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Biomedical subjects

A N Smith

Publications and source records attributed to A N Smith.

At least 91 records · Page 5Linked to original sources
PubMed1986

Anorectal function following colo-anal sleeve anastomosis for chronic radiation injury to the rectum.

Anorectal manometry and electrophysiological studies of the pelvic floor were performed in eight patients who had undergone anterior resection of the rectum with mucosal proctectomy and colo-anal sleeve anastomosis for radiation rectal injury. There is a severe reduction in the compliance of the neorectum and in the maximal tolerable volume. Maximum basal anal canal pressure and physiological sphincter length are also significantly reduced although the 'squeeze' pressure of the external anal sphincter and the latency of the pudendo-anal reflex were unaffected. Four patients had an absent rectosphincteric reflex, four patients involuntarily expelled the test balloon at the maximal tolerable volume during a proctometrogram and four patients demonstrated increased EMG activity of the pelvic floor on straining and on rectal distension. These abnormalities help to explain many of the patients' symptoms. Histological abnormalities of the myenteric plexus were a prominent feature in all the excised specimens and may be responsible for some of the functional abnormalities.

Aged↗
PubMed1986

Differential effects of sacral anterior root stimulation on anal sphincter and colorectal motility in spinally injured man.

The motility responses of the sigmoid colon, rectum and external anal sphincter to sequential electrical stimulation of the anterior sacral roots (S2, S3 and S4) were studied in five patients with traumatic spinal cord injury. Identical and reproducible results were obtained. S2 stimulation provoked isolated low-pressure colorectal contractions. S3 stimulation initiated high-pressure colorectal motor activity which appeared peristaltic and was enhanced with repetitive stimuli. This response appeared to be frequency-dependent. S4 stimulation increased colonic and rectal tone. External sphincter activity was stimulated in increasing order from S2 to S4. These observations directly elucidate the central control of colorectal motility and may have implications in the treatment of severe constipation following spinal injury.

Adult↗
PubMed1986

Reproducibility of the proctometrogram.

The reproducibility of a method of measuring rectal distensibility by continuous controlled fluid inflation with a balloon has been evaluated in 15 patients. The volume at sensation threshold, constant sensation and maximal tolerance, the pressures at these volumes and rectal compliance were measured. The mean coefficients of variation of the seven variables measured ranged from 4.7%-7.9%. The expected correlation between rectal compliance and maximal tolerable volume was confirmed (r = 0.85, p less than 0.001). The high reproducibility makes this investigation reliable for use in clinical practice and research.

Adolescent↗
PubMed1986

Function of the anal sphincters after chronic radiation injury.

Anorectal manometry was done in 10 men with chronic radiation proctitis and symptoms of urgency, frequency, and occasional incontinence of faeces. They were compared with 10 asymptomatic age and sex-matched controls. The maximum resting anal canal pressure and the physiological sphincter length were significantly lower (p less than 0.01) in the irradiated group. The rectosphincteric reflex was absent in one patient and showed abnormalities of recovery in four others, who had received radiotherapy. The squeeze pressure of the external sphincter was not significantly different. These results indicate that dysfunction of the internal anal sphincter may contribute to patients' anorectal symptoms after pelvic radiotherapy. Histological evidence suggests that damage to the myenteric plexus is mainly responsible. The manometric function of the external sphincter remains relatively unaffected.

Aged↗
PubMed1986

Electrophysiological observations on the human pudendo-anal reflex.

A reproducible electrophysiological technique is described to determine the latency of reflex contraction of the external anal sphincter in response to stimulation of the dorsal genital nerve: the pudendo-anal reflex. This was studied in 38 asymptomatic control subjects and 20 women with neurogenic faecal incontinence, supplemented by determination of the mean motor unit potential duration (MUPD) of the external anal sphincter and anorectal manometry. The reflex latency in the control group was 38.5 +/- 5.8 (SD) ms and appeared to be independent of age or sex. Three patients with faecal incontinence had absent reflexes; the remainder showed significant prolongation of latency (56 +/- 12.2 SD ms) and diminution of amplitude. MUPD was prolonged in incontinence and showed significant correlation with the corresponding reflex latency determination (tau = 0.56, p less than 0.001). The latency of this polysynaptic spinal reflex hence provides a reliable index of neuropathy of the external anal sphincter.

Adult↗
PubMed1986

Colonic muscle in diverticular disease.

The muscle abnormality in diverticular disease is seen most often in surgically excised specimens in the sigmoid colon, though a pancolonic form of the disease without muscle thickening also exists in the elderly. In terms of physiopathology, the condition has a raised intraluminal pressure operating on the wall locally, this being most readily demonstrated in symptomatic patients. In Western societies the colon loses its tensile properties throughout life. The anatomical and functional evidence is that the colon is outstandingly strong in infancy in both Africans and Europeans, but later the mechanical properties of the African colon become superior and they remain so throughout ensuing decades. The diminished tensile strength and elasticity of the wall is no different in the diverticular and non-diverticular subjects and this suggests that an additional factor, such as pressure, may be necessary in Europeans to cause the mucosal extrusion which constitutes each diverticulum. Fiber fills the colon with bulkier, moister feces, which necessitates less work, especially as it operates for most of the time as a low-pressure system, only occasionally evacuating by mass peristalsis into the rectum. Cereal fiber binds salt and water and there is evidence that this is mostly a physicochemical process, dependent on particle size. Certain types of fibers undergo chemical degradation in the cecum and increase the bacterial population of the stool. Population studies show that diverticular disease subjects consume less fiber and in countries where the fiber intake is reduced, fecal output is lessened, transit is slower, and intraluminal pressure may be rising. As a result of the adoption of high-fiber diets and the use of bulking agents elective operations for diverticular disease are less commonly performed. The number of operations in most Western countries may be increasing because of increasing longevity. Complications often arise after a relatively short history; most are explicable on the basis of sudden pressure increments. The recent important finding in this disease is the change in colonic wall compliance, which probably occurs because of a collagen failure. Contraction of the taeniae may follow elastosis, which may relate to under-filling; this produces the contracted structure seen in the excised colonic specimen. The strength of the colonic wall diminishes throughout life, due to changes in its composition; some of these changes are hastened by self-imposed stresses, which currently seem to be mainly of dietary origin.

Adult↗
PubMed1985

Erythrocyte pyrimidine-5'-nucleotidase activity as a sensitive indicator of lead exposure.

Since the red cell enzyme pyrimidine-5'-nucleotidase (PN) is inhibited by lead, we examined the feasibility of using the activity of this enzyme as a measure of lead exposure. Erythrocyte PN activity was measured in 110 blood samples obtained from subjects working in industries which utilize lead and 40 control subjects. The measurements were then compared with a number of traditional indices of lead poisoning. These included blood and urine lead concentrations and free erythrocyte protoporphyrin, erythrocyte zinc protoporphyrin, urinary coproporphyrin and urinary delta-aminolaevulinic acid levels. There was a highly significant negative correlation between erythrocyte PN activity and blood lead concentration (-0,83; P less than 0,0001), which was greater than that for any of the other measurements. It was therefore concluded that erythrocyte PN activity is an excellent indicator of lead exposure.

5'-Nucleotidase↗
PubMed1985

Erythrocyte zinc protoporphyrin determination for screening for lead exposure.

Free erythrocyte protoporphyrin (FEP), erythrocyte zinc protoporphyrin (EZP) and blood lead concentrations were measured in 150 male subjects, 110 of whom were employed in industries where lead exposure was possible. Eighty-seven per cent of these 110 workers had blood lead levels above the maximum safe level of 40 micrograms/dl, which suggests that the factory control of lead toxicity is inadequate. The AVIV dedicated front-face fluorometer (AVIV instruments, New Jersey, USA), which measures EZP, was evaluated as a simple, rapid method of screening for lead accumulation. EZP concentrations agreed well with conventional estimations of FEP (r = 0,987, P less than 0,0001), and both correlated well with the blood lead concentration (r = 0,558, P less than 0,0001 for EZP; r = 0,633, P less than 0,0001 for FEP). The specificity of the EZP level as a screening test was found to be high (98%) and the sensitivity moderately good (83%). In view of the ease and speed of operation of this portable fluorometer, it should prove useful as an aid to the detection of early lead intoxication.

Environmental Exposure↗
PubMed1985

Correlation of clinical and manometric abnormalities of rectal function following chronic radiation injury.

Continuous fluid-inflation proctometrograms were performed in men with the symptoms of chronic radiation proctitis and in age and sex-matched control subjects (n = 10). Rectal volumes and compliance were measured. There was a significant reduction in the rectal volumes at sensory threshold, constant sensation and maximal tolerance and in rectal compliance (P less than 0.01). Comparable pressure measurements did not demonstrate significant differences. The maximum tolerable volume, symptomatic and sigmoidoscopic scoring correlated to rectal compliance (r = 0.77, -0.8, -0.73; P less than 0.01, less than 0.01, less than 0.02, respectively). Reduction in volume and compliance is often not obvious radiologically. Histological evidence suggests that smooth muscle hypertrophy and myenteric plexus damage are contributory.

Aged↗
PubMed1985

Surgical aspects of intestinal injury due to pelvic radiotherapy.

Seventy-one patients with intestinal injury secondary to pelvic irradiation had predominantly large bowel lesions. Seventeen cases were treated conservatively and 54 came to surgery, 28 patients having more than one operation. Following this essentially salvage surgery there were more ileal than colonic anastomotic leaks. Thirty-four patients died during the follow-up period (2-12 years), 19 from recurrent malignancy, and nine as a result of continuing radiation effects. Seventy per cent of the patients who had a radiation fistula died as a result of malignancy. Of 42000 cases of pelvic malignancy treated by irradiation over the decade 1972-1982, surgical referrals for complications constituted 1.7%, with an overall radiation-related mortality of 0.2%. It is our opinion that colostomy alone has little part to play in this condition, and a policy based on excisional surgery is suggested.

Adult↗
PubMed1985

Mechanical properties of the rat colon: the effect of age, sex and different conditions of storage.

The mechanical properties of the rat colon were studied in old and young Sprague-Dawley rats which were also grouped by sex. Different storage media were used. Rings of colonic tissue were submitted to pulls on an Instron 1026 tensiometer. Gender did not affect the properties of the young rat colon. The rat colon has a tensile strength of around 50 g/mm2 (which places it between the dog and the cat). It increased in strength from proximal to distal, though the rectum was weaker than the colon. The pre-strain of the rat colon was 10% and it was capable of stretching to 200% of its original dimensions. The strength and ability to stretch fell with age, although it initially increased, in the first year of life. Physiological saline at 4 degrees C preserved the burst strength, percentage elongation, hysteresis and Young's modulus between 25 and 100 g stress for up to 1 week. Young's modulus between 125 and 200 g fell progressively with each day of storage. Stress relaxation rose in the first 24 h and thereafter remained constant. Salt appeared to be a good long-term storage medium. Irradiation of the colons before storage did not affect the mechanical properties.

Animals↗