Biomedical subjects

R K Smith

Publications and source records attributed to R K Smith.

At least 73 records · Page 4Linked to original sources

PubMed1980

alpha-Flupenthixol: an antagonist of dopamine-evoked fluid secretion by an insect salivary gland preparation.

1 We have demonstrated inhibition of secretory responses of cockroach salivary glands to dopamine, adrenaline, noradrenaline and neurotransmitter by alpha-flupenthixol. This inhibition was slow in onset (60 min) and in reversal (greater than 2 h). 2 Inhibition of responses to adrenaline and noradrenaline was non-competitive, since the maxima and slopes of dose-response curves of these agonists were reduced. 3 Although at low concentrations (less than 3 microM) the antagonism of responses to dopamine showed some characteristics of competitive inhibition, at higher doses non-competitive inhibition was clearly demonstrated. 4 These results are explained in terms of different efficacies of the agonists for the receptors antagonized by alpha-flupenthixol. 5 beta-Flupenthixol was shown to antagonize responses to dopamine; however it was 10 to 100 times less potent than alpha-flupenthixol.

Animals↗

PubMed1979

Ion and water transport by isolated cockroach salivary glands.

When the isolated salivary glands of the cockroach Nauphoeta cinerea Oliver are stimulated by dopamine, the putative neurotransmitter, they secrete a fluid containing (mM):Na, 121; K, 47; Cl, 143. Stimulation of glands by 5-hydroxytryptamine or the neuro-transmitter evokes a secretion identical in Na composition to this. Dopamine-evoked secretion is abolished in the absence of extracellular Na. The relationship between the rates of fluid secretion and Na transport is linear. However, at very low rates of secretion the Na concentration falls. Calcium, K and Cl ions can be removed from the bathing solution without abolishing fluid secretion. Our evidence suggests that (i) the primary secretion is formed by active transport of Na in the acini, and (ii) the ionic composition of this secretion is modified by re-absorption of Na and an independent secretion of K in the ducts.

Biological Transport↗

PubMed1979

Circadian periodicity of the cell kinetics of rat molar periodontal ligament.

Circadian periodicity of DNA synthesis (S) phase and mitosis over a complete 12-hour light/12-hour dark cycle was studied in rat molar periodontal ligament (PDL) with 3H-thymidine autoradiography. Maximum percent labeled cells was at 10 A.M. in all regions, and mean labeling (24-hour average) was 1.44, 0.93, and 1.46 percent for the crest, midroot, and apical areas of the PDL, respectively. Maximum percent mitotic figures were also at 10 A.M. in all areas studied, and the mean number of mitoses averaged over 24 hours was 0.19, 0.12, and 0.14, respectively for crest, midroot, and apical areas. Ratios of mean labeling and mitotic indices were 7.58, 7.75, and 10.43 from crest to apex. Duration of mitosis and S phase were estimated at 1.2 and 9 hours, respectively. Analysis of data suggested that stress/strain within the PDL, associated with masticatory function, has a regional influence on duration of S phase, mitotic rate, and percentage of cells in the S phase. These results help define an in vivo experimental model for assessing the PDL cellular response to biomechanically defined force systems. Clinical implications are discussed.

Animals↗

PubMed1979

Osseous lesions and pathologic fractures in congenital cytomegalic inclusion disease: report of a case.

A newborn infant with congenital cytomegalic inclusion disease had spontaneous fractures of the distal radii bilaterally, and involvement of the metaphyseal portions of the humeri, ulnas, femurs, and tibias. The fractures healed promptly without complications under ordinary management. At the present time, one can only speculate on the cause of these lesions. Viral osteomyelitis, osteomalacia secondary to hepatitis and malabsorption and a disturbance of endochondral ossification are all possibilities. There is a need for additional cases with histologic and biochemical studies of the bone lesions in congenital cytomegalic inclusion disease.

Bone Diseases↗

PubMed1979

The self in mission and hospitality.

The Catholic health care provider's self-definition must be "servant." Individuals and institutions are called upon to avoid selfism and to accept exhilarating tensions between "going-out" (mission) and "welcoming-in" (hospitality).

Catholicism↗

PubMed1979

Total hip replacement following failed femoral hemiarthroplasty.

Total hip-replacement arthroplasty performed for failed femoral hemiarthroplasty achieved results that were as good as those of the same operation done for other conditions. In forty-one patients who underwent such a procedure and who were followed for an average of three years, there was marked improvement in pain rating and range of motion. However, there were more cases of progressive loosening of the prosthesis than occur ordinarily, and three revisions had to be done. Fixation of the femoral component with cement was complicated by the presence of the fibrous membrane and bone deficiency preoperatively.

Adolescent↗

PubMed1978

On the receptors involved in the nervous control of salivary secretion by Nauphoeta cinerea Olivier.

1. It has been shown that the isolated salivary glands of Nauphoeta cinerea Olivier produce fluid secretion in response to nerve stimulation or bath applications of dopamine, noradrenaline, adrenaline and 5-HT. These catecholamines, of which dopamine is the most potent, evoked maximal responses matching that to nerve stimulation whereas 5-HT was less effective. 2. The receptors combining with 5-HT could be distinguished from those for the catecholamines and the transmitter at this salivary neuroglandular junction. 3. The results of experiments where glands were stimulated by dopamine in the presence of noradrenaline or adrenaline suggested that there are receptors with specific binding sites for dopamine. 4. The effects of several antagonists (Ginsborg, House & Silinsky, 1976) of the hyperpolarizing responses from acinar cells to nerve stimulation and the above agonists have been examined. Phentolamine reversibly suppressed the secretory responses to these stimuli whereas methysergide had no effect and ergometrine elicited fluid secretion in a dose-dependent manner.

Animals↗

PubMed1978

Competitive antagonism by phentolamine of responses to biogenic amines and the transmitter at a neuroglandular junction.

1. A quantitative study has been made of phentolamine's inhibition of the electrical and secretory responses of the isolated salivary glands of Nauphoeta cinerea Olivier to nerve stimulation and bath applications of agonists. 2. The results suggested that phentolamine is a competitive antagonist having an affinity constant of about 1 micrometer-1 for the receptors for dopamine, noradrenaline, adrenaline and the neurotransmitter. 3. Phentolamine also inhibited responses to 5-hydroxytryptamine in a manner seemingly more complex than competitive antagonism. Attempts to estimate the affinity constant gave values of about 0.08 and 0.015 microgram-1 for inhibition of the secretory and electrical responses respectively. 4. This investigation showed that phentolamine discriminates between two kinds of receptor in this gland, one binding 5-hydroxytryptamine and the other combining with catecholamines and the neurotransmitter.

Animals↗

PubMed1977