Chronic traumatic diaphragmatic hernia with pericardial rupture and associated gastroesophageal reflux.

Major thoracic and abdominal trauma damages the diaphragm 5% of the time. These injuries may be recognized when they occur but often are discovered months later during work up for related symptoms. Typically, the injury is to the left posterolateral aspect of the diaphragm. Rarely, rupture through the central diaphragmatic tendon into the pericardial space occurs and this results in different symptoms than the more common injury. We present the case of a patient who presented with chest pain, near syncopal episodes and refractory gastroesophageal reflux years after he was struck by a car and hospitalized. Radiographic imaging included a chest CT that demonstrated herniation of the transverse colon into the mediastinum. During exploration, a defect in the central diaphragm was found with free communication between the peritoneal and pericardial spaces. In this paper, we review our management of this unusual diaphragmatic hernia and the unique symptoms associated with it.

Mechanisms by which transcription can regulate somatic hypermutation.

Mechanisms for somatic hypermutation (SHM) have proven elusive. An actively transcribed substrate was analyzed to elucidate the role of stem-loop structures (SLSs) in SHM. Analysis with a new computer algorithm indicates that the location and mutability of a base are regulated by: (a) the extent to which it is unpaired, (b) the degree to which it is exposed by stabilization of SLSs containing and flanking it, and (c) the level of transcription that drives supercoiling, which creates and stabilizes SLSs containing unpaired bases vulnerable to mutation. New mechanisms are described by which transcription can differentially stabilize SLSs harboring targeted bases and establish specific base exposure patterns. Assuming that transcription levels correlate with the magnitude of superhelicity induced and the lengths of ssDNA forming SLSs, this analysis accounts for the location of all mutable bases during SHM.

Hypermutation in derepressed operons of Escherichia coli K12.

This article presents evidence that starvation for leucine in an Escherichia coli auxotroph triggers metabolic activities that specifically target the leu operon for derepression, increased rates of transcription, and mutation. Derepression of the leu operon was a prerequisite for its activation by the signal nucleotide, guanosine tetraphosphate, which accumulates in response to nutritional stress (the stringent response). A quantitative correlation was established between leuB mRNA abundance and leuB- reversion rates. To further demonstrate that derepression increased mutation rates, the chromosomal leu operon was placed under the control of the inducible tac promoter. When the leu operon was induced by isopropyl-D-thiogalactoside, both leuB mRNA abundance and leuB- reversion rates increased. These investigations suggest that guanosine tetraphosphate may contribute as much as attenuation in regulating leu operon expression and that higher rates of mutation are specifically associated with the derepressed leu operon.

Recurrent pancreatitis in Gardner variant familial polyposis: etiology, diagnostic approach, and interventional results.

HYPOTHESIS: Pancreatitis arising from an obstructing ampullary neoplasm in patients with Gardner variant familial polyposis is an infrequently described clinical entity. We reviewed all patients with Gardner variant polyposis presenting with pancreatitis during a 12-year period in our institution, hoping to better define etiology and the appropriate diagnostic and interventional approach. METHODS: A retrospective record review (1986-1998) defined patient demographics, presenting features, initial and subsequent endoscopic retrograde cholangiopancreatography (ERCP) findings, subsequent treatments, and both immediate and long-term outcomes. Particular consideration was given to initial post-ERCP diagnosis and to endoscopic interventions undertaken at that time. We also looked at those patients who eventually required surgical intervention after long-term failure of medical and endoscopic therapy, the indications for surgery, final pathological characteristics, and follow-up results. RESULTS: Eight patients (6 women and 2 men), with a mean age of 42 years at initial presentation, were found. Each patient was known to have Gardner variant familial polyposis at the time of the initial bout of pancreatitis. All had undergone prior colectomy and 4 of 8 had undergone prior cholecystectomy. None were known to be taking medications or ingesting pancreatoxic substances. Five of 8 patients had obstructing focal or diffuse adenomatous disease involving the ampulla. Two of 8 patients had pancreatitis attributed to other causes (divisum, stones) and a single patient had no clear etiology. Three of 5 patients with ampullary adenomatous disease underwent pancreaticoduodenectomy for recurrent adenomatous encroachment and ampullary stenosis, despite repetitive snare resection and papillotomy. All of these patients had ampullary and other duodenal adenomas, and none had malignant disease. CONCLUSIONS: Patients presenting with pancreatitis in the setting of Gardner variant familial polyposis will frequently have an obstructing ampullary neoplasm, although additional etiologies should be sought. Initial endoscopic therapy affords transient relief but may not be definitive. The abnormal scarring and fibrosis (keloid formation, desmoid reaction) that characterize this disease likely play a large role in endoscopic or subsequent surgical failure. A significant number of these patients will go on to require surgical referral and intervention.

Positive effects of acarbose in the diabetic rat are not altered by feeding schedule.

We previously demonstrated that chronic dietary treatment with acarbose, an alpha-glucosidase inhibitor, improves glucose homeostasis in the streptozotocin (STZ)-induced diabetic rat. In this study we evaluated the effects of 4 weeks of acarbose treatment on glucose homeostasis in STZ-diabetic rats for both meal-fed (three times daily) and ad libitum feeding conditions. Sprague Dawley male rats (n = 58) were started on a daily meal-feeding paradigm consisting of three 2-h feeding periods: 0700 to 0900 hours, 1300 to 1500 hours, and 1900 to 2100 hours. Following 2 weeks of adaptation, half of the animals were switched to ad libitum feeding. The feeding paradigm itself (meal fed versus ad lib.) affected neither body weight nor daily food intake. Twenty animals from each feeding group then received STZ (60 mg/kg i.v.), whereas control animals received vehicle injections only. Two days later, the diet of 10 STZ-treated animals from each paradigm was supplemented with acarbose (40 mg of BAY G 5421/100-g diet), and the groups were treated for 4 weeks. Untreated diabetic rats had lower body weight than vehicle-injected control rats at all time points after STZ treatment. Acarbose treatment delayed this effect on body weight. STZ treatment induced hyperphagia regardless of feeding paradigm, which was significantly attenuated by acarbose only for the first week of treatment. Untreated diabetic rats had fasting blood glucose values 4 times those of vehicle-injected controls in both the meal-fed and ad libitum-fed conditions. Acarbose significantly lowered fasting blood glucose in the treated STZ groups. Blood glucose was also assessed 0, 90, and 180 min following the start of a meal. The postprandial rise in blood glucose was significantly reduced in acarbose-treated meal-fed diabetic rats, to values not significantly different from those of vehicle-injected control rats. During the fourth week of treatment glycated hemoglobin levels were significantly higher in untreated diabetic groups compared to vehicle-injected control groups. Acarbose treatment significantly reduced this rise, regardless of the feeding paradigm. Collectively, the results demonstrate that acarbose reduces diabetes-induced increases of blood glucose and glycated hemoglobin and that the glycemic effects of acarbose are most apparent during the absorptive period. Feeding paradigm (ad lib. versus meal fed) has little or no influence on acarbose's metabolic effects, indicating that large meals are not required to realize the beneficial effects of the drug. The meal-fed STZ-diabetic rat may be a good model with which to test meal-based diabetes treatments.

Dietary and hypothalamic changes in delta 4-androstenedione-treated Zucker rats.

Dehydroepiandrosterone (DHEA) has been shown to alter hypothalamic monoamines and reduce energy intake (EI) in Zucker rats (ZRs). We hypothesized that a metabolite of DHEA, delta 4-Androstenedione (delta 4), may mediate these effects. Male lean and obese ZRs (LZR, OZR) were fed control chow (CC) for 7 days, during which basal EI was recorded, various concentrations of delta 4 for 7 days, during which 0.6 and 0.3% delta 4 reduced EI significantly, and CC for 7 days, which resulted in a return of EI to basal levels. After delta 4 administration, neurotransmitter contents of various hypothalamic areas were determined. Serotonin (5-HT) has been shown to be correlated with feeding inhibition, and we have shown DHEA to increase lateral hypothalamic 5-HT synthesis; however, after 1 day and 7 days of delta 4, the OZR exhibited an increased metabolism, not synthesis, of 5-HT in the lateral and paraventricular hypothalamus, respectively, delta 4 was compared to DHEA in a macronutrient self-selection study with female OZRs. One group was injected intraperitoneally (IP) with sesame oil (control), another with DHEA (100 mg/kg), and another with delta 4 (100 mg/kg). Previous studies have shown that DHEA decreases both EI and % calories from fat. In this study, delta 4 decreased % calories from fat, but did not decrease total EI. Contrary to DHEA's effect of reducing serum insulin through 28 days of treatment, delta 4 in chow reduced insulin only acutely (1 day). We conclude, based on these differences, that DHEA has unique effects not mediated by its metabolite, delta 4-Androstenedione.

Does selective gene activation direct evolution?

Mechanisms may have evolved such that the unique metabolic reaction to a particular environmental stress results in higher mutation rates of those genes most likely to solve the problem. Evidence is presented indicating that the environment in effect directs the evolution of organisms by (1) presenting various kinds of stress resulting in metabolic activities that target particular genes for increased rates of transcription and mutation, and (2) selecting among this specifically enriched mutant population those variants that alleviate the imposed stress. This process should be ongoing and would be expected to accelerate the rate of microbial evolution.

Models of metabolism in Rhizopus oryzae.

A flux analysis of glucose metabolism in Rhizopus oryzae was achieved using [14C]-labeled glucose and acetate. The rates of glucose utilization and end product production were estimated, and metabolite pool sizes and specific radioactivities were determined. These data were analysed using a specific radioactivity curve-matching program called TFLUX. The analysis is consistent with the existence of separate mitochondrial and cytosolic pools of pyruvate, malate and fumarate.

Effect of restraint on drug-induced changes in skin and core temperature in biotelemetered rats.

Temperature homeostasis is modulated by a number of neuroendocrine control systems. Both angiotensin II and isoproterenol have been shown to increase skin temperature. Withdrawal from opioid dependence using naloxone also results in an increased skin temperature and a decreased body core temperature. The effects of restraint stress on these tail skin temperature responses is unknown. We tested the effect of restraint or free movement on tail skin and core temperature responses to three thermoregulatory substances: isoproterenol and angiotensin II in naive rats and naloxone in morphine-dependent rats. In each case restrained rats had significantly lower baseline tail skin temperatures than free moving rats. Baseline core temperatures were not different between restrained and free moving animals. Each agent produced significant acute increases in tail skin temperatures. Restraint did not affect these responses. Both angiotensin II and naloxone also produced significant decreases in core temperatures that were not altered by restraint. This study is the first to show that radiotelemetry can be used to measure tail skin temperatures in rats. The results of this study show that when using three different thermoregulatory agents restraint failed to affect either baseline temperatures or maximal responsiveness to the agents in a detrimental manner. The lack of impairment of temperature changes due to restraint in these studies also validate previous studies that had used restraint in measuring core and tail skin temperatures in rodents.

The effect of the stringent response on mutation rates in Escherichia coli K-12.

The reversion rates of two isogenic Escherichia coli K-12 auxotrophs differing only in relA have been determined in the absence or presence of serine hydroxamate, which provokes the stringent response. Reversion rates of leuB- and argH- were significantly higher in the relA+ than in the relA- strain, and the reversion rates in both strains were enhanced by serine hydroxamate. A positive correlation was established between reversion rates and the synthesis of guanosine-5'-diphosphate-3'-diphosphate in the absence and presence of serine hydroxamate. It is proposed that mutation rates are dependent upon rates of transcription and upon the genes which regulate the level of the signal nucleotide, guanosine tetraphosphate.

Central effects of dehydroepiandrosterone in Zucker rats.

OBJECTIVES: To investigate whether dehydroepiandrosterone (DHEA), an adrenal/gonadal androgen, can act centrally to reduce energy intake in a model of genetic obesity, the Zucker fatty rat. To investigate a possible mechanism of action. DESIGN: Two experiments were performed in lean and obese female Zucker rats. In the first experiment, 24 h following administration of i.p. DHEA (200 mg/kg), three hypothalamic regions [lateral hypothalamus (LH), ventromedial nucleus (VMH), and paraventricular nucleus (PVN)] were analyzed for monoamine neurotransmitter concentrations. In the second experiment, DHEA (50 micrograms) was administered by i.c.v. injection. Energy intake for the following day was measured. MEASUREMENTS: In the first experiment, concentrations of norepinephrine (NE), epinephrine (EPI), dopamine (DA), serotonin (5HT), the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) were measured. Ratios of 5HT/5HIAA were calculated. In the second experiment, kilojoules consumed per 24 h were calculated. RESULTS: All LH monoamines, and PVN DA, displayed lower concentrations in obese than lean control rats. DHEA treatment reversed these reductions in obese rats without affecting lean rats. DHEA increased VMH EPI in obese rats only. DHEA increased PVN NE in both lean and obese rats. I.C.V. DHEA decreased energy intake in obese but not lean rats. CONCLUSION: The i.c.v. results suggest that DHEA exerts a phenotype specific, centrally mediated inhibitory effect on food intake. In addition, in doses previously shown to reduce energy intake in obese but not lean rats, i.p. DHEA reversed reduced concentrations of many monoamines, particularly in the LH, in obese animals only. These latter changes provide indirect evidence to suggest that these central neurotransmitters may play an important role in the antiobesity effect of DHEA in the Zucker fatty rat.

Chronic Losartan treatment blocks isoproterenol-induced dipsogenesis.

Previous studies suggest that beta-adrenergic receptor agonists and other hypotensive agents stimulate water intake via the renin-angiotensin system (RAS). However, a recent study reported that acute peripheral administration of Losartan, an angiotensin II (AII) type I receptor antagonist, failed to inhibit isoproterenol-induced water intake. In the current study we assessed the role of chronic Losartan treatment on isoproterenol-induced water intake. Male Sprague-Dawley rats were divided into two groups (n = 10/group). The experimental group was chronically treated with Losartan in the drinking water (120 mg/kg/day). Rats in the control group were maintained on normal tap water. At the end of each week, water intake in response to isoproterenol was determined. On the days of the dipsogenic study, water intake was determined 1 h prior to and 2 h following SC injection of isoproterenol (25 micrograms/kg). Isoproterenol-induced water intake in the experimental group was significantly lower than the control rats by 71% and 88% at the end of weeks one and two respectively (p < 0.01). Following ten days of Losartan treatment, dipsogenic response to AII likewise demonstrated a complete blockage of AII receptors (75% decrease compared to the controls). These data strongly suggest that water intake in response to isoproterenol is mediated in part by the RAS.

The effect of discontinuing dehydroepiandrosterone supplementation on Zucker rat food intake and hypothalamic neurotransmitters.

OBJECTIVE: Dehydroepiandrosterone (DHEA) decreases body weight and food intake of the obese Zucker rat, a model of youth-onset obesity associated with hyperphagia. The effects of discontinuing DHEA treatment on these parameters, however, has not been investigated. This question was studied in rats that had been maintained on DHEA-supplemented (0.0%, 0.06%, 0.15%, 0.3% or 0.6%) diets for 7 days. METHOD: The results were correlated with regional levels of hypothalamic neurotransmitters in rats treated with 0.6% DHEA for 7 days in a separate experiment. Neurotransmitter changes were evaluated after Day 0 (7 days of treatment), and Day +1 and Day+2 post-DHEA. RESULTS: Upon removing dietary DHEA, rats immediately (+1 day) consumed significantly more food than while on the DHEA-supplemented diet. Indeed, they consumed even more food than the group that had always been on the DHEA-free diet. This intake above control lasted for as long as +9 days post-DHEA treatment. After 7 days of DHEA treatment, lateral hypothalamic (LH) serotonin (5-HT) and dopamine (Dpm) were elevated significantly (P < 0.05) immediate changes in 5-HT and Dpm returned to baseline by day 2 of post-DHEA treatment. No significant changes occurred in either the ventromedial hypothalamus (VMH) or the paraventricular nucleus (PVN). CONCLUSIONS: These observations suggest that there is a possible relationship between increases of LH 5-HT and Dpm with 0.6% DHEA treatment. Both are inhibitory to food intake and DHEA at the 0.6% dose causes hypophagia after 7 days of treatment (i.e. 0 days). Subsequent decreases of these monoamines occurred during the post-DHEA period at both +1 and +2 days. Return of these inhibitory monoamines to baseline could be responsible for reversal of the hypophagia, however, they do not rule out the production of a separate stimulator of food intake.

Effects of streptozotocin-induced diabetes and insulin treatment on blood pressure in the male rat.

Hyperinsulinemia may link diabetes to hypertension. We evaluated the effects of insulin on blood glucose and blood pressure in control and streptozotocin (STZ)-induced (60 mg/kg, i.v.) diabetes. Insulin was given daily for 10-14 weeks to both diabetic (0, 1, 2, and 3 U) and control (0, 2, and 3 U) male rats (n = 7-8/group). Indirect and direct blood pressures were measured as were blood glucose and several metabolic parameters. All treated rats became hyperinsulinemic. Untreated and 1 U insulin-treated diabetic rats were hyperglycemic. Higher doses of insulin significantly reduced blood glucoses in diabetic animals. Indirect blood pressure measurements were unchanged between groups. However, when measured directly, the untreated diabetic rats had significantly lower pressures that did untreated controls. Insulin treatment at dosages above 1 U normalized blood pressure in diabetic animals. These same doses of insulin also restored to normal all the metabolic parameters associated with diabetes. Insulin treatment did not affect any of the parameters evaluated in nondiabetic rats. Collectively, the results show that STZ-induced diabetes results in a decrease in blood pressure and that insulin treatment can restore blood pressure in diabetic rats. Although the results suggest that insulin may be involved in restoring blood pressure in animals with a carbohydrate imbalance, the precise mechanism for elevating blood pressure is not known with certainty.

The tricarboxylic acid cycle in Dictyostelium discoideum. Two methods of analysis using the same data.

The results of using metabolic control theory versus biochemical systems theory to analyze a model of the tricarboxylic acid cycle in Dictyostelium are described. The two types of analysis give essentially the same results, except that smaller responses to perturbations are observed for the model analyzed by metabolic control theory. The basis for this difference is discussed.

Carbohydrate metabolism in Dictyostelium discoideum: I. Model construction.

A model of the transitional changes which occur in fluxes and metabolite concentrations during the course of differentiation of Dictyostelium discoideum is constructed, based on extensive experimental data collected from D. discoideum. Input to the model includes metabolite compartmentation and fluxes, determined by radiotracer analyses, and enzyme mechanisms and constants. This transition model reproduced experimentally measured changes in metabolite concentrations over the last 15 hr of differentiation. The real test of a mathematical model is its ability to correctly predict the effects of an altered environment or a mutation. This model demonstrates that ability. Constraints on model parameters are also examined, and many of the altered parameters result in a model which is unable to reproduce experimental data. These results imply that the model represents many aspects of metabolism in vivo and will provide a means of examining rate-limiting events during differentiation and aging of this organism.

Carbohydrate metabolism in Dictyostelium discoideum: II. Systems' analysis.

A transition model of carbohydrate metabolism during differentiation of Dictyostelium discoideum was described in Wright & Albe (1994, J. theor. Biol. 168, 231-241). From this base model, two steady-state models are derived in which concentration and flux are consistent with culmination (600 min) or young sorocarp (700 min) stages of development. These steady-state models are analyzed using metabolic control theory (MCT), and the summation property is met for metabolites, individual flux rates, and overall flux control coefficients. The MCT analyses show that flux control differs between the two stages. At culmination, cellulose synthetase is the major control point for overall pathway flux (C = 0.86) whereas at young sorocarp, glycogen phosphorylase is the major control point (C = 0.89). This is a reflection of the increased competition between the endproduct synthases, which are used to define overall pathway flux. Thus the specific metabolic state of the cells is important in assessing control distribution. The significance of this work in understanding the mechanisms controlling biochemical differentiation is discussed and related to the work of others in the field. For example, mutant analysis can reveal which enzymes are essential to differentiation (most are) but cannot reveal which enzymes are unique and/or rate-controlling.