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Biomedical subjects

M Davis

Publications and source records attributed to M Davis.

At least 379 records · Page 21Linked to original sources
PubMed1990

Emergency cardiopulmonary bypass support in patients with cardiac arrest in the catheterization laboratory.

Cardiac arrest in the catheterization laboratory is fatal if unresponsive to advanced cardiac life support (ACLS). Seven patients not responding to ACLS following cardiac arrest in the catheterization laboratory underwent percutaneously instituted cardiopulmonary bypass support. Cardiac arrest occurred following abrupt closure postcoronary angioplasty in three patients, during cardiogenic shock in three patients, and during diagnostic angiography in one patient. Cardiopulmonary bypass was instituted 10-45 min (mean, 21 min) following the onset of cardiac arrest. Flows on bypass ranged from 4.0 to 5.2 liter/min. Mean blood pressure ranged from 70 to 110 mm Hg on bypass. Six of the seven patients regained consciousness after the institution of bypass. Acid-base balance was normalized in all patients. Coronary bypass surgery was subsequently performed in three patients and coronary angioplasty in two. Four patients survived. One patient died following coronary bypass surgery. Two patients, who were not suitable candidates for revascularization, expired. Total bypass time was 1.5-8.5 hr (mean, 2.7 hr). At a mean follow-up of 6 months, all four survivors are alive and asymptomatic or NYHA class 1. We conclude that cardiopulmonary bypass support 1) can stabilize patients following cardiac arrest in the catheterization laboratory, 2) can facilitate emergency coronary angioplasty or transfer to the operating room for coronary bypass surgery, and (3) can improve survival in patients unresponsive to ACLS when instituted early following cardiac arrest in the catheterization laboratory.

Aged↗
PubMed1990

Percutaneous choledochoscopic choledocholithotomy in Caroli's disease.

Communicating cavernous ectasia of the intrahepatic bile ducts (Caroli's disease) is frequently accompanied by calculus formation. Percutaneous choledocholithotomy was successfully performed using a choledochoscope in a young adult with multiple calculi. To our knowledge this is the first reported case of choledocholithotomy using this technique in Caroli's disease.

Adult↗
PubMed1990

Apomorphine disrupts the inhibition of acoustic startle induced by weak prepulses in rats.

Separate experiments conducted in two different laboratories assessed the importance of the prepulse intensity in the ability of apomorphine to reduce prepulse inhibition of acoustic startle responses. Rats were presented with noise bursts alone or noise bursts 100 ms after presentation of prepulse stimuli ranging from 70 to 85 or 90 dB. Throughout testing, the background noise was maintained at 65 dB. In both laboratories, apomorphine markedly decreased the absolute magnitude of prepulse inhibition when the prepulse stimuli were no more than 10 dB above the background. With more intense prepulse stimuli, apomorphine had no significant effect on prepulse inhibition. Hence, apomorphine does not interfere with the inhibitory process which actually mediates prepulse inhibition, but appears to affect the detectability of the prepulse.

Acoustic Stimulation↗
PubMed1990

Percutaneous cardiopulmonary bypass support in the catheterization laboratory: technique and complications.

A safe and easily applied technique of percutaneous cardiopulmonary bypass support has been developed for use in the cardiac catheterization laboratory. The importance of this technique lies in its ability to maintain hemodynamic stability during high risk interventional procedures regardless of intrinsic cardiac function. Venous and arterial cannulas (18F) are inserted percutaneously over a stiff guide wire after sequential dilatation with 12F and 14F dilators. Bypass flow rates of up to 5 L/min can be achieved. This technique can be applied to support patients with cardiac arrest, hemodynamic collapse after abrupt closure during coronary angioplasty, and cardiogenic shock, as well as those undergoing high-risk elective coronary angioplasty. This form of support also permits transport of the patient to the operating room in a stable condition after an unsuccessful angioplasty. The complications are mostly related to cannula removal and can be minimized by the use of a proper technique. Although the ultimate role of this new technique remains to be completely defined, it appears that it will expand the patient population for whom coronary interventions can be applied.

Angioplasty, Balloon, Coronary↗
PubMed1990

The liver of MRL/lpr mice contains defective accessory cells and a population of immunosuppressive lymphocytes.

Immunoregulatory abnormalities in the MRL/lpr mouse strain include activation of macrophages and hepatic natural killer cells, spontaneous production of tumor necrosis factor, defective oral tolerance, and impaired production of interleukin-2. Because the liver is the major organ responsible for the clearance, degradation, and presentation of foreign antigens from the gastrointestinal tract, we have investigated antigen presentation activity of hepatic nonparenchymal cells (NPC) from MRL/lpr, MRL/++, and C3H/HeN female mice in the primary immune response as measured by stimulation of allogeneic one-way mixed lymphocyte response (MLR), and allogeneic cell-mediated lympholysis (CML). Whereas adherent NPC from C3H/HeN, MRL/++, and young MRL/lpr mice were effective stimulators, NPC from MRL/lpr mice older than 9 weeks were defective stimulators of both MLR and CML responses. This abnormality was not observed in splenic accessory cells from these mice. Moreover, a population of hepatic NPC from older MRL/lpr mice are immunosuppressive: mixing of MRL/lpr NPC with splenic stimulators from MRL/++ mice profoundly inhibited primary allogeneic CML responses. The inhibitory hepatic nonparenchymal cell population was nonadherent, radioresistant and was removed by pretreatment with antibodies to either asialoAGM-1 or Lyt-2 plus complement. This inhibition was not observed with the addition of MRL/++ NPC or supernates from cultured MRL/lpr NPC. These findings suggest a selective organ-specific and age-dependent impairment of antigen presentation and the presence of an immunosuppressive lymphocyte population in the liver of MRL/lpr mice which may contribute to the autoimmune process.

Age Factors↗
PubMed1990

Enhancement of electrically elicited startle by amygdaloid stimulation.

Previous experiments showed that acoustic startle amplitude can be enhanced by electrical stimulation of the amygdala. Because the acoustic startle pathway is organized in a serial fashion, startle can be elicited electrically with progressively shorter latencies by stimulating different points along this pathway [i.e., ventral cochlear nucleus (VCN), paralemniscal zone (PLZ), nucleus reticularis pontis caudalis (RPC) or medial longitudinal fasciculus (MLF)]. The present study evaluated the temporal characteristics of the facilitatory effect of amygdaloid stimulation on startle elicited electrically from different points along the acoustic startle pathway. A single 0.1-msec pulse was delivered to the central nucleus of the amygdala at various times before the onset of a 1-msec pulse in various sites in the startle pathway. The shortest amygdaloid stimulation-startle onset interval to significantly enhance startle was 0 msec for the VCN, 2 msec for the PLZ, 3 msec for the RPC and 7 msec for the MLF. These results indicate that amygdaloid stimulation enhances electrically elicited startle in a temporal manner that is complementary to facilitation of acoustic startle. The similarity of amygdala-stimulated enhancement and fear potentiation of electrically elicited startle is also discussed.

Acoustic Stimulation↗
PubMed1990

Animal models of anxiety based on classical conditioning: the conditioned emotional response (CER) and the fear-potentiated startle effect.

Stimuli consistently paired with shock become capable of suppressing ongoing operant or consummatory behavior (the conditioned emotional response--CER) or elevating the amplitude of the startle reflex (fear-potentiated startle). These changes are used to infer a central state of fear which involves the central nucleus of the amygdala and its efferent projections to the brainstem. The present paper reviews how psychoactive drugs affect these measures. Both the CER and fear-potentiated startle are reduced by benzodiazepines, barbiturates and opiates. Advantages and disadvantages of these animal tests of anxiety are discussed.

Animals↗
PubMed1990

Reversible neural inactivation by cooling in anesthetized and freely behaving rats.

The design and use of a miniaturized cryoprobe to allow reversible neural inactivation were investigated in the rat. Tissue temperature measurements around the cryoprobe in the cerebellum of anesthetized rats established that significant heat loss (lower than 20 degrees C) was localized within 1.5 mm of the cryoprobe tip. To physiologically test the effectiveness of the cryoprobe, two specific behaviors mediated by well defined neural structures were measured; electrically elicited hindleg flexion in ketamine-anesthetized rats, mediated by the pyramidal tract; and the acoustic startle reflex in freely behaving rats, mediated by the ventral nucleus of the lateral lemniscus. Cooling of the pyramidal tract at a tip temperature of -5 degrees C reversibly blocked electrically elicited hindleg flexions within about 21 s. Cooling of the ventral nucleus of the lateral lemniscus at 0 degrees C reversibly blocked the acoustic startle reflex. These effects were obtained when the cryoprobe tip was within 0.5 mm of the respective neural targets. The results suggest that cooling produces fully reversible neural blockade with a very rapid onset and offset. The advantages and limitations of cooling in the rat are discussed.

Anesthesia↗
PubMed1990

Oxytocin-stimulated inositol phosphate turnover in endometrium of ewes is influenced by stage of the estrous cycle, pregnancy, and intrauterine infusion of ovine conceptus secretory proteins.

Three experiments (Exp) assessed the influence of stage of the estrous cycle, pregnancy, and intrauterine infusion of ovine conceptus secretory proteins (oCSP) on turnover of inositol trisphosphate (the putative second-messenger for oxytocin-stimulated secretion of prostaglandin F2 alpha) in ovine endometrium during luteolysis and maternal recognition of pregnancy. In Exp 1, endometrium was collected from 5 cyclic (Cy) and 6 pregnant (P) ewes on Day 16 after onset of estrus. In Exp 2, endometrium was collected from Day 12 Cy (n = 5), Day 12 P (n = 3), Day 16 Cy (n = 4), and Day 16 P (n = 3) ewes. In Exp 3, 12 Cy ewes were allotted randomly, in a 2 x 2 factorial arrangement, to receive serum protein (SP), or oCSP and estradiol-17 beta (E2), or vehicle treatments. Ewes were injected i.v. with 0.5 mg E2 or vehicle on Day 12 and received twice-daily infusions of 1.5 mg SP or oCSP (containing 25 micrograms ovine trophoblast protein-1 by radioimmunoassay [RIA]) + SP (1.5 mg total protein) into each uterine horn on Days 12, 13, and 14. Blood samples for RIA of plasma progesterone were collected on Days 10-15 (before treatment on each day) and endometrium was collected on Day 15. For each Exp, 100 mg endometrium was incubated, in duplicate, for 2 h with 10 microCi [3H] inositol and treated with 0 or 100 nM oxytocin (OT) for 20 min, then [3H]inositol mono-, bis-, and trisphosphates (IP1, IP2, and IP3, respectively) were quantified.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Radionuclide imaging of a rectus sheath hematoma caused by insulin injections.

CT scanning, MRI, and ultrasonography are the imaging procedures of choice for the study of rectus sheath hematomas. A rectus sheath hematoma was evaluated scintigraphically after the intravenous administration of Tc-99m labeled RBC, which confirmed the hematoma, demonstrated the sites of bleeding, and revealed continued bleeding.

Abdominal Muscles↗
PubMed1990

DQw7 and the C4B null allele in rheumatoid arthritis and Felty's syndrome.

DQ beta and C4 null alleles have been defined in patients with rheumatoid arthritis, Felty's syndrome, and in control subjects. Comparison of DR4 positive subjects shows that rheumatoid disease without extra-articular features has no preferential associations with either DQ beta or C4 null variants. In Felty's syndrome there are significant associations with both the class II major histocompatibility complex (MHC) DQw7 allele (86% of DR4 positive patients with Felty's syndrome and 53% of DR4 positive controls) and the class III MHC C4B null allele (50% of patients with Felty's syndrome and 20% of DR4 positive controls). DQw7 and the C4B null allele are in linkage disequilibrium and the B44-Bf *S-C4A*3-C4B*Q0-DR4-DQw7 haplotype accounts for five of 24 DR4 positive haplotypes assigned in subjects with Felty's syndrome. The results were not accounted for by articular disease severity and suggest that articular and extra-articular forms of rheumatoid disease may be immunogenetically heterogeneous.

Alleles↗
PubMed1990

Lipid peroxidation and hepatic antioxidants in alcoholic liver disease.

The generation of hepatic liver peroxidation by free radicals has been proposed as a mechanism for ethanol induced hepatotoxicity. To investigate this hypothesis, lipid extracts from hepatic needle biopsy specimens from alcoholic subjects were examined for evidence of lipid peroxidation by measuring total conjugated dienes by derivative spectroscopy and, after hydrolysis of hepatic lipid extract and reverse phase high performance liquid chromatography, the molar ratio between a diene-conjugated linoleic acid isomer (18:2 (9,11)) and the parent linoleic acid isomer (18:2(9,12)). Changes were related to hepatic histology, iron deposition, glutathione and vitamin E values. Derivative spectroscopy minima suggestive of diene conjugation were identified at 233 and 242 nm and correlated weakly, suggesting these two minima may represent different classes of lipid dienes. There was a weak relation with inflammatory histological changes in the biopsy specimen but no correlation with hepatic iron grade, glutathione, or vitamin E lipid ratio. The proportion of 18:2(9,11) linoleic acid in hepatic lipids correlated significantly with inflammatory histological features and inversely with hepatic glutathione. Furthermore, hepatic glutathione was lower in biopsy specimens with greater iron staining. The ratio of vitamin E to lipid was not related to histological group, inflammation, or iron grade. These findings suggest that excess alcohol consumption leads to hepatic inflammation and lipid peroxidation.

Antioxidants↗
PubMed1990

Value of a centralised approach in the management of haematemesis and melaena: experience in a district general hospital.

All patients presenting with acute upper gastrointestinal bleeding between November 1986 and April 1988 were admitted to a centralised joint medical/surgical unit, with a policy of early clinical and endoscopic assessment and rapid surgical intervention in those at high risk. Of the 430 patients admitted 69.5% were over the age of 60 and 30% had significant additional medical conditions. 50.4% were bleeding from peptic ulcers and one third had been taking non-steroidal anti-inflammatory agents. Fifty five patients underwent surgery, which in two thirds was carried out within 24 hours of admission, usually for continued bleeding. In patients with peptic ulcer the operation rate was 21.6%. Overall mortality was 3.7%, and in those with bleeding gastric or duodenal ulcers 5.5%; surgical mortality in the later group was 15.2%. All patients who died had serious concomitant pathology and 87% were over 70 years of age. Adoption of a centralised approach to management of haematemasis and melaena is feasible in a District General Hospital and associated with an improved survival.

Adult↗
PubMed1990

Comparison of omeprazole and cimetidine in reflux oesophagitis: symptomatic, endoscopic, and histological evaluations.

Symptomatic patients with endoscopically verified reflux oesophagitis were randomised to a double blind trial in which they received either omeprazole (20 mg once daily) or cimetidine (400 mg four times daily) for four, and if necessary, eight weeks. In an 'intention to treat' analysis, oesophagitis was found to have healed after four weeks in 77 of 137 (56%) in the omeprazole group and in 34 of 133 (26%) in the cimetidine group (p less than 0.001). By eight weeks these values were 71% and 35% respectively; p less than 0.001. Histological assessments were available for 73% of the patients. At entry, 63% (66 of 104) in the omeprazole group and 60% (56 of 94) in the cimetidine group (ns) had abnormal histology. After the study, the proportions of patients who initially had had abnormal histology but who then progressed to normal were 67% (44 of 66: omeprazole) and 48% (27 of 56: cimetidine) respectively (p less than 0.001). All patients had reflux symptoms at entry. After four weeks, 46% in the omeprazole group and 22% (p less than 0.001) in the cimetidine group were asymptomatic. Diary cards completed for the first two weeks showed that patients treated with omeprazole experienced fewer reflux symptoms by day and night and used fewer antacids. Omeprazole, 20 mg once a day for four to eight weeks, healed a greater proportion of patients with reflux oesophagitis than cimetidine, 1.6 g per day, assessed endoscopically and histologically, and relieved more patients' symptoms.

Cimetidine↗
PubMed1990

Measurement of conjugated diene lipids by derivative spectroscopy in heptane extracts of plasma.

A series of experiments are described which show that second derivative spectroscopy can be used to quantify conjugated lipid dienes as markers of lipid peroxidation in heptane extracts of plasma from patients with rheumatoid arthritis, osteoarthritis, and healthy controls. Results obtained by this method gave reasonable agreement with those derived from the measurement of simple absorbance in chloroform/methanol extracts. Two minima were observed in the derivative spectrum of plasma lipid extracts. These minima occurred at 233 and 241 nm and corresponded to absorbance maxima in the conventional UV spectrum. Using a combination of phospholipase hydrolysis, reverse phase high performance liquid chromatography (HPLC) and second derivative spectroscopy we confirmed that these two minima can be attributed to a single fatty acid (9 cis-, 11 trans-linoleic acid) shown previously to account for greater than 90% of diene conjugation in human plasma samples. When the biological isomer 9 cis-, 11 trans-linoleic acid was separated by reverse phase HPLC from the mixture of other plasma phospholipid-2-esterified fatty acids we observed a change in derivative spectroscopy minima from 233 and 241 nm to 228 and 237 nm. Minima at the latter two wavelengths were also seen with pure preparations of the Paint Research Isomer (9 trans-, 11 trans-linoleic acid) which eluted later than biological 9 cis-, 11 trans-linoleic acid using reverse phase HPLC, suggesting that the absorption spectra of these pure cis-, trans and trans, trans dienes are similar but can be altered by the presence of other fatty acids in the extract.

Adult↗