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Biomedical subjects

D Richardson

Publications and source records attributed to D Richardson.

At least 181 records · Page 10Linked to original sources
PubMed1990

Survey of general practitioners' opinions on the role of radiology in patients with low back pain.

Ninety general practitioners responded to a questionnaire about the role of radiology in patients with low back pain. Their clinical indications for requesting radiographs were mostly in agreement with the opinions of radiologists, but nearly 80% requested investigations for their own or patients' reassurance. Understanding of the terms used by radiologists was good, although 25% thought that acute disc prolapse could be demonstrated on plain films. Previous training in radiology did not seem to influence knowledge. When general practitioners understood radiological terms they had clear therapeutic and specialist referral preferences. Poorly understood terms and those with which they were familiar but unclear about the implications for management were also identified.

Attitude of Health Personnel↗
PubMed1989

Pyridoxal isonicotinoyl hydrazone and analogues. Study of their stability in acidic, neutral and basic aqueous solutions by ultraviolet-visible spectrophotometry.

The ultraviolet-visible absorption spectra of the orally effective iron chelator, pyridoxal isonicotinoly hydrazone (PIH), and three analogues, pyridoxal benzoyl hydrazone (PBH), pyridoxal p-methoxybenzoyl hydrazone (PpMBH) and pyridoxal m-fluorobenzoyl hydrazone (PmFBH) have been measured in aqueous solution with various concentrations of added acid or alkali. Assignment of absorption bands to various molecular species in equilibrium in aqueous solution is made by reference to their acid ionisation constants. All four hydrazones were stable at physiologial pH, but hydrolysed in strongly acidic and basic solutions, resulting in the liberation of pyridoxal and the acid hydrazide. In acidic solutions this resulted in a dramatic decrease in the intensity of absorption at wavelengths of 225 nm and above 300 nm, allowing a quantitative estimate of the degree of acid-catalysed hydrolysis of the ligands. These results indicate that for oral administration the chelator should be administered with calcium carbonate or provided with an enteric coating to minimise acid-catalysed hydrolysis in the stomach. At high pH, base-catalysed hydrolysis occurred, resulting in a decrease in the absorption at a wavelength of 387 nm.

Drug Stability↗
PubMed1989

Morpheus: a conformation-activity relationships and receptor modeling package.

Our molecular modeling software package, MORPHEUS, allows the study of the interactions between biologically active molecules and their receptors. The package is capable of exploring the multidimensional conformational space accessible to each molecule of the data set under study. By specifying distance constraints or hypothetical receptor binding points, the package is able to filter the biologically accessible conformations of each active compound and deduce a three-dimensional model of the binding sites consistent with the properties of the agonists (or antagonists) under scrutiny. The electrostatic potentials in the environment of a putative binding site can also be investigated using the MORPHEUS package. The molecular modeling module CRYS-X, which is written in FORTRAN 77 for IBM PC machines, is capable of building, displaying and manipulating molecules.

Computer Graphics↗
PubMed1989

Effects of age on cutaneous circulatory response to direct heat on the forearm.

To investigate the effects of age on the response of skin blood flow in the forearm to direct heat, three groups of 20 male subjects each--young (20-39 yr); middle-aged (40-59 yr) and older (60-79 yr)--consented to have skin blood flow measured in the forearm by a TSI Model 403 laser Doppler flowmeter. This instrument detects changes in red blood cell velocity (LDV) in flow-active vessels and the volume of red blood cells flowing through these vessels (LDO). With the forearm in a 30 degrees C water bath there were no significant between-group differences in LDV or LDO. Elevating bath temperature to 35 degrees C elicited a significant increase in LDO in all three groups, but LDV did not significantly change. Increasing temperature to 40 degrees C elicited significant increases in both LDO and LDV with the former being of greater magnitude. At this temperature LDV values in both the middle-aged and older groups were significantly lower than those of the young subjects. Expressing the data during heating as percent change from 30 degrees C showed a significantly lower volume (LDO) response in the older group at 35 and 40 degrees C and a significantly lower LDV response at 40 degrees C for both the middle-aged and older subjects in comparison to the young group. It is concluded that aging decreases the response of cutaneous blood flow in the forearm to the direct effects of heat.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Bitewing radiographs of children taken with and without a film-holding device.

To help minimize radiation exposure, all dental radiographs must yield maximum diagnostic information. Film-holding devices have been recommended as a means of improving the diagnostic yield. Our study compared the diagnostic quality of bitewing radiographs of children taken with and without the aid of a film-holding device. 1014 bitewing radiographs (sizes 0, 1, 2) were taken of 338 children (aged 5-11 years) by senior dental students. Bitewing tabs were used for 554 radiographs and a film-holding device for the remainder. Diagnostic quality was calculated for each radiograph by dividing the number of non-overlapped contacts by the total number present. Both overall mean diagnostic yield and mean diagnostic yield for each size of film were found not to be significantly improved by use of the film-holding device. Position of overlapped contacts on each size of film was not equally distributed (P less than or equal to 0.01) among the contacts present. For size 0 and 1 films, overlap was most frequent between the maxillary first and second primary molars and for size 2 films between the maxillary first permanent molar and second primary molar/second bicuspid.

Adolescent↗
PubMed1988

Effect of pyridoxal isonicotinoyl hydrazone and other hydrazones on iron release from macrophages, reticulocytes and hepatocytes.

A model consisting of 59Fe-labelled macrophages was developed for screening potential iron-chelating drugs. Mouse peritoneal macrophages, induced by previous intraperitoneal injections of 3% thioglycollate, were labelled in vitro by their exposure to immune complexes of 59Fe-transferrin-antitransferrin antibody. Optimal conditions for macrophage labelling and subsequent 59Fe release were established. Sixty-two aromatic hydrazones, the majority of which had iron binding structures similar to pyridoxal isonicotinoyl hydrazone, were synthesized by condensation of aromatic aldehydes (pyridoxal, salicylaldehyde, 2-hydroxy-1-naphthylaldehyde and 2-furaldehyde) with various acid hydrazides prepared by systematic substitutions on the benzene ring. These compounds were examined for their potential to stimulate 59Fe release from 59Fe-labelled macrophages and also from reticulocytes and hepatocytes loaded with non-heme 59Fe. The majority of hydrazones derived from pyridoxal, salicylaldehyde and 2-hydroxy-1-naphthylaldehyde seemed to be equally effective in both the macrophage and reticulocyte testing systems. However, the pyridoxal hydrazones were much more active in hepatocytes than the other groups of hydrazones. Several compounds proved to be very potent in mobilizing 59Fe. These included hydrazones derived from 2-hydroxy-1-naphthylaldehyde and benzoic acid hydrazide, p-hydroxybenzoic acid hydrazide, 2-thiophenecarboxylic acid hydrazide, and also pyridoxal benzoyl hydrazone, pyridoxal m-fluorobenzoyl hydrazone and pyridoxal 2-thiophenecarboxyl hydrazone.

Animals↗
PubMed1988

Effects of gravity on regional and capillary blood flows in the human toe.

The purpose of this study was to investigate the relative effects of gravity on capillary and regional blood flows in human extremities. Eighteen male subjects 20 to 40 years of age consented to have capillary blood cell velocity (CBV) measured in nailfold vessels of the large toe via video densitometry, and to have total blood flow (TBF) to the toe measured via plethysmography. These measurements were made first with the foot at heart level (HL), then after the foot had been lowered an average of 56 cm below the heart (BH). In the HL position CBV and TBF averaged respectively 0.26 mm/sec and 2.0 ml/min/100 ml. Lowering the foot elicited a decrease in CBV in all vessels studied (P less than or equal to 0.001). Average CBV in the BH position was 0.11 mm/sec. By contrast TBF on the average increased to 2.9 ml/min/100 ml in the BH position (P less than or equal to 0.05). However, this was not a consistent finding since both increases and decreases in TBF were observed among the individual subjects. These results indicate that the immediate precapillary vessels in the cutaneous circulation of the toe will consistently vasoconstrict when the foot is placed in a dependent position. However, the net effect on vessels governing regional flow in this area, e.g., A-V shunts, appears to result from a competition between dilator and constrictor influences. The overall result of these adjustments is that during orthostasis blood is shifted away from the superficial capillaries of the lower extremities. The relevance of this to blood-tissue fluid balance is discussed.

Adult↗
PubMed1988

Differential neutrophil activation before and after endotoxin infusion in enterally versus parenterally fed volunteers.

This study was done to determine whether or not increased susceptibility to infection seen in enterally versus parenterally fed patients was caused by altered neutrophil (PMN) responsiveness. To determine the differential effects of route of feeding on human PMN activation, plasma C3a levels, circulating PMN counts, PMN migration to leukotriene B4 (LTB4), the peptide, N-formyl-methionyl-leucyl-phenylalanine (FMLP) and zymosan activated serum (ZAS) and generation of LTB4 were assayed before and after and infusion of endotoxin. Nine normal volunteers were enterally (n=4) or parenterally (n=5) fed a diet sufficient to maintain body weight for seven days prior to a standard challenge of endotoxin. Samples were taken prior to the infusion and hourly thereafter for six hours. Prior to the injection of endotoxin, significant differences were seen in the two feeding groups. Plasma C3a levels, absolute circulating PMN counts and chemotaxis to LTB4 were all significantly (p less than 0.02) elevated in the enterally fed group. Generation of LTB4 was higher in the intravenously fed group at base line than the orally fed group (p less than 0.05). Plasma C3a levels rose in the enterally fed group, but not in the intravenously fed group, at two hours after infusion. Neutrophil counts rose in both feeding groups after endotoxin infusion; but the change in percentage was greater in the enterally fed group than in the intravenously fed group. Chemotaxis to FMLP and ZAS was not different during the study and did not differ between the two feeding can have significant impact on neutrophil function and that parenteral nutrition may impair host responsiveness.

Chemotaxis↗
PubMed1987

Fish oil increases peripheral capillary blood cell velocity in humans.

Fish oils containing n-3 fatty acids have been shown in humans to decrease platelet aggregation in vitro, lower plasma triglycerides, and to increase bleeding time. The in vivo effects of fish oils on microcirculatory blood flow in humans has not been studied to date. Twenty-one male subjects were randomly assigned to either olive oil (n = 10) or fish oil (n = 11) supplemented groups to determine the effects of these oils on capillary blood flow velocity (CBV) in the nailfold area. The subjects were given the oils for three weeks (1.5 g oil/10 kg b.wt./day) in a single blind study design. In addition to CBV plasma lipid profiles, blood viscosity, blood pressure and platelet and erythrocyte fatty acids were also determined prior to and after the dietary intervention. Fish oil supplementation significantly increased CBV, by 1.75-fold (0.144 +/- 0.069 to 0.253 +/- 0.147 mm/s). The olive oil group remained unchanged. Increased levels of n-3 fatty acids were noted in platelets and erythrocytes of the fish compared to olive oil-supplemented groups. Blood viscosity was unaltered in both groups, however, blood pressure in the olive oil supplemented group was significantly decreased. Plasma triglycerides were significantly decreased in the fish oil supplemented group. These observations suggest that increases in CBV after fish oil supplementation are due to changes in vascular tone and not to alterations in blood pressure or blood viscosity.

Adult↗
PubMed1987

Effect of chronically elevated androgen or estrogen on the glucose tolerance test and insulin response in female rhesus monkeys.

Insulin concentrations, in response to an intravenous glucose bolus after a 24-hour fast, have been studied in female rhesus monkeys in which the circulating levels of androstenedione and testosterone or estrone and estradiol have been increased for as long as 4 1/2 years. No significant differences were observed in the basal insulin or C-peptide concentrations in the androgen or estrogen-treated animals compared with each other or with normal cycling, nontreated control animals. The insulin and C-peptide responses to intravenous glucose were similar in control and androgen-treated monkeys. Compared with both the control and androgen-treated monkeys, the responses of the estrogen-treated monkeys tended to be lower but were not significantly different. The glucose disappearance rate after the intravenous glucose bolus was not significantly different in androgen and control monkeys but was significantly slower during the initial 30 minutes in the estrogen-treated monkeys compared with both the control and androgen-treated monkeys. These studies suggest that chronically elevated androgen levels in the mature female subhuman primate do not lead to insulin resistance or overt glucose intolerance.

Androstenedione↗
PubMed1987

Gaze-evoked tinnitus.

Two patients developed gaze-evoked tinnitus in the year following removal of a cerebellopontine angle mass. The eighth nerve was transected in both cases. The noise was present with saccades, pursuit, and vestibuloocular eye movements. We postulate the tinnitus was due to an abnormal interaction between the vestibular nucleus and the cochlear nucleus, possibly secondary to neural sprouting.

Eye Movements↗
PubMed1987

Recent challenges to traditional assumptions about homosexuality: some implications for practice.

During the last decade there has been a change in professional attitudes toward homosexuality reflected in the development of new models of treatment. Rather than offering a cure the aim is to help homosexuals adjust positively to their orientation. Such attitudinal change on the part of the practitioners has not, in the main, questioned the fundamental assumptions of theories which seek to explain homosexuality. Recent theoretical inquiry into homosexuality, however, has done this, posing an important challenge to the traditionally held view that people have an essential sexuality that is either homosexual or heterosexual and which remains fixed and unchanging throughout their lives. This paper addresses some of the more important clinical implications of these recent developments, in particular, the suggestion that "the homosexual" as a certain type of person is an "invention." In addition, the therapeutic value and difficulties associated with an acknowledgement that sexual preference and identity may change over time are considered. Finally, there is consideration of what the goals should be in the case of the person who seeks professional help in changing from a homosexual to a heterosexual orientation.

Adaptation, Psychological↗