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Biomedical subjects

D Martin

Publications and source records attributed to D Martin.

At least 685 records · Page 38Linked to original sources
PubMed1987

Ventricular assist by cardiac cycle-specific increases in intrathoracic pressure.

Changes in intrathoracic pressure can influence cardiac performance by altering ventricular loading conditions. Since ventricular loading, both from systemic venous return (preload) and from left ventricular wall stress (afterload), varies during the cardiac cycle, we reasoned that appropriately placed, phasic, cardiac cycle-specific (synchronous) increases in intrathoracic pressure might augment ventricular ejection in acute ventricular failure. Recent studies in animals suggest that synchronous increases in intrathoracic pressure during systole increase ejection. We compared the hemodynamic effect of synchronous increases in intrathoracic pressure with similar increases delivered at random in the cardiac cycle in patients with congestive cardiomyopathy (n = 9). Intrathoracic pressure was estimated by measuring esophageal pressure. High-frequency jet ventilation (HFJV) synchronized with the electrocardiogram (synchronous HFJV) was compared with HFJV at a fixed frequency within 15 percent of the heart rate (asynchronous HFJV) and with intermittent positive-pressure breathing (IPPB) (tidal volume = 10 ml/kg; f = 15). All forms of ventilation resulted in the same mean airway pressure and esophageal pressure. Mean pulmonary arterial occlusion pressure and arterial pressure were constant in all conditions. Cardiac output was greater with synchronous HFJV than with either IPPB or asynchronous HFJV (4.5 +/- 0.7 L/min compared with 3.5 +/- 0.7 and 3.4 +/- 0.6 L/min [mean +/- SE], respectively; p less than 0.05). Mixed venous oxygen saturation covaried with cardiac output (p less than 0.05), such that calculated oxygen consumption remained constant for all conditions. We conclude that synchronous HFJV augments cardiac output more efficiently than do similar increases in intrathoracic pressure delivered randomly in the cardiac cycle.

Adult↗
PubMed1987

Changes in ethanol concentration during incubation in multiwell tissue culture trays.

Ethanol can have direct effects in tissue culture and is often used as a solvent. Analysis of these effects will require a precise knowledge of the concentration over time in the particular system employed. We measured the disappearance rate of ethanol from multiwell culture trays (open system) containing single or multiple concentrations of ethanol over a 48-hr time period. The ethanol concentration was also measured at 72 hr in stoppered Erlenmeyer flasks (closed system). In multiwell culture trays, 1 and 0.3% ethanol (V/V) evaporated with a t1/2 of 6 to 12 hr. Media containing no ethanol but adjacent to wells with 1% ethanol accumulated ethanol with a peak of 0.2% at 12 hr. The evaporation of 0.3% ethanol was slower from wells adjacent to those containing 1% ethanol. At 72 hr, stoppered Erlenmeyer flasks, which originally contained 1% ethanol, still had a concentration of 0.85%. Since both evaporation and transfer can occur in an open system, it is necessary to specify precise conditions or measure concentrations in such systems. Alternatively, a closed system in which the concentration of ethanol is maintained can be employed.

Chemical Phenomena↗
PubMed1987

Noninvasive differentiation of carotid artery occlusion from high-grade stenosis.

The differentiation of high-grade carotid artery stenosis from occlusion can be a difficult but important diagnostic dilemma. The authors used a combination of duplex scanning, pulsed spectrum analysis, audible analysis of continuous wave doppler signal, and peri-orbital doppler compressions to accurately differentiate high-grade stenosis from occlusion in a series of 24 patients.

Arterial Occlusive Diseases↗
PubMed1986

Oligonucleotide duplexes containing inosine, 7-deazainosine, tubercidin, nebularine and 7-deazanebularine as substrates for restriction endonucleases HindII, SalI and TaqI.

Synthetic hexadecanucleotide duplexes containing a single purine nucleotide analogue in the recognition sites of the restriction endonucleases HindII, SalI and TaqI were used to investigate the restriction site determinants required by these enzymes for sequence recognition and phosphodiester bond cleavage. The enzymes were, in general, unaffected by changes introduced into the minor groove of the helix. SalI was found to be inhibited by the major groove modifications introduced into the fourth position of its recognition sequence GTCGAC. HindII and TaqI were, by contrast, able to cleave the sites containing the analogues at this position. TaqI and, to a lesser extent, HindII could also be shown to tolerate "mismatch analogues" at this site.

Base Sequence↗
PubMed1986

Guanine and adenine analogues as tools in the investigation of the mechanisms of mismatch repair in E. coli.

The efficiency of in vivo correction of five "mismatch analogues", incorporated into M13mp9 DNA, was studied in an attempt to elucidate the structural determinants required for mismatch recognition by the repair machinery of E. coli. Inosine was efficiently removed from an I/T mismatch, presumably by the action of hypoxanthine glycosylase. The mismatch analogues DI/T (DI = 7-deazainosine), Tu/C (Tu = tubercidin), N/C (N = nebularine) and DN/C (DN = 7-deazanebularine) were left largely unrepaired, giving rise to high yields of mutant phenotype. The efficiency of correction of these mismatch analogues could be correlated with their structure within the base-pair.

Adenine↗
PubMed1986

Restriction endonucleases HindII and TaqI cleave DNA with mismatched nucleotides within their recognition sequences.

Restriction endonucleases HindII and TaqI, but not SalI, were found to efficiently cleave synthetic hexadecanucleotide duplexes which contained either an A/C or a G/T mismatch within their respective restriction sites. Double-stranded M13 DNAs with identical mismatches were also cleaved under the assay conditions. These results suggest that the distortion of the DNA duplex, caused by these purine/pyrimidine mismatches is not sufficiently large so as to interfere with the recognition and the subsequent cleavage of the DNA by these two enzymes. HindII and SalI, but not TaqI, were furthermore shown to hydrolyze the two strands of the duplex with different rates. The differences between the mode of recognition of their respective restriction sites by these three enzymes are discussed.

Base Sequence↗
PubMed1986

Do kappa opioids mimic sigma agonists as amino acid antagonists?

The kappa opioids tifluadom and U-50,488 H, when tested on spinal neurones of rats in vivo and frogs in vitro, had no selective effect on responses to microelectrophoretically or bath applied N-methyl-D-aspartate, quisqualate or kainate. In the same preparations ketamine selectively reduces responses to N-methyl-D-aspartate. Amino acid antagonism by dissociative anaesthetics and sigma opioids is thus not mediated by that binding site which kappa and sigma opioids have been reported to have in common.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1986

Cardiovascular depression secondary to ionic hypocalcemia during hepatic transplantation in humans.

Cardiovascular function, serum ionized calcium (Ca+2), and serum citrate were measured intraoperatively in patients (n = 9) undergoing orthotopic hepatic homotransplantation. Serum citrate increased 20-fold (P less than 0.0006) following transfusion of citrated blood products in the absence of a functional liver. Serum ionized calcium decreased (P less than 0.003) with concomitant decreases in cardiac index (P less than 0.005), stroke index (P less than 0.004), and left ventricular stroke work index (P less than 0.001). Hemodynamic depression and ionic hypocalcemia were reversed following the administration of CaCl2. In contrast to patients with normal hepatic function, who may tolerate large amounts of citrated blood, patients with end-stage liver disease demonstrate acute ionic hypocalcemia with concomitant hemodynamic depression when receiving citrated blood products during the course of hepatic transplantation.

Calcium Chloride↗
PubMed1986

REM latency and core temperature relationships in primary depression.

REM latency and rectal and ear canal temperature were studied simultaneously in 11 controls and nine depressed patients; seven of the patients were studied when recovered. REM latency was shorter in the depressed group compared with controls and lengthened with recovery. The nocturnal and ear canal temperatures were higher in the depressed group compared with controls and decreased with recovery. REM latency and the nocturnal rectal temperature were negatively correlated when all the nights of the depressed patients were analyzed (r = -0.44) and when all the nights of the subjects were analyzed (r = -0.44). REM latency and nocturnal ear canal temperatures were negatively correlated when all the nights of the control group were analyzed (r = -0.34). The timing of the temperature rhythm did not appear to be correlated with the REM latency.

Adult↗
PubMed1986

Prevalence of anxiety disorders in patients with mitral valve prolapse.

Most previous research on mitral valve prolapse investigated its prevalence in patients whose primary diagnosis was one of the anxiety disorders. This study explored the inverse, i.e., the prevalence of anxiety disorders in patients manifesting mitral valve prolapse. There were no significant differences between patients (N = 48) and control subjects (N = 49) in panic disorder, phobic disorder, or generalized anxiety disorder or in the Zung depression score. The patient group scored significantly higher than control subjects on the Zung Anxiety Scale but significantly lower than Zung's patients with "anxiety neurosis". These results cast doubt on the hypothesis that mitral valve prolapse is etiologically related to the pathogenesis of the anxiety disorders.

Adolescent↗
PubMed1986

Oxygen radical-mediated lung damage associated with alpha-naphthylthiourea.

Lungs were damaged with alpha-naphthylthiourea (ANTU) and various compounds were used to block its effect. Although the results are variable, superoxide dismutase, catalase and dimethylsulfoxide all protected against ANTU, indicating that OH radicals are responsible for this type of lung injury. Leukocytes do not appear to be required for the damage to occur; however, hydroxurea (given over 2 days) did block the ANTU damage when neutrophils were decreased to 1/2 normal values or when administered acutely. The free radicals may be generated by the cyclooxygenase pathway since ibuprofen blocked the ANTU damage, whereas blocking xanthine oxidase using allopurinol failed to prevent the lung damage.

Animals↗
PubMed1986

Adherence of gram-positive and gram-negative bacterial strains to human lung fibroblasts in vitro.

The adherence to eukaryotic cells of Escherichia coli, Neisseria gonorrhoeae, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis and the yeast Candida albicans was studied by light microscopy with an in vitro micromethod involving different cell lines. The method is inexpensive, consumes little time and material, and is reproducible. It was used to show that the gram-positive Cowan I strain of S. aureus, which naturally forms protein A on its surface, adheres in much larger numbers to human lung fibroblasts than the protein A-free Wood 46 strain, the strain of S. epidermidis, and the encapsulated Smith strain. The presence of a capsule on the latter strain apparently prevented its attachment to the fibroblasts. Among the gram-negative species studied, a piliated clinical isolate of N. gonorrhoeae, displaying the opaque colonial phenotype, adhered in larger numbers than another isolate lacking pili and displaying the transparent phenotype. E. coli K12 attached slightly to the cell line, whereas P. aeruginosa adhered to it moderately. One strain of C. albicans tested did not attach in any detectable numbers. No clear correlation between bacterial cell surface hydrophobicity, as evaluated by the hexadecane assay, and adherence to eukaryotic cells could be demonstrated for these microorganisms. With our method, bacterial attachment proceeded best at 37 degrees C and did not require more than 1 h of contact with the cell monolayer. The method described revealed differences in the adherence to eukaryotic cells, not only among species, but also between strains of the same species.

Candida albicans↗
PubMed1986

Renal vein entrapment syndrome: frequency and diagnosis. A lesson in conservatism.

Two boys investigated for gross hematuria and left loin pain were found on ultrasound (US) to have left renal vein (LRV) entrapment associated with isomorphic urinary red blood cells, but normal renal venograms. Over the next 18 months ten children with gross hematuria were investigated and two more boys were discovered with the LRV entrapment syndrome, i.e., isomorphic red cells and a diagnostic US. Venography has a low yield in detecting renal venous compression, and since urinary red cell morphology may localize the origin of renal bleeding, we strongly recommend simple procedures, i.e., phase microscopy and renal US to evaluate all cases of hematuria before employing invasive or radiation dependent investigations. Since there is a range of LRV compression and associated dilatation in asymptomatic patients, strict criteria must be applied to diagnose renal vein entrapment.

Adolescent↗