Preoperative anthropomorphic radiographic measurements can predict postoperative pancreatic fistula formation following pancreatoduodenectomy

BACKGROUND

Postoperative pancreatic fistulae (POPF) are a major contributing factor to pancreatoduodenectomy-associated morbidity. Established risk calculators mostly rely on subjective or intraoperative assessments. We hypothesized that various objective preoperatively determined computed tomography (CT) measurements could predict POPF as well as validated models and allow for more informed operative consent in high-risk patients.

METHODS

Patients undergoing elective pancreatoduodenectomies between January 2013 and April 2018 were identified in a prospective database. Comparative statistical analyses and multivariable logistic regression models were generated to predict POPF development. Model performance was tested with receiver operating characteristics (ROC) curves. Pancreatic neck attenuation (Hounsfield units) was measured in triplicate by pancreatic protocol CT (venous phase, coronal plane) anterior to the portal vein. A pancreatic density index (PDI) was created to adjust for differences in contrast timing by dividing the mean of these measurements by the portal vein attenuation. Total areas of subcutaneous fat and skeletal muscle were calculated at the L3 vertebral level on axial CT. Pancreatic duct (PD) diameter was determined by CT.

RESULTS

In the study period 220 patients had elective pancreatoduodenectomies with 35 (16%) developing a POPF of any grade. Multivariable regression analysis revealed that demographics (age, sex, and race) were not associated with POPF, yet patients resected for pancreatic adenocarcinoma or chronic pancreatitis were less likely to develop a POPF (10 vs. 24%; p = 0.004). ROC curves were created using various combinations of gland texture, body mass index, skeletal muscle index, sarcopenia, PDI, PD diameter, and subcutaneous fat area indexed for height (SFI). A model replacing gland texture with SFI and PDI (AUC 0.844) had similar predictive performance as the established model (p = 0.169).

CONCLUSION

A combination of preoperative objective CT measurements can adequately predict POPF and is comparable to established models relying on subjective intraoperative variables. Validation in a larger dataset would allow for better preoperative stratification of high-risk patients and improve informed consent among this patient population.

The distinct effects of subchronic antipsychotic drug treatment on macronutrient selection, body weight, adiposity, and metabolism in female rats

INTRODUCTION

Treatment with some antipsychotic drugs may result in excessive body weight gain which can have detrimental effects on patient compliance, morbidity and mortality. The aim of the present study was to investigate the effect of atypical antipsychotic drugs on dietary macronutrient selection, body weight, body composition and biochemical parameters related to obesity in female rats.

MATERIALS AND METHODS

Forty pair-housed, adult female hooded-Lister rats (250 +/- 5 g) were habituated to three diets containing principally protein, fat, or carbohydrate in a home cage self-selection paradigm. Olanzapine (2 mg/kg), risperidone (0.5 mg/kg), ziprasidone (2.5 mg/kg), or vehicle was injected intraperitoneally once daily for 22 days; food selection, water intake, and body weight were recorded daily, while body composition and plasma hormones (insulin, glucose, nonesterified free fatty acid, total cholesterol, glycerol, triacylglycerol, leptin, and prolactin) were analyzed at the end of the study.

RESULTS

Only olanzapine significantly increased body weight and food intake. Macronutrient selection was significantly altered after olanzapine and risperidone treatment (increased protein and decreased fat preference). Only olanzapine increased carcass fat content. Locomotor activity was significantly reduced in all treatment groups. Both olanzapine and risperidone significantly increased plasma prolactin. Olanzapine was without effect on any other biochemical parameter measured. Ziprasidone significantly reduced plasma leptin and nonsignificantly reduced NEFA, while risperidone significantly reduced fasting plasma glucose.

CONCLUSION

This study supports our previous work demonstrating weight gain and increased feeding behavior induced by olanzapine and could have important implications for enhancing our understanding of the mechanisms by which olanzapine and other atypical antipsychotics induce weight gain in the clinic.

Tinted contact lenses as an alternative management for photophobia in stationary cone dystrophies in children

BACKGROUND

Intense photophobia is a debilitating symptom of the stationary cone dystrophies. The dark-tinted glasses with side-shields and floppy hats used to manage this are very conspicuous and can cause marked psychological morbidity to the children and their families. We assess the use of tinted contact lenses as an alternative management for the photophobia.

METHODS

Three children, aged 5 to 13, with cone dystrophies, all with markedly reduced visual acuity, color vision, and profound photophobia were fitted with Lunelle ES70 Solaire 70% brown contact lenses. The child's parents completed two Children's Visual Function Questionnaires, the first pertaining to the period when the child wore tinted glasses; the second pertaining to the period of tinted contact lens wear.

RESULTS

Subjectively, two of the children and their parents described a striking improvement in their quality of life, with improved confidence, interactions with other children, and cessation of name-calling and bullying. The Children's Visual Function Questionnaires gave objective evidence for this improvement in one child and was not significantly different in the other. The third child was reluctant to wear the contact lenses despite her parents' active encouragement.

CONCLUSION

Tinted contact lenses offer an alternative management of the photophobia associated with stationary cone dystrophies in children. Marked improvements in their quality of life were observed in this case series.

Contamination of disposable tonometer prisms during tonometry

AIM

Due to the theoretical possibility of prion transmission in applanation tonometry, many ophthalmological units in the United Kingdom now use disposable tonometer prisms. We have investigated the potential for bacterial and viral transmission from the health practitioner to the patient via disposable prisms.

METHODS

All staff who perform applanation tonometry at the Sussex Eye Hospital (SEH) received a questionnaire to evaluate if the applanating face of the prism is touched during tonometry and the ease of use of the disposable prism compared to the reusable prisms that were previously used. We then cultured prisms handled by a random sample of staff members for common bacteria. Finally, we constructed a model to investigate the possibility of interpatient adenoviral transmission via disposable tonometer prisms.

RESULTS

The questionnaire revealed that almost 50% of the staff admit to touching the applanating face of the tonometer prism prior to applanation. Cultures of the prisms grew a range of bacteria including Staphylococcus epidermidis, Staphylococcus aureus, and Bacillus species. The viral model suggested that adenovirus could be transmitted by applanation tonometry.

CONCLUSION

The use of disposable prisms for applanation tonometry may reduce the risk of prion transmission but is not bacteriologically or virologically aseptic. This is a potential infection risk to patients.

Fetal surveillance in pregnancy complicated by diabetes mellitus: is it necessary?

This article provides a literature review and opinion concerning the need for fetal surveillance in diabetic pregnancy. Low rates of intervention for suspected fetal jeopardy accompany well-controlled diabetic pregnancies in the absence of vascular disease or hypertension. The clinical utility of routine tests of fetal surveillance in uncomplicated type 1 and type 2 diabetic and gestational diabetic pregnancy has not been established. A randomized trial designed to establish whether a benefit exists to fetal testing in this population is not feasible, largely owing to sample size considerations.

Improved reduction in pain in chronic pancreatitis with combined intraoperative celiac axis plexus block and lateral pancreaticojejunostomy

PURPOSE:Severe abdominal pain secondary to chronic pancreatitis is often multifactorial in origin. Lateral pancreaticojejunostomy (LPJ) is currently the accepted surgical treatment of choice when the main pancreatic duct is dilated. Chemical ablation of the celiac plexus for the treatment of intractable pain in chronic pancreatitis has been used without clear benefit. The aim of this study is to compare treatment outcomes of 2 groups of patients with the diagnosis of chronic pancreatitis and intractable abdominal pain (LPJ alone versus LPJ with intraoperative alcohol celiac ablation).Between 1994 and 1997, 34 patients underwent LPJ to control intractable pain secondary to chronic pancreatitis. These patients were divided into 2 groups, group 1 was LPJ only (16 patients) and group 2 was LPJ and intraoperative celiac ablation with 50% absolute alcohol (18 patients). Preoperative diagnosis and treatment criteria were similar for both groups. The clinical characteristics and outcome of both groups were retrospectively analyzed. Fisher exact test was used for statistical analysis.Demographic characteristics were similar in both groups. Pain control at short- and long-term follow-up was significantly improved in group 2 compared with group 1 (p < 0.035).Intraoperative celiac ablation in addition to LPJ appears to have a better response than does LPJ alone. Even though the number of patients is small, these results provide a basis for pursuing a prospective, randomized study to definitively answer this question.

The biotransformation of nitrogen containing xenobiotics to lactams

The metabolism of nitrogen heterocyclics may lead to lactam formation. In early studies on xenobiotic metabolism lactams were identified as metabolites of nicotine, cyproheptadine, tremorine and prolintane. Now, because of the increasing availability of powerful analytical techniques, there are many instances of lactams being identified as metabolites. Lactam metabolites are formed from either iminium ions or carbinolamines. These two intermediates may have distinct mechanisms of formation but they can interconvert. There is evidence that the iminium ions are oxidized to lactams by aldehyde oxidases (cytosolic molybdenum hydroxylases). The tissue distribution and enzyme activities of aldehyde oxidase have been studied in several animal species. However, it is also known that iminium ions can undergo spontaneous hydrolysis to the corresponding carbinolamine. If the latter is stable it may undergo oxidation by cytochrome P-450 to form the lactam. Thus, species differences in lactam formation might be caused by differences in the concentrations of either cytochrome P450 isozymes or aldehyde oxidases. It appears that lactam formation is an end stage in the metabolism of N-heterocycles in that it is unlikely that the lactam will undergo hydrolysis to the corresponding amino acid. Such amino acids probably arise from the amino aldehydes that may be produced from ring opening of unstable carbinolamine intermediates. When microsomal preparations are incubated with the appropriate substrate in the presence of sodium cyanide the iminium ion may be trapped to produce a cyano compound. Such reactions have led to the proposal that iminium ions might react with nucleophilic sites of cellular macromolecules and so contribute to both the pharmacology and toxicology of N-heterocyclic compounds. Other pathways for the formation of lactam metabolites involve the internal cyclization of precursor metabolites, e.g. the self-condensation of an aldehyde group (formed during metabolism) with a neighboring amide group. However, spontaneous ring closures of amino acids to form lactams seem unlikely since it would be anticipated that the amino acid residue would exist as a stable zwitterion under physiological conditions. Thus, it is unlikely that lactams will undergo futile metabolism via hydrolytic ring opening followed by ring closure. Under extreme conditions such unanticipated ring closures may occur and the conditions of metabolite isolation may contribute to the occurrence of artifacts.

Carcinoid tumor of the hepatic duct presenting as a Klatskin tumor in an adolescent and review of world literature

This is a case presentation of a 14-year-old boy with the radiological diagnosis of cholangiocarcinoma occluding the hepatic duct bifurcation. His only symptom at presentation was jaundice and further workup confirmed a mass at the porta hepatis. Surgical treatment resulted in a resection of the hepatic bifurcation tumor with a final pathological diagnosis of a carcinoid tumor of the hepatic duct bifurcation. To our knowledge, this is only the second case presented of a resected carcinoid tumor in adolescence. In this communiqué we present the above case and review of the world literature of biliary neuroendocrine tumors.

In vitro and in vivo studies on the metabolism of tirofiban

Tirofiban hydrochloride [L-tyrosine-N-(butylsulfonyl)-O-[4-(4-piperidinebutyl)] monohydrochloride, is a potent and specific fibrinogen receptor antagonist. Radiolabeled tirofiban was synthesized with either (3)H-label incorporated into the phenyl ring of the tyrosinyl residue or (14)C-label in the butane sulfonyl moiety. Neither human liver microsomes nor liver slices metabolized [(14)C]tirofiban. However, male rat liver microsomes converted a limited amount of the substrate to a more polar metabolite (I) and a relatively less polar metabolite (II). The formation of I was sex dependent and resulted from an O-dealkylation reaction catalyzed by CYP3A2. Metabolite II was identified as a 2-piperidone analog of tirofiban. There was no evidence for Phase II biotransformation of tirofiban by microsomes fortified with uridine-5'-diphospho-alpha-D-glucuronic acid. After a 1 mg/kg i.v. dose of [(14)C]tirofiban, recoveries of radioactivity in rat urine and bile were 23 and 73%, respectively. Metabolite I and unchanged tirofiban represented 70 and 30% of the urinary radioactivity, respectively. Tirofiban represented >90% of the biliary radioactivity. At least three minor biliary metabolites represented the remainder of the radioactivity. One of them was identified as I. Another was identified as II. When dogs received 1 mg/kg i.v. of [(3)H]tirofiban, most of the radioactivity was recovered in the feces as unchanged tirofiban. The plasma half-life of tirofiban was short in both rats and dogs, and tirofiban was not concentrated in tissues other than those of the vasculature and excretory organs.

Hypotensive ischemic optic neuropathy and peritoneal dialysis

PURPOSE

To report anterior ischemic optic neuropathy associated with systemic hypotension in a patient undergoing continuous ambulatory peritoneal dialysis.

METHODS

Case report. A 58-year-old man undergoing continuous ambulatory peritoneal dialysis developed painless blurred vision in both eyes and bilateral optic disk swelling with an altitudinal field defect in the left eye. Twenty-four-hour ambulatory blood pressure monitoring was requested in addition to other routine investigations.

RESULTS

Routine blood pressure measurement in the clinic was 130/86 mm Hg, but ambulatory blood pressure monitoring demonstrated pronounced early morning hypotension with individual readings as low as 91/41 mm Hg.

CONCLUSIONS

Renal dialysis can render patients hypotensive, and this may be associated with anterior ischemic optic neuropathy. The overnight drop in blood pressure may not be appreciated with routine blood pressure measurement. Therefore, 24-hour ambulatory blood pressure monitoring should be considered when investigating patients with suspected anterior ischemic optic neuropathy who are undergoing renal replacement.

Immunoaffinity localization of the enzyme xanthine oxidase on the outside surface of the endothelial cell plasma membrane

BACKGROUND

Reactive oxygen metabolites generated from endothelial xanthine oxidase (XO) trigger reperfusion injury in many organs. We evaluated the possibility that endothelial XO was localized on the endothelial cell surface, as well as within the cytoplasm.

METHODS

Primary cultures of bovine (BAECs) and porcine (PAECs) aortic endothelial cells were grown in media documented to be free of XO. Polyclonal and monoclonal antibodies were developed against XO. These antibodies were used to evaluate BAEC and PAEC for cell surface XO through immunofluorescence staining, hybridoma cell surface labeling, and endothelial cell surface binding.

RESULTS

These antibodies bound specifically to the surface of these cells when the membrane was shown to be intact and impermeable (and the cytoplasm inaccessible) to immunoglobulins Moreover, hybridoma cells expressing monoclonal antibody to XO bound specifically to the endothelial cell surface. Finally, intact endothelial cells bound specifically to the anti-XO polyclonal antibodies immobilized to the surface of a Petri dish. The integrity of these endothelial cell plasma membranes was demonstrated by the subsequent growth and replication of these cells in culture.

CONCLUSIONS

These findings indicate that XO is present on the outside surface of the endothelial cell plasma membrane. This would not only explain the known in vivo efficacy of intravascularly administered large molecular weight antioxidants (such as superoxide dismutase) but could have important implications for inflammatory signaling.

Development of orally active oxytocin antagonists: studies on 1-(1-[4-[1-(2-methyl-1-oxidopyridin-3-ylmethyl)piperidin-4-yloxy]-2- methoxybenzoyl]piperidin-4-yl)-1,4-dihydrobenz[d][1,3]oxazin-2-one (L-372,662) and related pyridines

The previously reported oxytocin antagonist L-371,257 (2) has been modified at its acetylpiperidine terminus to incorporate various pyridine N-oxide groups. This modification has led to the identification of compounds with improved pharmacokinetics and excellent oral bioavailability. The pyridine N-oxide series is exemplified by L-372,662 (30), which possessed good potency in vitro (Ki = 4.1 nM, cloned human oxytocin receptor) and in vivo (intravenous AD50 = 0.71 mg/kg in the rat), excellent oral bioavailability (90% in the rat, 96% in the dog), good aqueous solubility (>8.5 mg/mL at pH 5.2) which should facilitate formulation for iv administration, and excellent selectivity against the human arginine vasopressin receptors. Incorporation of a 5-fluoro substituent on the central benzoyl ring of this class of oxytocin antagonists enhanced in vitro and in vivo potency but was detrimental to the pharmacokinetic profiles of these compounds. Although lipophilic substitution around the pyridine ring of compound 30 gave higher affinity in vitro, such substituents were a metabolic liability and caused shortfalls in vivo. Two approaches to prevent this metabolism, addition of a cyclic constraint and incorporation of trifluoromethyl groups, were examined. The former approach was ineffective because of metabolic hydroxylation on the constrained ring system, whereas the latter showed improvement in plasma pharmacokinetics in some cases.

Metabolism of MK-499, a class III antiarrhythmic agent, in rats and dogs

MK-499 [(+)-N-[1'-(6-cyano-1, 2, 3, 4-tetrahydro-2(R)-naphthalenyl)-3, 4-dihydro-4(R)-hydroxyspiro(2H-1-benzopyran-2, 4'-piperidin)-6-yl]methanesulfonamide] monohydrochloride is an investigational class III antiarrhythmic agent for treatment of malignant ventricular tachyarrhythmias. The disposition of [3H]MK-499 and [14C]MK-499 was studied in rats and dogs after oral and iv administration. MK-499 was concentrated in organs of excretion and the heart. In the rat, urinary radioactivity elimination values after iv (0.5 mg/kg) and oral (6.25 mg/kg) doses were 21 +/- 3% and 10 +/- 2%, respectively. Corresponding fecal recoveries were 68 +/- 6% and 78 +/- 7%. Similar results were found after corresponding doses of [14C]MK-499. In dogs, urine and feces accounted for 16 +/- 3% and 75 +/- 4% of recovered radioactivity after a [3H]MK-499 iv dose (0.1 mg/kg). Corresponding recoveries after an oral dose (1 mg/kg) were 12 +/- 2% and 76 +/- 3%. Biliary (0-24 hr) excretion accounted for 39 +/- 5% and 41 +/- 18% of [3H] and [14C] oral doses in rats, respectively. Dogs excreted 34% of [3H] oral dose in (0-24 hr) bile. The data indicated that a substantial amount of MK-499 was absorbed by rats and dogs. MK-499, metabolite I (formed by loss of N-substitution), and metabolite II (an acid formed by metabolic scission across the benzopyran ring) each represented 30% of rat urinary label. Rat bile contained MK-499 (10%), II (20%), and IV (10%), which was formed by carbon-4 hydroxylation of the tetralin ring. Additionally, rat bile included glutathione (V) and N-acetyl-1-cysteine (VI) conjugates of a ring-opened metabolite. Metabolite III, a positional isomer of IV, was excreted in rat urine. The major labeled species excreted in dog bile were unchanged MK-499 and its glucuronide (VII), which, respectively, represented 50% and 30% of the biliary radioactivity. MK-499 and a small amount of I represented dog urinary radioactivity. The bioavailability of MK-499 was high in dogs (100%) but low in rats (17%). This difference was probably due to the more extensive presystemic metabolism of MK-499 in rats.

Duplication of the 15q11-13 region in a patient with autism, epilepsy and ataxia

Various developmental abnormalities can give rise to the clinical syndrome of autism, and some are due to chromosomal anomalies. One syndrome has been identified in which behavioural disorder is associated with the clinical features of epilepsy and ataxia, and with the chromosomal anomaly of an extra marker chromosome containing a duplication of 15q11-13. The authors report a boy with autism, epilepsy, ataxia and an interstitial duplication of 15q, in whom molecular analysis reveals duplication of the GABRA5 and GABRB3 genes on the maternally derived chromosome.

Disposition of MK-852, a fibrinogen receptor antagonist, in rats and dogs

MK-852, an antagonist of the platelet fibrinogen receptor GPIIb/IIIa, is the cyclic disulfide N-acetyl-cys-asn-(5,5-dimethyl-4-thiazolidine-carbonyl)- (4-aminomethyl-phe)-gly-asp-cys, monoacetate (all L-amino acids). Radiolabeled MK-852 was synthesized with either a 3H label in the N-acetyl group of the cystine residue or a 14C label in the aminomethyl group. Plasma concentrations of unchanged MK-852 in five rats declined with a mean terminal half-life of 0.92 hr after a 2.5 mg/kg i.v. dose of MK-852; plasma clearance and Vd were 23.1 ml/min/kg and 1.81 liters/kg, respectively. More label was excreted in urine (74-76%) than in feces (7-15%) when either [3H]MK-852 or [14C]MK-852 was given intravenously to groups of four rats (2.5 mg/kg). High concentrations of 3H in rat kidney were consistent with high renal clearance of MK-852, and MK-852 accounted for virtually all of the urinary 3H (and 14C) label. Following a 0.6 mg/kg i.v. dose, the half-life, plasma clearance, and Vd of MK-852 in four dogs were 0.84 hr, 3.93 ml/min/kg, and 0.28 liters/kg, respectively. In dogs, the excretion patterns of radioactivity were similar to those of rats, except that 14C urinary recoveries (79%) were higher than 3H (63%). Unchanged MK-852 represented essentially all of the urinary 3H label. Fractionation of dog 14C urinary radioactivity yielded one major and several minor polar labeled species. The major species was unchanged [14C]MK-852 (quantitated by radioimmunoassay as approximately 80% of the label).(ABSTRACT TRUNCATED AT 250 WORDS)

A male with a de novo translocation involving loss of 15q11q13 material and Prader-Willi syndrome

A male proband is described who carries a de novo translocation between chromosomes Y and 15 associated with Prader-Willi syndrome. In situ hybridisation and molecular studies were used to show loss of the paternally derived 15q11q13 region in the translocated chromosome. Lack of further symptoms indicate that this region was lost with no apparent deletion of the Y chromosome.

Metabolic disposition of simvastatin in patients with T-tube drainage

A study to investigate the disposition and biliary excretion of simvastatin (SV) was conducted in four cholecystectomy patients with T-tube drainage. Each patient received a single oral dose of 100 mg of [14C]SV (20 microCi). Of the 14C-labeled dose, approximately 35% was excreted in urine, 25% in bile, and 20% in feces. Thus, at least 60% of the oral dose was absorbed from the gastrointestinal tract. Of the AUC for radioactivity in plasma, 13% was contributed by the HMG-CoA reductase inhibitors. In addition, only 2% of the 14C-dose was eliminated in urine as HMG-CoA reductase inhibitors. Thus, most of the SV-related compounds in plasma and urine have little or no HMG-CoA reductase inhibitory activity. The same is probably true for these compounds in bile. Two major active metabolites were present in the bile. Based on HPLC and MS/MS data, they were identified as 6' beta-COOH-SVA and 6'-OH-SVA. In general, the majority of the radioactivity in the bile and urine was excreted within 24 hr postdose. Of the radioactivity excreted in the 0- to 24-hr bile, on average, approximately 30% was contributed by 6' beta-COOH-SVA and 6'-OH-SVA. These two metabolites accounted for the majority of HMG-CoA reductase inhibitory activity in the bile. Little or SV or no SVA was present in the bile.

In vivo and in vitro metabolism studies on a class III antiarrhythmic agent

The metabolism of L-691,121 (I), a class III antiarrhythmic agent, was studied in vivo in rats and dogs and in vitro by using liver S9 or slices from these species and humans. After oral doses of [14C]I to rats (5 mg/kg) and dogs (1 mg/kg), urinary recoveries of label were, respectively, 6% and 28%. Biliary excretion (0-24 hr) accounted for 68% of a 5 mg/kg, po dose in rats and 19% of a 10 mg/kg dose, po in dogs. Metabolites were identified by application of FAB/MS, NMR, and diode-array UV spectroscopy. The major dog metabolites were the secondary alcohol (II) produced by carbonyl reduction and its glucuronide conjugate (III). It was estimated that II and III represented 24 and 36%, respectively, of the dog biliary radioactivity. After a 50 mg/kg dose of I, II represented approximately 50% of the dog urinary label. A minor metabolite (IV) in dog urine was produced by reduction and loss of N-substitution. There were species differences in that, relative to dogs, II represented a much smaller fraction of the excreted dose in rats and there was no evidence for excretion of III in rats. N-Dealkylated I (V) was excreted, along with IV in rat bile. Dog liver slices and S9 fractions were most efficient (relative to human and rat liver tissues) at reducing I to II. Metabolic reduction of I to II was highly stereoselective and yielded the (-)-antipode as determined by chiral chromatography.

Mesenteric vasoconstriction in cardiogenic shock in pigs

The quantitative impact of mesenteric vasoconstriction on the systemic hemodynamic response to cardiogenic shock induced by pericardial tamponade was evaluated. Graded increases in pericardial pressure produced corresponding decreases in cardiac output to 44% +/- 2% and arterial pressure to 64% +/- 3% of baseline and increases in total peripheral vascular resistance to 131% +/- 4% of baseline. Total mesenteric blood flow decreased disproportionately, to 28% +/- 3% of baseline, because of a disproportionate increase in mesenteric vascular resistance to 223% +/- 6% of baseline. Nonmesenteric vascular resistance increased only to 119% +/- 4% of baseline. Thus mesenteric vasoconstriction accounted for 42% of the increase in total peripheral resistance. Prior blockade of the renin-angiotensin axis ablated this response and eliminated the mesenteric contribution to systemic vascular resistance, while confirmed blockade of the alpha-adrenergic system or vasopressin system had no effect. Without shock, central intravenous infusions of angiotensin II (but not norepinephrine or vasopressin) closely mimicked this selective vasoconstriction. Angiotensin-mediated selective mesenteric vasoconstriction accounts for more than 40% of the overall increase in systemic vascular resistance in cardiogenic shock.

Studies on the metabolic inversion of the 6'chiral center of simvastatin

In two simvastatin (SV) metabolites the 6' alpha-methyl of SV is oxidized to either 6' beta-CH2OH (I) or 6' beta-COOH (II). A possible intermediate is 6' exomethylene SV (III). When Sprague Dawley rats received an i.v. dose of [14C] III (1 mg/kg) metabolite II was excreted in bile. When dogs received an i.v. dose of [14C] III together with either [3H] SV (1 mg/kg) or its hydroxy acid form, [( 3H] SVA) (10 mg/kg), both 3H and 14C I and II were excreted in bile. These results strongly indicate that I and II are secondary metabolites of SV formed from III perhaps via a common aldehyde intermediate.

Single-dose pharmacokinetics of 14C-lovastatin in chronic renal failure

An open study on the pharmacokinetics of lovastatin was conducted in six patients with chronic renal failure (mean creatinine clearance, 0.40 ml/sec; range, 0.20 to 0.65 ml/sec) and seven healthy subjects. Plasma levels of 3-hydroxy-3-methylglutaryl-coenzyme reductase inhibitory activity (total and active) and total radioactivity were determined over 168 hours after a single dose of 80 mg 14C-lovastatin. The mean area under the plasma concentration-time curve for active inhibitors were 606 +/- 346 and 282 +/- 138 ngEq.hr/ml (p = 0.04) in patients and control subjects, respectively. Total inhibitors in plasma and total radioactivity were similarly elevated in patients with chronic renal failure. Results indicate that patients with severe renal dysfunction have altered elimination kinetics of lovastatin. Current ongoing clinical studies in patients with renal dysfunction will allow better assessment of the pharmacodynamic meaning of our observations.

Molecular biology of circulatory shock. Part II. Expression of four groups of hepatic genes is enhanced after resuscitation from cardiogenic shock

Despite an initially successful resuscitation from circulatory shock, multiple organ failure (MOF) develops in some patients. The marked biochemical alterations associated with shock and MOF include clinically important changes in gene expression, such as altered rates of albumin and procoagulant synthesis. To characterize the MOF-associated changes at the cellular level, sequential liver biopsies were obtained from a swine model of cardiogenic shock associated with MOF. Preshock and postresuscitation biopsies were used not only to create a complementary DNA (cDNA) library but also to screen, to confirm, and, in nine out of 12 cases, to specifically identify genes whose expression is enhanced at least fivefold after resuscitation. The twelve genes thus characterized can be separated according to function into distinct groups, including the acute-phase genes and the heat-shock genes. Expression of acute-phase genes is liver specific and is essential for systemic homeostasis; heat-shock gene expression is generic to all cells and important for intracellular homeostasis.

In vitro and in vivo biotransformation of simvastatin, an inhibitor of HMG CoA reductase

Simvastatin (SV), an analog of lovastatin, is the lactone form of 1', 2', 6', 7', 8', 8a'-hexahydro-3,5-dihydroxy-2', 6'-dimethyl-8' (2", 2"-dimethyl-1"-oxobutoxy)-1'-naphthalene-heptanoic acid (SVA) which lowers plasma cholesterol by inhibiting 3-hydroxy-3-methylglutaryl-CoA reductase. SV but not its corresponding hydroxy acid form SVA underwent microsomal metabolism. Major in vitro metabolites were 6'-OH-SV (I) and 3"-OH-SV (III) formed by allylic and aliphatic hydroxylation, respectively, and 6'-exomethylene-SV (IV) formed by dehydrogenation. In rats, dogs, and humans, biliary excretion is the major route of elimination. Biliary metabolites (as both hydroxy acids and lactones) also included 6'-CH2OH-SV (V) and 6'-COOH-SV (VI) in both of which the 6'-chiral center had been inverted. High levels of esterase in rodent plasma favored the formation of SVA from SV. The formation of 1', 2', 6', 7', 8', 8a'-hexahydro-2', 6'-dimethyl-8'-(2",2"-dimethyl-1-oxobutoxy)-1'-naphthalene-pentano ic acid (VII) only in rodents represented a species difference in the metabolism of SV. It is proposed that VII is formed by beta-oxidation pathways of fatty acid intermediary metabolism. Several metabolites resulting from microsomal oxidation (after subsequent conversion from lactones to hydroxy acids) are effective inhibitors of 3-hydroxy-3-methylglutaryl-CoA reductase and may contribute to the cholesterol lowering effect of SV. Qualitatively, the metabolism of SV closely resembles that of lovastatin.

Metabolic disposition studies on simvastatin, a cholesterol-lowering prodrug

The biosynthesis of cholesterol is mainly regulated by 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. Because the liver is the major site of cholesterol synthesis, it is the primary target of the class of drugs known as HMG-CoA reductase inhibitors. Simvastatin (SV) is a lactone prodrug which undergoes reversible metabolism. In the hydroxy acid form (SVA) it is a potent inhibitor of HMG-CoA reductase. SV is well absorbed by rats, dogs, and humans. After an oral dose of SV, tissue distribution studies were consistent with high hepatic extraction of SV and relatively poor tissue penetration of SVA. The majority of a radioactive dose of SV is eliminated in bile. A high portal/systemic gradient for 6'-OH-SVA, an active biliary metabolite, suggests its probable reentry and indicates potential for prolongation of HMG-CoA reductase inhibition. AUC comparisons in dogs after simultaneous iv (3H) and intraportal (14C) infusions indicate that hepatic extraction is high with only 8% of SV reaching the systemic circulation unchanged. Approximately 98% and 96% of SV was bound to human and dog plasma protein, respectively. The physiological disposition of SV in dog appears to be a suitable paradigm for man. Because of its high hepatic extraction SV should be both specific and selective with respect to the inhibition of HMG-CoA reductase.

The physiological disposition of lovastatin

Lovastatin is a pro-drug lactone whose open chain beta-hydroxy-acid (HA) is a potent inhibitor of hydroxymethylglutaryl-CoA-reductase and thus of cholesterol synthesis. Because the liver is the major site of cholesterolgenesis, it is the principal target organ for agents of this class. In animals, lovastatin is not as well absorbed as HA given per se, but that fraction that is absorbed reaches the portal circulation largely unchanged and is more efficiently extracted by the liver, after which it is reversibly biotransformed to HA and irreversibly to other enzymatically active products. These, like HA, maintain high hepatic gradients relative to all tissues examined. The minimal systemic burden for HA is attributable in part to the metabolic equilibrium, lovastatin in equilibrium HA, the opposing reactions for which appear to be present in most tissues. Excretion is very largely biliary in all species. Detailed comparisons of absorption, distribution, metabolism, and excretion profiles presented here and elsewhere indicate dogs to be the most appropriate paradigm for humans for study of lovastatin disposition.

Botulinum toxin therapy for squint

Four hundred and five patients have been treated with injections of Botulinum neurotoxin A to extraocular muscles in the Botulinum Toxin Clinic at Moorfields Eye Hospital from November 1982 until the present. The indications and outcome of therapy are described and discussed.

The diagnosis and surgical management of acquired bilateral superior oblique palsy

Thirty-four patients with surgically treated bilateral superior oblique palsy are presented. The patients are divided into three groups: Symmetrical palsies, Asymmetrical palsies, A group in whom the bilaterality was initially masked. Bilaterality should be suspected in all cases of traumatic IVth nerve paresis, and particularly in cases with a large 'V' pattern, excyclo deviation of more than 10 degrees on down-gaze and when right hypertropia switches to left hypertropia on lateral down-gaze. Bilateral Harada-Ito procedures alone 'cured' 11 of 17 patients (65 per cent) in groups 1 and 2, and is the operation of choice in acute bilateral superior oblique palsy. Cyclo deviation was reduced by a mean of 5.5 degrees in the primary position and by 6-10 degrees in down-gaze. Patients initially managed with other surgery had a more complicated surgical course and required more operations. Seven patients who initially demonstrated only gross fusion recovered good fusion after Harada-Ito surgery.

Retinal detachment following Nd:YAG posterior capsulotomy

Five hundred and eighty-two patients who underwent Nd:YAG laser posterior capsulotomy at Moorfields Eye Hospital were reviewed retrospectively. Twelve patients (2 per cent), nine of whom were previously myopic, subsequently developed rhegmatogenous retinal detachment. Comparison with other studies suggests there is no greater risk of retinal detachment associated with Nd:YAG laser capsulotomy than with surgical discission. The relevance of the damage mechanisms of Nd:YAG lasers are discussed.

Aphakic retinal detachment

A study of 132 cases of aphakic retinal detachment (ARD) following mainly intracapsular cataract surgery has been made. Forty-nine cases (37%) were found to have vitreous incarcerated into the cataract section out of a total of 54 (41%) cases who had suffered a vitreous complication during cataract surgery. A study of the characteristics of ARD reveals that those cases having had a vitreous complication in the management of their cataracts are more likely to develop detachment within three months than those not suffering from such a complication. The occurrence of these early post-extraction retinal detachments is not influenced by the presence of underlying axial myopia. When we compared ARD in patients whose cataract extractions had been complicated by vitreous incarceration with those ARDs following uncomplicated cataract surgery, we found that the characteristics of the detachments were very similar. Thus distribution of underlying myopia, extent of detachment, length of time of detachment, and multiplicity and type of retinal holes were generally similar. However, ARD following complicated cataract surgery is more likely to suffer from periretinal fibrosis. The findings confirmed the risk of ARD following complicated intracapsular cataract surgery and support the tendency to perform the extracapsular operation.

Carnitine and glucuronic acid conjugates of pivalic acid

The [1-14C]pivaloyloxyethyl ester of methyldopa administered to man and cynomolgus monkeys resulted in the elimination in the urine of 14C-pivalic acid metabolites. Pivaloyl glucuronide and pivaloyl carnitine were identified as the major radioactive urinary metabolites in monkey urine and human urine, respectively. N.m.r. analysis indicated that pivaloyl carnitine had a cyclic structure. Although the role of carnitine is in the transport of fatty acids across mitochondrial membranes, it may also function in the conjugation of carboxylic acid xenobiotics in humans.

Sensitive high-performance liquid chromatographic assay using electrochemical detection for a novel prodrug ester of methyldopa, pivaloyloxyethyl 3-(3,4-dihydroxyphenyl)-2-methylalaninate, in plasma and urine

The pivaloyloxyethyl ester of methyldopa is an antihypertensive prodrug possessing improved bioavailability properties over methyldopa. A sensitive cation-exchange, high-performance liquid chromatographic assay using electrochemical detection has been developed for the ester in plasma and urine in order to determine the extent of its hydrolysis after oral administration. The chromatographic conditions involve two Altex Partisil 10 SCX columns (25 cm X 4.6 mm) in series; a mobile phase consisting of methanol, potassium phosphate buffer, pH 3.0, and EDTA disodium dihydrate; and an electrochemical detector set at 0.5 V. The pivaloyloxyethyl ester in plasma or urine is extracted into ethyl acetate, back-extracted into 0.1 M sulfuric acid, and analyzed directly by high-performance liquid chromatography. For urine, the ethyl acetate extract is washed with a buffer (pH 8.0) prior to the back-extraction step. The assay gives a linear response over the concentration range of 10-160 ng/ml in plasma and 20-400 ng/ml in urine.

Metabolism of methyldopa in man after oral administration of the pivaloyloxyethyl ester

In a crossover study, the pivaloyloxyethyl ester (POE) of methyldopa, labeled either with 3H in the methyldopa moiety or 14C in the pivalic acid moiety, was administered orally to four volunteers in 1000-mg single doses (equivalent to 500 mg of methyldopa). The majority (93%) of either the 3H- or 14C-labeled dose was excreted in the urine. Methyldopa, which was assayed by a fluorometric technique, peaked (approximately 6 micrograms/ml) at 1 hr in the plasma. Forty-five per cent of the dose was excreted as methyldopa as opposed to 18% normally seen after oral methyldopa dosages. Intact POE was absent in the urine of three volunteers and present in only trace amounts in urine from a fourth volunteer. Thus, the oral dose of POE was well absorbed and rapidly hydrolyzed to methyldopa. After oral administration of methyldopa, methyldopa sulfate is the principal urinary metabolite in man. However, after administration of POE, a relatively small fraction (13%) of the dose was excreted as methyldopa sulfate. The major urinary metabolite of POE, other than methyldopa, was 3-OCH3 methyldopa. Methyldopamine was a minor metabolite. It was concluded that a shift from sulfation to methylation occurred in the metabolic profile of methyldopa when it was administered as POE and that the metabolites of POE (including conjugated pivalic acid) were rapidly eliminated from the body.