Amlodipine treatment of cocaine dependence

Preclinical studies indicate that dihydropyridine-type calcium channel antagonists modulate dopamine neurotransmitter function and can reduce cocaine-reinforced behaviors. Amlodipine, a long-acting dihydropyridine-type calcium channel antagonist related to isradipine and nifedipine, was administered in open label fashion for 12 weeks to 26 cocaine-dependent patients. In subjects expressing cocaine craving, craving significantly declined during the course of the 12 weeks. Five individuals reported flushing, headache, fatigue, nocturia, nausea, and lightheadedness. No conclusions regarding efficacy can be made due to the small number of subjects and the open-label design.

Work production and work absorption in muscle strips from vertebrate cardiac and insect flight muscle fibers

Stretch activation, which underlies the ability of all striated muscles to do oscillatory work, is a prominent feature of both insect flight and vertebrate cardiac muscle. We have examined and compared work-producing and work-absorbing processes in skinned fibers of Drosophila flight muscle, mouse papillary muscle, and human ventricular strips. Using small amplitude sinusoidal length perturbation analysis, we distinguished viscoelastic properties attributable to crossbridge processes from those attributable to other structures of the sarcomere. Work-producing and work-absorbing processes were identified in Ca(2+)-activated fibers by deconvolving complex stiffness data. An 'active' work-producing process ("B"), attributed to crossbridge action, was identified, as were two work-absorbing processes, one attributable to crossbridge action ("C") and the other primarily to viscoelastic properties of parallel passive structures ("A"). At maximal Ca(2+)-activation (pCa 5, 27 degrees C), maximum net power output (processes A, B and C combined) occurs at a frequency of: 1.3 +/- 0.1 Hz for human, 10.9 +/- 2.2 Hz for mouse, and 226 +/- 9 Hz for fly, comparable to the resting heart rate of the human (1 Hz, 37 degrees C) and mouse (10 Hz, 37 degrees C) and to the wing beat frequency of the fruit fly (200 Hz, 22 degrees C). Process B maximal work production per myosin head is 7-11 x 10(-21) J per perturbation cycle, equivalent to approximately 2 kT of energy. Process C maximal work absorption is about the same magnitude. The equivalence suggests the possibility that a thermal ratchet type mechanism operates during small amplitude length perturbations. We speculate that there may be a survival advantage in having a mechanical energy dissipater (i.e., the C process) at work in muscles if they can be injuriously stretched by the system in which they operate.

Hereditary non-polyposis colorectal cancer syndrome

Hereditary non-polyposis colorectal cancer (HNPCC) syndrome may account for up to 4% of the total colorectal cancer burden in our community. It is assuming an increasingly important role, both as a clinical management issue and as a model for the application of laboratory and clinical genetic services in cancer detection and prevention. Recent developments in the understanding of the molecular biology of the condition have underpinned recommendations for consideration of genetic testing for DNA mismatch repair gene mutation, recommendations that may have far-reaching implications in terms of the numbers of patients offered genetic testing and for associated costs (both financial and psychological). The aim of this review is to highlight the clinical, pathologic and molecular biologic features of HNPCC that underlie the clinical management of affected index patients and their at-risk family members.

Ventral hippocampal ibotenic acid lesions block chronic nicotine-induced spatial working memory improvement in rats

Chronic nicotine infusions have been found to significantly improve working memory performance in the radial-arm maze. This effect is blocked by co-infusions of the nicotinic antagonist mecamylamine. Acute nicotine injections also improve working memory performance in the radial-arm maze. This effect is also blocked by mecamylamine co-administration. Recent local infusions studies have demonstrated the importance of the ventral hippocampus for nicotinic involvement in memory. Local infusions of mecamylamine, DHbetaE or MLA impair working memory performance on the radial-arm maze. The current study was conducted to determine the importance of the ventral hippocampus for the chronic effects of nicotine. Rats were trained on the working memory task in an eight-arm radial maze. After acquisition they underwent either infusions of ibotenic acid lesions or vehicle infusions and received subcutaneous implants of osmotic minipumps that delivered either nicotine at a dose of 5 mg kg-1 day-1 or vehicle in a 2x2 design. The rats then were given 2 days of recovery and were tested on the radial-arm maze three times per week for the next 4 weeks. As seen in previous studies, in the sham lesioned group nicotine infusions caused a significant improvement in choice accuracy. In contrast no nicotine-induced improvement was seen in the rats after ibotenic acid lesions of the ventral hippocampus. The effect of nicotine was blocked even though this lesion did not cause a deficit in performance. Previous work showed that chronic nicotine infusion still caused a significant improvement in working memory performance in the radial-arm maze after knife-cut lesions of the fimbria-fornix carrying the septo-hippocampal cholinergic innervation. Thus it appears that it is the postsynaptic nicotinic receptors in the ventral hippocampus which are critically important for the expression of the chronic nicotine induced working memory improvement.

Hoof size, shape, and balance as possible risk factors for catastrophic musculoskeletal injury of Thoroughbred racehorses

OBJECTIVE

To evaluate hoof size, shape, and balance as risk factors for catastrophic musculoskeletal injuries (CMI), including suspensory apparatus failure (SAF) and cannon bone condylar fracture (CDY) in Thoroughbred racehorses.

ANIMALS

95 Thoroughbred racehorses that died between 1994 and 1996.

PROCEDURE

38 quantitative measures of hoof size, shape, and balance were obtained from orthogonal digital images of the hoof and were compared between case horses with forelimb CMI (70), SAF (43), and CDY (10) injuries and control horses whose death was unrelated to the musculoskeletal system (non-CMI, 25). Comparison of group means between cases and controls was done using ANOVA, and multivariable logistic regression was used to estimate odds ratios.

RESULTS

Odds of CMI were 0.62 times lower for a 5mm increase in ground surface width difference and 0.49 times lower for a 100-mm2 increase in sole area difference. Odds of SAF were 6.75 times greater with a 10 degrees increase in toe-heel angle difference and 0.58 times lower with a 100-mm2 increase in sole area difference. Odds of CDY were 0.26 times lower with a 3 degrees increase in toe angle, 0.15 times lower with a 5-mm increase in lateral ground surface width, and 0.35 times lower with a 100-mm2 increase in sole area difference.

CLINICAL RELEVANCE

Decreasing the difference between toe and heel angles should decrease risk of SAF for Thoroughbred racehorses and should be considered in addition to increasing toe angle alone to help prevent catastrophic injury. Trimming the hoof to perfect mediolateral symmetry may not be a sound approach to avoiding injury.

The usefulness of CD64, other monocyte-associated antigens, and CD45 gating in the subclassification of acute myeloid leukemias with monocytic differentiation

Immunophenotyping by flow cytometry is widely used in the diagnosis and subclassification of acute myeloid leukemia (AML). CD14 is the monocyte-associated antigen most widely used to identify AML with monocytic differentiation (French-American-British classes M4 and M5); however, we observed that CD14 expression is frequently diminished or absent in such cases. To identify monocyte-associated antigens that might improve recognition of AML M4 and M5, we used 3-color flow cytometry and a panel of antibodies reported to distinguish cells of monocytic lineage in 44 cases of AML. In addition, CD45 vs logarithmic side scatter plots were analyzed in all cases. As expected, CD14 was highly specific but was only moderately sensitive for monocytic differentiation. CD64 had the best-combined sensitivity and specificity for AML M4 and M5. CD45 vs logarithmic side scatter analysis showed a higher percentage of monocytes in AML M4 and M5 compared with nonmonocytic AML. CD64 was expressed in 5 of 5 cases of acute promyelocytic leukemia (AML M3), but the intensity of staining was significantly less in AML M3 than in AML M4 and M5. Our findings show that addition of CD64 and CD45 vs logarithmic side scatter analysis to CD14 greatly improves flow cytometric detection of AML with monocytic differentiation and that CD64, also expressed in AML M3, may help distinguish AML M3 from other subtypes.

Do gastrointestinal symptoms vary with the menstrual cycle?

This systematic review presents both the physiological and symptom-based studies which have explored gastrointestinal variation across the menstrual cycle. Understanding this variation may be helpful in identifying the origin of pelvic pain, particularly as the symptoms associated with causes, such as endometriosis, also vary across the cycle. One-third of otherwise asymptomatic women may experience gastrointestinal symptoms at the time of menstruation, and almost 50% of women with irritable bowel syndrome report a perimenstrual increase in symptoms.

An investigation into the effects of sodium citrate ingestion on high-intensity exercise performance

This study examined the effect of sodium citrate ingestion on high-intensity cycling performance in repeated 45-sec bouts. Twelve subjects (9 male and 3 female) ingested either a sodium citrate solution (0.3 g x kg-1 body mass[BM]) or a placebo 90 min prior to exercise. Postingestion blood HCO3 concentrations were significantly higher in the citrate trial (p<.01), but there was no difference over the five bouts (p<.05) and postexercise blood lactate concentrations significantly increased over the five bouts (p<0.01), but there were no differences between trials. We conclude that sodium citrate ingestion (0.3 g x kg-1 BM) is not an effective ergogenic aid for high-intensity, intermittent exercise as simulated in this protocol.

Compulsive sexual behaviors--difficult aeromedical disposition

Axis I psychiatric disorders generally are considered incompatible with both the issuance and subsequent maintenance of aeromedical clearance certificates. Little doubt exists as to the impact that conditions such as anxiety disorders, mood disorders, or substance-related disorders have on the conduct of safe flight. Nevertheless, different compulsive sexual behaviors (CSBs), which now are thought to share similar origins and associated comorbidity, can similarly affect impulse control, judgment, concentration, and insight. Yet, these conditions frequently are handled administratively (if not legally). Moreover, in practice CSBs fall within a spectrum of behaviors from "normative" nonparaphilic sexuality to more deviant paraphilic behavior. Through the presentation of five selected cases seen at the Naval Operational Medicine Institute, this article explores examiner difficulty in establishing a diagnosis, discusses models useful in understanding the origins of these disorders, and highlights critical elements in establishing aeromedical disposition. The authors conclude that CSBs may be associated with anxiety, dysphoria, a pattern of increased risk taking, a high threshold for arousal, and poor judgment, which may impact the safety of flight. A comprehensive psychiatric evaluation is essential in determining aeromedical disposition, and consideration should be given to reviewing these cases from a medical perspective prior to any administrative disposition.

Reciprocal changes in hypothalamic receptor binding and circulating leptin in anorectic tumor-bearing rats

Although reduced biological activity of the obese gene product, leptin, has been associated with obesity, little information is available concerning leptin alterations during anorexia. Therefore, we measured circulating leptin concentrations and hypothalamic leptin binding in anorectic tumor-bearing and pair-fed control rats. Plasma concentrations of leptin decreased in tumor-bearing rats early in the course of tumor growth, and fell to nearly non-detectable levels during severe anorexia. The pair-fed control rats that ate the same amount of food as did the anorectic tumor-bearing rats exhibited a 50% decrease in plasma leptin concentration. Concentrations of free fatty acids were elevated in both tumor-bearing and pair-fed groups, while circulating levels of triglycerides were increased only in anorectic tumor-bearing rats. Leptin receptor density was doubled in the hypothalamus of tumor bearing rats, while binding affinity was decreased by 50%. These results suggest that peripheral leptin production is down-regulated, perhaps due to increased lipolysis in tumor-bearing rats. It appears that hypothalamic leptin systems up-regulate receptor numbers in response to decreased blood leptin level, however, the decrease in binding affinity may compensate for these alterations. Therefore, the influence of leptin on hypothalamic neuropeptide Y feeding systems may be minimal in anorectic tumor-bearing rats.

Non-malignant bone marrow necrosis: a report of two cases

We present two cases of bone marrow necrosis not associated with malignancy, infection or sickle cell disease. The first case, a 28 year old woman with the antiphospholipid syndrome and a factor V Leiden abnormality, suffered an illness characterised by multiple organ thromboses, anemia and refractory thrombocytopenia. She had documented bone marrow necrosis of the posterior iliac spine and numerous hot spots on bone scanning suggestive of widespread marrow necrosis. This patient also suffered hepatic infarcts and a miscarriage and may represent an explanation for the previously described "catastrophic antiphospholipid syndrome". The second patient developed widespread bone pain over a three week period, underwent a cholecystectomy and suffered major post-operative complications including a delayed transfusion reaction and disseminated intravascular coagulation. Pancytopenia developed and bone marrow trephines from numerous foci revealed widespread bone marrow necrosis. The only predisposing factor to account for this presentation was that the patient had been sniffing glue for two months prior to the illness, as the foci of necrosis had healed on repeat marrow examination eight weeks later when the patient had abstained from glue sniffing. This case may represent a reversible, toxic cause of bone marrow necrosis.

Altered cell surface expression and signaling of leptin receptors containing the fatty mutation

Leptin and the leptin receptor are key players in the regulation of body weight. In an attempt to dissect the molecular mechanism of the Zucker fatty rat leptin receptor mutation (Gln269 --> Pro) we analyzed the effects of this mutation on leptin receptor signaling and expression in three different expression systems: 1) 32D cells expressing leptin/erythropoietin receptor chimeras, 2) COS-7 cells expressing a leptin receptor short form, and 3) 293 cells expressing soluble receptor forms. To determine if the Gln269 --> Pro mutation is critical for the observed phenotype, we made a similar Gln --> Pro mutation at a vicinal residue two amino acids upstream of the fatty mutation to see if it would have similar effects. Incorporation of either of the Gln --> Pro mutations into wild type receptor forms did not interfere with leptin binding, but it resulted in a signaling-incompetent receptor. In addition, the majority of the mutant receptor protein was localized intracellularly. Our results suggest that the obese phenotype resulting from the Gln269 --> Pro mutation in the leptin receptor of the Zucker fatty rat may be due not only to a reduced cell surface expression of this form of the leptin receptor, but also to a post-leptin binding malfunction of the receptor that interferes with subsequent signal transduction.