Optimization and Control of Agent-Based Models in Biology: A Perspective

Agent-based models (ABMs) have become an increasingly important mode of inquiry for the life sciences. They are particularly valuable for systems that are not understood well enough to build an equation-based model. These advantages, however, are counterbalanced by the difficulty of analyzing and using ABMs, due to the lack of the type of mathematical tools available for more traditional models, which leaves simulation as the primary approach. As models become large, simulation becomes challenging. This paper proposes a novel approach to two mathematical aspects of ABMs, optimization and control, and it presents a few first steps outlining how one might carry out this approach. Rather than viewing the ABM as a model, it is to be viewed as a surrogate for the actual system. For a given optimization or control problem (which may change over time), the surrogate system is modeled instead, using data from the ABM and a modeling framework for which ready-made mathematical tools exist, such as differential equations, or for which control strategies can explored more easily. Once the optimization problem is solved for the model of the surrogate, it is then lifted to the surrogate and tested. The final step is to lift the optimization solution from the surrogate system to the actual system. This program is illustrated with published work, using two relatively simple ABMs as a demonstration, Sugarscape and a consumer-resource ABM. Specific techniques discussed include dimension reduction and approximation of an ABM by difference equations as well systems of PDEs, related to certain specific control objectives. This demonstration illustrates the very challenging mathematical problems that need to be solved before this approach can be realistically applied to complex and large ABMs, current and future. The paper outlines a research program to address them.

The panzootic white-nose syndrome: an environmentally constrained disease?

White-nose syndrome (WNS) is an emerging disease of hibernating bats probably caused by a pathogenic fungus, Geomyces destructans. The fungus has dispersed rapidly in the Northeastern United States and Canada and is presently a serious risk to hibernating bats of the mid-southern United States. Our objectives were to investigate how the environmental factors of temperature and resources impact the physiology of bats and apply this to explore possible effects of the fungus G. destructans on bats. Using a dynamic, physiologically based model parameterized for little brown bats (Myotis lucifugus), we found that the survival region defined in terms of minimal and maximal cave temperatures and bat lipid reserve levels exhibits plasticity as a function of cave temperature. During the pre-hibernation period, constellations of increased availability of fall and winter prey, reduced energy expenditure and lipogenic factors provide fat deposition in hibernator species that engender survival throughout the hibernation period. The model-derived survival region is used to demonstrate that small increases in lipid reserves allow survival under increasing maximum temperatures, which provides flexibility of bat persistence at the higher cave temperature ranges that may occur in the Southern United States. Antipodally, the lower-temperature survival range is bounded with minimum temperatures. Our results suggest that there is an environmental distinction between survival of bats in Southern and Northern US states, a relationship that could prove very important in managing WNS and its dispersal.

A long-lasting response to sorafenib treatment in an advanced hepatocellular carcinoma patient

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide. No effective systemic treatment has been established, except for sorafenib chemotherapy. In fact, sorafenib has proved to provide a statistically significant survival extension of about two months in two phase III trials in the North America-Europe area and in the Asia-Pacific area, which respectively reported a median survival after treatment of 10.7 and 6.5 months, respectively. We report the case of an HCC patient, who received a four-month therapy with sorafenib with a clinical, biochemical and radiographic response, but had to interrupt treatment because of a myocardial infarction. Surprisingly, despite no antitumor treatment having been administered for about a year, the patient has shown no tumor progression and is currently on a close follow-up. Should other similar cases be presented, a subset of patients with long-lasting response to sorafenib might be identified.

Is Hypogammaglobulinemia a Constant Feature in Good's Syndrome?

Thymomas are rare tumors, which can be associated to a variety of paraneoplastic syndromes, including a fatal hypogammaglobulinemia, namely Good's Syndrome (GS). Although the combination of thymoma and hypogammaglobulinemia is regarded as sufficient for diagnosis of Good's syndrome, some thymoma patients with a clear clinical picture of immunodeficiency present normal levels of immunoglobulins. We describe the case of a patient, with a 20-year history of thymoma, who underwent several operations and lines of chemotherapy, and suffered from recurrent infections, including one rare skin infection from Pseudoallescheria boydii. The patient constantly presented normal levels of gammaglobulins.

Preliminary results of phase II study of capecitabine and gemcitabine (CAP-GEM) in patients with metastatic pretreated thymic epithelial tumors (TETs)

BACKGROUND

No previous prospective trials have been reported with capecitabine and gemcitabine (CAP-GEM) in patients with metastatic thymic epithelial tumors (TETs). We conducted a multicenter study to determine the activity and tolerability of this regimen in pretreated TETs.

PATIENTS AND METHODS

A total of 15 patients were enrolled in the first stage of phase II study. All patients received CAP-GEM every 3 weeks. The primary end point was objective response rate (RR); secondary end points were toxicity, progression-free survival (PFS) and overall survival.

RESULTS

Complete responses (CR) and partial responses were observed in three (20%) and three (20%) patients for a 40% RR, respectively. Grade 1-2 neutropenia, anemia and thrombocytopenia were the most common side-effects, noted in seven (46.7%), five (33.3%) and five (33.3%) patients, respectively. The most common grade 3 toxicity was neutropenia in three patients (20%). Median PFS was 11 months (95% confidence interval 4-17). The 1- and 2-year survival rates were 80% and 67%, respectively.

CONCLUSION

We have decided to publish the preliminary results because this regimen was more active than that expected. Although our results are preliminary, CAP-GEM shows activity and safety in pretreated TETs. Furthermore, multicenter trials, also in first-line setting, are necessary to confirm our results.

Gemcitabine-capecitabine in platinum-refractory patients with thymic epithelial tumors

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Background: Platinum based combination chemotherapy is the actual standard of care for advanced and recurrent Thymic epithelial tumours-TET (thymoma and thymic carcinoma). Additional agents are needed in this setting. We have designed a pilot study, phase II multicenter, to evaluate the efficacy and safety of no tested schedule gemcitabine-capecitabine in patients refractory to platinum based chemotherapy. Methods: Eligible patients had pathologically confirmed TET and were treated with at least 2 lines of chemotherapy, one of this being a platinum based schedule. From January 2007 to September 2008 twelve pts were enrolled. Treatment Schedule: Gemcitabine 1,000 mg/m2 by 30-minute infusion on days 1 and 8 every 3 weeks plus oral capecitabine 650 mg/m2 twice daily on days 1 to 14. Response was evaluated at 3 and 6 cycles. Results: Pts Characteristics: 12 pts (7 M-5F, Median Age 51,3 yrs,range 27–76). 7 pts had received Thymectomy and 4 of this had received also surgery for metastatic disease. 5 pts have received only thymic biopsy. Performance status sec. Karnofsky was 90% (range 80–100). Site of disease: liver, lung, bone, nodal, pleural and pericardium. All pts were staged IVB sec. Masaoka. Tumors were classified by WHO classification as follows: 4-B2, 8-B2/B3. All pts were evaluated as concerns performance status and all had Karnofcky 90% (range 80–100). Sites of metastatic disease were: liver,lung,bone,nodal, pleural and pericardium. Associated paraneoplastic syndromes were: myasthenia in 7 pts, B-lymphopenia 11 pts. The minimum number of cycles administered on study was 3 (range 3–8).Among the 12 enrolled pts there were 10 objective response: 2 CR, 8 PR. 2 pts had SD. Prolonged maintenance of absence of disease was obtained in the 2 pts reporting a CR (more than 6 months in 1 patient). Treatment was well tolerated, no grade 4 toxicities was registered. Conclusions: The combination schedule gemcitabine-capecitabine have an high activity in Thymic malignancies in pts heavily pretreated with advanced recurrent TET and appears to be a safe option in platinum-refractory TET pts. This schedule must be proposed to be used also in randomized clinical trial compared with platinum based treatment.

No significant financial relationships to disclose.

Longitudinal study of MRS metabolites in Rasmussen encephalitis

This study analyses the evolution of metabolite changes in an 8-year-old boy with focal Rasmussen encephalitis. Five MRI examinations, including magnetic resonance spectroscopy (MRS) were performed over 9 months. Following complex partial status, T2-weighted imaging showed transient dramatic signal increase in the left superior temporal gyrus and mesial temporal structures. Subsequent scans showed resolution of the swelling and signal normalization, with development of slight focal atrophy. MRS after status showed a reduction in N-acetylaspartate, total creatine and trimethylamines. Subsequent scans showed complete resolution of these metabolite abnormalities, followed later by development of further abnormal metabolite values. Lactate and glutamine/glutamate were elevated after status. After surgery, ex vivo high-field (1)H and (31)P MRS confirmed metabolite abnormalities (elevated choline and decreased aspartate, N-acetylaspartate, [(1)H]glutamate together with altered [(31)P]phospholipid ratios. These findings suggested active disease process in the anterior region of the excised superior temporal gyrus. We conclude that Rasmussen encephalitis is a combination of progressive encephalitic damage and fluctuating seizure effects, in which neuronal injury and recovery can occur. MRS measurements at a single time point should consider the fluctuating metabolite profile related to seizure activity.

Effects of selenium and zinc supplementation on nutritional status in patients with cancer of digestive tract

OBJECTIVE

To evaluate the effect of oral administration of selenium and zinc tablets in patients with cancer of the digestive tract during chemotherapy.

DESIGN

A case-control, randomized study.

SETTING

Medical Oncology, II University of Naples, Naples, Italy.

SUBJECTS

A total of 60 patients (median age 55 y, range 46-61 y) with diagnosis of gut cancer were randomized in 1999. Patients were treated for 60 days with chemotherapy.

INTERVENTIONS

Trace elements were measured by atomic absorption spectroscopy. The nutritional status of the patients was assessed by biochemical and bio-impedance analysis (BIA) parameters in basal condition and after 60 days of treatment. Oral administration of selenium and zinc in oral tablet form for 50 days was Se 200 microg/day (50 microg/tablet) and Zn 21 mg/day (7 mg/tablet).

RESULTS

Both in the basal condition and at 60 days all patients were malnourished. Selenium and zinc concentrations were significantly lower (P < 0.01) whereas copper concentration was significantly higher (P < 0.01) in cancer patients than in control subjects. However, 21/30 (70%) of those treated with Se and Zn did not showed a further worsening of nutritional status and experienced a significant decrease of asthenia with an increase of appetite. On the other hand, 24/30 (80%) untreated patients had a significant decline of all parameters studied after 60 days (prealbumin, cholesterol, transferrin, P < 0.05 vs 0 time; total proteins, albumin/globulin ratio, P < 0.01 vs 0 time; fat-free mass, fat mass, Na+/K+ ratio, body mass index P < 0.05 vs 0 time; fat free mass/fat mass, total body water, extra cellular/intra cellular water, basal metabolic rate: P < 0.01 vs 0 time).

CONCLUSIONS

Data indicate that Se and Zn supplementation may improve the clinical course of general conditions in patients with gut cancer. These effects of Se and Zn require confirmation in an independent trial of appropriate design before new public health recommendations regarding Se and Zn supplementation can be made.

Reversible parkinsonism and hyperammonemia associated with portal vein thrombosis

Portal-systemic encephalopathy may be seen with hyperammonemia that complicates chronic liver disease. We report an unusual case of reversible parkinsonism associated with hyperammonemia and portal vein thrombosis. An active 90-year-old male developed motor slowing and resting hand tremor over 6 months. Examination showed asterixis, bradykinesia, cogwheel rigidity, rest tremor, and a parkinsonian gait. Serum venous ammonia was elevated at 145 microM. The next day, the patient became comatose and serum ammonia was 178 microM. With lactulose therapy, serum ammonia level normalized and examination showed only minimal parkinsonism after 1 week. An abdominal CT scan identified portal vein thrombosis with porto-systemic shunting that reversed after 7 months of treatment. Examination 2 years later showed no signs of parkinsonism. Parkinsonism can dominate the clinical picture of patients with hyperammonemia before the onset of encephalopathy.

Multifocal motor neuropathy improved by IVIg: randomized, double-blind, placebo-controlled study

OBJECTIVE

To determine the effect of IV immunoglobulin (IVIg) on neurologic function and electrophysiologic studies in multifocal motor neuropathy with conduction block (MMN).

BACKGROUND

MMN is characterized by progressive, asymmetric, lower motor neuron weakness and is probably immune-mediated. IVIg treatment has been shown to have beneficial effects in several open-label studies and in one small controlled trial. However, larger randomized controlled studies are lacking.

METHODS

The authors recruited 16 patients with MMN. All subjects were given each of two treatments (IVIg [0.4 g/kg/d for 5 consecutive days] or placebo [dextrose or saline]) that were assigned according to a randomized, crossover design under double-blind conditions. Patients were evaluated before and about 28 days after trial treatment for subjective functional improvement, neurologic disability score, grip strength, distal and proximal compound muscle action potential amplitude, and conduction block.

RESULTS

Subjective functional improvement with IVIg treatment was rated as dramatic or very good in nine patients, moderate in one, mild in one, and absent in five patients. This improvement was absent after placebo. The neurologic disability score improved by 6.7+/-3.3 points with IVIg treatment, whereas it decreased by 2.1+/-3.0 with placebo (p = 0.038). Grip strength on the weaker side was increased by 6.4+/-1.9 kg with IVIg treatment; it decreased by 1.0+/-0.8 kg with placebo (p = 0.0021). Conduction block worsened by 12.98+/-6.52 % with placebo, but improved by 12.68+/-5.62 % with IVIg treatment (p = 0.037). Conduction block was reversed in five patients with IVIg but not placebo.

CONCLUSION

IVIg improved conduction block as well as subjective and objective clinical measures of function in patients with MMN.

Glomerular filtration rate in severely overweight normotensive humans

The study examined whether indexing glomerular filtration rate (GFR) for body surface area is appropriate for people who are severely overweight. Twenty normotensive adult men who were severely overweight but without microalbuminuria were enrolled into this study. The control group consisted of 20 healthy subjects matched for age, sex, and height. GFR was determined by measuring insulin with the continuous-infusion method. The clearance of endogenous creatinine was also measured after two daily urine collections. Renal plasma flow (RPF) was measured by p-aminohippurate clearance using the continuous-infusion method. Lean body weight was measured by impedentiometry. Adjusting for body surface area (in 1.73 m(2)) caused a significant reduction in GFR (P < 0.0001) in overweight humans (84.1 +/- 2.32 versus 109.6 +/- 3.07 mL/min/1.73 m(2)). The difference disappeared when GFR/height criteria were adopted. No difference between obese and healthy controls occurred after adjusting for lean body weight. Data for creatinine clearance paralleled those with insulin clearance; a significant reduction (P < 0.001) occurred after indexing for basal surface area, which disappeared after correction for height, as well as for lean body weight.

Imaging the induction and spread of seizure activity in the isolated brain of the guinea pig: the roles of GABA and glutamate receptors

1. The induction and spread of seizure activity was studied using imaging and electrophysiological techniques in the isolated whole brain of the guinea pig. We examined the role of GABA and glutamate receptor subtypes in controlling the spread of seizure activity across the olfactory cortex from a focus in the entorhinal cortex. Seizure spread was monitored by video imaging of intrinsic optical signals (reflectance changes) combined with multiple extracellular recordings. Both the unilateral and bilateral spread of seizure activity was monitored in different experiments. 2. Electrical stimulation of the lateral entorhinal cortex (10-15 V, 5 Hz, 5-10 s) evoked seizure activity that originated in the entorhinal cortex/hippocampus and later spread preferentially toward the posteromedial cortical amygdaloid nucleus ipsilaterally and bilaterally. The pattern of seizure spread in a given brain was highly reproducible. 3. The influence of gamma-aminobutyric acid (GABA) receptors on the spread of seizure activity was monitored at higher resolution on one side of the brain. Perfusion of a low concentration of the GABAA antagonist bicuculline methiodide (20 microM) resulted in spontaneous seizures that spread to the posteromedial cortical amygdaloid nucleus more rapidly than electrically evoked seizures [spread times: 5.5 +/- 3.7 s vs. 15.5 +/- 2.7 s, respectively (means +/- SE)]. Seizure spread was also more extensive in the presence of bicuculline involving the posterior perirhinal cortex and larger areas over the medial amygdala. Higher concentrations of bicuculline (100 microM) resulted in even more widespread propagation of spontaneous seizure activity throughout the olfactory cortex as well as to the perirhinal, insular, and occipital cortices. This concentration of bicuculline also further reduced the time required for seizure activity to spread from the entorhinal cortex to the posteromedial cortical amygdaloid nucleus (spread time = 2.3 +/- 1.7 s). The GABAB antagonist, CGP 35348 (200 microM), in contrast, had no significant effect of seizure induction or propagation. 4. The role of glutamate receptor subtypes in seizure propagation was studied by examining the bilateral spread of seizures. Perfusion of the kainate/alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (K/A) receptor antagonist (6-cyano-7-nitroquinoxaline-2,3-dione, CNQX, 20 microM) completely and reversibly suppressed stimulus-evoked seizure activity as detected electrophysiologically and optically. CNQX also reduced the magnitudes of field potentials recorded in the isolated brain in a reversible manner by an average of 70.8 +/- 2.21% of control. The N-methyl-D-aspartate (NMDA) receptor antagonist dibenzocyclohepteneimine (MK-801) did not significantly alter the magnitudes or shapes of field potentials recorded in the isolated brain nor did it significantly alter seizure activity measured optically or electrophysiologically. 5. Perfusion of the metabotropic glutamate receptor agonist [trans-1-amino-(IS,3R)-cyclopentanedicarboxylic acid (trans-ACPD), 150 microM] completely and reversibly suppressed stimulus-evoked seizure activity as detected electrophysiologically and optically. The magnitudes of field potentials recorded in the isolated brain also were reduced by trans-ACPD an average of 75.4 +/- 5.39% of control values. 6. These results demonstrate that GABAA-mediated transmission is functionally present and may play an important role in epileptic tissue in limiting the spread of seizure activity from the entorhinal cortex to the posteromedial cortical amygdaloid nucleus and in creating functional pathways or preferential routes of seizure spread. GABAB-mediated postsynaptic inhibition played no significant role in the induction or spread of seizure activity in this study. K/A receptors but not NMDA receptors are necessary for the induction and subsequent spread of seizure activity originating in the entorhinal cortex/hippocampus.

[Evaluation of activity in intensive care. A comparison of administrative and epidemiologic data]

This paper reports on results of a formal comparison of data excerpted from 3 different data sources regarding patients cared for in Italian Intensive Care Units (ICU) in 1992. The analysis was carried out in order to assess whether the administrative data routinely collected for reimbursement and policy issues are valid when compared with data from epidemiologic studies. First, using data from the Central Service for Health Planning (SCPS) a general description of the whole national scenario is shown. All the Italian data from 265 Italian hospitals having at least one ICU were analyzed. In these hospitals there were 2,357 ICU beds (4.3 beds/1000 inhabitants, with large regional variability). About 100,000 cases were identified (1% of all the hospital admissions received ICU care at some moment during the stay), with an overall hospital mortality rate of 17%. This estimate was largely different from those obtained from GiViTI data base (5100 patients from a national sample of 114 ICUs), where mortality rates were always higher (25 and 30%, for ICU and hospital mortality). Second, a more detailed analyses and comparison was carried out in the subsample of cases admitted in the Hospitals of the Regione Lombardia. In this case, beside the data from SCPS (No = 20580) and from GiViTI (No = 1121), the Regional data-base formed by all the discharge from 41 hospitals having at least one ICU were available (NO = 16674), allowing a formal comparison between estimates obtained from 3 different sources. In this sub-sample, although administrative data showed a good capability and satisfactory accuracy to describe the volume and socio-demographic and clinical characteristics of the cases when compared with GiViTI estimates, still a systematic underestimate of the overall ICU and hospital mortality was present. Moreover, an unexpected high rate of cases were apparently discharged alive from ICU (16.5 versus 32.6% in GiViTI). Tentative explanations and implications of these phenomena are discussed in the text. Finally, in the Lombardia sub-sample a formal description of the case-mix using the Diagnosis Related Group (DRG) system was carried out in order to identify strengths and limitations of this approach when adopted in the ICU setting. Overall, when data are analyzed according to the kind of Major Diagnostic Category (MDC), 75% of all cases were concentrated in 5 alone, with very peculiar concentration in some specific categories. For example, 45% of all the hospital admissions related to the multiple trauma were actually admitted in the ICU setting. At DRG level, fifty of the 493 DRGs available explained 65% of all the cases, showing an unexpected capability of this system to detect the ICU case-mix. The most represented surgical DRG was the number 107 (Coronary Arterial Bypass Graft, without catheterization) and the corresponding medical was the 28 (Cerebro Vascular Accident, excluding TIA).

[Hypothyroidism associated with retrobulbar optic neuritis. A clinical case]

The authors have described a hypothyroidism clinic event with both non-specific symptoms and retrobulbar neuritis. They conclude that the above-mentioned pathology is somewhat insidious since, affecting the whole body, it can arise with non-specific symptoms thus averting towards a wrong diagnosis.

[The nephrotic syndrome and pheochromocytoma. A report of a rare clinical case]

In clinical practice, the coincidence of nephrotic syndrome with pheochromocytoma is very rare. The case is described of a 23-year-old woman who in June 1988 presented with recurrent hypertensive crises, severe asthenia, abundant sweats, orthostatic hypertension and massive proteinuria. Diagnostic tests performed (abdominal ultrasound and CT, urinalysis, renal function tests, plasma levels of metanephrine and normetanephrine, as well as urinary VMA determination) revealed the presence of a pheochromocytoma of the left adrenal gland combined with nephrotic syndrome. Surgical removal of the left adrenal led to immediate normalization of blood pressure and absence of urinary abnormalities. The authors therefore suggest either an immunological pathogenesis or one due to glomerular hyperfiltration.

[Cardiomyopathy in hypothyroidism. Description of a clinical case]

The authors describe a case of hypothyroidism the only symptom of which at presentation was myopathy. Hypothyroidism was diagnosed only after abnormalities of thyroid hormones, thyroid scanning, and antithyroglobulin and antimicrosome antibodies were found. The authors conclude that the diagnosis of hypothyroidism is very difficult in the absence of the typical signs, such as drowsiness, edema, dry skin, hoarse voice, alopecia, etc.

[The public-private mix in hospital care in the Lombardy region]

OBJECTIVES

1) to compare complexity and severity of the case-mix in the public and private sector, overall and across individual hospitals, and to examine their relative efficiency, by contrasting DRG and/or stage specific average length of stay (ALOS); 2) to assess the impact of a new contractual scheme based on a preassigned number of beddays for a restricted list of specific conditions.

DATA SOURCES

Discharge data on 940.670 admissions to 101 public hospitals and 185.161 admissions to 55 private hospitals in the Regione Lombardia in 1990, assigned to HCFA-DRGs, 8th version and to stages and substages of principal and unrelated diagnostic categories, based on Disease Staging.

RESULT

The spread of the case-mix is higher in the private sector, which also shows a higher concentration of admissions across hospital for specific medical and surgical conditions. The proportion of more advanced stages of disease is higher in the public sector, for most of the most frequent diagnostic categories. Obstetric care, including abortion, is the largest single public sector activity, while it is virtually not existent in the private sector. Elective surgical procedures, including ENT, cataract and varicose veins surgery make up a substantial proportion of the private hospitals' case load. DRGs-specific ALOS is longer in public hospitals for the most frequent surgical DRGs, mainly due to their preoperative LOS. The net impact of the proposed contractual scheme will save substantial proportion of beddays for most of the conditions considered, except cataract and varicose veins surgery.

Mapping patterns of neuronal activity and seizure propagation by imaging intrinsic optical signals in the isolated whole brain of the guinea-pig

Image analysis techniques were used to examine changes in the intrinsic optical properties in the isolated brain of the guinea-pig in order to map normal neuronal activity patterns and seizure propagation in the olfactory cortex. Electrical stimulation of the lateral olfactory tract decreased light reflectance in distant cortical areas where fibres of the tract are known to project. These areas included the amygdalar, anterior and posterior piriform, and entorhinal cortices, as well as the olfactory tubercle. Stimulation of the lateral entorhinal cortex decreased reflectance in a more circumscribed area in the lateral and medial entorhinal cortex. By imaging intrinsic signals in real-time, we also demonstrated that seizure activity elicited in the entorhinal cortex/hippocampus preferentially propagated to the posteromedial cortical amygdaloid nucleus. The magnitudes of the intrinsic optical signals were correlated with the amplitudes of field potentials recorded in laminae II or III of the olfactory cortex of the same preparations. These signals had onset times of approximately 3 s during 5 Hz stimulation, consistently recovered and were graded with stimulation frequency. The generation of the intrinsic signals required postsynaptic activation, since attenuating synaptic transmission with kynurenic acid (an excitatory amino acid antagonist) eliminated the signals. The intrinsic signals exhibited maxima at 425-450, 550 and 600 nm, suggesting that they arose from changes in light absorption by cytochromes. Intrinsic signals of relatively constant magnitude were also present at 400, 475-500 and 575 nm, and at wavelengths greater than 600 nm. This suggested that an additional component of the intrinsic signal arose from changes in light scattering, possibly due to cellular swelling.

Vasopressin perfusion within the medial amygdaloid nucleus attenuates prostaglandin fever in the urethane-anaesthetized rat

The antipyretic effect of arginine vasopressin (AVP) introduced into the ventral septal area (VSA) by push-pull perfusion was investigated in the urethane-anaesthetized rat. In addition, experiments were carried out to determine whether AVP could suppress fever when similarly perfused within the medial amygdaloid nucleus (meA). During push-pull perfusion of artificial cerebrospinal fluid within the VSA or meA, PGE1 injected intracerebroventricularly evoked fevers with respective magnitudes of 1.3 +/- 0.2 degrees C and 1.4 +/- 0.3 degrees C above baseline. Perfusion of AVP (6.5 micrograms/ml) within the VSA had significantly reduced the magnitude of PGE1 fever to 0.3 +/- 0.3 degrees C above baseline, while having no significant effect on afebrile colonic temperature. Perfusion of AVP (6.5 micrograms/ml) within the meA had significantly attenuated the magnitude of PGE1 fever to 0.7 +/- 0.2 degrees C above baseline, while having no significant effect on afebrile colonic temperature. These results support further the utility of the urethane-anaesthetized rat model for future investigations of the central control of fever and antipyresis. In addition, these data are consistent with the hypothesis that AVP may act within the meA as an endogenous antipyretic.

Vasopressin-induced antipyresis in the medial amygdaloid nucleus of conscious rats

Experiments were undertaken to characterize a possible receptor mediating antipyretic action of arginine vasopressin (AVP) within the medial amygdaloid nucleus (meA) in the conscious rat. Additional experiments were directed at determining whether the action of endogenously released AVP can be revealed in the meA during fever in the conscious rat. These objectives were achieved using vasopressin analogues directed against vasopressor (V1a) and antidiuretic (V2) receptors. Bilateral injection of AVP (40 pmol) into the meA of conscious rats suppressed fever evoked by intracerebroventricular (icv) administration of prostaglandin E1 (PGE1, 50 ng). The V2 receptor agonist 1-desamino-8-D-AVP (40 pmol) injected into the meA evoked only moderate antipyresis compared with AVP, possibly because of interaction of this agonist with V1a receptors. The antipyretic effect of AVP was blocked when injection of the peptide was preceded by a bilateral injection of the V1a antagonist 1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid)-2-(O-methyl)tyrosine AVP [d(CH2)5Tyr(Me)AVP, 400 pmol] into the meA. Injection of d(CH2)5Tyr(Me)AVP alone into the meA was without significant effect on afebrile core temperature. Injection of d(CH2)5Tyr(Me)AVP or 1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid)-2-D-valine,4-valine AVP (a V2 antagonist) alone into the meA before icv PGE1 resulted in fevers that were not significantly different from artificial cerebrospinal fluid controls. These data are consistent with the possibility that AVP might act within the meA to evoke antipyresis via receptors that resemble V1a (vasopressor) receptors. However, the action of AVP endogenously released into the meA does not appear to be an absolute requisite in the normal modulation of PGE1 fever.

[Correlation between hormonal and metabolic profiles in women with polycystic ovary syndrome]

To investigate the sex hormone status of women with polycystic ovary syndrome (PCO) and to relate this to serum levels of glucose, insulin, lipids and lipoproteins, 90 women with PCO (30 obese: BMI greater than 30 kg/m2; 30 overweight: BMI greater than 25- less than 30 kg/m2; 30 non obese: BMI less than 25 kg/m2) and 60 normal ovulatory women (20 obese; 20 overweight; 20 non obese) were studied. The women with PCO had significantly increased LH, FSH and androgen levels and significantly decreased SHBG levels compared to the normal women. Obese women with PCO had higher concentrations of fasting glucose, fasting insulin, incremental glucose area, incremental insulin area and lipid than overweight and non obese women with PCO and overweight and non obese control subjects, but were similar in obese normal women. There were decreases in high-density lipoproteins levels in both the obese groups (obese PCO and obese control women). Lipid and lipoprotein concentrations did not differ in the obese, overweight and non obese PCO women compared to the normal groups while HDL cholesterol were decreased in obese PCO and obese control women. The correlations between hormone, glucose, insulin, lipid and lipoprotein levels were different among the six groups. Non obese PCO women had: inverse correlations between free testosterone and incremental glucose area (r = -0.5128, P = 0.03); positive correlations between SHBG and alpha-lipoproteins (r = 0.9159, P = 0.001). Non obese normal women had: positive correlations between fasting insulin and total testosterone (r = 0.5272, P = 0.043) and between SHBG and beta-lipoproteins (r = 0.7445, P = 0.014) and LDL cholesterol (r = 0.7360, P = 0.010).(ABSTRACT TRUNCATED AT 250 WORDS)

Glucagon-independent renal hyperaemia and hyperfiltration after an oral protein load in Child A liver cirrhosis

The work was designed to study the effects of a meat meal on glomerular filtration rate (GFR), renal plasma flow (RPF), and plasma concentrations of glucagon, insulin, growth hormone, renin, aldosterone, total amino acids, and NH3 in healthy humans (H) as well as in patients with Child A liver cirrhosis (LC). The meat meal produced renal hyperaemia and hyperfiltration without changes in the filtration fraction. Fractional Na excretion in urine increased significantly after the meat meal only in LC. Hyperinsulinaemia and hyperglucagonaemia were seen at baseline in LC and were not affected by the meat meal, whereas in H glucagon concentration increased significantly over baseline within 30 min from the meat meal and insulin within 60 min. Growth hormone concentration was normal at baseline in LC and increased significantly 120-180 min after the meal, whereas it was not affected in H. Renin and aldosterone were stable in both H and LC. Plasma amino acid concentration began to increase 60 min after the meat meal, when hyperfiltration was present. The data indicate that in human Child A cirrhosis of the liver renal haemodynamic response to a meat meal is independent of changes in glucagon.

Hypopituitarism following a direct bullet injury to the pituitary. A case report

A 29-year old man was referred for hypogonadism. At 14 years of age he was struck by a gun bullet in the head, receiving a frontomedial open fracture with leakage of cerebral tissue. The bullet could not be extracted at the operation. At 16 years of age he noticed a stop of pubertal development, weight gain and a fall in visus on the left eye. The clinical examination and the endocrinological data (low F-T4 and F-T3; low plasma cortisol and testosterone; normal plasma prolactin; sub-normal pituitary response to intravenous administration of insulin, GnRH, TRH and GRF) demonstrated that the patient was hypopituitaric. A radiological skull X-ray showed that the bullet was lodged in the sellar and parasellar region. This seems to be the seventh case of hypopituitarism following a direct injury to the pituitary region described in the literature so far.

Effects of benfluorex in obese patients with metabolic disorders

Fifty obese (BMI = 40.1 +/- 1.5) subjects (21 men and 21 women; average age 38.6 +/- 3.8 years) were prescribed a 600 cal/day diet (carbohydrates 30 g, proteins 60 g, lipids 10 g). Thirty patients were also given benfluorex (three tablets/day) for six months (Group A), whereas the other 20 patients (Group B) were treated with the dietary measures only. Apart from grade II and III obesity, several patients suffered from dyslipidaemia (Group A: n = 10; Group B: n = 7), non-insulin-dependent diabetes mellitus (NIDDM) (Group A: n = 4; Group B: n = 3) or IGT (Group A: n = 8; Group B: n = 6). The usual blood and biochemical tests and clinical examinations were carried out on Days 0, 90 and 180, together with the OGTT and glucagon test to determine blood glucose levels, IRI and CPR. There was no statistical difference between the weight loss of Group A and that of Group B. In Group A there was a statistically significant reduction (p less than 0.001) in total cholesterol, triglycerides, total/HDL-cholesterol and beta/alpha-lipoproteins and a significant increase in HDL-cholesterol and alpha-lipoproteins (p less than 0.001), whereas in Group B only a significant reduction in triglycerides (p less than 0.001) was observed. In NIDDM patients treated with benfluorex, normalisation of basal blood glucose levels was accompanied by an improvement in the OGTT blood glucose curve which was statistically significant relative to Group B. Benfluorex was well tolerated by all patients and no adverse event was reported.(ABSTRACT TRUNCATED AT 250 WORDS)

Single-unit activity in the bed nucleus of the stria terminalis during fever

Arginine vasopressin, released from nerve terminals in the septal region, probably exerts endogenous antipyretic activity. A major source of vasopressin to this area is the bed nucleus of the stria terminalis (BST). In order to characterize electrophysiologically the BST-septal pathway and its potential role in the control of fever, single-unit, extracellular recordings were made from neurons in the BST of anesthetized rats. Afferent and efferent connections were identified by electrical stimulation of the medial amygdaloid nucleus and the ventral septal area (VSA). BST neurons received both inhibitory and excitatory synaptic input from the amygdala and VSA. Efferents to the VSA were identified by stimulus-evoked antidromic spike invasion. Some BST neurons were responsive to peripheral skin temperature (thermoresponsive). The activity of putative vasopressin neurons was studied during prostaglandin E1-induced fever. Although a majority of BST units was unaffected by fever, a proportion of the cells examined increased their firing rates in accordance with reported release of vasopressin in the VSA during fever.

Inhibition of the in vivo parathyroid hormone-mediated calcemic response in rats by a synthetic hormone antagonist

The parathyroid hormone (PTH) analog, [Tyr34]bovine PTH-(7-34)-amide, can inhibit the PTH-mediated elevation of plasma calcium in thyroparathyroidectomized rats in vivo. The analog is devoid of PTH-like agonist activity in this system. Repeated doses of analog inhibit the animal's calcemic response to PTH. The elevation in serum calcium levels mediated by PTH in this assay reflects PTH action (calcium mobilization) on bone. Earlier studies demonstrated antagonist properties of the analog in a renal-based assay; PTH-stimulated increases in urinary phosphate and cyclic AMP excretion were completely inhibited by the synthetic analog. Along with previous studies, this report indicates that [Tyr34]bovine PTH-(7-34)-amide is an effective in vivo antagonist for several major parameters of PTH action in both kidney and bone.

[Effect of sex on annual variations in plasma LH and FSH levels in prepubertal subjects]

We studied, from 1977 to 1979, 61 females and 72 males (aged 6 to 10 years) in order to demonstrate the occurrence of FSH and LH circannual variations. The data were fitted a cosine function by least square method in order to describe any rhythm and to estimate its parameters:mesor, amplitude, acrophase. Our data suggest that in prepubertal age the behaviour of FSH secretion is different in two sexes, but without circannual rhythm. LH instead shows a statistically significant circannual rhythm in both groups, without differences in mean levels between the two sexes.

[Effect of sex on annual variations in GH response to insulin hypoglycemia in prepuberal subjects of small stature]

86 males and 66 females, aged 6 to 10 years, affected by short stature (SDs -2 according to Tanner), were investigated from 1977 to 1979 in order to evidence any circannual rhythm in the GH response to insulin test. The patients were hospitalized one week before the study starting and they observed the following life schedule:nocturnal rest from 2200 to 0600, meals at 0800, 1300, 1800. The insulin test (0,1 UI/Kg body weight) were administered at 0800. Plasma samples were taken before and after 20, 40, 60, 90 minutes. The single basal data and the peak were fitted a cosine function by least square method in order to describe amy rhythm and to estimate its parameters:mesor, amplitude, acrophase. A significative circannual rhythm in the GH response to insulin is present in the female subjects, with acrophase in December (-354.85 degrees +/- 21.93). Our study suggest that the sex may influence the circannual response of GH to insulin stimulus from prepubertal age.

[Effect of pretreatment with metoclopramide on plasma prolactin response to methergoline]

The Authors examined 20 voluntary women without endocrine diseases. The women took 4 mg of metergoline orally and 30-60-90-120-180-240 minutes after the medicament was given the serum prolactin levels were tested. After 3 weeks, 14 among 20 subjects repeated the test assuming during the 3 days before 50 mg of metoclopramide orally once a day. The Authors found a remarkable decline of prolactin serum levels after metergoline administration in all subjects. After metoclopramide administration prolactin serum levels increased meaningly. Metergoline administration gave again considerable fall of prolactin serum levels in the 14 subjects. From the data the Authors affirm that metergoline inhibits prolactin secretion with an antiserotonine action

[Effect of surgical stress on TSH and on the extra-thyroid metabolism of T4 (preliminary experiment)]

The effect of the surgery on the TSH and on the extra thyroid T4 metabolism was studied in thirty euthyroid patients. The TSH showed a light increase thirty minutes after the skin cut. There were no remarkable changes of T4 serum levels, while the serum triiodothyronine concentration fell during and after the operation, with a concomitant rise in reverse triiodothyronine.

Thyrotropin releasing hormone: development of inactivation system during maturation of the rat

Whereas thyrotropin releasing hormone is rapidly and extensively degraded by plasma of adult rats, no appreciable loss of biological or immunological activity is caused by plasma from rats 4 or 16 days old. The plasma of neonatal rats does not appear to contain an inhibitor of thyrotropin releasing hormone peptidase or a peptidase with altered substrate affinity. The development of an active peptidase in rat plasma suggests a physiological role for inactivation of thyrotropin releasing hormone.

Pituitary-thyroid axis in neonatal and adult rats: comparison of the sexes

Systematic comparisons have been made of the development of the pituitary-thyroid axes of male and female rats, by measuring plasma thyrotropin (TSH) and thyroxine (T4) concentrations in neonates and adults. Observations were made in untreated groups as well as in rats treated with various regimens of exogenous T4, thyrotropin-releasing hormone, or TSH. All hormone determinations were by radioimmunoassay (RIA). Salient findings include the following: 1) In early neonatal life, untreated rats showed no significant sex difference in the plasma concentrations of either TSH or T4. 2) In adulthood, the plasma TSH of untreated males attained levels strikingly higher than those of neonates-the differences averaged 5-fold more. For females, the increase in plasma TSH during development was less marked, averaging slightly less than 2-fold more. Thus, untreated adults exhibited a clear sex difference in circulating TSH concentrations; the male TSH levels averaged 2.8-fold higher than those of females. 3) Plasma T4 concentrations also increased markedly during development. For both sexes, adult T4 levels were approximately 3-fold greater than the T4 levels in early neonatal life. Among untreated adults, the female T4 concentrations averaged 28% greater than those of males. 4) Plasma TSH and T4 concentrations exhibited only minor fluctuations, of borderline statistical significance, during the female estrous cycle. 5) A significant reduction in responsiveness to exogenous TRH was observed in adult male rats which had been treated with high doses of T4 in neonatal life, although the effect was not completely consistent. No significant reduction was observed in females which received the same treatment. We have concluded that major changes occur in the circulating hormone levels of the pituitary-thyroid axis of the rat between birth and adulthood, and that such changes are not identical for the two sexes.