Biomedical subjects

M L Baker

Publications and source records attributed to M L Baker.

At least 19 recordsLinked to original sources

PubMed1999

Ontogeny of the immune system of the brushtail possum, Trichosurus vulpecula.

The numbers and distribution of T and B cells in the thoracic thymus, spleen and intestinal tissue and the proliferation of T lymphocytes were examined during pouch life and in the adult to determine when the developing brushtail possum reaches immunological maturity. CD3-positive cells were observed in the thoracic thymus at day 2 post-partum indicating that the thymus produces T lymphocytes at or soon after birth. By day 25 the thymus was fully populated with CD3-positive T lymphocytes and they were observed in distinct regions of the cortex and medulla. By day 48 post-partum, B and T lymphocytes were identified in the follicles and parafollicular areas of the spleen. Although the numbers of T and B cells in the spleen increased significantly from day 25 to day 100 post-partum (P < 0.005), fewer cells were present at day 150 post-partum than in the adult (P < 0.05). Peyer's patches were not observed in the intestines up to day 73 post-partum. However, both T and B cells were observed in the intestinal lymph nodes. Although the T lymphocytes at weaning showed a proliferative response, the response was not as great as that observed in the adult possum. Thus, the immune system of the possum is not fully developed at weaning but continues its development after pouch life.

Animals↗

PubMed1999

Physiological changes in the brushtail possum (Trichosurus vulpecula) following relocation from Armidale to Brisbane, Australia.

To determine the effect of relocation on the health of possums the body weights and hormone and immune responses of six male and nine female brushtail possums were monitored for 20 weeks following transfer from the environs of Armidale into enclosures in Brisbane. Over the first 6 weeks of captivity, male possums lost 11.0% of their original body weight and females lost 16.8%. The mean concentrations of plasma cortisol in the male and female possums were 14.5 and 29.4 ng/mL, respectively, and did not change over the 20-week period. Male and female possums displayed a similar pattern of thyroxine secretion over the 20 weeks, with low concentrations up to week seven (2.1 and 2.7 ng/mL, respectively) increasing to 6.9 and 5.8 ng/mL in weeks 7-12 (P < 0.005). This increase in the concentration of thyroxine corresponded with the increase in body weight. The number of white blood cells (WBCs) and the percentage of neutrophils increased from the capture to week 6-10. However, during the last 10 weeks of captivity the number of WBCs and the percentage of neutrophils decreased, indicating recovery of the immune system. This was in accord with the proliferative response of lymphocytes to the T cell mitogen PHA that increased from weeks 11-15 to weeks 16-20 in both male and female possums. The results above suggest that the Armidale possums, like the Brisbane possums, were stressed following their relocation; however, their immune systems were able to gradually recover as they adjusted to their new environment in Brisbane. The death rate of pouch young and of adult female possums after relocation was considerably higher in the Armidale possums compared to Brisbane possums. The mortality rate of Brisbane possums over the first 20 weeks of captivity was 8.3% and 19.6% for male and female possums, respectively, and for Armidale possums 16.6% and 47.1%, respectively. The possums transferred from the environs of Armidale into captivity in Brisbane were under greater stress than possums captured in Brisbane and placed in captivity in Brisbane.

Adaptation, Physiological↗

PubMed1998

Physiological changes in brushtail possums, Trichosurus vulpecula, transferred from the wild to captivity.

To determine the effect of relocation on the health of possums, the body weights and hormone and immune responses of 11 male and 9 female brushtail possums were monitored following transfer from the environs of Brisbane into an established breeding colony in Brisbane. The possums were monitored weekly for the first 20 weeks of captivity, and their immune responses assessed again 12 months after capture. Over the first 5 weeks of captivity, male possums lost a mean of 8.8% of their original body weight, and females lost 15.3% over the first 6 weeks. Variation between individual possums was evident, and the 11 male possums could be divided into two groups, those that gained weight (number of animals, N = 4) and those that lost weight (N = 7) in captivity. Four males gained weight following capture, and their body weight after 20 weeks of captivity was higher than at capture. The remaining seven males lost weight over the 20 weeks following introduction into captivity, resulting in a lower weight at week 20 than at capture. All of the nine female possums lost weight and were slower to regain weight compared to the males. Plasma cortisol concentrations did not vary greatly over the 20 weeks in male possums, and the mean plasma concentration of cortisol for the 11 male possums was 7.8 ng/ml (number of samples, n = 220). The female possums showed a different pattern. The concentration of cortisol for the nine female possums at week 1 was 34.0 ng/ml, which was significantly higher than 13.3 ng/ml at week 20 (P < 0.016). No significant variation in the mean concentration of plasma thyroxine of 5.7 ng/ml occurred in the 11 male possums over the 20-week period (n = 220). The plasma concentration of thyroxine for the nine female possums was 2.5 ng/ml (n = 54) for the first 6 weeks. At week 6, an increase in the concentration of thyroxine occurred, and a peak concentration of 6.9 ng/ml was reached at week 13. This increase correlated with the females regaining body weight. A low concentration of thyroxine is often associated with stress, thus an increase in the concentration of this hormone, combined with an increase in body weight, may indicate that these females had begun to adjust to their new environment. The seven male possums that lost weight following introduction into captivity displayed a significantly higher concentration of cortisol (9.1 compared with 5.3 ng/ml P < 0.01), and a lower concentration of thyroxine compared to the four males that gained weight following capture (4.7 compared with 7.3 ng/ml, P < 0.005). Over the 20-week period, the total number of white blood cells increased, and the number of neutrophils increased in both males and females. The proliferative response of lymphocytes from male possums to the T-cell mitogen, phytohaemagglutin (PHA) decreased significantly over the 20-week period (P < 0.002). In females an initial decrease in the reactivity of lymphocytes observed over the first 10 weeks was followed by an increase in this response over the remaining 10-week period. Twelve months following capture, the white blood cell parameters of both males and females had returned to similar levels to those of the first 1-5 weeks. The reactivity of lymphocytes from male possums that had been in captivity for 12 months was significantly higher than that of the first 20 weeks of captivity (P < 0.005). Females that had been in captivity for 12 months displayed lymphocyte responses similar to those observed at weeks 16-20. The body weight and hormonal results would suggest that possums undergo a more severe stress response than males immediately following their capture. In contrast, the immune response of males is lower than females and is depressed for a longer period following capture.

Animals↗

PubMed1998

Structure of double-shelled rice dwarf virus.

Rice dwarf virus (RDV), a member of the Reoviridae family, is a double-stranded RNA virus. Infection of rice plants with RDV reduces crop production significantly and can pose a major economic threat to Southeast Asia. A 25-A three-dimensional structure of the 700-A-diameter RDV capsid has been determined by 400-kV electron cryomicroscopy and computer reconstruction. The structure revealed two distinctive icosahedral shells: a T=13l outer icosahedral shell composed of 260 trimeric clusters of P8 (46 kDa) and an inner T=1 icosahedral shell of 60 dimers of P3 (114 kDa). Sequence and structural comparisons were made between the RDV outer shell trimer and the two crystal conformations (REF and HEX) of the VP7 trimer of bluetongue virus, an animal analog of RDV. The low-resolution structural match of the RDV outer shell trimer to the HEX conformation of VP7 trimer has led to the proposal that P8 consists of an upper domain of beta-sandwich motif and a lower domain of alpha helices. The less well fit REF conformation of VP7 to the RDV trimer may be due to the differences between VP7 and P8 in the sequence of the hinge region that connects the two domains. The additional mass density and the absence of a known signaling peptide on the surface of the RDV outer shell trimer may be responsible for the different interactions between plants and animal reoviruses.

Amino Acid Sequence↗

PubMed1996

Relationships between bilayer structure and phospholipase A2 activity: interactions among temperature, diacylglycerol, lysolecithin, palmitic acid, and dipalmitoylphosphatidylcholine.

Bilayers composed of phosphatidylcholine initially resist catalysis by phospholipase A2. However, after a latency period, they become susceptible when sufficient reaction products (lysolecithin and fatty acid) accumulate in the membrane. Temperatures near the main bilayer phase transition and saturated long-chain diacylglycerol in the bilayer modulate the effectiveness of the reaction products. The purpose of this study was to identify possible mechanisms for these effects of temperature and diacylglycerol. Various fluorescent probes were used to asses changes in the ability of the reaction products to perturb the bilayer and promote enzyme binding to he membrane surface. Temperature appeared to cause three effects. First, the degree of binding of enzyme at the end of the latency period was greatest near the phase transition temperature where the latency was shortest. Second, the bilayer was more sensitive to perturbation by reaction products near the transition. Third, the disturbance provoked by the products was confined to the membrane surface below the transition but affected deeper regions at higher temperature where the latency period was greater. The latter two effects of temperature required the presence of calcium. Diacylglycerol promoted lateral segregation of reaction products in the bilayer. This effect corresponded with the tendency of diacylglycerol to reduce the length of the latency period at temperature below the phase transition. Therefore, it appeared that temperature affects the latency period by alternating the binding of the enzyme and the depth and magnitude of the bilayer perturbation caused by reaction products. Alternatively, diacylglycerol may enhance the effectiveness of reaction products by inducing them to segregate in the bilayer and thus create local regions of increased impact on the bilayer surface.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1995

Effects of temperature and glycerides on the enhancement of Agkistrodon piscivorus piscivorus phospholipase A2 activity by lysolecithin and palmitic acid.

The effect of temperature and various glycerides to modulate the ability of lysolecithin and fatty acid to promote high phospholipase A2 activity was studied using dipalmitoylphosphatidylcholine large unilamellar vesicles as substrate. The length of the lag phase prior to the accumulation of sufficient hydrolysis products (lysolecithin and fatty acid) to support high phospholipase activity was shortest at temperatures near the thermotropic phase transition of the phospholipid substrate. A reduction in the lag phase correlated with a reduction in the requirement for hydrolysis products at the phase transition temperature, where the bilayer exists in a state of fluctuating domains of gel and liquid crystal. Dipalmitoylglycerol and tripalmitoylglycerol also reduced the length of the lag phase. This reduction was both concentration-dependent and temperature-dependent relative to the phase transition in the presence of the glycerides. As with the effect of temperature, the ability of di- and triglycerides to decrease the lag time correlated with a decrease in the amount of reaction products necessary to promote high phospholipase activity. This effect coincided with the tendency of the glycerides to form domains in the bilayer. Glycerides that did not form domains either had no effect (monopalmitoylglycerol) or increased the length of the lag phase (dicaprylglycerol). These data suggest that the effect of the reaction products to increase phospholipase A2 activity is aided by the presence of fluctuations in lipid domains within the bilayer.

Agkistrodon↗

PubMed1995

Enhancement of Agkistrodon piscivorus piscivorus venom phospholipase A2 activity toward phosphatidylcholine vesicles by lysolecithin and palmitic acid: studies with fluorescent probes of membrane structure.

The activity of phospholipase A2 from snake venom to hydrolyze bilayers of phosphatidylcholines is greatly enhanced by the presence of the hydrolysis products, lysolecithin and fatty acid, in the bilayer. The fluorescence of several probes of membrane structure was used to monitor changes in bilayer physical properties during vesicle hydrolysis. These changes were compared to emission spectra and fluorescence polarization results occurring upon direct addition of lysolecithin and/or fatty acid to the bilayer. The excimer to monomer ratio of 1,3-bis(1-pyrene)propane was insensitive to vesicle hydrolysis, suggesting that changes in the order of the phospholipid chains were not relevant to the effect of the hydrolysis products on phospholipase activity. The fluorescence of 6-propionyl-2-(dimethylamino)-naphthalene (Prodan) suggested that the polarity of the bilayer in the region of the phospholipid head groups increases as the hydrolysis products accumulate in the bilayer. The fluorescence of 6-dodecanoyl-2-(dimethylamino)naphthalene (Laurdan) confirmed that such effects were restricted to the bilayer surface. Furthermore, the lysolecithin appeared to be the product most responsible for these changes. These results suggested that lysolecithin increases the activity of phospholipase A2 during vesicle hydrolysis by disrupting the bilayer surface, making the phospholipid molecules more accessible to the enzyme active site.

2-Naphthylamine↗

PubMed1995

Cellular mechanisms involved in morphine-mediated suppression of CTL activity.

Based on a plethora of data from many laboratories, we have proposed the following mechanisms by which morphine alters immune homeostasis and immunocompetence in vivo (Fig. 2). Specifically, the administration of morphine subcutaneously via routing through blood interacts directly with opioid receptors on cells of the immune system or on receptors within the central nervous system. Although there is currently no evidence to support the direct involvement of morphine on lymphocyte opioid receptors, in vitro studies show the existence of functional, naloxone-sensitive opioid receptors (25). In addition, pharmacological and biochemical characterization of lymphocyte opioid receptors has been shown to be consistent in many instances, with the profile of neural-derived opioid receptors (25-27). Finally, recent molecular studies using oligonucleotide primers specific for the delta-class opioid receptor cloned from NG-108-15 cells (28) have been used in reverse transcription-polymerase chain reactions to generate a 400 bp product in SL which has 100% sequence homology with a published opioid receptor cloned from a brain library (35). However, future studies are necessary to establish the role of lymphocyte opioid receptors following the in vivo administration of opioids (e.g. fentanyl, methadone, and morphine). Since the administration of morphine subcutaneously appears to predominately interact with brain opioid receptors (3) located in the mesencephalon (5), other neuroendocrine systems become candidates for activation and subsequent direct modulation of immune function: (i) the HPA axis and (ii) the sympathetic nervous system (SNS).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Fentanyl-related 4-heteroanilido piperidine OHM3295 augments splenic natural killer activity and induces analgesia through opioid receptor pathways.

Recently, the fentanyl-related compound OHM3295 has been shown to induce a naltrexone-sensitive, dose-related analgesia in CD1 mice. However, unlike morphine or fentanyl, which are potent immunosuppressive drugs, OHM3295 has been found to augment splenic natural killer (NK) activity in a dose-related and naltrexone-reversible manner. The present study investigated the type (delta, kappa or mu) of opioid receptor involved in analgesia and immunomodulation after acute administration of OHM3295. CD1 mice pretreated with beta-funaltrexamine (beta-FNA, 40.0 mg/kg) showed an insignificant induction of analgesia (8.4 +/- 3.7%) after 3.2 mg/kg OHM3295, whereas mice pretreated with vehicle, norbinaltorphimine (10.0 mg/kg) or naltrindole (20.0 mg/kg) exhibited 43.6 +/- 12.6% of maximal analgesia, as determined by the tail-flick latency test. Consistent with previous results, acute administration of OHM3295 (3.2 mg/kg) augmented splenic NK activity (20.7 +/- 3.4 lytic units [LU]) relative to vehicle-treated mice (8.2 +/- 0.7 LU). Pretreatment with beta-FNA (40.0 mg/kg) completely blocked (9.0 +/- 1.9 LU) OHM3295-mediated augmentation of NK activity, whereas pretreatment with norbinaltorphimine (10.0 mg/kg) partially blocked (15.8 +/- 2.2 LU) the drug-induced effect. However, pretreatment with naltrindole (20.0 mg/kg) did not antagonize OHM3295-induced increases in splenic NK activity but rather further enhanced (32.3 +/- 4.2 LU) the effect. NK-enriched effector cells from OHM3295-treated mice displayed an increase in conjugation with YAC-1 target cells, an increase in the percent killing of target cells and a significant increase in the number of active killer cells compared with NK-enriched effector cells from vehicle-treated mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesics↗

PubMed1994

Significance of overall treatment time for the development of radiation-induced intestinal complications. An experimental study in the rat.

BACKGROUND: Late normal tissue reactions generally are believed to be independent of treatment time. However, previous studies suggest a relationship between acute mucosal injury and development of intestinal obstruction and enterocutaneous fistula formation. Thus, the pathogenesis of late intestinal complications may be complex, and mucosal cell proliferation during treatment may be important. This study assessed the influence of overall radiation treatment time on development of intestinal injury and complications after localized fractionated irradiation of rat ilium. METHODS: Ninety-four male rats underwent orchiectomy, and a loop of small intestine was transposed to the scrotum. Orthovoltage irradiation was administered to the transposed, but functionally intact, intestine using 9 fractions of 5.6 Gy with interfraction intervals of 24, 48, or 72 hours. The animals were observed for complications and killed in groups 2 and 26 weeks after irradiation for assessment of injury. Incidence of intestinal complications and quantitative and semiquantitative histopathologic assessment of injury were used as endpoints. RESULTS: Increasing total treatment time by extending interfraction intervals from 24 to 48 hours significantly reduced radiation injury and the incidence of intestinal complications. Differences in mucosal and fibrotic changes were most prominent. No significant differences were found between groups with interfraction intervals of 48 and 72 hours. CONCLUSIONS: Overall treatment time significantly influenced development of chronic radiation enteropathy. Thus, rapidly proliferating cells, as found in the intestinal mucosa, appear to be involved in the pathogenesis of intestinal complications. This probably represents consequential damage secondary to disruption of mucosal integrity.

Animals↗

PubMed1994

Prevention of chronic radiation enteropathy by dietary glutamine.

BACKGROUND: Nearly 50% of all cancer patients receive therapeutic radiation during the course of their disease. The risk of late complications is the main dose-limiting factor in the delivery of radiation therapy. The small intestine, the major site of chronic radiation enteropathy, is also the principal organ of glutamine consumption. We therefore hypothesized that the provision of supplemental glutamine may have a protective effect on the development of chronic radiation enteropathy. METHODS: This study evaluated the effects of supplemental oral glutamine on the development of chronic radiation (XRT) enteropathy. After scrotalization of a loop of small intestine, rats were randomized to receive 1 g/kg/day glutamine (GLN) or glycine (GLY) by gavage. After 2 days of prefeeding, rats were randomized to 1 of 4 groups: GLN + XRT (n = 10), GLY + XRT (n = 10), GLN only (n = 10), GLY only (n = 10). Twenty Gy was delivered to the scrotalized bowel in the GLN + XRT and GLY + XRT groups via a collimated beam. Gavage was continued for 10 days. Animals were then pair-fed chow. Rats were killed at 2 months postirradiation. Chronic radiation injury was assessed microscopically. RESULTS: Injury scores in GLN + XRT were similar to those of unirradiated bowel and significantly different from GLY + XRT (1.89 +/- 0.48 in XRT + GLN vs. 6.42 +/- 1.55 in the XRT + GLY, p < 0.01). Elevated Injury Scores in the XRT + GLY group correlated with gross thickening and fibrosis, a 10-fold decrease in gut GLN extraction (1.40 +/- 4.3% in GLY + XRT vs. 16.0 +/- 5.1% in GLN + XRT, p < 0.05), and a 30% decrease in glutathione content (2.46 +/- 0.19 and GLY + XRT vs. 3.17 +/- 0.17 GLN + XRT, p < 0.05). CONCLUSIONS: Provision of GLN during abdominal/pelvic XRT may prevent XRT injury and decrease the long-term complications of radiation enteropathy.

Administration, Oral↗

PubMed1994

OHM3295: a fentanyl-related 4-heteroanilido piperidine with analgesic effects but not suppressive effects on splenic NK activity in mice.

The immunoregulatory effects of fentanyl and a fentanyl-related compound, OHM3295, were studied in mice. Male CD1 mice treated with a range of fentanyl doses (0.1-1.0 mg/kg, subcutaneously) showed suppression of splenic natural killer (NK) activity following 0.25-0.50 mg/kg fentanyl dose but not higher (0.75-1.0 mg/kg) or lower (0.1 mg/kg) doses. Fentanyl (0.01-32.0 mg/kg) also induced dose-related analgesia as measured by an increase in tail flick latency; these analgesic effects were antagonized by naltrexone (1.0-10.0 mg/kg). Pretreatment with naltrexone (1.0-3.2 mg/kg) resulted in significant suppression of splenic NK activity following fentanyl (10.0-32.0 mg/kg) administration. In comparison to fentanyl, OHM3295 (3.2-25.0 mg/kg) augmented splenic NK activity in a naltrexone-reversible manner. Similar to fentanyl, OHM3295 (1.0-32.0 mg/kg) also induced a naltrexone-sensitive, dose-related analgesia as measured by an increase in tail flick latency. These results with OHM3295 demonstrate a novel profile of effects which includes naltrexone-sensitive analgesic effects in the absence of immunosuppressive effects. In addition, this is the first reported case in which a compound with opioid analgesic effects has been shown to potentiate natural killer cytolytic activity following in vivo administration.

Analgesics↗

PubMed1993

Serum levels of mullerian inhibiting substance in boys throughout puberty and in the first two years of life.

Serum levels of Mullerian inhibiting substance (MIS) have been measured in 91 boys throughout normal pubertal development. MIS levels fell sharply after pubertal stage 1 and were mostly undetectable at pubertal stage 6. The relationship between MIS concentration and pubertal stage was similar when compared with age. Seven patients with precocious puberty and 12 with delayed puberty were also investigated and found to have MIS levels consistent with their degree of pubertal development. Precocious puberty was associated with MIS levels that were abnormally low for age, while delayed puberty resulted in persistence of high MIS levels. Serum MIS levels were also measured in 29 boys less than 2 yr of age undergoing minor surgery. High levels were found throughout this time period, which is consistent with previous reports. MIS levels appear to be inversely related to levels of gonadotropins, steroids, and inhibin, which fall in the first 2 yr of life and rise throughout puberty.

Adolescent↗

PubMed1993

Induction of tolerance to and physical dependence on pentobarbital continuous intracerebroventricular administration.

A new model of barbiturate tolerance and dependence was developed using i.c.v. infusion of pentobarbital. Male Harlan Sprague-Dawley rats weighing 250 to 300 were implanted with i.c.v. cannulae and infused with sodium pentobarbital (500 micrograms/10 microliters/hour) for 6 days. The pentobarbital-infused group had a shorter duration of pentobarbital-induced loss of righting reflex than the saline-infused group. When i.c.v. pentobarbital- and saline-infused rats were injected with sodium pentobarbital (60 mg/kg i.p.), the time course of pentobarbital levels in the serum and in the brain were not significantly different. The infusion of pentobarbital also did not induce hepatic drug-metabolizing enzymes. The depth of thiopental-induced hypothermia was decreased by i.c.v. pentobarbital infusion. During the course of the infusion, the basal body temperature of the pentobarbital-infused rats did not change. Two days after the infusion was discontinued, the basal body temperature was elevated. The increase in body temperature lasted for 8 days. Twenty-four hours after the infusion was discontinued, the pentobarbital-infused rats had a significantly shorter onset of t-butylbicyclophosphorothionate (TBPS)-induced convulsions. These studies show that i.c.v. infusion can be used to induce pentobarbital tolerance and dependence. This model has the advantage that issues related to induction of hepatic drug-metabolizing enzymes are eliminated, and it may be useful in the study of barbiturate addiction.

Animals↗

PubMed1992

The acceleration of gallstone destruction with synchronous biliary lithotripsy and contact dissolution in vitro using three cholesterol-solubilizing solvent.

In the first-known application of its kind, shockwave lithotripsy and contact-solvent dissolution of large, calcified gallstone burdens were performed simultaneously with three chemical solvents, each tested separately in an in vitro model, with the combined effects on gallstone eradication examined. Two solvents, ethyl propionate and isopropyl acetate, were chosen for their solubilizing ability and potentially high level of patient safety. The third solvent, a 70%:30% mixture of methyl tert-butyl ether (MTBE) and dimethyl sulfoxide (DMSO), was chosen for its known ability to accelerate the dissolution of calcium-containing gallstones. All stones were matched for size, weight, and number. Gallstone lithotripsy performed in ethyl propionate was significantly more effective (P less than .02) in the production of fragments less than 2 mm when compared with bile; lithotripsy with isopropyl acetate and the MTBE/DMSO mixture showed no statistically significant effect. Biliary lithotripsy performed in an ethyl propionate medium may enhance gallstone dissolution and the production of small fragments (diameter less than 2 mm).

Acetates↗

PubMed1991

The effect of ionizing radiation on the viability of Trichomonas vaginalis.

1. The effects of continuous gamma radiation on the viability of Trichomonas vaginalis (ATCC 30001) were assessed by a colony count technique. 2. A triphasic survival curve showed an initial shoulder (Dq) of 3 Gy followed by three linear curves with D0 values of 34, 300, and 90 Gy. 3. Sterilization of 10(6) cells/ml occurred from 1600 to 1800 Gy of radiation. 4. Population growth, subsequent to radiation exposure of 17-100 Gy, showed an increased lag time followed by a faster rate of growth, compared with unirradiated cells. 5. Trichomonas vaginalis is more sensitive to ionizing radiation than free-living protozoa and appears as radiosensitive as those parasitic protozoa examined in radioattenuation experiments.

Animals↗

PubMed1991

Axis fracture in ankylosing spondylitis: case report.

Ankylosing spondylitis is a chronic inflammatory disease that results in the slow progressive transformation of the normal spine into a rigid and brittle tube containing the normal neural elements. This pathological condition predisposes the patient to fractures of this structure and a potential for neurological damage greater than that of the normal population. We present a spontaneous fracture of the C1-C2 complex through the base of the dens, with impending neurological deficits in such a patient. We have reviewed the pertinent literature and emphasized several points relative to the management of similar patients.

Axis, Cervical Vertebra↗

PubMed1991

In vitro cholesterol gallstone dissolution: comparison of methyl tert-butyl ether with three new ester solvents.

The in vitro effectiveness of three new cholesterol gallstone solvents that have a potential for clinical use--ethyl propionate, isopropyl acetate, and n-propyl acetate--was compared with that of the well-known cholesterol solvent methyl tert-butyl ether (MTBE). Ten sets of matched gallstones were initially weighed, imaged with radiography and computed tomography (CT), and analyzed for content. One stone from each set was incubated in one of the four solvents at 37 degrees C. Solvents were changed at 30-minute intervals. The study was stopped either when the stones were completely dissolved or at the end of 7 hours. Any residual fragments were weighed, reimaged, and reanalyzed for content. There were no statistical differences between dissolution times of the stones in MTBE compared with those in the three new solvents. Ethyl propionate and n-propyl acetate appear to be as efficacious as MTBE in dissolving cholesterol stones and could be attractive alternatives for gallstone chemolysis.

Acetates↗