of acetate in bacterial cultures is described, though it should also be applicable to other biological fluids and foodstuffs.     

Activation of Na+/H+ exchange in lymphocytes by osmotically induced volume changes and by cytoplasmic acidification

After swelling in hypotonic solutions, peripheral blood mononuclear cells (PBM) shrink toward their original volumes. Upon restoration of isotonicity, the cells initially shrink but then regain near-normal size again. This regulatory volume increase (RVI) is abolished by removal of Na+o or Cl-o or by addition of amiloride. RVI is unaffected by removal of K+o or by ouabain and is only partially inhibited by 1 mM furosemide. As a result of increased influx, the cells gain both Na+ and K+ during reswelling. In contrast, only Na+ content increases in the presence of ouabain. Amiloride largely eliminates the changes in the content of both cations. Using diS-C3-(5), no significant membrane potential changes were detected during RVI, which suggests that the fluxes are electroneutral. The cytoplasmic pH of volume-static cells was measured with 5,6-dicarboxyfluorescein. After acid loading, the addition of extracellular Na+ induced an amiloride-inhibitable alkalinization, which is consistent with Na+/H+ exchange. Cytoplasmic pH was not affected by cell shrinkage itself, but an internal alkalinization, which was also amiloride sensitive and Na+ dependent, developed during reswelling. In isotonic lightly buffered solutions without HCO-3, an amiloride-sensitive acidification of the medium was measurable when Na+ was added to shrunken PBM. K+ was unable to mimic this effect. The observations are compatible with the model proposed by Cala (J. Gen. Physiol. 1980. 76:683-708), whereby an electroneutral Na+o/H+i exchange is activated by osmotic shrinking. Cellular volume gain occurs as Cl-o simultaneously exchanges for either HCO-3i or OH-i. Na+i is secondarily replaced by K+ through the pump, but this step is not essential for RVI.     

Vagotomy and Pyloroplasty for Gastric Ulcer

In a series of 68 patients with gastric ulcer who were treated by vagotomy and pyloroplasty there were no operative deaths, though one patient who received massive transfusions died 14 weeks later from hepatic necrosis probably associated with serum hepatitis. Four patients developed recurrent peptic ulceration requiring further surgical treatment. The clinical condition of all but three of the remainder was satisfactory after an average follow-up period of three years and two months. Of the 14 patients who presented with an acutely bleeding gastric ulcer, one subsequently required gastrectomy for continued bleeding; in all the others the immediate and long-term results were satisfactory. Of 21 patients with a “high” ulcer and 29 with combined gastric and duodenal ulceration one (4·8%) and three (10%) respectively suffered recurrences. We conclude that vagotomy and pyloroplasty is a satisfactory form of treatment for a high or bleeding gastric ulcer, but that for all other gastric ulcers some form of gastric resection is preferable.