Biomedical subjects
A Simpson
Publications and source records attributed to A Simpson.
Evaluation of a method of simulating reduced frequency selectivity.
The accuracy of a method of simulating reduced frequency selectivity by the spectral smearing of complex stimuli has been evaluated. First an excitation pattern that would be evoked by a given nonsmeared stimulus in an impaired ear with broad auditory filters was estimated. Then the spectral smearing of the stimulus that would be necessary to create the same excitation pattern in a normal ear was calculated. The smearing was based on the shapes of simulated broad auditory filters; both symmetric and asymmetric broad filters were simulated. The method was used to process notched noise, and tones in notched noise, and the processed stimuli were used in a series of experiments with normally hearing subjects measuring the threshold for the tone in notched noise. The resulting data were used to derive auditory filter shapes. The derived filter shapes were generally similar to the expected shapes (based on the type of spectral smearing used), but there were some systematic discrepancies and some individual differences. The discrepancies do not seem to be due to the use of information derived from phase locking, since they were observed both at 1 kHz (where phase locking occurs) and at 6 kHz (where phase locking probably does not occurs). The discrepancies also do not seem to be due to the transmission characteristics of the outer/middle ear, since they occurred both when these characteristics were taken into account in the fitting procedure, and when the stimuli were preshaped to compensate for these characteristics. The influence of the subjects' own auditory filters probably can explain some of the discrepancies; the excitation pattern evoked by the spectrally smeared stimuli can be significantly influenced by the subjects' own filters when those filters are not much sharper than the simulated filters used to produce the smeared stimuli. Finally, some of the discrepancies can probably be explained by subjects combining information across auditory filters, rather than just using the single 'best' filter in each condition; this represents a limitation of the fitting procedure rather than of the simulation itself. Overall, the simulation worked reasonably well, especially when the smearing was based on symmetric filters.
Cytomegalovirus infection during OKT3 treatment for renal allograft rejection.
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Molecular interactions in the eye lens.
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Susceptibility of Enterococcus faecium to ampicillin.
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A comparison of four culture methods for diagnosing infection in continuous ambulatory peritoneal dialysis.
Dialysate effluent from 41 patients presenting with 54 episodes of CAPD peritonitis was examined by four culture techniques, three employing methods for the lysis of peritoneal leucocytes. The most efficient method employed a distilled water lysis-centrifugation technique (81% of episodes culture-positive). Filtration (without leucocyte lysis) was less effective (74% culture-positive). The results of a mechanical leucocyte lysis technique were less satisfactory still, the culture positive rate of 74% being compromised by the recovery of the infecting organism in low numbers, and by an association with a high incidence of plate contamination. The results of a bile-salt lysis technique were the least satisfactory (67% culture-positive).
The effect of anti-Rho(D) and non-specific immunoglobulins on monocyte Fc receptor function: the role of high molecular weight IgG polymers and IgG subclasses.
Anti-Rho(D) immunoglobulin (anti-D) contained more high molecular weight (HMW) IgG polymers than intravenous non-specific immunoglobulin (i.v. Ig). The low-dose anti-D and high-dose i.v. Ig regimens used to treat idiopathic thrombocytopenic purpura (ITP) therefore contained similar total amounts of HMW IgG. In vitro, the HMW IgG polymers were more effective competitive inhibitors of monocyte phagocyte Fc receptors than monomeric IgG. The IgG subclass composition of anti-D and i.v. Ig were both similar to normal human plasma. We conclude that the HMW IgG content but not the IgG subclass composition of anti-D may explain its low-dose therapeutic efficacy in ITP.
Hepatic drug metabolism is increased in poorly controlled insulin-dependent diabetes mellitus.
In addition to increased glycosylation of hemoglobin, abnormalities of other heme proteins such as cytochrome P-450 might also occur in patients with insulin-dependent diabetes mellitus. Antipyrine is a useful marker drug for cytochrome P-450 dependent hepatic drug metabolism. Antipyrine kinetics and urinary excretion of antipyrine metabolites were measured in 14 patients with insulin-dependent diabetes mellitus in poor metabolic control. Improvement in diabetic control in 9 patients, as measured by more normal HbA1 values, led to normalization of plasma antipyrine half-time (t1/2) and metabolism: the mean antipyrine t1/2 slowed from 4.7 +/- 0.2 (SEM) initially to 7.8 +/- 0.3 h in these 9 patients and was thus nearly identical to that of normal subjects 8.6 +/- 1.0. Antipyrine plasma clearance improved in the 9 diabetic patients whose diabetic control improved. The apparent volume of distribution was normal on both occasions in the diabetic patients. These findings provide a new argument for tight metabolic control in patients with insulin-dependent diabetes mellitus.
Expression of the vitronectin receptor during embryonic development; an immunohistological study of the ontogeny of the osteoclast in the rabbit.
The development of the osteoclast during embryogenesis was studied in the rabbit by immunohistological techniques. Two monoclonal antibodies, 13C2 and 23C6, which react with the alpha-chain of the vitronectin receptor were used to define mono and multi-nucleate osteoclasts; being unreactive with other haemopoietic cells these antibodies could discriminate between osteoclasts and cells of the mononuclear phagocyte system. Staged rabbit embryos, from 14 to 28 days of age, were analysed and compared with findings from newborn and adult rabbits. No 13C2/23C6 immunoreactivity was seen in any of the tissues studied prior to day 17. 13C2/23C6-positive, mononuclear cells--presumptive osteoclast precursors--were first observed in the outer perichondrium of long-bones adjacent to the zone of hypertrophic cartilage in day 17 embryos. From day 17 onwards mono and multi-nucleate cells accumulated progressively in the perichondrium/periosteum, and by day 22 within the developing bone marrow cavity attached to bone spicules. No cells expressing the vitronectin receptor were seen at sites of embryonic or foetal haemopoiesis in yolk sac or foetal liver, that is, prior to the formation of the marrow cavity. Macrophages, defined by cross-reactivity with an antibody to human HLA-DR, first appeared in developing marrow spaces 11 days after the first osteoclast precursor appeared, suggesting that osteoclasts and definitive macrophages might develop from separate cell lineages, or that they diverge at an early stage of differentiation of haemopoietic stem cells.
Noninvasive diagnosis of left ventricular pseudoaneurysm: role of two dimensional echocardiography and radionuclide gated pool imaging.
This report describes a case of left ventricular pseudoaneurysm diagnosed with two dimensional real time echocardiography. The two dimensional echocardiogram identified not only the pseudoaneurysmal sac but also the site of left ventricular rupture. When supplemented with radioisotope gated cardiac blood pool scanning, the noninvasive studies demonstrated combined true and false left ventricular aneurysms. Left ventricular pseudoaneurysm can be diagnosed using two dimensional echocardiography and nuclear imaging, permitting early operative intervention before fatal rupture.
Neural mechanisms of reflex facilitation and inhibition of gastric motility to stimulation of various skin areas in rats.
1. Experiments were performed on chloralose-urethane anaesthetized rats to determine the involvement of extrinsic gastric autonomic nerves in reflex facilitation and inhibition of gastric motility when mechanical nociceptive stimulation was delivered to either hind paw or abdominal skin, respectively. 2. After bilaterally sectioning the splanchnic nerves in vagal intact animals, the reflex facilitation of gastric motility produced by hind paw stimulation persisted, but the reflex inhibition previously produced by abdominal skin stimulation disappeared. 3. Hind paw stimulation increased efferent activity of the gastric branch of the vagus nerve, but stimulation of abdominal skin had little influence. 4. Bilateral vagotomy in splanchnic nerve intact animals did not influence the gastric reflex inhibition by abdominal skin stimulation, but either abolished gastric reflex facilitation produced by hind paw stimulation or reversed the reflex facilitation response to slight reflex inhibition. 5. Efferent activity of the gastric sympathetic nerve was greatly increased by abdominal skin stimulation, and was either slightly increased or not influenced by hind paw stimulation. 6. It was concluded that reflex increase of efferent activity of the gastric vagi was responsible for the gastric motility facilitation produced by hind paw stimulation, and also that reflexly increased efferent activity of the gastric sympathetic nerves resulted in gastric motility inhibition produced by abdominal skin stimulation. It is suggested efferents are inhibitory. 7. After spinal transection at the cervical level, the reflex facilitation of gastric motility previously produced by stimulation of a hind paw was completely abolished, or reversed to slight reflex inhibition, while reflex inhibition of gastric motility produced by stimulation of abdominal skin remained. It was concluded that the gastric reflex inhibition was a spinal reflex. 8. Interaction between reflex facilitation and inhibition of gastric motility during simultaneous stimulation of both hind paws and abdominal skin was observed as partial cancellation of each effect by the other. However, sympathetic reflex inhibition of gastric motility seemed to be much stronger than the vagal reflex facilitatory effect.
A simplified antepartum high-risk pregnancy scoring form: statistical analysis of 5459 cases.
An antenatal high-risk assessment form has facilitated the identification of the fetus at risk, Although such a form in general has potential limitations its simplicity and demonstrated ability to assist in high-risk selection makes it worth including in an antenatal high-risk program.
Modified axial lead system in children.
Preliminary studies have been made on the use of the modified axial lead system in infancy and childhood. A highly significant correlation between internipple distance and height suggested that internipple distance be used as an index for the selection of a template to facilitate placement of the chest electrodes (Z and X). A series of 4 triangular templates was designed. The use of a template one size too large or too small was shown not to lead to any significant error in waveform measurement. A further study showed that the reference level for the application of the praecordial electrodes should be the 5th intercostal space as for adults, but that no serious diagnostic error was likely to arise if the 4th or 6th intercostal space was chosen by mistake. A study of the Frank lead system suggested that the use of the 5th intercostal space as a reference level was more appropriate than the 4th intercostal space, which is generally adopted by users of that system. The conclusion reached was that the axial lead system is the preferred orthogonal lead system for children, with templates for 4 ranges of internipple distance (less than 10 cm; 15 to 20 cm; and less than 20 cm--adult build) being proposed to simplify electrode placement.
Constant current device for drug application studies in the central nervous system.
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Temporary transcaecal ileal diversion in prevention of anastomotic leak in planned colonic surgery (an alternative to proximal colostomy).
An alternative to proximal colostomy in planned colonic resection is reported in 30 patients. The physiopathological background for this procedure of temporary transcaecal ileal diversion is explained together with details of the operation and the results obtained.
Antitumor, antiviral and immunopotentiating activities of pine cone extracts: potential medicinal efficacy of natural and synthetic lignin-related materials (review).
Several antitumor substances that effectively inhibited the growth of ascites and solid tumor cells transplanted in mice were isolated from pine cone NaOH extract by acid- and ethanol-precipitation. These antitumor substances were also potent antiviral agents against human immunodeficiency virus, herpes simplex virus and influenza virus; they induced antimicrobial activity against Staphylococcal aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Candida albicans, and induced antiparasite activity against Hymenolepis nana in mice. Chemical analysis of these substances by IR, UV, NMR, ESR and partition chromatography on cellulose-TLC plate disclosed that they had lignin-related structures complexed with sugars or polysaccharides. Chlorinated decomposition of the lignin portion significantly reduced their antiviral activity. In agreement with this, the antiviral activity of synthesized lignins prepared by polymerization of phenylpropanoid precursors was comparable to that of the undecomposed counterparts of the pine cone extract. Acid hydrolysis of the polysaccharide portion significantly reduced the ability of the substances to induce antitumor and antimicrobial activities in mice. With an appropriate eliciting agent, intravenous administration of natural lignified substances transiently induced endogenous production of a cytotoxic factor (possibly tumor necrosis factor) in normal mice. Their priming activity was significantly higher than that of their component units or degradation products. These data suggest the importance of conjugating lignins with polysaccharides for in vivo expression of various kinds of immunopotentiating activity. As possible explanations for their induction of a variety of immunopotentiating activities, these natural and synthetic lignins stimulated macrophage NBT-reducing activity, polymorphonuclear cell (PMN) iodination and splenocyte DNA synthesis and inhibited poly (ADP-ribose) glycohydrolase, RNA-dependent DNA polymerase (reverse transcriptase) and RNA-dependent RNA polymerase activities.
Induction of immunopotentiation activity by a protein-bound polysaccharide, PSK (review).
A protein-bound polysaccharide, PSK, extracted from the mycelium of Coriolus versicolor (Fr.) Quel, has been recognized for its host-mediated induction of antitumor and antimicrobial activities in mice. Intravenous administration of PSK, in association with OK-432 (Picibanil), transiently induced endogenous production of a cytotoxic factor (CF) (possibly tumor necrosis factor, TNF) in normal mice. The ability to produce CF depended greatly on both dose and interval between administration of the PSK and OK-432. Although PSK has been reported to contain several active ingredients, unfractionated PSK has been used in almost all experiments performed so far. We recently reported that, of the four subfractions separated by successive filtration through membrane filters, only the highest molecular weight fraction F4 (MW greater than 200 kD) induced significant antimicrobial activity in mice. PSK stimulated the NBT-reducing activity of mouse peritoneal macrophages and the iodination (incorporation of radioactive iodine into an acid-insoluble fraction) of human peripheral blood polymorphonuclear cells (PMN). Among the subfractions of PSK, the highest molecular weight fraction F4, and the fraction precipitated at pH 4.0-4.5 (Fr. 4), stimulated macrophage NBT-reducing activity and PMN iodination most. In contrast, natural and chemically modified glucans had little or no stimulating activity. PSK, F4 or Fr. 4 additively or synergistically stimulated TNF-induced cytotoxicity against L-929 cells, differentiation of human myelogenous leukemia cell lines toward monocytes/macrophages, and iodination of human peripheral blood PMN. The active PSK subfractions significantly reduced the down regulation of specific 125I-TNF or 125I-IFN-gamma binding to cellular receptors. These data suggest that (i) immunopotentiation activity of PSK might be ascribed, at least in part, to stimulation of cytokine action and production, and (ii) PSK might have some unique structural features.