Target Organ Toxicity in Rats After Subchronic Oral Exposure to Soil Extracts Containing a Complex Mixture of Contaminants.

Complex mixtures of unknown contaminants present a challenge to identify toxicological risks without using large numbers of animals and labor-intensive screens of all organs. This study examined soil extracts from a legacy-contaminated pesticide packaging and blending site. HepG2 cytotoxicity was used as an initial screen of 18 soil samples; then, three extracts (A, B and C) from different locations at the study site were used for testing in animals. The first two extracts were identified as the most toxic in vitro, and the latter extract obtained from a location further from these two toxic sampling sites. Then, target organ toxicities were identified following biweekly oral gavage for one month of three soil extracts (0.1% in polyethylene glycol or PEG) compared to vehicle control in male Sprague-Dawley rats (n = 9-10/group). Exposure to extract A significantly increased neutrophils and lymphocytes compared to control. In contrast, all extracts increased plasma α-2 macroglobulin and caused mild-to-moderate lymphocytic proliferation within the spleen white pulp, all indicative of inflammation. Rats exposed to all soil extracts exhibited acute tubular necrosis. Cholinesterase activity was significantly reduced in plasma, but not brain, after exposure to extract A compared to control. Increased hepatic ethoxyresorufin-o-deethylase activity compared to control was observed following exposure to extracts A and B. Exposure to soil extract C in rats showed a prolonged QTc interval in electrocardiography as well as increased brain lipid peroxidation. Candidate contaminants are organochlorine, organophosphate/carbamate pesticides or metabolites. Overall, HepG2 cytotoxicity did not successfully predict the neurotoxicity and cardiotoxicity observed with extract C but was more successful with suspected hydrocarbon toxicities in extracts A and B. Caution should be taken when extrapolating the observation of no effects from in vitro cell culture to in vivo toxicity, and better cell culture lines or assays should be explored.

Genotoxicity of methyl acrylate and ethyl acrylate and its relationship with glutathione.

Methyl acrylate (MA) and ethyl acrylate (EA) had previously tested positive for mutagenicity in vitro, but in vivo studies were negative. One of the metabolism pathways of alkyl acrylates is conjugation with glutathione. The glutathione availability is restricted in standard in vitro test systems so that they do not reflect the in vivo metabolism in this respect. We investigated whether the addition of glutathione to the in vitro L5178Y/TK+/- mouse lymphoma mutagenicity test prevents alkyl acrylate's mutagenicity in vitro. We also investigated whether the quantitative relationships support the notion that the GSH supplemented in vitro systems reflect the true in vivo activity. Indeed, glutathione concentrations as low as 1 mM completely negate the mutagenicity of MA and EA in the L5178Y/TK+/- mouse lymphoma mutagenicity test up to the highest concentrations of the two acrylates tested, 35 µg/ml, a higher concentration than that previously found to be mutagenic in this test (14 µg MA/ml and 20 µg EA/ml). 1 mM Glutathione reduced the residual MA and EA at the end of the exposure period in the mutagenicity tests by 96-97%, but in vivo up to 100 mg/kg body weight MA and EA left the glutathione levels in the mouse liver and forestomach completely intact. It is concluded that the in-situ levels of glutathione, 7.55 ± 0.57 and 2.84 ± 0.22 µmol/g mouse liver and forestomach, respectively, can efficiently protect against MA and EA-induced mutagenicity up to the high concentration of 100 mg MA and EA/kg body weight and that the negative in vivo mutagenicity tests on MA and EA reflect the true in vivo situation.

Evaluation of a large-scale donation of Lifebox pulse oximeters to non-physician anaesthetists in Uganda.

Pulse oximetry is widely accepted as essential monitoring for safe anaesthesia, yet is frequently unavailable in resource-limited settings. The Lifebox pulse oximeter, and associated management training programme, was delivered to 79 non-physician anaesthetists attending the 2011 Uganda Society of Anaesthesia Annual Conference. Using a standardised assessment, recipients were tested for their knowledge of oximetry use and hypoxia management before, immediately following and 3-5 months after the training. Before the course, the median (IQR [range]) test score for the anaesthetists was 36 (34-39 [26-44]) out of a maximum of 50 points. Immediately following the course, the test score increased to 41 (38-43 [25-47]); p < 0.0001 and at the follow-up visit at 3-5 months it was 41 (39-44 [33-49]); p = 0.001 compared with immediate post-training test scores, and 75/79 (95%) oximeters were in routine clinical use. This method of introduction resulted in a high rate of uptake of oximeters into clinical practice and a demonstrable retention of knowledge in a resource-limited setting.

Changes in frailty-related characteristics of the hip fracture population and their implications for healthcare services: evidence from Quebec, Canada.

SUMMARY: This study provides evidence that a number of frailty-related characteristics (older age, de novo admission to long-term care (LTC), comorbidities [Charlson Index, osteoporosis, osteoporosis risk factors, sarcopenia risk factors, and dementia]) have increased in the hip fracture population from 2001-2008. This will have significant impact on community resources, as the number of people discharged to the community is also increasing. INTRODUCTION: The aim of this study is to estimate secular changes in the prevalence of selected frailty-related characteristics among the hip fracture population in the Canadian province of Quebec (2001-2008) and the potential impact of these changes on healthcare services. METHODS: The Quebec hospitalization database was used to identify nontraumatic hip fractures for the purposes of calculating age- and sex-specific rates. Also estimated were time trends for selected frailty-related characteristics and discharge destinations. RESULTS: A significant decline in fracture rates was evident for all age groups except for those <65; sex differences were also observed. Almost all frailty-related characteristics increased over time, ranging from 2 to 14 % per year, which translates to an estimated increase from 16 to 112 %, over the study period. For those whose prior living arrangement was LTC, rates of hip fractures declined significantly (women OR = 0.93, 0.91-0.95; men OR = 0.97, 0.94-0.99). In-hospital mortality and discharge to inpatient rehabilitation decreased, while discharges back to community and to LTC increased. CONCLUSIONS: Although hip fracture rates decreased for older hip fracture patients, the absolute number and prevalence of specific frailty-related characteristics increased. Policy makers should review care models to ensure that adequate resources are provided to the community to offset the expected increase in demand arising from ongoing changes in patients' characteristics.

Molecular test to determine toxigenic capabilities in GDH-positive, toxin-negative samples: evaluation of the Portrait toxigenic C. difficile assay.

New recommendations for testing and reporting of Clostridium difficile were introduced in the NHS in 2012. These guidelines have improved identification of potential C. difficile infection (CDI) cases, but questions remain around the management of glutamate dehydrogenase (GDH)-positive, toxin-negative patients. This study aims to assess the introduction of the Portrait C. difficile assay as the third step to identify the presence of the toxigenic C. difficile B (tcdB) gene and thus determine toxigenic capability. Stool samples with a GDH-positive, toxin-negative result were tested using the Portrait analyser to detect the presence of tcdB. A retrospective evaluation was performed, assessing the clinical course of patients who were isolated as a result of the current algorithm using GDH enzyme immunoassay (EIA) and toxin EIA. Of the stool samples tested, 40% carried the tcdB gene. Four tcdB-positive stool samples initially toxin A/B-negative subsequently became positive. Thirteen patients were isolated, four of which did not have the tcdB gene. The total time to 'process' a positive CDI case was 102 hours and cost pounds 592. The additional time and cost of incorporating the Portrait toxigenic C. difficile assay was 105-115 minutes and pounds 46.48 to pounds 51.88. This study confirms that toxigenic capabilities in GDH-positive, toxin-negative specimens can facilitate effective treatment and infection prevention, and results show there is potential value in repeat toxin testing.

An evaluation of the effects of a service change from epidurals to rectus sheath catheters on postoperative pain.

Epidurals are frequently used as part of multi-modal perioperative analgesia. They are widely accepted as providing excellent pain relief but are associated with side-effects, have a significant failure rate and can limit a patient's mobility. We report on our use of rectus sheath catheters (RSCs), in conjunction with intravenous opiate via patient controlled analgesia (PCA), as a means of providing analgesia post-laparotomy for gynaecological oncological patients. Our experience is that this offers an alternative method of providing equivalent analgesia, avoiding the risks associated with epidural use and possibly has a role in reducing length of patient stay, although this requires further investigation.

Cytosine arabinoside transport and metabolism in acute leukemias and T cell lymphoblastic lymphoma.

Cytosine arabinoside (araC) has proven efficacy in acute myeloid leukemia (AML), but its place in the treatment of acute lymphoblastic leukemia (ALL) and T lymphoblastic lymphoma is uncertain. The therapeutic potential of araC has been assessed in patients with AML, ALL, and T lymphoblastic lymphoma by measuring the conversion of araC to its active metabolite, the 5'-triphosphate of araC (araCTP), in purified blasts from patients as well as in normal polymorphs and lymphocytes. In all leukemias, araCTP was the major intracellular metabolite of araC. The highest araCTP formation was in blasts from T lymphoblastic lymphoma, which formed threefold more nucleotide than myeloblasts, and in turn myeloblasts formed twofold more araCTP than lymphoblasts from ALL. The mean araCTP formation in myeloblasts was sixfold greater than polymorphs, but in contrast, lymphoblasts and lymphocytes formed low and similar amounts of this nucleotide. Reasons for the sixfold range in araCTP accumulation in the various leukemic blasts were studied. The mean size of myeloblasts was 35-70% larger than lymphoblasts when compared on the basis of protein or intracellular water content, but T lymphoblastic lymphoma blasts and lymphoblasts were the same size. Activities of deoxycytidine kinase, deoxycytidylate deaminase, and pyrimidine nucleoside monophosphate kinase were not different between any of the leukemic cell types. The number of nucleoside transport sites on blasts was estimated by measuring the equilibrium binding of [3H]nitrobenzylthioinosine (NBMPR), which binds with high affinity to the transporter. Scatchard analysis yielded mean values of 27,500 sites/cell for T lymphoblastic lymphoma blasts, 10,000 sites/cell for myeloblasts, and 2,300 sites/cell for lymphoblasts. Our previous work has shown that araC influx correlates with the maximum number of 3H-NBMPR binding sites in leukemic and normal white cells. A strong correlation was observed between the number of nucleoside transport sites per leukemic blast cell and the accumulation of intracellular araCTP from extracellular araC at 1 microM. Membrane transport of araC at the low concentrations (approximately 1 microM), which are achieved therapeutically, is a major rate-limiting step in its conversion to araCTP by leukemic blast cells. Myeloblasts form more araCTP than lymphoblasts because of both higher nucleoside transport capacity and larger cell size. The highest nucleoside transport capacity and largest conversion of araC to araCTP is in T lymphoblastic lymphoma, which suggests that araC may be effective in the treatment of this disease.

Effect of thymidine on the sensitivity of cultured mouse tumor cells to 1-beta-D-arabinofuranosylcytosine.

Assays of thirteen cell lines, derived from mouse lymphomas, myelomas, myeloid tumors, and a mastocytoma, for sensitivity to growth inhibition by 1-beta-D-arabinofuranosylcytosine (ara-C) revealed a spectrum between the most and least sensitive which differed 100-fold from each other. An inverse correlation between sensitivity and cellular deoxycytidine 5'-triphosphate (dCTP) content was found, and this suggested that sensitivity of cells might be increased if the dCTP content was lowered during cell exposure to ara-C. Previous work has shown that thymidine treatment of cells lowers their dCTP content, and the effect of thymidine on the sensitivity of six of the cell lines to ara-C was therefore measured. Concentrations of thymidine below those inhibitory to cell growth by themselves caused an increase in ara-C sensitivity by up to 3-fold in 4 cell lines in which thymidine causes a depression in dCTP content but not in 2 myeloid lines in which the dCTP content was found not to be depressed by the same thymidine treatment. The results confirm an important role for dCTP in determining cellular sensitivity to ara-C. The finding that the sensitivity of 2 lymphoma cell lines to ara-C could be increased by concentrations of thymidine in the region of 10 micrometer, which are attainable clinically in humans, suggests that a combination of ara-C with thymidine might be useful in the treatment of some human tumors.

Degradation of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate in human leukemic myeloblasts and lymphoblasts.

The intracellular half-life for retention of the active triphosphate metabolite 1-beta-D-arabinofuranosylcytosine 5'-triphosphate (araCTP) of 1-beta-D-arabinofuranosylcytosine was measured in vitro in blast cells from patients with acute myeloblastic leukemia, acute lymphoblastic leukemia, and T-cell lymphoblastic lymphoma. araCTP accumulation from 1 microM 1-beta-D-arabinofuranosylcytosine in leukemic blast cells was closely correlated with the nucleoside transport capacity as measured by equilibrium binding of [3H]nitrobenzylthioinosine. The half-life of araCTP retention was related to araCTP accumulation only when the level of araCTP was expressed as a percentage of total intracellular 1-beta-D-arabinofuranosylcytosine metabolites. Accumulation of 1-beta-D-arabinofuranosyluracil 5'-monophosphate was inversely related to the half-life of araCTP retention and directly related to dCMP deaminase activity in cell free extracts. No conversion of 1-beta-D-arabinofuranosyluracil to 1-beta-D-arabinofuranosyluracil 5'-monophosphate was detectable in intact cells. The end product of araCTP degradation was 1-beta-D-arabinofuranosyluracil and it is proposed that conversion of 1-beta-D-arabinofuranosylcytosine 5'-monophosphate to 1-beta-D-arabinofuranosyluracil 5'-monophosphate is a step in the degradative pathway of araCTP. However, it is the cells' nucleoside transport capacity which primarily determines the level of intracellular araCTP accumulation.

Regulation of aspartate carbamoyltransferase of Escherichia coli by the interrelationship of magnesium and nucleotides.

Purified aspartate carbamoyltransferase from Escherichia coli K12 (carbamoylphosphate: L-aspartate carbamyltransferase, EC 2.1.3.2) shows greater activity with nucleotide effectors as the magnesium nucleotide complex than with similar amounts of the sodium nucleotide. Regulation of aspartate carbamoyltransferase activity in vivo may occur by changes in the total concentration of regulatory nucleotides or, under conditions of magnesium-limited growth, by variation of the saturation of the nucleotides with magnesium.

Effects of hydroxyurea on DNA synthesis in mouse L-cells.

The effect of the anti-metabolite hydroxyurea on DNA synthesis in mouse L-cells has been examined. It was shown previously that when DNA synthesis was diminished to very low levels by treatment with the drug there was preferential incorporation of added [3H]dThd into low molecular weight fragments (Martin, R.F., Radford, I. And Pardee, M. (1977) Biochem. Biophys. Res. Commun. 74, 9-15). On the basis of several criteria it is concluded here that these fragments are a product of semi-conservative nuclear DNA replication. The preferential labelling of DNA fragments, but not their size, is shown to be dependent on the hydroxyurea concentration used. These DNA fragments are also shown, by comparison with normal DNA replication intermediates, to comprise a heterogeneous population of 'larger-than-normal' fragments. Different models to account for these findings are considered and it is concluded that the results are compatible with a loss of coordination of DNA synthesis following drug treatment.

Inhibition of DNA synthesis and cell death.

The association between DNA synthesis inhibition and cell death in mouse L-cells was investigated using the drug hydroxyurea. This drug produces a preferential labelling of low molecular weight DNA and dose-response studies revealed a correlation between this effect and cytoxicity. Investigation of the reassociation kinetics of DNA labelled during hydroxyurea inhibition showed an over-replication of middle repetitive sequences, but the concentration dependence of this effect was quite different to that of cytotoxicity.

Deoxyribonucleoside triphosphate pools and differential thymidine sensitivities of cultured mouse lymphoma and myeloma cells.

The effects of various concentrations of thymidine on DNA synthesis and deoxyribonucleoside triphosphate contents of a highly thymidine-sensitive cultured mouse lymphoma cell line (WEHI-7) and a relatively resistant mouse myeloma cell line (HPC-108) have been studied by 32P-labelling techniques. DNA synthesis in the myeloma cells was inhibited by thymidine at concentrations of 10(-3) M or greater, while DNA synthesis in the lymphoma cells was inhibited by concentrations 30-fold lower, consistent with the 25-fold difference between the two cell lines in sensitivity to growth inhibition by thymidine. Thymidine caused marked elevation of the dTTP and dGTP pools, slight elevation or no change in the dATP pool and a marked decrease in the dCTP pool in cells of both lines. The greater resistance of HPC-108 cells to thymidine inhibition was related to the finding that they normally contained a much higher concentration of dCTP than did the WEHI-7 cells. Pool size measurements on thymidine-treated (10(-4) M) cells of an additional seven sensitive lymphoma and six relatively resistant myeloma cell lines indicated that in all 15 lines studied, with one exception, a critical concentration of dCTP of about 32 nmol per ml of cell volume was required for the maintenance of normal rates of DNA synthesis. The dCTP content found normally in the lymphoma cells was only a little above this concentration. Amongst the myeloma lines, three contained similarly low levels of dCTP, but were more resistant to thymidine inhibition probably because of their inefficient production of dTTP from thymidine. Cells of the other four myeloma lines (including HPC-108) normally contained much higher dCTP concentrations. The mechanism of thymidine action was explained by reference to the known allosteric properties of ribonucleotide reductase.

Autocrine regulation of milk secretion.

Mammary development and the rate of milk secretion are regulated by frequency and completeness of milk removal. This regulation occurs through chemical feedback inhibition by a milk constituent. Novel, immunologically related milk proteins able to perform this function have been isolated from caprine, bovine and human milk, based on their ability to inhibit milk constituent synthesis in mammary tissue and cell cultures, and to decrease temporarily milk secretion when added to milk stored in the mammary gland. Inhibition is concentration-dependent, suggesting that milk accumulation and removal is accompanied by cyclical changes in inhibitor accretion and depletion in milk. Feedback inhibition is an autocrine mechanism: the caprine inhibitor, termed FIL (feedback inhibitor of lactation) is synthesized by mammary epithelial cells in primary culture. Inhibition is by reversible blockade of the secretory pathway, an effect which, by down-regulating cell-surface hormone receptors, has longer-term consequences on epithelial cell differentiation. Treatment of goat mammary epithelial cell cultures with caprine FIL initially decreased milk protein secretion and subsequently reduced milk protein messenger RNA abundance. Thus the actions of a single milk constituent can bring about both the effect of milking frequency on milk secretion rate and a sequential modulation of cellular differentiation which acts to sustain the secretory response. Long-term regulation, through changes in galactopoietic hormone receptors, also provides an efficient mechanism for integrating acute intramammary regulation of lactation with strategic endocrine control of mammary tissue development.

A multicenter, randomized, double-blinded trial of pyridostigmine in postpolio syndrome.

BACKGROUND: Postpoliomyelitis syndrome (PPS) is likely due to degeneration and dysfunction of terminal axons of enlarged postpolio motor units. Age-related decline in growth hormone and insulin-like growth factor (IGF-I) may be a contributing factor. Neuromuscular junction abnormalities and decreased IGF-I levels may respond to the anticholinesterase pyridostigmine, with consequent improvement in strength, fatigue, and quality of life. OBJECTIVES: To determine the effect of pyridostigmine in PPS on health-related quality of life, isometric muscle strength, fatigue, and serum IGF-I levels; and to assess the safety of pyridostigmine in PPS. METHODS: The study was a multicenter, randomized, double-blinded, placebo-controlled trial of a 6-month course of pyridostigmine 60 mg three times per day in 126 PPS patients. The primary data analysis compared mean changes of outcomes between treatment and control groups at 6 months using an intention to treat approach. Secondary analyses included a comparison of outcomes at 6 and 10 weeks, and in compliant patients. RESULTS: The study showed no significant differences in pyridostigmine and placebo-treated patients with regard to changes in quality of life, isometric strength, fatigue, and IGF-I serum levels at 6 months in the primary analysis and in compliant patients. There were no differences in outcomes at 6 and 10 weeks between groups. However, very weak muscles (1 to 25% predicted normal at baseline) were somewhat stronger (p = 0.10, 95% CI of difference -9.5 to 73.3%), and in compliant patients IGF-I was somewhat increased (p = 0.15, 95% CI of difference -6.4 to 44.8 ng/mL) at 6 months with the medication. Pyridostigmine was generally well tolerated. CONCLUSIONS: This study showed no significant differences between pyridostigmine and placebo-treated PPS patients on measures of quality of life, isometric strength, fatigue, and serum IGF-I.

The cardiovascular effects of intraventricular clonidine and Bay 1470 in conscious hypertensive cats.

1 Intraventricular administration of clonidine (5-30 mug) and an analogue, BAY 1470 (15-30 mug) to conscious renal hypertensive cats produced a fall in mean blood pressure lasting for approximately 3 hours. This fall in blood pressure was accompanied by a marked bradycardia.2 Pretreatment with intraventricular phentolamine (100-200 mug), piperoxan (40-200 mug) or tolazoline (75-200 mug) abolished the cardiovascular effects of intraventricular clonidine (20 mug).3 The cardiovascular effects of intraventricular clonidine (20 mug) were not modified by the pretreatment with either haloperidol (1 mg/kg i.p.) or desmethylimipramine (1 mg/kg i.p.).4 Emesis was observed 1-2 min after the administration of either clonidine (5-20 mug) or BAY 1470 (30 mug). This preceded the cardiovascular actions and was still seen after pretreatment with haloperidol, desmethylimipramine, phentolamine, piperoxan or tolazoline.5 It is concluded that the centrally mediated cardiovascular responses observed after intraventricular administration of small doses of clonidine are due to stimulation of central alpha-adrenoceptors and are independent of central catecholamine uptake mechanisms and dopamine receptors.

Cardiovascular reactivity in the experimental hypertensive rat.

1. In pithed preparations, deoxycorticosterone (DOCA)/NaCl-induced hypertensive rats showed increased cardiovascular reactivity to injected noradrenaline, DMPP, tyramine, angiotensin and to sympathetic nerve stimulation.2. Pithed, chronic renal hypertensive rats showed similar hyperreactivity to noradrenaline, DMPP and tyramine but responses to sympathetic nerve stimulation were within normal limits.3. In the isolated, Krebs perfused mesentery preparation, vessels obtained from both DOCA/NaCl and renal hypertensive rats showed hyperreactivity to injected noradrenaline. Responses to periarterial nerve stimulation were also markedly increased in preparations from DOCA/NaCl hypertensive rats, while preparations from renal hypertensive rats showed this effect only at higher rates of stimulation (12 and 25 Hz).

An increased reactivity in hypertensive rats unaffected by prolonged antihypertensive therapy.

1. Isolated perfused mesenteric arteries obtained from chronic experimental hypertensive rats (deoxycorticosterone/NaCl) exhibited an increased reactivity to noradrenaline, 5-hydroxytryptamine and adenosine 5'-triphosphate (ATP) when compared with similar preparations from age-matched normotensive animals. 2. The dose-response curves to all three vasoconstrictor agents obtained from hypertensive animals exhibited a steeper slope, and higher maximum without any significant change in the threshold dose suggesting that adaptive/structural changes in the blood vessels had taken place. 3. Ten week treatments with antihypertensive combinations of hydrallazine, hydrochlorothiazide and reserpine or hydrallazine and mecamylamine lowered the systolic blood pressures of the hypertensive rats to those of normotensive animals and also reversed secondary changes such as periarteritis nodosa of the mesentery and cardiac hypertrophy. 4. The reactivity of these blood vessels to all these vasoconstrictor agents from the hypertensive rats with a normalized blood pressure was similar to those obtained with untreated hypertensive animals. 5. The persistent increased reactivity in the hypertensive rats after long-term anti-hypertensive treatment suggests that the hyperresponsiveness is secondary to the elevated blood pressures and that the adaptive/structural changes of the blood vessels in chronic hypertensive rats cannot be reversed by prolonged antihypertensive therapy.

Further evidence for a central hypotensive action of alpha-methyldopa in both the rat and cat.

1. alpha-Methyldopa (300 mg/kg i.p.) produced a fall in blood pressure in conscious genetic hypertensive rats. Pretreatment with intraventricular 6-hydroxydopamine prevented this hypotensive effect of alpha-methyldopa, whilst intravenous 6-hydroxydopamine reduced but did not prevent the hypotension.2. The hypotensive effect of alpha-methyldopa was prevented or reversed by intraventricular injection of phentolamine (200 mug/rat).3. Pressor responses obtained by stimulation of the entire sympathetic outflow in the Gillespie & Muir preparation, were unaffected by pretreatment with alpha-methyldopa (300 mg/kg i.p.).4. Vasoconstrictor responses to periarterial nerve stimulation of the isolated renal artery preparation of the rat were markedly reduced by pretreatment with alpha-methyldopa. Furthermore, alpha-methylnoradrenaline was found to have one-eighth the vasoconstrictor potency of noradrenaline in this particular artery preparation.5. Pressor responses obtained by stimulation of the posterior hypothalamus or midbrain reticular formation in the rat anaesthetized with urethane were markedly reduced by pretreatment with alpha-methyldopa. FLA-63, a selective dopamine-beta-hydroxylase inhibitor, prevented the reduction of the pressor responses to hypothalamic stimulation produced by alpha-methyldopa.6. Stimulation of the posterior hypothalamus in the anaesthetized cat caused both an increase in sympathetic nerve activity and a rise in blood pressure. These responses were markedly reduced 3-4 h after the injection of alpha-methyldopa (100 mg/kg i.v.).7. These results strongly suggest that the central actions of alpha-methyldopa are important for its hypotensive effect, although a possible peripheral effect cannot be excluded.