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Biomedical subjects

G S Smith

Publications and source records attributed to G S Smith.

At least 19 recordsLinked to original sources

Two populations of cells that express preprocholecystokinin mRNA in ventral periaqueductal grey.

Cells expressing preprocholecystokinin (CCK) mRNA in the rat midbrain periaqueductal grey area and Edinger-Westphal nucleus were analysed using in situ hybridization combined with liquid emulsion techniques. Semi-quantitative image analysis revealed that there were two populations of cells which expressed CCK mRNA. The first group of cells were large and heavily labelled and were confined to the Edinger-Westphal nucleus. The second group of cells were small and lightly labelled and were found scattered throughout ventral parts of the anterior periaqueductal grey.

Animals

Psychoactive substance dependence among trauma center patients.

INTRODUCTION: The practice of assessing only trauma patients with elevated blood alcohol concentrations (BACs) or positive drug screens for psychoactive substance use disorders (PSUDs) was evaluated. METHODS: Twenty-four BAC-negative (BAC-) (BAC, 0) and 21 BAC-positive (BAC+) (BAC, greater than or equal to 22 mmol/L or 100 mg/dL; mean, 41 mmol/L; range, 24.3 to 79 mmol/L) adult trauma patients were evaluated for alcoholism and other PSUDs using the Structured Clinical Interview (SCI) from the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition (DSM-III-R). Approximately half were vehicular crash victims and 78% were men. RESULTS: A total of 64 PSUDs were diagnosed in 31 (68.9%) of the 45 patients; all but one was for dependence (vs abuse). Of the BAC+ patients, 14 (66.7%) met DSM-III-R criteria for alcohol dependence, 11 (78.6%) of whom also had other PSUDs not related to alcohol. Two other BAC+ patients had nonalcohol PSUDs. Of the BAC- patients, 11 (45.8%) had alcohol dependence, six (54.5%) of whom also had nonalcohol PSUDs. Another four BAC- patients had nonalcohol PSUDs. Overall, 76.2% of the BAC+ patients and 62.5% of the BAC- patients had a diagnosis of psychoactive substance dependence. CONCLUSION: All patients admitted to trauma centers should be assessed for alcoholism and other PSUDs.

Alcoholism

Topography of cross-sectional and longitudinal glucose metabolic deficits in Alzheimer's disease. Pathophysiologic implications.

Positron emission tomographic studies of cerebral glucose metabolism have shown high diagnostic specificity in distinguishing among the degenerative dementias and differentiating between Alzheimer's disease (AD) and normal aging. The current investigation was undertaken to characterize the regional glucose metabolic deficits in AD, using cross-sectional and longitudinal study designs. All subjects met the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for AD (n = 45) or were normal (n = 20), and the AD subjects were subdivided into incipient and mild AD and moderate plus moderately severe subgroups based on the Global Deterioration Scale. The subjects underwent a non-contrast computed tomographic scan and a positron emission tomographic (PETT VI) scan. The AD subjects (n = 14) and normal control subjects (n = 15) received evaluations 2 to 3 years after baseline study. The brain regions that show glucose metabolic deficits cross-sectionally (temporal and parietal association areas, with lesser degrees of deficit in subcortical gray matter structures), over the stages of AD, also show further deficits longitudinally within the same AD subjects. The reduction in glucose metabolism is greater than would be expected from the degree of brain atrophy. The glucose metabolic deficits are discussed in the context of neuropathologic findings and neurotransmitter deficits in AD.

Aged

Protective effect of dimethylthiourea against mucosal injury in rat stomach. Implications for hydroxyl radical mechanism.

The present study was undertaken to determine whether dimethylthiourea (DMTU), a hydroxyl radical scavenger, could prevent gastric injury in the rat stomach induced by various noxious agents. Fasted rats (N = 6-8/group) were given a 1-ml oral bolus of saline or DMTU over the dose range 10-500 mg/kg. After 30 min, animals received 1 ml of 100% ethanol orally and were sacrificed 5 min later. At sacrifice, stomachs were harvested and the degree of macroscopic damage was assessed by planimetry. In selected animals, specimens of gastric mucosa were also processed for histology. Saline pretreatment prior to ethanol exposure resulted in 22.5% injury to the glandular epithelium when assessed macroscopically. DMTU pretreatment prevented such injury in a dose-related fashion with only 2% of the mucosa showing injury with a 500 mg/kg dose (P less than 0.01 vs control). Although the superficial injury involving surface mucous cells induced by ethanol was not altered by DMTU, the deep damage to gastric glands was almost completely prevented. Other experiments in which DMTU was given intraperitoneally demonstrated similar protective effects against ethanol injury. Additional studies showed that indomethacin did not prevent the protective effects of oral or intraperitoneal DMTU, excluding a role for endogenous prostaglandins, and that DMTU was equally protective when administered within minutes or as long as 2 hr prior to ethanol exposure. Furthermore, DMTU was also shown to be protective against gastric injury induced by concentrated acid or base. In in vitro studies in which hydroxyl radicals were actually generated, DMTU was noted to scavenge the hydroxyl radical in a dose-related fashion. The ability of DMTU to prevent gastric injury by three different damaging agents suggests that the hydroxyl radical may play a major role in the pathogenesis of such injury and that DMTU mediated its protective action by scavenging this radical species.

Animals

Influence of shock on development of infection during acute pancreatitis in the rat.

This study tested the hypothesis that hypovolemic shock elicits or promotes the development of infection during acute pancreatitis. Pancreatitis was induced in rats by ligation of the common biliopancreatic duct; nonlaparotomized animals served as controls. After 24 hr, the animals were subjected to either sham-shock (instrumented only) or to shock by withdrawal of blood through a femoral artery line by maintaining the mean arterial blood pressure at 30 mm Hg for 1 or 2 hr. After completion of the shock period, the shed blood was returned to the animal. All animals were sacrificed 24 hr later and specimens obtained from portal and systemic blood, liver, spleen, pancreas, and mesenteric lymph nodes for bacteriologic culture using standard techniques. The pancreas was also analyzed by morphometric techniques. The histologic changes of pancreatitis induced by biliopancreatic obstruction were characterized by marked edema with accompanying mild inflammation, hemorrhage, and necrosis. Concomitant with these morphologic findings was an associated translocation of enteric organisms to the mesenteric lymph nodes without spread to distant organs. Shock by itself induced only a mild edema in the pancreas and did not cause bacterial translocation. Furthermore, shock failed to aggravate the morphologic alterations of acute pancreatitis and did not promote bacterial spread to mesenteric nodes over that observed with pancreatitis alone. Thus, we conclude that periods of severe shock lasting up to 2 hr do not play a major role in the pathogenesis of infection in our model of pancreatitis.

Acute Disease

Musculoskeletal injuries in the Afghan war.

Among the 1274 patients admitted to a Pakistan border hospital from 1985 to 1987, the distribution and outcome of musculoskeletal war injuries differed from those seen in other conflicts. Serious complications from injuries were found in approximately 50 per cent of patients, of which most were wound infections, chronic osteomyelitis, and restriction of joint motion. Guerrillas in the Afghan war had no access to acute medical treatment in the field. Many patients died before reaching the hospital, as reflected in the low proportion of paraxial injuries; very high complication rates were noted for all injuries. Although some complications, such as soft tissue infection and foreign body retention are not site specific, other complications such as contracture, non-union, loss of range of motion, and chronic osteomyelitis are highly related to the region injured. Early surgical management and evacuation of those with musculoskeletal war injuries can greatly improve the outcome from war trauma and reduce the subsequent disability. However, the increasing use of hand-held anti-aircraft missiles may prevent the rapid evacuation of the wounded in future conflicts, and may make the situation seen in Afghanistan more common.

Adolescent

Intermittent acceleration as a countermeasure to soleus muscle atrophy.

The centrifuge proposed for the Space Station will most likely be used, in part, for countermeasure studies. At present, there is a paucity of information concerning the duration and frequency of acceleration necessary to counteract the atrophy process associated with microgravity. The present study was designed to investigate intermittent acceleration during non-weight bearing of the soleus muscle and its resultant effects on muscular atrophy. Each day rats were removed from hindlimbs suspension and accelerated to 1.2 g for four 15-min periods evenly spaced over a 12-h interval. The soleus muscle experienced non-weight bearing the remaining 23 h each day. This paradigm, when repeated for 7 days, did not completely maintain the mass of soleus muscle, which was 84% of control. Interestingly, the identical protocol utilizing ground support in lieu of acceleration successfully maintained the soleus muscle mass. The failure of the centrifugation protocol to adequately maintain soleus muscle mass might be due to an undefined stress placed on the animals inherent in centrifugation itself. This stress may also explain the transient decline in food intake of the intermittent acceleration group on the 2nd and 3rd days of treatment. Also, these data support the concept that the frequency of exposure, as opposed to the duration of exposure, to weight bearing during hindlimb unweighting seems to be the more important determinant of maintaining postural muscle mass.

Acceleration

Struvite urolithiasis in a B6C3F1 mouse.

In a 2 year carcinogenicity bioassay using B6C3F1 mice, one male mouse developed clinical signs near termination of the study, comprising skin sores around the prepuce, penile prolapse and urine scalding. The predominant finding at necropsy was a markedly distended urinary bladder filled with numerous crystallized particles. Microscopically, there was subacute cystitis with marked hyperplasia of the transitional epithelium. X-ray diffraction analysis of the crystals showed a diffraction pattern characteristic of struvite (ammonium magnesium phosphate). The implications of the spontaneous occurrence of bladder stones in rodents on long-term toxicology studies are discussed.

Animals

Early aspects of locoweed toxicosis and evaluation of a mineral supplement or clinoptilolite as dietary treatments.

Sixteen crossbred beef heifers were used to determine the efficacy of serum clinical profiles as diagnostic tools for detection of early stages of locoweed toxicity and to test the ability of two mineral supplements for prevention or therapy of toxicosis. Dietary treatments were (DM basis) 1) 100% sorghum sudangrass hay, 2) 80% sorghum sudangrass hay:20% locoweed, 3) 80% sorghum sudangrass hay:20% locoweed plus 100 g of Silent Herder Mineral Mix (a mineral supplement reported to alleviate locoweed toxicity), and 4) 80% sorghum sudangrass hay:20% locoweed plus 100 g of clinoptilolite (a natural zeolite clay). Diets were fed at 1.5% of BW for 28 d, after which heifers had ad libitum access to sorghum sudangrass hay for 14 d. Jugular blood was sampled before feeding every 7 d, and at 2, 4, 6, and 8 h after feeding on d 28. Compared with controls, heifers fed locoweed had elevated (P less than .01) serum alkaline phosphatase activities from d 7 through 35. On d 42, alkaline phosphatase activities in heifers previously fed locoweed were lower (P less than .05) than in control heifers. Serum glutamic oxaloacetic transaminase activities were elevated (P less than .01) in heifers fed locoweed from d 7 through 42 compared with control heifers. In heifers fed locoweed, serum Fe concentrations were less (P less than .01) on d 7 through 28, but no treatment effects were noted (P greater than .10) on d 35 or 42.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase

GABAergic inhibition of endogenous dopamine release measured in vivo with 11C-raclopride and positron emission tomography.

Extensive neuroanatomical, neurophysiological, and behavioral evidence demonstrates that GABAergic neurons inhibit endogenous dopamine release in the mammalian corpus striatum. Positron emission tomography (PET) studies in adult female baboons, using the dopamine D2-specific radiotracer 11C-raclopride, were undertaken to assess the utility of this imaging technique for measuring these dynamic interactions in vivo. 11C-raclopride binding was imaged prior to and following the administration of either gamma-vinyl-GABA (GVG), a specific suicide inhibitor of the GABA-catabolizing enzyme GABA transaminase, or lorazepam, a clinically prescribed benzodiazepine agonist. Striatal 11C-raclopride binding increased following both GVG and lorazepam administration. This increase exceeded the test/retest variability of 11C-raclopride binding observed in the same animals. These findings confirm that changes in endogenous dopamine concentrations resulting from drug-induced potentiation of GABAergic transmission can be measured with PET and 11C-raclopride. Finally, this new strategy for noninvasively evaluating the functional integrity of neurophysiologically linked transmitter systems with PET supports its use as an approach for assessing the multiple mechanisms of drug action and their consequences in the human brain.

Aminocaproates

The driver's role in fatal two-car crashes: a paired "case-control" study.

This population-based study examines drivers' characteristics associated with driving errors that resulted in fatal motor vehicle crashes. Routinely collected data from the Fatal Accident Reporting System were used to assess whether a driver initiated the crash (case) or was passively involved (control) in 6,506 two-car collisions (81% of 7,993 eligible events). A paired comparison of cases and controls avoided confounding by environmental factors, exposure to traffic, and differences in case fatality. The strongest predictor of crash initiation is alcohol (odds ratio (OR) = 11.5; 95% confidence interval (CI) 9.57-13.9). Odds ratios are elevated even at the lowest blood alcohol concentration levels and increase dramatically as alcohol levels rise. Drivers aged 40-49 years are least likely to initiate crashes; odds ratios rise in a U-shaped manner to 3.35 in teenagers (95% CI 2.72-4.13) and to 22.1 in drivers over 80 years (95% CI 14.2-34.5). Other risk factors for initiating a fatal crash are the following: not wearing a seat belt (OR = 1.54; 95% CI 1.35-1.75), driving without a valid driver's license (OR = 2.16; 95% CI 1.72-2.73), and having had a crash within the last year (OR = 1.21; 95% CI 1.07-1.38). Driving errors leading to fatal crashes do not occur at random, but are associated with specific driver characteristics. The risk factors for crash initiation among crash-involved drivers are similar to risk factors for crash involvement found in other studies. These findings suggest that driving errors often explain high rates of crash involvement, invite further use of crash initiation in traffic injury research, and underscore the value of population-based registries for analytic epidemiology.

Accidents, Traffic

Methodological issues in using hospital discharge data to determine the incidence of hospitalized injuries.

Estimates of the incidence of hospitalized injuries based on hospital discharge data are inconsistent because of variations in 1) the definition of injury and 2) the criteria for excluding repeat admissions for the same injury event. Using 1983 data from the Uniform Hospital Discharge Data Set for the state of Rhode Island, the authors demonstrate the effects on injury incidence rates associated with the various definitions and exclusion criteria used in previous studies. The overall injury rate (11.9/1,000 population) was substantially reduced (rate difference, 1.7; 95% confidence interval 1.2-2.1) when adverse effects or complications of medical and surgical care ("medical injuries"), not usually defined as injuries by injury researchers, were excluded. Estimates of the incidence of "true" injury hospitalizations (excluding medical injuries, late effects, and complications of care) ranged from 9.9/1,000, when repeat admissions identified as transfers from another acute facility were excluded, to 7.2/1,000, when repeat admissions identified as elective admissions were excluded. Marked variability in incidence rate estimates by age, sex, nature of injury, and state of residence of victim was also noted. The addition to hospital discharge data sets of a separate variable to identify readmissions for the same problem would result in more valid incidence estimates for injury research and surveillance.

Adolescent

Transmembrane domain length variation in the evolution of major histocompatibility complex class I genes.

The fifth exons of major histocompatibility complex (MHC) class I genes encode a transmembrane domain (TM) that is largely responsible for class I antigen cell-surface expression usually through conventional hydrophobic amino acid-membrane interactions or, less often, through phosphatidylinositol linkage. In this report we show that Peromyscus leucopus, a Cricetidae rodent, has MHC class I genes (Pele-A genes) encoding three distinct sizes of TMs. Increases in TM lengths were due to tandem duplications of sequences similar to human hypervariable minisatellite repeats and the lambda chi site. We discerned remnants of a similar duplication event in comparable rodent and primate MHC class I genes. Furthermore, several duplications and deletions appear to have occurred independently in H-2, RT1, Pele-A, and ChLA genes in near-identical positions. Accumulated data suggests that sequences in the fifth exon of MHC class I genes may, therefore, constitute a mutational or recombinational hot spot that is mediated by minisatellite- and chi-like sequences imbedded within the coding region. The MHC class I genes may thus have recruited "selfish" DNA in their evolution to encode cell surface proteins. Expression of Pele-A genes was examined by the polymerase chain reaction (PCR) using oligonucleotide primers specific for exon 4 and 5 sequences. The PCR product sizes indicated that genes encoding each TM domain length are ubiquitously transcribed.

Animals

The role of the gut in the development of sepsis in acute pancreatitis.

The pathogenesis of sepsis in acute pancreatitis is unknown. Since the intestinal tract has recently been identified as a possible source for sepsis in other conditions, we explored whether the gut may serve as a reservoir for bacteria causing systemic and pancreatic infection in acute pancreatitis. Bacterial translocation, alterations of intestinal microflora, and intestinal motility, as reflected by gut propulsion, were studied in a rat pancreatitis model. Acute pancreatitis was induced by biliopancreatic obstruction (AP); sham manipulated animals served as controls (sham). Bacteriologic cultures were obtained from various segments of the intestinal tract and from blood, liver, spleen, pancreas, and mesenteric lymph nodes 48 and 96 hr after induction of AP or sham. Bacteria were recovered from mesenteric lymph nodes of all 12 animals with AP, but only from 3/14 sham animals (P less than 0.05). Spread to distant organ sites occurred in 4 of 12 animals with AP compared to none of the sham animals (P less than 0.05). A disruption of the intestinal microflora was found in the cecum, where the gram-negative bacterial count (log/g) was significantly higher during AP when compared with sham controls: 10.62 +/- 1.04 vs 8.05 +/- 1.45 at 48 hr and 7.92 +/- 0.62 vs 6.79 +/- 0.87 at 96 hr, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease

Adaptive cytoprotection against alcohol injury in the rat stomach is not due to increased prostanoid synthesis.

This study evaluated the effects of 25% ethanol, a mild irritant, on endogenous prostanoid synthesis in the rat stomach before and after exposure to oral 100% ethanol. Rats received water or 25% ethanol orally. After 15 min, a portion of each group was sacrificed and the remaining animals treated with 100% ethanol prior to sacrifice one minute later. Microsomal membrane fractions were prepared from the glandular gastric mucosa in all groups and incubated with 14C arachidonic acid in the presence of cofactors. Endogenous mucosal prostanoid synthesis was analyzed by radiochromatography and results correlated with the presence or absence of gastric injury macroscopically. Prostanoids measured included PGI2, PGF2 alpha, PGE2, PGD2, PGA2, and thromboxane A2. Additional experiments were performed in like manner to those just described with the exception that indomethacin (5 mg/kg intraperitoneally) pretreatment was rendered. Stomachs exposed to water or 25% ethanol alone demonstrated a modest and equivalent level of synthesis of all prostanoids measured. Exposure to 100% ethanol (with and without mild irritant pretreatment) significantly increased prostanoid synthesis (especially PGI2, PGF2 alpha, and PGE2) compared with stomachs exposed to water or 25% ethanol alone; only mild irritant treated mucosa was protected from injury by 100% ethanol. Indomethacin pretreatment reversed the increased prostanoid synthesis in mucosa exposed to 100% ethanol, with or without mild irritant pretreatment, and partially reversed the protective effect of 25% ethanol. Other experiments using tissue slices in which perturbations in mucosal levels of prostanoids were measured by radioimmunoassay under identical experimental conditions exhibited similar results. These data dispute the notion that adaptive cytoprotection is mediated by increased endogenous prostanoid synthesis. The partial reversal of this process by indomethacin was most likely secondary to some other action of this agent, such as a reduction in gastric blood flow, rather than direct effects on prostanoid synthesis.

Animals

Preclinical toxicity studies of an adenosine agonist, N-(2,2-diphenylethyl) adenosine.

N-(2,2-Diphenylethyl)adenosine (DPEA) has been identified as a potential antipsychotic agent acting via stimulation of adenosine receptors. The projected human therapeutic dose, based on animal studies, is 2-3 mg/kg. DPEA has been tested for potential toxicity in mice, rats, dogs and monkeys. Following single oral doses, median lethal dose values were approximately 10-fold greater in rats than in mice, although similar clinical signs including reduced activity, prostration, and necrosis of the tail were seen in both species. DPEA was well tolerated at daily doses up to 40 mg/kg in rats for 2 weeks. A no observed effect level (NOEL) was not identified in the dog or monkey studies. Reduced activity, dacryorrhea, ptosis, hypothermia, necrosis of the tail, and death occurred in rats given 120 and 160 mg/kg. Pathologic changes consisted of pancreatitis, gastric erosion/ulceration, lymphocyte depletion of the thymus, and pulmonary congestion and hemorrhage at 80 mg/kg or greater. In dogs, sporadic emesis was noted at 12.5 mg/kg and greater, and significant pathologic changes consisted of coronary arteritis associated with myocardial lesions and lymphocyte depletion at 25 and 50 mg/kg, pancreatic acinar necrosis at 50 mg/kg, and renal tubular degeneration at 12.5 mg/kg and greater. Emesis and depression were noted at 25 and 50 mg/kg in monkeys. Renal tubular dilatation and degeneration at 25 and 50 mg/kg were noted in the monkeys. These studies demonstrated that DPEA produced a range of adverse effects in common laboratory animal species.

Adenosine

Protection against ethanol injury in the canine stomach: role of mucosal glutathione.

The present study determined the role that mucosal glutathione (GSH) levels play in mediating the protective effects of a prostaglandin and a mild irritant against alcohol-induced gastric injury. An in vivo canine chambered stomach preparation was used in which the exteriorized mucosa was partitioned into two equal halves, one serving as control. Animals (5-8/group) received a subcutaneous injection of either normal saline (NS) or the GSH depletor N-ethylmaleimide (NEM; 50 mg/kg) and then were assigned to one of a variety of groups based on the perfusate used to bathe the experimental side of the chamber; NS bathed the control mucosa. At completion of the studies, mucosa from each side of the chamber was assayed for total GSH (mumol/g wet wt) and evaluated for microscopic damage. Both 16,16-dimethyl prostaglandin E2 (PGE2) (1 microgram/ml) and the mild irritant 8% ethanol, when topically applied to the gastric epithelium, increased mucosal GSH levels by approximately 20% compared with control values, and elicited no deleterious effects to the mucosa. Treatment of animals with NEM prevented these GSH effects by PGE2 and 8% ethanol without damaging the mucosa. Application of 40% ethanol to the mucosa markedly reduced levels of GSH and caused significant injury to the mucosal surface, much of it extending to the level of the gastric glands. When mucosa was pretreated with PGE2 or 8% ethanol before 40% ethanol exposure, deep gastric gland injury was virtually abolished. In animals receiving NEM, the protective effects of these agents against injury by 40% ethanol were prevented. Perturbations in tissue levels of GSH under these various experimental conditions failed to correlate histologically with the status of gastric mucosal integrity.

Animals