Thymic epithelial defects and predisposition to autoimmune disease in BB rats

We report an association between thymic epithelial defects and predisposition to autoimmunity. Diabetes-prone (DP) BB rats develop spontaneous hyperglycemia and are deficient in T cell subsets expressing the RT6 alloantigen. Diabetes resistant (DR) BB rats become diabetic if depleted of RT6+ T cells. The inciting immune system defects are unknown. We made the following observations: 1) Regions of thymic cortex and medulla devoid of thymic epithelium exist in DP-BB, DR-BB, and Lewis rats, all of which are susceptible to autoimmune disorders. Such defects were absent in eight normal rat strains. 2) Thymic epithelial defects are absent at birth, but present in BB rats at 4 weeks of age. 3) The genetic predisposition to thymic epithelial defects is an autosomal dominant trait. 4) The observation of thymic defects in (DP x WF)F1 rats led to the prediction that such animals, which never develop spontaneous autoimmunity, might be susceptible to its induction. Following depletion of RT6+ T cells we observed diabetes in 91%, and thyroiditis in 43%, of treated F1 animals (n = 23). Pancreatic insulitis was uniformly present. Because thymic epithelium participates in the positive and negative selection of developing thymocytes, we propose that thymic epithelial defects may play an important role in the predisposition of BB rats to autoimmunity.

Identification of futility in intensive care

Rising costs of intensive care and the ability to prolong the life of critically ill patients creates a need to recognise early those patients who will die despite treatment. We used changes in a modified APACHE II score (organ failure score) to make daily predictions of individual outcome in 3600 patients. 137 patients were predicted to die and of these, 131 (95.6%) died within 90 days of discharge from hospital (sensitivity 23.4%, specificity 99.8%); a false-positive diagnosis rate of 4.4%. 2 of the 6 survivors have subsequently died but 4 are alive with good quality of life. Patients predicted to die stayed 1492 days in intensive care and incurred 16.7% of total intensive care expenditure and 46.4% of the cost of all patients that died. Median survival after a prediction to die was 2 days, accounting for 62% of intensive care patient days in this patient group, giving an effective intensive care cost per survivor of UK 129,651 pounds. If used prospectively, this algorithm has the potential to indicate the futility of continued intensive care but at the cost of 1 in 20 patients who would survive if intensive care were continued.

Tau-mutant hamster SCN clock neurones express a 20 h firing rate rhythm in vitro

In vitro neurophysiological studies have demonstrated a circadian rhythm with a period of 24 h in spontaneous neuronal discharge frequency within the rodent suprachiasmatic nucleus (SCN) circadian clock. This report examines the 'circadian' firing rate rhythm in the SCN of the homozygous Tau-mutant Syrian hamster which expresses a short period behavioural rhythm. The spontaneous SCN neuronal firing rate patterns are similar to those observed in wild types. The Tau SCN firing rate rhythm displays a peak in neuronal activity occurring 5-6 h before the predicted onset of wheel-running activity, with a peak-to-peak period of 20 h. This period of the rhythm of spontaneous neuronal discharge within the Tau-mutant SCN parallels the behavioural free-running period of 20 h.

The relation between biliary lipids, nucleation time, and number of gallbladder stones after percutaneous gallbladder puncture

BACKGROUND

Biliary lipids and nucleation time are increasingly of importance in the understanding of the cholesterol nucleation process in gallstone patients.

METHODS

Biliary lipids, total lipid concentration (TLC), cholesterol saturation index (CSI) and nucleation time (NT) were studied in 221 bile samples from patients with solitary (n = 120) and multiple (n = 101) gallbladder stones.

RESULTS

Biliary cholesterol concentration and CSI did not differ between patients with solitary or multiple stones; however, it was positively correlated with the CSI (r = 0.93; p < 0.01). We found a negative correlation between CSI and TLC (r = -0.77 for solitary stones and r = -0.79 for multiple stones; p < 0.01). Furthermore, levels of total bile acids and phospholipids were similar in cases with solitary and multiple gallbladder stones. TLC did not correlate with single or multiple stones, whereas NT was determined to be negatively correlated with the number of gallstones (r = -0.39; p < 0.01). Patients with solitary stones had a significantly (p < 0.01) longer NT than those with multiple gallbladder stones (7.5 +/- 4.2 days versus 2.3 +/- 1.5 days).

CONCLUSIONS

Our findings suggest that there exists a nucleation-promoting activity, which seems to be more pronounced in patients with multiple gallbladder stones than in those with solitary stones, indicating a major risk factor for the higher recurrence rate seen in these patients.

The effect of ursodeoxycholic acid on nucleation time in patients with solitary or multiple gallbladder stones

OBJECTIVE

The objective of this study was to determine the effect of ursodeoxycholic acid (UDCA), 1000 mg/day, on nucleation time and cholesterol saturation index (CSI) in human gallbladder bile.

METHODS AND RESULTS

In 48 patients with cholesterol gallbladder stones undergoing extracorporeal shockwave lithotripsy, bile samples exhibited a significant longer median nucleation time in the case of solitary stones (7.9 +/- 5.1 days) than in patients with multiple stones (1.7 +/- 1.0 days; p < 0.0001). Stone number and nucleation time were correlated inversely (r = -0.79). UDCA led to a significant prolongation of nucleation time (solitary stones 17.9 +/- 5.8 days, multiple stones 18.0 +/- 5.7 days; p < 0.01) with a concomitant disappearance of cholesterol liquid crystals and cholesterol monohydrate crystals in gallbladder bile. Initially, there was no difference in the CSI between patients with solitary stones or multiple gallbladder stones (1.4 +/- 0.3 vs. 1.4 +/- 0.4, respectively). UDCA caused a significant decrease in CSI by 64.3% (p < 0.01).

CONCLUSIONS

We conclude that UDCA prolongs the nucleation time by decreasing the cholesterol saturation index, as well as by diminishing cholesterol liquid crystals and cholesterol monohydrate crystals in gallbladder bile from patients with cholesterol gallstones. Second, recurrent stones essentially occur in patients with multiple cholesterol gallstones, reflected by a concomitant short nucleation time.

Erythropoietin in pregnancies complicated by pyelonephritis

OBJECTIVE

To determine whether antepartum pyelonephritis causes an acute or delayed alteration in erythropoietin production.

METHODS

Serum erythropoietin concentrations were determined prospectively using an enzyme-linked immunosorbent technique in 36 pregnant women admitted to Parkland Hospital with pyelonephritis. Healthy nonanemic pregnant women served as controls.

RESULTS

Serum erythropoietin levels in women with antepartum pyelonephritis were not different from those measured in normal pregnant women. Specifically, there were no differences in erythropoietin levels in women who had anemia at admission (n = 6; 13.8 mU/mL), hemolysis (15.4 versus 12.9 mU/mL), or renal insufficiency (14.5 versus 12.9 mU/mL) secondary to renal infection as compared to controls.

CONCLUSION

We conclude that antepartum pyelonephritis does not alter erythropoietin production either acutely or within several days of infection. Because erythropoietin production was not decreased, we suggest that hemolysis is the major factor contributing to anemia associated with renal infection.

The effects of BTS 54,505, a metabolite of sibutramine, on monoamine and excitatory amino acid-evoked responses in the rat dorsolateral geniculate nucleus in vivo

1. The effects of BTS 54,505, the primary amine metabolite of the non-tricylic putative antidepressant sibutramine, on the responses evoked by visual stimulation and ionophoretic application of noradrenaline (NA), 5-hydroxytryptamine (5-HT) and excitatory amino acids (EAAs) in the rat dorsolateral geniculate nucleus (dLGN) have been investigated. 2. Ionophoretic application of 5-HT to dLGN neurones attenuated visually-evoked (n = 46), NMDA-evoked (n = 21) and AMPA-evoked responses (n = 21), while ionophoretic application of NA potentiated visually-evoked activity in these cells (n = 27). 3. Simultaneous application of BTS 54,505 with 5-HT (over 120 s) resulted in a prolongation of the recovery time (i.e. the period required by a neurone to recover by 50%, RT50) from the 5-HT-mediated suppression of discharge activity (approximately 275% increase in RT50). BTS 54,505 also prolonged the recovery time from a NA-mediated potentiation of firing (approximately 450% increase in RT50). These effects on recovery time are attributed to the inhibition of uptake of both 5-HT and NA by BTS 54,505. The amplitude of the response to 5-HT or NA was unaffected by co-ejection of BTS 54,505. 4. Ionophoretic application of N-methyl-D-aspartate (NMDA) produced a current-dependent increase in neuronal firing, as did application of the non-NMDA receptor agonist alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). A simultaneous 120 s application of BTS 54,505 inhibited the NMDA response in all cells studied (mean ED50 = 16 +/- 5 nA) but had no effect on AMPA-evoked activity in the majority of the same cells (n = 15/21).5. Short 10 s applications of BTS 54 505, at ejecting currents (>30 nA) that attenuated NMDA-evoked activity in all cells studied, had no effect on either response amplitude or recovery time from ionophoretic application of 5-HT, suggesting that inhibition of NMDA-evoked activity by BTS 54 505 was not mediated by 5-HT uptake blockade.6. These results suggest that BTS 54 505 inhibits NMDA-evoked activity, and the observation that this effect is unlikely to be due to raised levels of endogenous 5-HT following monoamine uptake blockade indicate that BTS 54 505 may interact directly with the NMDA receptor ionophore complex.

Evidence for functional dissociation of dependence and tolerance in guinea-pig isolated ileal segments following 20 hour exposure to morphine in vitro

1. In the present study we have examined the relationship between tolerance and dependence in isolated ileal segments from the guinea-pig under three different conditions: fresh preparations not previously exposed to morphine (fresh/morphine naive); preparations stored overnight at 4 degrees C in modified Krebs-Henseleit saline (overnight-stored/morphine-naive); preparations stored overnight at 4 degrees C in Krebs-Henseleit saline containing 10 microM morphine and extensively washed with modified Krebs-Henseleit saline to remove residual morphine (overnight-stored/morphine-exposed). 2. Morphine produced a concentration-dependent inhibition of the response of ileal segment to 0.1 Hz, 1 ms and 10 V transmural field stimulation in fresh/morphine-naive, overnight-stored/morphine-naive and overnight-stored/morphine-exposed preparations. The maximum effect observed was similar in all three preparations-approximately 80% inhibition. Although, morphine was significantly more potent in the fresh/morphine-naive preparations (pD2 6.72 +/- 0.05, n = 8) than either the overnight-stored/morphine-native (pD2 6.42 +/- 0.11, n = 8) or the overnight-stored/morphine-exposed (pD2 6.44 +/- 0.14, n = 8), there was no significant difference between the overnight exposure to ileal segments to 10 microM morphine at 4 degrees C failed to induce tolerance to morphine. 3. The mu opiate receptor antagonist, naloxone (10 microM), produced contractions in both fresh/morphine-naive and overnight-stored/morphine-naive ileal segments following acute exposure to 10 microM morphine. Naloxone (10 microM) also produced contractions in 2/9 fresh/morphine-naive, 1/9 overnight-stored/morphine-naive and 7/9 overnight-stored/morphine-exposed preparations in the absence of morphine. The greater incidence of naloxone-induced contractions in overnight-stored/morphine-exposed preparations,suggests that dependence in this model is the product of adaptive changes that outlive the presence of morphine.4. The selective alpha2-adrenoceptor agonists, clonidine (0.3 microM) and 5-bromo-6-[2-imidazolin-2-ylamino]-quinoxaline bitartrate (UK-14304, 1 microM), inhibited naloxone-induced contractions in overnight-stored/morphine-exposed preparations of ileal segments (n = 4 preparations for each agonist), suggesting that the response is due to transmitter release from the myenteric plexus.5. The findings in the present study indicate that tolerance and dependence to morphine in ileal segments of the guinea-pig can be functionally dissociated by overnight exposure to morphine at 4 degrees C.The development of tolerance to morphine, unlike dependence, appears to be a temperature-dependent process. This also raises the possibility that naloxone possesses intrinsic negative agonism at morphine sensitive receptors, which is manifested as a functional response only after adaptive changes in the myenteric plexus following exposure to morphine.

Assessment of splanchnic oxygenation by gastric tonometry in patients with acute circulatory failure

OBJECTIVE

To investigate the importance of splanchnic ischemia in patients with acute circulatory failure by comparing gastric intramucosal pH as measured by tonometry with conventional methods of assessing adequacy of tissue oxygenation.

DESIGN

Prospective cohort of patients with acute circulatory failure in first 24 hours after admission to the intensive care unit.

SETTING

Two general intensive care units in London, England.

PATIENTS

Consecutive sample of 83 patients of varying diagnostic categories that required pulmonary artery catheterization.

MAIN OUTCOME MEASURES

Gastric intramucosal pH and hemodynamic, oxygen transport, and metabolic variables were measured on admission and at 12 hours and 24 hours after admission. Prediction of outcome (death or survival) by each measurement was assessed by sensitivity, specificity, and logistic regression analysis.

RESULTS

Mean 24-hour Acute Physiology and Chronic Health Evaluation (APACHE II) score was 20.3. There were significant differences in mean gastric intramucosal pH between survivors and nonsurvivors on admission and at 24 hours, (7.40 vs 7.28, 7.40 vs 7.24, respectively; P < .001). Admission heart rate was higher (116 vs 101 beats per minute; P < .003) and mean arterial pressure lower (82 vs 97 mm Hg; P < .01) in nonsurvivors. There were no consistent differences in cardiac index, oxygen delivery, and oxygen uptake between survivors and nonsurvivors. Admission arterial pH was significantly lower (7.3 vs 7.36; P < .003), base excess more negative (-5.3 vs -1.9; P < .001), and lactate concentration higher (3.14 vs 1.91 mmol/L; P < .03) in nonsurvivors. Gastric intramucosal pH had a sensitivity of 88% for predicting death and a likelihood ratio of 2.32, higher than for any other variable. Only gastric intramucosal pH at 24 hours independently predicted outcome.

CONCLUSIONS

Gastric intramucosal pH was the most reliable indicator of adequacy of tissue oxygenation in this group of patients. Inadequate regional blood flow as detected by a reduction in gastric intramucosal pH, but not by systemic measures, is an important contributor to morbidity and mortality in intensive care units.

Depression, demoralization and control over psychotic illness: a comparison of depressed and non-depressed patients with a chronic psychosis

This paper explores the hypothesis that depression in chronic schizophrenia is in part a psychological response to an apparently uncontrollable life-event, namely the illness and its long-term disabilities. It is suggested that depression is linked to patients' perception of controllability of their illness and absorption of cultural stereotypes of mental illness. Clinically and operationally diagnosed schizophrenic and manic-depressive patients receiving long-term maintenance treatment were studied. The cross-sectional prevalence of depression in schizophrenics was 29% and 11% for patients with bipolar affective illness. The hypothesis was supported. Multivariate analyses revealed that patients' perception of controllability of their illness powerfully discriminated depressed from non-depressed psychotic patients. Although those patients who accepted their diagnosis reported a lower perceived control over illness and an external locus of control, label acceptance was not associated with lowered depression, self-esteem or unemployment. The cross-sectional nature of the study makes the direction of causality and the role of intrinsic illness variables difficult to ascertain; however, the results set the scene for prospective and intervention studies and the various possibilities are discussed.

A neurophysiological study of a lithium-sensitive phosphoinositide system in the hamster suprachiasmatic (SCN) biological clock in vitro

Lithium lengthens the period of free-running circadian rhythms in many species. In mammals the hypothalamic suprachiasmatic nucleus (SCN) has been identified as a biological clock which generates circadian rhythms. The effect of lithium-induced depletion of the intracellular pool of inositol, leading to decreased intracellular second messengers IP3 and DAG, was examined neurophysiologically. Extracellular recordings were obtained from spontaneously discharging SCN neurones maintained in vitro. Superfusion of slices with lithium-containing (0.1-30 mM) aCSF, but not rubidium-containing aCSF, suppressed neuronal firing in a dose-dependent manner. Lithium-induced suppressed firing was reversed by myo-inositol, but not by epi-inositol. These studies provide evidence for basal phosphoinositide turnover in neurones and implicate a lithium-sensitive phosphoinositide system in the maintenance of the spontaneous discharge activity of SCN neurones.

Evidence for direct vasoconstrictor activity of melatonin in "pressurized" segments of isolated caudal artery from juvenile rats

Responses of isolated, 60 mmHg 'pressurized' segments of the distal caudal artery of adult and juvenile Wistar rats to melatonin and the selective alpha 2-adrenoceptor agonist 5-bromo-6-[2-imidazolin-2-ylamino]-quinoxaline bitartrate (UK-14304) were examined using the Halpern pressure myograph. Melatonin showed no direct vasoconstrictor activity in vessels from adult rats, whereas UK-14304 produced moderate vasoconstriction (pD2-7.43 +/- 0.09). In the presence of phenylephrine-induced tone, melatonin produced a variable but small constrictor response (less than 10 microns reduction in diameter) in some vessels; the response to 1 mumol/l UK-14304 was less than in the absence of tone. In vessels isolated from juvenile rats, melatonin caused concentration-dependent vasoconstriction with a maximum response about 70% of the maximum response elicited by UK-14304. Vessels from juvenile rats were more sensitive to melatonin (pD2-9.40 +/- 0.07) than they were to UK-14304 (pD2-8.12 +/- 0.14). In the presence of phenylephrine-induced tone, the vasoconstrictor responses to both melatonin and IK-14304 were markedly less; the sensitivity to melatonin was not different from that seen in the absence of tone. These findings indicate that 'pressurized' segments of the isolated distal caudal artery may provide a simple and convenient, functional model of melatonin receptors. The findings also appear to implicate melatonin in thermoregulatory processes in juvenile rats.

Role of the antrum in the gastric emptying of a non-nutrient liquid in the rat

Forty male Wistar rats underwent liquid gastric emptying analysis with a non-nutrient liquid--99mTC-tin colloid in physiologic saline. Twenty then had two-thirds resection of the glandular stomach with Billroth-II-type reconstruction. Twenty served as controls: 10 unoperated and 10 with a laparotomy alone. Emptying was studied weekly for 4 weeks, then monthly for 4 months. Emptying was unchanged in unoperated controls. Laparotomy alone caused delayed emptying for 2 months (p less than 0.05). After Billroth-II resection emptying was delayed for 4 months (p less than 0.01). This delay included both the early and late phases of gastric emptying. We conclude that a laparotomy alone delays gastric emptying. The addition of an antrectomy causes a greater emptying delay, which persists for longer than that due to laparotomy alone. Thus, in a situation in which the small bowel and gastric feedback mechanisms are inoperative, the antrum is seen to play an important role in the gastric emptying of liquids. This supports the concept in man that antral contractions are important in ensuring the normal active emptying of liquids from the stomach.

A simple and rapid method for improving recording characteristics using multibarrelled micropipettes

A method for the simple and rapid fabrication of multibarrelled micropipettes with improved signal-to-noise characteristics is described. The process of silicone coating the exterior of the multibarrel assembly was found to improve recording characteristics greatly and to reduce recording noise during the passage of ionophoretic current. This simple process of fabrication and silicone coating is completed within 15-20 min and is technically undemanding.

Poor palliation of colorectal malignancy with the neodymium yttrium-aluminium-garnet laser

The neodymium yttrium-aluminium-garnet (NdYAG) laser was used to palliate the symptoms of 38 patients with rectal carcinoma unsuitable for radical surgery. All patients with small tumours (n = 6) reported resolution of their symptoms. In contrast, those with large tumours frequently showed little improvement (n = 18) and alternative surgical management was necessary in 12 patients. The overall early mortality rate (less than 1 month after first treatment) was 21 per cent. The NdYAG laser offers good palliation and may even cure small colorectal tumours in patients who are unsuitable for surgery. For large circumferential tumours, those associated with obstruction and those close to or involving the anal sphincters, however, the results are poor and better symptom control may be achieved by other means.

Comparative hemodynamic effects of Org 7797, flecainide, and propafenone in anesthetized pigs with developing myocardial infarcts

The hemodynamic effects of a new Ic antiarrhythmic agent (Org 7797) were compared with those of flecainide and propafenone in anesthetized pigs with developing myocardial infarcts. One hour after acute coronary artery occlusion, the only significant hemodynamic effect of an intravenous (i.v.) dose of Org 7797 (0.5 mg/kg) known to prevent ischemia-induced ventricular fibrillation (VF) in dogs was a decrease in heart rate (HR) (of 3%) while cardiac output (CO), stroke volume (SV), and left ventricular (LV) dP/dtP-1 were unchanged. At four times this dose, the only sustained and significant responses to Org 7797 were decreased CO and bradycardia, whereas decreases in arterial and LV pressures (BP and LVP) and LVdP/dtP-1 were transient. In contrast, a therapeutic dose of flecainide (2 mg/kg) induced sustained reductions in CO, SV, LVdP/dtP-1, and LVP whereas a similar (therapeutic) dose of propafenone decreased LVP, reduced CO partly as a result of bradycardia and decreased LVdP/dtP-1 but not sufficiently to decrease SV. Two electrical deaths occurred in each of the propafenone (n = 6) and flecainide (n = 7) groups, but arrhythmic deaths did not occur in Org 7797- or saline-treated animals. We conclude that Org 7797 in therapeutic doses, unlike propafenone and especially flecainide, is not cardiodepressant in animals whose cardiac function is already compromised. In addition, there was no evidence of proarrhythmogenicity at the doses of Org 7797 used.

Metabolic studies in kidney stone disease

Patients with kidney stones (n = 59) and healthy controls (n = 31) collected a 24-hour urine sample and later underwent a 6-hour 'fast and load' test in which an oral calcium load was taken after 2 hours. In the 24-hour urine sample, mean calcium excretion was higher in patients than controls, while mean urate, oxalate and citrate levels were similar. The patients had higher levels of fasting plasma calcium, serum calcitriol and fasting urinary calcium, and lower levels of plasma phosphate than did the controls. Following the calcium load, plasma and urinary calcium increased similarly in both groups. Serum parathyroid hormone (PTH) levels were similar in both groups and decreased similarly following the calcium load. Multiple linear regression, relating the presence or absence of stone formation to all variables, found the only variables significantly related to stone formation to be plasma levels of calcium (p less than 0.001) and phosphate (p = 0.001) and fasting urinary urea (p less than 0.001), and 24-hour urinary calcium excretion (p less than 0.05). Urinary oxalate and citrate were not related to stone formation. The data do not support the hypothesis that primary stimulation by calcitriol produces a normal fasting plasma calcium level, with an exaggerated increase after an oral calcium load. The findings instead suggest an abnormality of parathyroid cell 'set point', such that PTH secretion continues until the plasma calcium level is a little higher and the phosphate a little lower than in controls.

Exit-site/tunnel infection and catheter outcome in peritoneal dialysis patients

STUDY OBJECTIVE

To study exit-site/tunnel infections and catheter outcomes in peritoneal dialysis patients.

DESIGN

The study was designed to investigate exit-site (ESI)/tunnel infections (TI) and catheter losses in all chronic PD catheters inserted in ESRD patients from 9/88 to 9/91.

SETTING

Tertiary-referral university hospital.

PATIENTS AND METHODS

Seventy-three patients (40 males, 33 females) underwent 78 double-cuff coiled swan-neck catheter implantations surgically. The curettage of exit site was performed weekly for tunnel infection refractory to medical management. The subcutaneous cuff was excised in persistent ESI/TI.

RESULTS

Fifty-nine episodes of ESI/TI in 34 patients were observed over 946 patient-months. Thirty-nine patients experienced no ESI/TI, 27 patients had one and seven had two or more episodes of ESI/TI. Four patients had five episodes of peritonitis associated with ESI/TI. Eight recurrent episodes of ESI/TI with S. aureus in 8 patients were treated successfully with Rifampin. Seven subcutaneous cuffs were excised successfully in 7 patients with tunnel infection, five with S. aureus and two with Pseudomonas aeruginosa. No catheter was removed due to ESI/TI or ESI/TI associated peritonitis.

CONCLUSIONS

Aggressive exit site care including repeated curettage, excision of the subcutaneous cuff and appropriate antibiotics reduced significantly catheter losses related to ESI/TI.

Geniculo-hypothalamic tract lesions block chlordiazepoxide-induced phase advances in Syrian hamsters

Administration of the benzodiazepine triazolam at the appropriate time in the circadian cycle has been shown to induce phase shifts in hamster circadian rhythms. These phase shifts can be blocked by geniculo-hypothalamic tract (GHT) ablation or by restraint of activity. The present study examined the effects of the benzodiazepine chlordiazepoxide on running-wheel activity rhythms of hamsters. The phase-advancing effect of intraperitoneal injections of chlordiazepoxide administered at circadian time 6 (CT 6) was dose-dependent. Average shifts ranged from 6 min at a dose of 0.05 mg/kg to 135 min at a dose of 200 mg/kg. Four of twenty hamsters did not show a phase shift to any dose tested. Phase advance shifts to chlordiazepoxide (CT 6; 100 mg/kg) were blocked by GHT lesions. Chlordiazepoxide injections at doses which induced phase shifts were often followed by sedation. These results indicate that chlordiazepoxide is similar to triazolam, in that its ability to induce phase shifts at circadian time 6 is blocked by GHT lesions.

The effects of GABA and benzodiazepines on neurones in the suprachiasmatic nucleus (SCN) of Syrian hamsters

Administration of benzodiazepines at appropriate times in the circadian cycle induce phase-shifts in circadian locomotor activity. The possibility that benzodiazepine-induced shifts are mediated at the level of the suprachiasmatic nuclei (SCN), identified as the circadian pacemaker in mammals, was examined electrophysiologically. Extracellular recordings were made from Syrian hamster (Mesocricetus auratus) hypothalamic SCN neurones in vitro to assess (1) the effects of gamma-aminobutyric acid (GABA) on SCN neuronal activity and (2) the effects of benzodiazepines (chlordiazepoxide and flurazepam) on GABA-evoked responses. Of 93 SCN cells tested, 86 were suppressed by iontophoresed GABA (20 mM) in a current(dose)-dependent manner, while 6 were unaffected; suppression was found during both the projected light and dark phases of the circadian cycle. Application of bicuculline methiodide alone elevated mean discharge activity, while GABA-evoked suppressions were blocked by bicuculline (n = 9/11 cells). Iontophoresis of chlordiazepoxide or flurazepam (20 mM; 1-10 nA) alone produced a current(dose)-dependent prolonged suppression of cell firing which was antagonised by bicuculline. These results indicate that benzodiazepine/GABA-evoked responses are at least partially mediated by GABAA receptors within the SCN and suggest that SCN may be a possible locus for the action of benzodiazepines in their induction of phase-shifts in circadian function.

Trace element analysis in body fluids by glow discharge mass spectrometry: a study of lead mobilization by the drug cis-platin

A method is described, using glow discharge mass spectrometry, to measure lead and platinum levels at the p.p.b. level in the urine of patients receiving cancer chemotherapy with the drug cis-platin. Using bismuth added as an internal standard, the method is found to compare very favourably with other quantitative techniques, and requires relatively little sample preparation. The data obtained support the idea that normally stored body lead is displaced by the platinum complexed in the drug, but only to a small extent.

The effects of continuous light exposure on Syrian hamster suprachiasmatic (SCN) neuronal discharge activity in vitro

The circadian variation in neuronal discharge activity recorded in vitro from the Syrian hamster suprachiasmatic nucleus (SCN), identified as a circadian clock, was used as an index of SCN circadian function. SCN neurones (n = 89) following in vitro commissural section of the paired SCN showed a similar peak in spontaneous discharge activity during the projected light phase (between CT 06.00 and 08.00 h) as the commissural intact LD 12:12 preparations (n = 230 neurones). Long-term exposure to continuous lighting (LL) may induce either arrhythmicity or splitting of locomotor behaviour. Circadian variation in SCN discharge activity was absent in hamsters (44 cells, 6 animals) showing LL-induced arrhythmicity. In 4 hamsters exhibiting split free-running behaviour two peaks in SCN discharge activity (n = 32 cells) were observed. Fifteen LL free-running animals showed no evidence of splitting or arrhythmicity and subsequent SCN recordings revealed only a single peak in SCN discharge activity. These LL-induced changes in overt circadian behaviour appeared paralleled by changes in neuronal discharge activity of the SCN circadian clock and support the view that the paired SCN act as a mutually coupled circadian oscillator.

Mechanisms of hemolysis and anemia associated with acute antepartum pyelonephritis

Anemia develops in about a fourth of women whose pregnancy is complicated by pyelonephritis, although its exact mechanism has not been defined clearly. In this study of 18 women with antepartum pyelonephritis, although only a third had anemia (hematocrit less than 30 vol/dl), there was evidence for hemolysis in all 18. Specifically there was a mean decrease in hematocrit of 5 vol/dl from admission to discharge. With scanning electron microscopy, we compared erythrocyte morphologic aberrations that were found in women with renal infection with those of normally pregnant women, and the former had significantly increased proportions of echinocytes in particular, but schistocytes and spherocytes were increased also (total 10.3% vs 1.4%, p less than 0.0001). These changes, especially echinocytosis, have been induced in vitro by lipopolysaccharide, and they are known to lead to premature red blood cell destruction in vivo. We conclude that hemolysis with subsequent anemia in pregnant women with pyelonephritis is caused by lipopolysaccharide-induced red blood cell membrane damage.

Effects of idazoxan on dorsal raphe 5-hydroxytryptamine neuronal function

The effects of the alpha 2-adrenoceptor antagonist idazoxan on 5-hydroxytryptamine (5-HT) neuronal firing and release have been investigated. Idazoxan, administered i.v. (10 micrograms/kg and 0.5 mg/kg) increased dorsal raphe nucleus (DRN)-5-HT neuronal firing rate in a dose-dependent fashion. At the higher dose, a voltammetric study revealed increases in extracellular 5-HT and 5-hydroxyindole acetic acid (5-HIAA) levels, there was no effect with the lower dose. Intra-raphe administration of idazoxan (1 ng) also elevated the firing rate of 5-HT neurones in the dorsal raphe, suggesting that idazoxan may produce the increase in firing by a direct effect in the DRN. However, microiontophoretic application of idazoxan did not increase the firing rate of 5-HT neurones in the DRN. Thus the increase in the firing rate of 5-HT neurones in the DRN observed with systemic and local administration of idazoxan is probably not due to a direct action of idazoxan on the 5-HT neurone. Possibly the idazoxan acted at alpha 2-adrenoceptors located on noradrenergic terminals thus stimulating noradrenaline release and consequently increased 5-HT activity. Chronic administration of idazoxan (0.8 mg/kg per h for 14 days), using osmotic mini-pumps, caused an elevation in basal firing rate and an attenuation of the inhibitory response of DRN 5-HT neurones to the 5-HT1A agonist, 8-hydroxy-2-(di-n-propylamino) tetralin (8-OHDPAT) (10 micrograms/kg i.v.). This finding suggests that chronic infusion with idazoxan leads to desensitisation of the 5-HT1A somatodendritic autoreceptor.

Effect on gait using various prosthetic ankle-foot devices

Five different commonly prescribed ankle-foot devices for below-knee prostheses were tested for effects on gait: SACH, SAFE, SEATTLE, SINGLE AXIS, and MULTIPLE AXIS. Subjective ratings by the amputees served to resolve which physical variables determined the preferred ankle-foot device. Ratings were related to age, body weight, length of residual limb, and ratio of stride frequency to stride length. Distinctions in performances were derived from analyses of anterior-posterior angular accelerations occurring in the prosthesis immediately following heel strike. The accelerations were characterized as a damped oscillatory waveform. These objective findings, when related to the subjective ratings, showed that the amputees preferred devices which developed the lesser shock and greater damping.

Mesenteric blood flow in patients with diabetic neuropathy

We examined flow velocities in the superior mesenteric artery and celiac artery in normal controls (group C, n = 11), diabetic patients (group D, n = 8), and diabetic patients with clinically evident autonomic neuropathy (group DN, n = 6) to further define the usefulness of duplex examination in the evaluation of the mesenteric circulation in normal and disease states. By use of a 3 MHz duplex scanner, peak systolic velocity, peak diastolic forward velocity, end-diastolic forward velocity, and peak diastolic reverse velocity were measured in centimeters per second before and after a standardized meal. The vessels' diameters in centimeters were also measured. After the meal peak diastolic reverse velocity disappeared in all patients. The average vessel diameter in the superior mesenteric artery (0.7 cm) and celiac artery (0.8 cm) did not change. Flow velocities in the celiac artery were not significantly altered by the meal. In the control group, peak systolic velocity in the superior mesenteric artery increased 38%, peak diastolic forward velocity rose 66%, and end-diastolic forward velocity increased by 70%. In the diabetic nonneuropathic group the changes were 15%, 98%, and 100%, respectively. These changes were statistically significant (p less than 0.01). On the other hand, the patients with diabetic autonomic neuropathy presenting a picture of gastroparesis did not exhibit the expected increases in postprandial velocities. Moreover, this alteration in blood flow velocity, although similar to that encountered in patients with intestinal angina, did not appear to be due to occlusive arterial disease on the basis of clinical examination and B-mode scanning.

Neurophysiological responses to melatonin in the SCN of short-day sensitive and refractory hamsters

The pineal hormone melatonin plays a central role in the regulation of seasonal reproductive cycles in mammals and several studies have implicated the suprachiasmatic nucleus (SCN) as a target on which melatonin acts. The Syrian hamster is a long-day breeder which exhibits gonadal regression when housed in short (less than 12.5 h) daily photoperiods or injected daily with melatonin in long photoperiods. In the present paper we address the question whether melatonin affects firing rates of SCN neurones and whether these effects change as the animals become refractory to short photoperiods. In long-day (LD14:10) hamsters SCN neurones were suppressed (31%), activated (15%) or unaffected (54%) by melatonin. In contrast, there was an increased proportion of melatonin insensitive cells (88%) in short-day (refractory) hamsters. Melatonin-responsive cells were found primarily during the late projected day and early projected night in both long-day and short-day animals. This reduced responsiveness of SCN neurones to melatonin in hamsters refractory to short-day exposure may represent part of the mechanism underlying the development of gonadal refractoriness and the onset of gonadal growth in anticipation of long spring photoperiods.

The aetiology of gastric stump carcinoma in the rat

This study investigated the aetiology of gastric stump carcinoma in the rat. These carcinomas were induced by duodenogastric reflux without the need to administer carcinogens. Carcinoma was only detected when pancreatic exocrine secretions were present in the reflux. Malignant change was associated with dysplasia but not intestinal metaplasia or adenocystic proliferation of glands. The extent of resection increased tumour yield, but a truncal vagotomy did not. No difference was detected in intragastric pH, bacterial flora, or bile acid concentration between animals with and without carcinoma.

Ulceration and osteomyelitis

The pathophysiology, mortality, and morbidity of osteomyelitis and ulcers are discussed, including making the diagnoses. Treatments described include topical and surgical methods as well as hyperbaric oxygen therapy.

Analysis of below-knee suspension systems: effect on gait

Seven different suspension systems for below-knee prostheses were tested on 20 adult, unilateral amputees. All subjects walked with a prosthesis. Gait was evaluated with regard to longitudinal and vertical accelerations of the body, forward velocity, axial (piston) movement of amputated limb in the socket, and knee movement. Harmonic analyses of variable waveforms provided the primary method to discriminate performances among the suspensions. The appropriateness of a given suspension system depended on both the length and the shape of the residual limb.

Prioritising waiting lists

The 'top 22' patient conditions on the general surgical waiting list at Guy's Hospital were rated independently by five general surgeons. Each surgeon estimated the peri-operative mortality rates associated with each treatment; the proportion of patients who failed to benefit; the effect of successful treatment on life expectancy and on the patients' quality of life. the mean values were used to estimate the expected net benefits (in terms of quality-adjusted life-years) from treatment one year earlier than might otherwise have been the case. These benefits were then related to the operating times and length of stay associated with each treatment; this identified which treatments offered the greatest benefit per unit of each constrained resource. Of all conditions examined anal fissures where shown to be the least resource intensive in relation to the benefits generated, whilst varicose veins and epigastric hernias proved otherwise. For the full potential of this approach to be realised it needs to be repeated in other places and in other specialties. It nevertheless offers a more rational basis for interpreting waiting list data than presently exists and by using the short-cut methods is a relatively cheap way of generating much useful data.

Effect of potential antidotes on the acute toxicity, tissue disposition and elimination of selenium in rats

Treatment of male Wistar rats with sodium selenate (2.24 mg Se/kg, s.c.) inhibited their body weight gain for 24 hr, after which the animals recovered. Intraperitoneal injections of sodium-2,3-dimercaptopropane-1-sulphonic acid (60 mg/kg), meso-2,3-dimercaptosuccinic acid (50.9 mg/kg) and calcium disodium ethylenediamine-tetraacetate (500 mg/kg) 15 min after Se had no protective effect, whilst 2,3-dimercaptopropanol (15 mg/kg) inhibited the recovery of the Se-treated animal. Sodium diethyldithiocarbamate (DDTC, 70 mg/kg, i.p.) reduced the Se-induced loss of body weight but had no effect on the tissue disposition of 75Se when injected 15 min, 3 hr or 6 hr after a s.c. injection of sodium [75Se] selenite (50 microCi, 17.4 micrograms Se/kg). The citrate salts of bismuth (2.5 and 5 mg Bi/kg, s.c.), antimony (1.5 and 3 mg Sb/kg, s.c.) and germanium (40 mg Ge/kg, s.c.) also reduced the selenate-induced loss of body weight, whilst germanium citrate (40 mg Ge/kg) and bis-carboxyethyl germanium sesquioxide (80, 200 and 400 mg Ge/kg) promoted significant dose-related increases in the 24 hr urinary excretion of 75Se when given 15 min after sodium [75Se] selenite (30 microCi, 0.5 mg Se/kg, s.c.).

Serum vitamin D metabolites are not responsible for low turnover osteoporosis in chronic liver disease

We measured the concentrations of vitamin D-binding protein (DBP), total 25-hydroxyvitamin D, total 1,25-dihydroxyvitamin D [1,25-(OH)2D], and free 1,25-(OH)2D in sera of 107 patients with histologically proven chronic liver disease. Bone density measurements and dynamic skeletal histomorphometry were also performed. Osteoporosis, as defined by arbitrary criteria, was found in 42 patients (39%), while no patient had osteomalacia. Serum concentrations of vitamin D-binding protein, 25-hydroxyvitamin D, total 1,25-(OH)2D, and free 1,25-(OH)2D were reduced in patients with cirrhosis, but not in the noncirrhotic patients. Bone formation rates, which were low in 55 patients (51%), were correlated with liver functions, but not with the concentrations of either vitamin D metabolite. A subgroup of 44 patients with low serum 1,25-(OH)2D concentrations and low bone formation rates failed to show an appropriate increase in serum bone Gla protein after 1,25-(OH)2D3 administration even though serum concentrations of 1,25-(OH)2D rose normally. These data suggest that the bone disease in patients with hepatic disorders is not related to the serum concentrations of vitamin D metabolites or the effect of these metabolites on osteoblast function.

Antiarrhythmic effects of selective beta 1- and beta 2- and nonselective beta-adrenoceptor blockade in normokalaemic and dietary-induced hypokalaemic rats

Hypokalaemia (HK) is a risk factor for development of clinical arrhythmias, and epinephrine (Epi), released after myocardial infarction, may itself induce HK. The effects of selective beta 1- and beta 2-blockade with metoprolol (M) and ICI 118551 (I), respectively, and non-selective blockade with propranolol (P) against early ischaemia-induced arrhythmias were therefore compared in normokalaemic (NK) and dietary-induced HK rats. Plasma Epi, norepinephrine (NE), and K+ levels were also measured. All three blockers [5-10 mg/kg intravenously (i.v.)] were antifibrillatory in NK rats, whereas I and P (2-10 mg/kg) additionally reduced the number of ventricular premature beats. Coronary artery ligation increased plasma Epi levels in both NK an HK rats, but plasma NE increased further in HK rats. HK was also associated with an increased arrhythmia severity and negation of the antifibrillatory action of M. In contrast, I and P retained antiarrhythmic and antifibrillatory effects in HK animals and increased survival. Both I and P increased plasma K+ levels in both NK and HK animals whereas M did not. We concluded that beta 2-receptor-mediated HK after coronary occlusion may play a substantial role in arrhythmogenesis. Protection afforded by beta 2-blocking agents may be due to alleviation of HK in HK rats or to induction of hyperkalaemia in NK rats.

The expansion of interventional radiology. Report of a survey conducted by the Royal College of Radiologists

The Interventional Radiology Group of the Royal College of Radiologists sent a questionnaire to major hospitals in the United Kingdom in 1982 and 1987 in order to assess the impact of the introduction and growth of interventional procedures on patient management over the 5-year period and to consider the implications of these data for the future staffing and equipment requirements of radiology departments. In the 194 hospitals correctly completing the most recent survey, a total of 30,794 interventional procedures were performed in a 12 month period, representing an overall increase of 116% since the previous survey of 1982.

Preoperative positioning of the protruding premaxilla in the bilateral cleft lip patient

The rationale and technique for preoperative retraction of a protrusive premaxilla in the bilateral complete cleft lip and palate patient are presented. Two types of pinned intraoral appliances are presented that can expand the palatal shelves while retracting the premaxillary segment. Findings from lateral cephalometric x-ray studies of eight appliance patients and six control patients with bilateral clefts but no appliance treatment are presented at age 15. The data indicate that the cephalometric values at age 15 are within the normal range for most patients. Incisor angulation was quite varied among the subjects.

The electrophysiological effects of melatonin and a putative melatonin antagonist (N-acetyltryptamine) on rat suprachiasmatic neurones in vitro

Several studies have implicated the suprachiasmatic nuclei (SCN) as a target for the action of melatonin in its regulation of seasonal and circadian behaviour. Single-unit activity from the SCN and adjacent paraventricular area and anterior hypothalamus was recorded using the in vitro rat hypothalamic slice preparation. Neurones were tested for responses to iontophoresed or pressure ejected melatonin (n = 62) and serotonin (5-HT, n = 80). The majority (n = 24-26) of melatonin-sensitive SCN neurones were inhibited by melatonin in a dose-dependent manner during the latter portion of the projected light phase of the circadian light-dark cycle. A putative melatonin antagonist, N-acetyltryptamine, exhibited concentration dependent mixed agonist-antagonist effects on melatonin-evoked responses.