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Biomedical subjects

M King

Publications and source records attributed to M King.

At least 433 records · Page 24Linked to original sources
PubMed1981

Is cystic fibrosis mucus abnormal?

It has been known for some time that the viscosity of sputum from cystic fibrosis (CF) patients differs from that in other disease types characterized by pulmonary hypersecretion. However, it has never been established that there is in fact any abnormalities in the rheologic properties of CF sputum. We have recently developed techniques to examine the rheology and mucociliary transportability of tracheal secretions from dogs utilizing the small quantities of mucus available from a healthy animal. In the present study, these in vitro techniques were applied to sputum samples obtained from 15 adult CF patients. For mucoid and mucopurulent CF sputum samples, the viscoelastic properties were remarkably similar to those observed for control canine tracheal mucus samples. For purulent CF sputum, elasticity and viscosity tended to be higher and the viscosity/elasticity ratio lower than for either the nonpurulent sputum or the canine tracheal mucus. The logarithm of elasticity at 1 rad/sec was 2.55 +/- 0.35 (S.D.) for purulent sputum, 2.05 +/- 0.49 for mucoid and mucopurulent sputum, and 2.17 +/- 0.36 for canine tracheal mucus. From the viscoelastic properties of CF sputum, one would have predicted the in vitro mucociliary transportability, at least for the nonpurulent samples, to be the same as that of canine tracheal mucus. However, the frog palate assay indicated a consistently lower rate of transport (mean difference, 13%) than that predicted from previous studies. This result would, therefore, suggest that if the prediction from canine tracheal mucus is applicable there is a factor in the CF sputum that results in a temporary inhibition of frog palate ciliary beating. This apparent inhibition of mucociliary transport is, however, relatively minor, and it is perhaps more remarkable that for none of the sputum samples collected was the in vitro ciliary transport rate particularly low; i.e., observed values ranged from 65 to 100% of frog palate control.

Animals↗
PubMed1981

[Aneurysm formation on dacron prosthesis after 84 months of use. Pathology, structural and chemical evaluation of the explanted device (author's transl)].

A 56 year old patient fitted with a femoro-popliteal Dacron prosthesis (Weavenit-Meadox Medical) 84 months earlier, presented with a severe palpable dilation in the middle part of the graft. The dilated segment of the prosthesis was resected locally and spliced to a new fabric device. The explanted section of prosthesis was analyzed; the dilation was found to extend only over several centimeters near the centre of the prosthesis. The degree of "healing" was found to be satisfactory except in the part which was most distended; this area also revealed mild bacterial colonization. Physico-chemical analysis of the fabric revealed that the dilation had taken place subsequently to hydrolytic degradation of the polyester fibres. Manufacturing conditions may have contributed to predisposing parts of the prosthesis to accelerated biodeterioration in vivo.

Biodegradation, Environmental↗
PubMed1980

Sulfur dioxide induced airway hyperreactivity in allergic sheep.

The effects of a four-hour exposure (via a Plexiglas hood) to sulfur dioxide (SO2) on airway reactivity was studied in both normal and allergic conscious sheep. Allergic sheep were defined as animals in whom inhalation of Ascaris suum extract resulted in an increase in mean pulmonary flow resistance (RL). Airway reactivity (delta RL) was assessed by measuring the increase in RL after 18 breaths of 0.25% carbachol, from an initial value obtained after 18 breaths of buffered saline. RL and delta RL were determined prior to, immediately after and 24 hours following SO2 exposure in three groups of sheep: six normal sheep exposed to 5 ppm SO2 (group A); six normal sheep exposed to 10 ppm SO2 (group B) and seven allergic sheep exposed to 5 ppm SO2 (group C). RL was not affected by SO2 exposure in any group but both groups B and C showed increases in delta RL 24 hours after exposure. Since the increase in delta RL was greater in group C than in either groups A or B, we conclude that allergic sheep have enhanced susceptibility to the injurious airway effects of SO2.

Airway Resistance↗
PubMed1980

Intussusception due to inflammatory fibroid polyps of the ileum: a report of 12 cases from Africa.

Eleven cases of inflammatory fibroid polyp of the ileum from Malawi and 1 from Sierra Leone are described. All 12 patients presented with acute intestinal obstruction as a result of an intussusception caused by the polyp. The lesions are characterized by a variable proliferation of fibroblasts and small vessels which may involve the whole thickness of the bowel wall. Tissue mast cells and eosinophils were noted in the polyps. The aetiology of these lesions remains obscure but they appear to be reactive rather than neoplastic. The condition appears to occur more commonly in Malawi than in the United Kingdom or North America and is an important cause of small bowel obstruction in that part of Africa.

Adult↗
PubMed1980

A SEM investigation of the trauma to prostheses and arteries during vascular reconstruction procedures.

Scanning electron microscopy was used to diagnose incidents of trauma and the pattern of healing following surgical implantation of microporous blood vessel substitutes. Vascular reconstruction procedures using autogenous or synthetic prosthetic materials inflict damage to the adjacent tissues as well as the prosthesis. This effects the thrombotic behavior and healing pattern of the area. The prognoses for long term success are, as a consequence, directly influenced. Various vessel occluding devices were evaluated on canine models with respect to their ability to damage blood vessels at the clamped site. The impact of suture needles on tissues and prosthetic materials was also considered. Of the various vessel clamping devices which are commercially available, those which have elastomeric shields on the clamping components were found to be the most satisfactory. The development of less traumatic surgical devices and possible modifications in the surgical protocols are discussed with the aim of further reducing surgical trauma.

Animals↗
PubMed1980

Viscoelastic properties of airway mucus.

Mucus is a viscoelastic gel that exhibits both liquid-like and solid-like properties. Viscoelasticity can be determined in both transient and dynamic experiments, which give in principle the same information; the latter, however, offer a simpler interpretation. The principal determinant of mucus viscoelasticity appears to be mucin content; pH, added salts, serum proteins, and DNA have also been found to affect mucus viscoelasticity. However, agreement between studies, even equalitative, is far from complete. Acute pharmacologic interventions can significantly alter airway mucus viscoelasticity. The mechanism by which the changes occur remains to be explored, but alterations in epithelial ion transport and membrane permeability to protein offer rational explanations for the observations.

Animals↗
PubMed1979

Effect of pentobarbital anesthesia on rheology and transport of canine tracheal mucus.

Tracheal mucus samples were collected from six tracheostomized dogs before and after induction of pentobarbital anesthesia. The dynamic mechanical properties of the mucus were determined by the magnetic microrheometer technique. In 15 experiments, the mean value of elasticity at 1 rad/s rose from 67 dyn/cm2 before anesthesia to 212 dyn/cm2 in the period 15-90 min after induction. At the same time, mean viscosity at 1 rad/s rose from 24 to 79 P. The mucociliary transportability of some of the mucus samples was assayed by means of in vitro frog palate technique. In 10 experiments, the relative transport rate for dog tracheal mucus went from 98% of frog palate control befor anesthesia to 79% during pentobarbital anesthesia. A negative relationship between from palate transport rate and mucus elasticity was found. A negative correlation between transport and mucus viscosity at constant elasticity was also discovered. Finally, the mucus collection rate was reduced by a factor of about 8 during anesthesia, suggesting a reduction in the average depth of mucus.

Animals↗
PubMed1979

Effect of methacholine chloride on rheology and transport of canine tracheal mucus.

The effect of methacholine chloride (M) on tracheal mucus was investigated in three conscious tracheostomized dogs. Aerosols of M in concentrations of 2--32 mg/ml were delivered intratracheally for 1 min. Mucus was sampled with a cytology brush at 2 min postchallenge and at irregular intervals thereafter. The mechanical properties of each sample were determined in the magnetic microrheometer, and correlated with mucociliary transportability as assayed by the frog palate technique. With high doses of M, there was an increase in volume of secretion collected per unit time. The elastic modulus (G') at 2 min postchallenge went up (to 1.5 x 2.3 x control for 16 and 32 mg/ml, respectively) then fell below control before returning to base line after 30 or 45 min. With low doses of M (2--8 mg/ml) the secretion rate was also above control, but only a decrease in G' (to 0.54 x control) was observed. The decrease in G' at low doses did not significantly alter the frog palate transport rate; however, the increase at higher doses did impede mucociliary transport.

Animals↗
PubMed1979

Influence of vagal tone on rheology and transportability of canine tracheal mucus.

The influence of vagal tone on the rheology of tracheal mucus was studied in 6 conscious, tracheostomized dogs. Mucus was sampled via the tracheostomy with a cytology brush before and after administration of atropine. After vagal blockade, a clear decrease in the mucus collection rate was seen. The viscoelastic properties of the mucus were not altered by atropine when control elasticity was high, but when control elasticity was low, administration of atropine led to increased elasticity. In neither case was there a significant change in transportability of the mucus samples. The increase in elasticity from a small initial value was consistent with the blocking of moderate vagal activity, because administration of methacholine in the same group of dogs had been shown to cause a decrease in mucus elasticity.

Animals↗