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Biomedical subjects

C A Williams

Publications and source records attributed to C A Williams.

At least 163 records · Page 9Linked to original sources
PubMed1987

Psychopharmacological activity of immune complexes in rat brain is complement dependent.

Sprague-Dawley male rats implanted with chronic indwelling cannulae at the perifornical hypothalamus eat excessively during the sixth hour following administration of exogenous immune-complexing reactants to the brain site. Rabbit anti-HSA was injected, followed in 30 min by a 20-fold excess of antigen. Anaphylatoxin C5a has also been shown to induce excessive intake, an effect similar to that of norepinephrine at this brain site. If the anaphylatoxins or other byproducts or consequence of the complement cascade were responsible for the immune complex effect, interference with the initiation of the cascade or with the conversion of C3 to C3a and C3b should abolish the behavioral response. These experiments demonstrate that immune complexes formed with the non-complement-fixing F(ab')2 fragment of the rabbit anti-HSA do not induce eating, and that normally active IgG antibody complexes do not induce eating if the site has been pretreated with goat anti-rat C3. This latter treatment had no effect, however, on the ability of the animals to respond to norepinephrine or to C5a. We conclude that the immune complex effect is complement dependent.

Animals↗
PubMed1987

Possible catecholaminergic-opioidergic control of blood pressure during muscular contraction.

The effects of an alpha 2 adrenoceptor blocker, yohimbine, and an alpha 1 adrenoceptor blocker, phenoxybenzamine, and the central alpha 2 adrenoceptor agonist, clonidine, on changes in arterial blood pressure and heart rate were studied during fatiguing muscular contractions to determine whether an adrenergic-opioidergic system might be involved in the mediation of cardiovascular function. Fatiguing contractions of the gastrocnemius and plantaris muscles of cats caused an increase in mean arterial blood pressure to 150-170 mmHg from resting values of 110-120 mmHg. Injection of clonidine into the cerebral aqueduct eliminated the increase in blood pressure; this effect was dose dependent. Naloxone antagonised the effects of the highest dose of clonidine (5 micrograms). Injections of yohimbine (1 microgram) into the cerebral aqueduct had no significant effect on this pressor response. Yohimbine (1 microgram) effectively counteracted the antipressor effects of clonidine when the two drugs were injected together until higher doses of clonidine (2-5 micrograms) were used. Phenoxybenzamine had no effect on the pressor response itself but unlike yohimbine was able to attenuate the effects of clonidine only when injected together. These data suggest that activation of muscle ergoreceptor afferent nerve fibres (group III and IV fibres) during muscular contractions may cause an increase in arterial blood pressure by interfering with an inhibitory adrenergic-endorphinergic pathway in the medullary region of the brainstem.

Animals↗
PubMed1987

Effects of carotid artery occlusion on the pressor response induced by sustained isometric contraction in the cat.

The effects of clonidine, a central alpha 2 agonist, on changes in blood pressure caused by muscle afferent nerve (ergoreceptor) activation and baroreceptor manipulation were studied in cats. Prolonged isometric contractions (ergoreceptor activation) of the gastrocnemius and plantaris muscles increased mean arterial pressure by 53 mmHg. This pressor response was not altered by naloxone (0.5 mumol.litre-1) but was eliminated by clonidine (0.5-2.0 micrograms) when injected into the cerebral aqueduct. Brief occlusion of the carotid artery (15-30 s) caused mean arterial pressure to increase by 32-42 mmHg at rest. Neither naloxone nor clonidine altered the magnitude of the reflex pressor response to carotid occlusion. Similar increases in pressure were measured when occlusion was applied during fatiguing isometric contractions; thus baroreceptor induced increases in pressure were superimposed on the ergoreceptor induced blood pressure changes. Naloxone did not affect the changes in pressure caused by either reflex response. Clonidine continued to eliminate the pressor response to muscular contraction but did not affect the pressure increase when the carotid occlusion was applied during contractions. Electrical stimulation of the carotid sinus nerve caused blood pressure to decrease by 36 mmHg during rest and by 41 mmHg during fatiguing isometric contractions. Clonidine did not alter the depressor response to carotid sinus nerve stimulation. These data may indicate that separate pathways centrally mediate the changes in blood pressure caused by ergoreceptor and baroreceptor afferent activation. The integration of the ergoreceptor pathway may involve a catecholaminergic-opioidergic system but the present results do not suggest a similar interaction for the baroreceptor integration.

Animals↗
PubMed1987

Influence of glucose, alcohol and glycerol on galactose tolerance in man.

Six volunteers were given 0.5 g galactose/kg body weight alone (A) or with 0.5 g glucose/kg (B) or with 0.5 g glycerol/kg body weight (C). Meals A and B were also given 15 min after ingestion of 300 mg ethanol/kg body weight. Glycerol did not influence the serum galactose response to galactose. Glucose reduced the serum galactose response as was expected. Administration of alcohol prior to a galactose test meal increased the mean area under the serum galactose response curve (p less than 0.01); when glucose was given with galactose after alcohol ingestion, the serum galactose response was significantly reduced (p less than 0.01) when compared to the serum galactose response to galactose after alcohol, but remained higher than after the galactose and glucose test meal. Glucose, therefore, can reduce the effect of alcohol on galactose levels but alcohol can abolish the effect of glucose on galactose metabolism.

Adult↗
PubMed1987

Hepatitis B virus transmission in a public school: effects of mentally retarded HBsAG carrier students.

In 1980, 18 institutionalized children, carriers of hepatitis B virus (HBV), were enrolled into two special education schools, and staff and students were monitored for HBV markers. Eleven HBV exposures were observed and those exposed were given hepatitis B immune globulin. After 3.5 years, no remaining staff showed serological evidence of HBV infection but three of 61 susceptible students did so. The three students probably acquired the infection outside the school. At the conclusion of the project, one school located in the community decided not to institute a vaccine program for students or staff. The other school, located inside the mental retardation institution, established an organized vaccine initiative. Indications for use of hepatitis vaccine in schools should be individualized to accommodate for differences in student and staff interaction, physical design of the school, and number and behaviors of HBsAg carrier students.

Adolescent↗
PubMed1986

Extracellular proteolysis: developmentally regulated activity during chick spinal cord histogenesis.

The present study was performed to identify at which stages during spinal cord histogenesis the extracellular proteolysis (i.e. the plasmin-generating system) is expressed by the developing tissue. We report that the embryonic chick spinal cord in the course of its histogenesis produces the protease, plasminogen activator. Specific activity of plasminogen activator in the developing embryo was monitored daily, in whole cords (from day 4 until hatching) and in the ventral and dorsal halves of the cord (6-17 days) and was biochemically determined by the fibrinolytic assay. The enzyme-specific activity of the developing cord was found to be very low at early embryonic stages when neuroblasts proliferate and it is markedly enhanced (14-fold at its maximal level) at later stages when the neurons are postmitotic and only the glial cells proliferate. The pattern of plasminogen activator specific activities does not remain at a constant level: it appears to be developmentally regulated, since it is decreased and enhanced during 3 temporal stages of the spinal cord histogenesis. These coincide with the stages when a transient increase in cell proliferation, presumably of glia, was monitored as determined daily by the spinal cord DNA content (microgram DNA/mg protein). Furthermore, on days 7-9 of embryonic age, the two halves of the cord differ in their plasminogen activator specific activities; activity levels of the ventral halves were found to be higher than their dorsal counterparts with significant difference on day 7. These correspond with the well-established differentiation gradient in the ventral-to-dorsal axis of the cord.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Feline dental disease.

Periodontal disease and chronic gingivitis/stomatitis are the most common feline dental diseases. With routine dental care and increased emphasis on home oral hygiene, these diseases can be controlled. Cats can be seen with a number of other dental disorders, and improved treatment methods such as restorations of early subgingival resorptive lesions, endodontic therapy, and orthodontic therapy can be performed successfully. More study and research are necessary about the gingivitis/stomatitis syndrome and subgingival resorptive lesions so that improved prevention and treatment recommendations can be made.

Animals↗
PubMed1986

Endodontics.

It is known that pets with broken teeth or teeth with other diseases of the pulp suffer considerable pain and frequent infection. To ignore these problem teeth would not only be inhumane, it would risk chronic infection, abscessation, and tooth loss. Although extraction of these teeth is sometimes necessary, the procedure is often difficult to perform and painful for the animal. The resultant tooth loss is cosmetically displeasing and, frequently, there is compromise in function. The endodontic treatment of these teeth, on the other hand, is relatively easy to perform. It almost always results in immediate cessation of pain and will usually allow the tooth to remain functional for the lifetime of the pet.

Animals↗
PubMed1986

Restorative dentistry. Clinical applications.

Restorative techniques for human teeth have been used and refined for centuries. Most of these techniques can be applied with few modifications to restore diseased or damaged teeth in animals. The results can be both functionally sound and cosmetically pleasing.

Animals↗
PubMed1986

The value of hepatic ultrasound and biochemical liver tests in screening for liver metastases.

The records of 92 patients with a known diagnosis of extrahepatic cancer who had undergone hepatic ultrasound, biochemical liver tests (alkaline phosphatase, SGOT, lactic dehydrogenase, and bilirubin levels), and subsequent liver biopsy or autopsy within a 6-week period were reviewed. The sensitivity, specificity, and accuracy of the ultrasound and biochemical tests in the detection of metastatic liver disease were calculated. Although there was no significant difference in the sensitivity of either examination, the ultrasound demonstrated higher specificity and accuracy than the biochemical liver tests. The high sensitivity of hepatic ultrasound prevailed even in patients with normal biochemical liver tests. The sensitivity of hepatic ultrasound was significantly lower in patients with lymphoma compared with patients with colorectal cancer (50% v 100%, P less than .05). Notable incidental extrahepatic findings were reported in 25% of the ultrasound examinations. In institutions skilled in sonography, hepatic ultrasound may be a superior tool in the detection of liver metastases in most solid tumors, excluding lymphoma, and offers the additional advantage of simultaneous biliary tract and perihepatic visualization.

Alkaline Phosphatase↗
PubMed1986

Cyclical gonadotrophin and progesterone secretion in women with minimal endometriosis.

Concentrations of LH, FSH, oestradiol (E) and progesterone (P) were measured in serum of 12 women with minimal endometriosis and otherwise unexplained infertility. Values were compared with those on corresponding days relative to the pre-ovulatory LH peak (Day 0) in six fertile women. Three women exhibited cycle profiles of LH, FSH, E and P indistinguishable from those in the control group. In the remaining nine women cycle profiles for FSH and follicular phase profiles for LH were normal but eight exhibited a delay in P secretion and reduced total P output. LH concentrations were elevated during the early luteal phase in five subjects, two of whom had a second LH surge. These data suggest that luteal dysfunction and abnormal secretory patterns for LH may be contributory to infertility associated with endometriosis.

Adult↗
PubMed1985

Sympathetic control of the forearm blood flow in man during brief isometric contractions.

Experiments were performed to assess the possible neurally mediated constriction in active skeletal muscle during isometric hand-grip contractions. Forearm blood flow was measured by venous occlusion plethysmography on 5 volunteers who exerted a series of repeated contractions of 4 s duration every 12 s at 60% of their maximum strength of fatigue. The blood flows increased initially, but then remained constant at 20-24 ml X min(-1) X 100 ml(-1) throughout the exercise even though mean arterial blood pressure reached 21-23 kPa (160-170 mm Hg). When the same exercise was performed after arterial infusion of phentolamine, forearm blood flow increased steadily to near maximal levels of 38.7 +/- 1.4 ml X min(-1) X 100 ml(-1). Venous catecholamines, principally norepinephrine, increased throughout exercise, reaching peak values of 983 +/- 258 pg X ml(-1) at fatigue. Of the vasoactive substances measured, the concentration of K+ and osmolarity in venous plasma also increased initially and reached a steady-state during the exercise but ATP increased steadily throughout the exercise. These data indicate a continually increasing alpha-adrenergic constriction to the vascular beds in active muscles in the human forearm during isometric exercise, that is only partially counteracted by vasoactive metabolites.

Adult↗
PubMed1985

Changes in isometric function following rhythmic exercise.

Seven male subjects exercised for 1, 3, 10 and 20 min on a cycle ergometer at 20, 60 and 80% VO2max, and then held to fatigue a sustained contraction of the quadriceps at 40% maximal voluntary contraction in order to determine what influence various levels of dynamic exercise would have on isometric function of the same group of muscles. Muscle temperature was measured before and within 15 s of the completion of the cycling to determine whether changes in muscle temperature might influence the subsequent isometric performance. Isometric endurance was shorter as the severity of the cycling increased beyond 20% VO2max, and as the duration of cycling increased up to 10 min. There were discrete linear relationships between muscle temperature and isometric endurance associated with cycling at 60% and 80% VO2max. There was a direct inverse relationship between quadriceps strength after cycling and muscle temperature, yet a significant reduction in strength occurred only after cycling at 80% VO2max. These results suggest that the encroachment on endurance and strength are controlled by different mechanisms. The heart rates during the isometric contractions were dependent on the preceding rhythmic exercise and decreased after exercise at 60 or 80% VO2max. In contrast, the blood pressure always increased during the isometric contractions, reaching similar values at the point of fatigue, regardless of the severity of the previous rhythmic exercise. These data provide additional evidence that separate mechanisms control changes in heart rate and blood pressure.

Blood Pressure↗