The ecology of echo

Echo is a generic ecosystem model in which evolving agents are situated in a resource-limited environment. The Echo model is described, and the behavior of Echo is evaluated on two well-studied measures of ecological diversity: relative species abundance and the species-area scaling relation. In simulation experiments, these measures are used to compare the behavior of Echo with that of a neutral model, in which selection on agent genotypes is random. These simulations show that the evolutionary component of Echo makes a significant contribution to its behavior and that Echo shows good qualitative agreement with naturally occurring species abundance distributions and species-area scaling relations.     

2H( gamma,p)n cross section between 20 and 440 MeV

Rate control in acetylcholinesterase (AChE) involves a single anionic site whose anionic center controls rate-related biochemical and conformational changes in the E (free enzyme) and EA (acylated enzyme) conformers. Change in conformer structure and biochemistry affect binding, acylation, and hydrolysis. It is significant that the anionic-esteratic intersite distance is not altered during conformer change as E is converted to EA. In this enzyme system, cationic acetylcholine and anionic AChE are true structural, functional, and biochemical counterparts. The anionic center in the E conformer lies at the bottom of a sterically restricted, hydrophobic cleft < 8 A wide at the top and > 3 A wide at the bottom, while the anionic center in the EA conformer is relatively open. It is characterized by a decrease in the relative binding of hydrophobic cations and by an ability to bind large organic cations. Binding of acetylcholine, H+, or organic cations at the anionic site controls k2(acylation) in the E conformer and k3(hydrolysis) in the EA conformer. Acetylcholine binding forms the ES complex in which the cation maximizes k2. In the EAS complex, the cation reduces k3 and provides allosteric control. Anionic site structure and biochemistry and the effect of pH on k2 and k3 differentiates AChE from butyrylcholinesterase. This comprehensive study of kinetic and thermodynamic processes in AChE was made possible by the synthesis and/or use of families of over 30 cationic and acylation probes of known stereochemistry. They act as rulers of the E and EA conformers of AChE and provide comparative data on kinetic-based and thermodynamic-based constants. Cationic inhibitors affect decarbamylation rates in AChE and provide an additional set of comparative data related to the mechanism of substrate hydrolysis by AChE. Acridine araphanes are unique neural receptor and cholinergic enzyme probes. Their parallel plane and coplanar conformations are related to bridge length. Two parallel plane acridine araphanes are pure uncompetitive inhibitors of AChE. Scatchard plots of the binding of methylacridinium and 9-aminoacridine with the E conformer and 9-aminoacridine with the EA conformer indicate binding at a single anionic site. No ternary complex (EII or EAII) from two-site binding was detected. In AChE, nonspecific, low-level binding at surface ionic and hydrophobic areas is ubiquitous. Binding affinity differences greater than two orders of magnitude distinguish binding at the anionic site from low level binding at surface moieties. Surface binding provides environmental and stability changes in the enzyme but does not modify the fundamental biochemistry of the E and EA conformers.     

Positron emission tomography for the evaluation of pancreatic disease

Efficient techniques for native-labeling of amino acids have been combined successfully with emission tomography to yield significant improvements in pancreatic imaging. Carbon-11-labeled tryptophan appears to be the best agent available currently for imaging the pancreas. Optimum scanning times begin 30 min after tracer administration. Positron emission tomography with 11C-tryptophan is capable of defining both morphological and functional alterations in the pancreas. Tumors as small as 2 cm in diameter can be detected, but reliable differentiation of pancreatic cancer from pancreatis may not be possible even with this improved imaging technique. Longitudinal multiplane emission tomography in single-photon mode with the Pho/Con provides an efficient and satisfactory approach to pancreatic imaging with the positron-emitting radiopharmaceuticals.     

Predictors of weight change following smoking cessation

Smoking behavior and weight change over a 5-year period were studied in 1,749 adult males of the Normative Aging Study. While men who quit smoking generally gained more weight than those in other smoking categories, 36% either lost weight or maintained the same weight after quitting. The major research focus was to predict the direction of weight change after smoking cessation. Among the characteristics most related to weight gain after quitting were heavier tar consumption, younger age, and leanness of body build. Conversely, traits related to weight loss were lighter smoking, older age, and stoutness of build.     

CSF testosterone and 5-HIAA correlate with different types of aggressive behaviors

We studied the potential roles of testosterone and serotonin in various forms of aggressive and violent behaviors by measuring each biochemical and behaviour in free-ranging adolescent male nonhuman primates. Our results showed that (1) CSF free testosterone concentrations were positively correlated with overall aggressiveness, but not with measures of impulsivity. (2) CSF 5-HIAA concentrations were negatively correlated with impulsive behavior, and severe, unrestrained aggression, but not with overall rates of aggression. High rates of impulsive behavior were positively correlated with severe, unrestrained aggression, but not overall rates of aggression. (3) Dimensional analyses showed that while subjects with low CSF 5-HIAA exhibited high rates of aggression, high CSF testosterone further augmented rates and intensity of aggression in subjects with low CSF 5-HIAA. We conclude that high CSF free testosterone concentrations are associated with competitive aggression, while low CSF 5-HIAA concentrations are associated with severe aggression which results from impaired impulse control, and perseverance.     

Glucose effectiveness, peripheral and hepatic insulin sensitivity, in obese and lean prepubertal children

Vascular injuries in lumbar disk surgery, although rare, are serious complications which may be overlooked due to a broad range of clinical manifestations. It is important that surgeons and radiologists be aware of these potentially fatal complications and develop an appropriate symptom-based diagnostic paradigm. We reviewed 8099 consecutive cases of lumbar disk surgery, performed over a 14-year period at a single institution, for postoperative vascular complications. We identified four patients (0.05%) with lumbar disk surgery-related vascular complications: intraoperative lacerations of the abdominal aorta and median sacral artery, an arteriovenous fistula between the left common iliac artery and vein detected 19 days postdiskectomy, and a partially thrombosed aortic aneurysm with an arteriovenous fistula between the aneurysm and the inferior vena cava, diagnosed 11 months after surgery. The majority of cases in the literature of vascular injury in lumbar disk surgery were reported prior to 1965. Diagnostic approaches described in that period do not reflect the great range of diagnostic techniques available today. Angiography remains the gold standard for diagnosis and guidance as to surgical repair. However, a high index of suspicion based on clinical signs and/or the use of sonography or CT is important in the detection of these complications.     

Altered retinoblastoma and p53 protein status in non-small cell carcinoma of the lung: potential synergistic effects on prognosis

Routinely processed pathological specimens from 119 patients with stage I and II adenocarcinomas or squamous cell carcinomas were examined by immunohistochemical analysis for altered retinoblastoma (RB) and/or p53 protein expression. Absent RB nuclear staining (RB-) indicating loss of RB function occurred in 19 (16%) of the cases studied, whereas expression of a putative mutant p53 nuclear protein (p53(+)) was found in 54 (45%) of the tumors. The median survival was 39 versus 12 months for patients with RB+ and RB- tumors, respectively (P = 0.05 by log rank analysis). Similarly, the median survival was 41 months for patients whose tumors had no expression of mutant p53 (p53(-)) compared with 24 months for individuals with p53 (+) tumors (P = 0.01). These differences in survival, however, were not statistically significant by multivariate analysis. Nevertheless, individuals with RB-/p53(+) tumors had a significantly shorter median survival (12 months) than those with RB+/p53(-) tumors (41 months), as determined by both log rank and multivariate analyses (P = 0.005 and 0.03, respectively). In addition, 66 large cell carcinomas from all stages were examined. Again, a more significant difference in survival (48 versus 8 months) was found between patients with RB+/p53(-) versus RB-/p53(+) tumors (P = 0. 006). These results suggest that RB and p53 status might be used synergistically as prognostic factors in a subset of non-small cell lung carcinomas.     

Cataracts in cichlid fish

Bilateral cataracts were detected in a group of aquarium-raised tilapia (Sarotherodon mossambicus). Vision impairment was manifested as random swimming into objects, but the fish appeared to function normally otherwise. Most of the lens was opaque, with the outer extent of the cortex and subcapsular region remaining transparent. Skeletal abnormalities, ie, deformed fins, abnormal jaws, and curvature of the spine, were observed in affected individuals. Histologically, there was progressive degeneration of the cataractous portion as the affected fish matured. Preliminary breeding experiments indicated that the condition may be inherited.     

Subunit peptide cancer vaccines targeting activating mutations of the p21 ras proto-oncogene

BACKGROUND AND OBJECTIVES: Physicians in the 1920s and 1930s began to treat patients with chronic pain syndromes using regional anesthetic techniques for both temporary and permanent block of pain pathways. The founding of the American Society of Regional Anesthesia (ASRA) in 1923 provided a unique venue for the dissemination of information concerning regional anesthesia for both surgery and chronic pain management. METHODS: The growth of chronic pain management on a national basis was assessed by using the Quarterly Cumulative Index to the Medical Literature to trace the distribution of information on regional anesthesia. From the Minutes of Meeting of the American Society of Regional Anesthesia, presented papers and the discussion that followed were analyzed. RESULTS: Inquiries into regional anesthesia during the 1920s and 1930s predominantly dealt with technique. For the first time pain papers were listed under the regional anesthesia heading in the Index. The papers presented at ASRA meetings during the period helped develop the use of regional anesthesia for both chronic pain management and surgical anesthesia. CONCLUSIONS: The ASRA was instrumental in bringing together physicians interested in regional anesthesia and pain management. During the 1930s physician anesthetists came to predominate as the organization's officers and members and helped translate the work of the ASRA into a part of the knowledge required to be a specialist physician in anesthesia.     

Purification and characterization of a lipid-mobilizing factor associated with cachexia-inducing tumors in mice and humans

A scheme is described for the purification of a lipid-mobilizing factor from a cachexia-inducing murine tumor (MAC16) using a combination of ion exchange (Mono Q), exclusion (Superose), and hydrophobic (C8) chromatography. This process yields an active material with an apparent molecular weight of 24,000 with an overall purification of 3,500 from the tumor homogenate and representing 0.005% of the total protein present. The material tends to aggregate to high molecular mass, is acidic (pI < 4), and displays heterogeneity of charge as evidenced by a broad elution profile on ion exchange and exclusion chromatography and multiple peaks on hydrophobic columns. The purified material was heat and alkali (pH 10.4) labile and activity could be completely inhibited by sulfatase, suggesting that the negative charge could arise from sulfate residues. There was no evidence that the material possessed triglyceride lipase activity. Animals transplanted with the MAC16 tumor and with a delayed weight loss contained in their serum antibodies that recognized a M(r) 24,000 band on Western blots. This material copurified with the lipid-mobilizing factor. Such antibodies were not present in the serum of mice transplanted with the MAC13 tumor, which does not induce cachexia, suggesting that the antibodies were directed to the induction of cachexia rather than the tumor itself. Urine from patients with cancer cachexia also contained a lipid-mobilizing factor which adhered to DEAE-cellulose and gave an apparent M(r) of 24,000 by exclusion chromatography. Western blotting using serum from MAC16 tumor-bearing animals showed the presence of a band of M(r) 24,000 in such fractions, which was not detected using serum from mice bearing the MAC13 tumor. This band was not present in Western blots of urine from normal subjects. The fact that serum from mice bearing the MAC16 tumor can detect the human lipid-mobilizing activity suggests a high degree of structural similarity between the two and raises the possibility that cachexia in humans may be caused by the same species as in the mouse.