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Biomedical subjects

A Richards

Publications and source records attributed to A Richards.

At least 145 records · Page 8Linked to original sources
PubMed1986

Parathyroid glands, calcium, and vitamin D in experimental fluorosis in pigs.

The purpose of this study was to determine whether total serum calcium, parathyroid gland structure, and/or levels of parathyroid hormone, 1,25 and 24,25 DHCC, are altered in pigs with dental and skeletal fluorosis. Eight experimental animals receiving 2 mg F-/kg b.w. per day from age 8-14 months were compared with eight controls. Concentrations of plasma fluoride and total plasma calcium were assessed at intervals throughout the experiment and during a 48 hour period at day 110-111 of the experiment. At the same time, concentrations of immunoreactive parathyroid hormone were measured using a homologous labeled antibody for porcine hormone, and a radioimmunoassay was used to assess concentrations of 1,25 DHCC and 24,25 DHCC. Parathyroid tissue volumes were assessed at the end of the experiment by quantitative histology using volumetry and point counting. Plasma fluoride increased from 0.0007 +/- 0.0001 mmol/liter to 0.0127 +/- 0.002 mmol/liter in pigs receiving fluoride. In spite of this increase, total plasma calcium remained the same throughout the experiment. Volumes of parathyroid tissue, and levels of circulating parathyroid hormone 1,25 DHCC and 24,25 DHCC, were not significantly changed. It was therefore concluded that disturbance of calcium homeostasis is not an obligatory finding in dental and skeletal fluorosis and consequently does not play an essential role in the pathogenesis of these hard tissue lesions.

Animals↗
PubMed1986

Dental fluorosis developed in post-secretory enamel.

The aim of this study was to test whether dental fluorosis can be produced by administration of chronic doses of fluoride during only the post-secretory stage of enamel mineralization. Eight control and eight experimental pigs matched by weight and litter were fed a low-fluoride diet (less than 0.05 mg F-/kg b.w. daily) from weaning to slaughter at 14 months. The test group received an oral dose of 2 mg F-/kg b.w. per day from 8 months of age. Lower fourth pre-molars were at the post-secretory stage at the start of fluoride administration (confirmed by tetracycline marker) and were just erupting at slaughter. All of the fourth pre-molar teeth from the test group developed diffuse enamel hypomineralization indistinguishable from human fluorosis. No such lesions were seen in any of the teeth from the control animals. It was concluded that enamel fluorosis may be caused by fluoride exposure in the maturation phase only. The pathogenic mechanism may be an effect either on the selective loss of protein or on the influx of mineral, both of which occur during the post-secretory or maturation stage of enamel formation.

Amelogenesis↗
PubMed1985

The incidence of major abdominal surgery after septic abortion--an indicator of complications due to illegal abortion.

That there is a high morbidity associated with illegal abortion is well known, but its exact extent is difficult to assess, since detailed statistics are not available and the nature of the morbidity is diffuse. We have assumed that abortal sepsis is a consequence of illegal interference with pregnancy. The incidence of major abdominal surgery after a septic abortion is used as an indicator of serious complications. This incidence is compared with that following legal abortion.

Abortion, Illegal↗
PubMed1985

The effect of the synthetic steroid Org OD14 on fibrinolysis and blood lipids in postmenopausal women.

Two groups of postmenopausal women were compared. One group of 13 was given the synthetic steroid Org OD14 to suppress climacteric symptoms and one group of 14 was given placebo. After a 2 week baseline period the subjects received daily for 12 weeks, either 2.5 mg Org OD14 or placebo. There were no significant differences between the groups pre-treatment. Compared with the placebo group, during treatment, the Org OD14 group showed the following significant differences: higher haemoglobin, haematocrit, platelet count, plasminogen, fibrinolytic activity on fibrin plates and antithrombin III and lower fibrinogen. No significant differences between the groups were found in alpha 2 antiplasmin levels, total cholesterol, total triglycerides, bilirubin or transaminase levels but the Org OD14 group had significantly lower levels of HDL cholesterol. With the exception of the haemoglobin and haematocrit levels all of the differences had disappeared by 2 weeks post treatment.

Adult↗
PubMed1985

Malaria in pregnancy.

Malaria is a potentially lethal disease. In pregnancy its deleterious effects are aggravated by the depressed immune state. Every pregnant patient presenting with pyrexia of unknown origin should be screened for malarial parasites, especially if she has travelled to or come from an area in which malaria is endemic. Case histories of 2 pregnant women with malaria are presented and the diagnosis, treatment and chemoprophylaxis thereof are discussed.

Adult↗
PubMed1985

Cardiopulmonary arrest after the administration of magnesium sulphate. A case report.

The death of a patient from cardiopulmonary arrest after the administration of magnesium sulphate for imminent eclampsia is reported. It has long been recognized that magnesium sulphate provides rapid control of convulsions in eclamptic patients with minimal sedative effects on both mother and fetus. However, because of the neuromuscular blocking action of magnesium and the narrow margin between therapeutic and toxic serum levels, the drug must be given with caution. A regimen for magnesium sulphate administration is advocated which allows safe and effective control of convulsions in eclampsia.

Eclampsia↗
PubMed1985

Plasmacytoid myoepithelioma of a minor salivary gland.

Plasmacytoid myoepitheliomas are rare salivary gland neoplasms that probably represent a variant of the pleomorphic adenoma. They appear to occur more frequently in the minor salivary glands of the mouth. The mean average age at time of diagnosis of intraoral lesions is 18.8 years. Cytologic pleomorphism is a frequent histologic feature, which has led to a questionable diagnosis of malignancy in five out of ten cases. Caution is advocated in the evaluation of a salivary gland neoplasm with such features, and confusion with primary squamous cell or undifferentiated carcinoma of the salivary glands should be avoided. Patients who have cytologically pleomorphic lesions should be assessed for evidence of metastases. Rapid growth, neurologic evidence of sensory or motor dysfunction, and bone invasion should be regarded as ominous clinical parameters. Therapy should be directed toward complete surgical extirpation.

Adult↗
PubMed1985

Male transmission of the gene for isolated gonadotropin-releasing hormone deficiency.

Three black women, daughters of the same father but three unrelated mothers, presented with isolated gonadotropin deficiency (IGD). Clinically, the patients had no midline defects and intact smell and taste senses. Biochemically, the essential feature was very low unstimulated and stimulated follicle-stimulating hormone and luteinizing hormone levels, even after priming with gonadotropin-releasing hormone over a 5-day period. Growth hormone response to insulin-induced hypoglycemia was somewhat blunted, but prolactin, cortisol, and thyroid-stimulating hormone responses were quite normal. All three patients had the 46,XX karyotype; clinical or biochemical aberrations could not be demonstrated in any of the remaining family members. The disorder was, apparently, transmitted by the deceased father, who manifestly did not have an IGD deficiency nor any of the midline stigmata associated with IGD. The mode of inheritance seems most likely to be autosomal dominant with variable penetrance.

Adolescent↗
PubMed1985

Absorption of delayed-release prednisolone in ulcerative colitis and Crohn's disease.

The absorption and urinary excretion of [3H]prednisolone after oral ingestion was examined using hard gelatin capsules with and without a coating of Eudragit-S which delayed release of the contents. In 6 patients with ulcerative colitis absorption was delayed until the preparation reached the colon but the total absorption was unchanged. In 6 patients with Crohn's disease and ileal strictures the preparation broke proximal to the stricture and absorption was delayed until this occurred (within 4-12 h). In 5 patients with Crohn's disease and intestinal resections the capsules broke unreliably.

Adult↗
PubMed1985

Pharmacokinetics of chronic fluoride ingestion in growing pigs.

The present study was undertaken to estimate bio-availability and biological half-life of fluoride and accumulation of fluoride in bone in the domestic pig. Eight animals receiving 2 mg F-/kg b.w. per day from age 8 to 14 months were compared with eight controls. Plasma fluoride concentrations just prior to the daily oral dose were measured at regular intervals. After 112 days post-dose, plasma fluoride levels were measured over a 48-hour period following the daily oral dose or a single intravenous dose. Mean bio-availability factor for the oral dose was 0.3 (range 0.2-0.4), and mean biological half-life was 59 days (range 49-72). Bone fluoride content calculated from the pharmacokinetic parameters derived from plasma data was similar to the content of fluoride measured in the bone at slaughter. The study showed that accumulation of fluoride in bone influences plasma fluoride levels during chronic administration of fluoride to growing pigs. The long biological half-life found showed that it was not possible to achieve steady-state plasma levels within the six-month experimental period used. This means that, for dose-response studies of dental fluorosis in this animal, it is not possible to achieve steady-state plasma concentrations as a basis for correlations to the degrees of pathological change observed in the teeth.

Administration, Oral↗
PubMed1985

Prolactin dynamics and tumour size in the prediction of surgical outcome for prolactinoma.

Each of 62 females were studied for a period of between two and 72 months (mean 36 months) following the removal of a prolactinoma by transsphenoidal pituitary surgery. Our aims were to define the relationships between pre- and post-operative features, the operative findings and the functional outcome. Pre-operative serum prolactin (PRL) concentrations correlated with tumour diameter (r = 0.55, p less than 0.001). Following surgery two groups of patients were identified: Group 1, 46 spontaneously and regularly menstruating patients and Group 2, 16 patients with persistent amenorrhoea. The patients in Group 1 had significantly lower pre-operative and post-operative serum (PRL) concentrations (p less than 0.02 and p less than 0.001 respectively) and significantly greater PRL responses to thyrotrophin releasing hormone (TRH) and metoclopramide stimulation after surgery (p less than 0.001). There was not a significant difference in tumour size between the groups. Forty-four (96 per cent) of the patients in Group 1 had normal post-operative serum PRL concentrations within one week of surgery. By comparison (p less than 0.001) only 42 and 20 per cent respectively of Group 1 patients who were tested had normal TRH and metoclopramide evoked PRL secretion following surgery. Return of regular menstruation was associated with cessation of galactorrhoea in 44 patients (96 per cent) and ovulation occurred in 37 of 38 menstruating patients for whom data are available. All patients with normal TRH and metoclopramide stimulation tests menstruated spontaneously. Nevertheless most patients who menstruated did so in spite of retaining suppressed PRL responses. Of 46 patients followed to date whose serum PRL was normal one week after surgery, seven later were found to have an elevation of serum PRL outside the normal range but in only two has this been persistent. We suggest that a single measurement of serum PRL one week following transsphenoidal pituitary surgery for prolactinoma provides a good basis for deciding about the future management of patients who desire menstruation and pregnancy.

Female↗
PubMed1984

Radiologic assessment of bone maturity and cortical thickness in experimental osteo-fluorosis in the young pig.

Radiographs of the left forelimb were obtained after slaughter in 16 14-month-old pigs. From age 8-14 months, eight pigs in the experimental group received 2 mg F-/kg body weight per day. Bone maturity in F-animals was the same as in controls. Cortical thickness was increased by 10 per cent in the fluorotic animals (p less than 0.01) and their plasma-fluoride levels increased throughout the experimental period to approximate those reported for man in endemic fluorosis areas. Thus fluoride given in the dose used and over that period, did not affect maturation in the long bones but increased cortical bone mass in the diaphyses.

Animals↗
PubMed1984

Experimental osteo-fluorosis in the domestic pig: a histomorphometric study of vertebral trabecular bone.

The experiment aimed at describing effects of fluoride on structure and remodeling of vertebral trabecular bone in pigs. Eight animals receiving a supplement of 2 mg F-/kg b.w. per day from age eight to 14 mo were compared with eight controls. Plasma fluoride increased from 0.7 +/- 0.1 microM/1 to 12.7 +/- 2.0 microM/1 in pigs receiving fluoride. At slaughter, the concentration of fluoride in dry fat-free bone was 149.3 +/- 10.5 mM/kg for fluorotic animals and 9.5 +/- 0.9 mM/kg for controls. Morphologic changes were assessed in un-decalcified specimens of the fourth lumbar vertebra by quantitative histology using fluorochromes as intra-vital tissue time markers. The volume of trabecular bone tissue (bone + marrow) was unchanged in fluorotic animals, but the volume density of bone was increased by 17%. Surface densities of cancellous bone were almost unchanged, whereas the thickness of trabeculae increased in fluorosis. Fluoride enhanced remodeling of trabecular surfaces: The fraction of surface occupied by resorption lacunae increased 40%, and the formative surface approximately 30%. No changes were demonstrated at surface points undergoing formation: Osteoid thickness, calcification rate, lamellar thickness, and completed wall thickness were normal. It is concluded that the observed findings cannot be explained by fluoride-induced changes in a single cell. Fluoride appears to affect all cells involved in remodeling by direct or indirect mechanisms.

Animals↗
PubMed1984

Future of depot neuroleptic therapy: pharmacokinetic and pharmacodynamic approaches.

The future of depot neuroleptic therapy is discussed in terms of pharmacokinetic and pharmacodynamic research opportunities. Analytic methods for neuroleptic assays, including chromatographic, radioreceptor, nuclear magnetic resonance, and radioimmunoassay techniques, are briefly reviewed. Elucidation of depot neuroleptic multicompartment kinetics utilizing nonlinear mixed-effects modeling and the usefulness of these data in interpreting plasma levels are discussed. The clinical significance of plasma monitoring of depot fluphenazine, including the development of dosage conversion guidelines, is presented. The relationships between haloperidol and its metabolite reduced haloperidol (RH) are discussed in terms of dosage form and response. Clinical advantages resulting from the availability of more depot neuroleptics are discussed.

Adult↗
PubMed1982

Fluoride pharmacokinetics in the domestic pig.

Plasma fluoride concentrations were studied in 11 pigs following single oral or intravenous doses of fluoride. The results showed a less-than-20% bioavailability of fluoride when administered with calcium-rich food. Pharmacokinetic analyses showed that the plasma half-life varied from 0.6 to 1.4 h, depending on diet and route of fluoride administration. These data are comparable to those reported for man, and thus illustrate the suitability of the pig for studies of effects of fluoride on hard tissues.

Animals↗