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Biomedical subjects

P D Richards

Publications and source records attributed to P D Richards.

17 recordsLinked to original sources
PubMed2001

Correlation between shell colour and ultrastructure in pheasant eggs.

1. The histochemistry and ultrastructure of pheasant eggs were compared on the basis of blue or brown shell colour. 2. Differences in lectin histochemistry of the outer shell membrane calcification surface indicate a biochemical disruption of the calcification sites in blue eggs. 3. Significant differences were observed in all aspects of eggshell ultrastructure with blue eggs having thinner shells with structural defects. 4. Poor hatchability of blue eggs may reflect high rates of weight loss associated with a defective eggshell.

Animals↗
PubMed2000

Ultrastructural characteristics of ostrich eggshell: outer shell membrane and the calcified layers.

The ultrastructure of the eggshell of the domestic hen has been well researched and structural studies of other avian species, such as the ostrich, often base their interpretation of egg shell structure on that of the chicken. In the ostrich, lowered hatchability and hatching trauma may be due to shell ultrastructural abnormalities. In the present study the ultrastructure of the calcified portion, and the outer shell membrane (OSM), of domesticated ostrich eggshells was investigated using standard electron microscopic techniques. Transmission and scanning electron microscopy studies demonstrated intimate contact between cup-shaped structures present on the OSM and the mammillary layer of the calcified portion of the shell. The initial calcium carbonate growth of the calcified shell was of a dendritic nature with nucleation sites on the surface of the cup's contents. The dendritic growth gave way to a more randomly-orientated, smaller crystallite growth structure, which changed in form as it neared the vertical crystal layer (VCL). The VCL is described as being both amorphous and 'crumbly' depending on the plane of fracture. These observations suggest that firstly, initial calcification is contained within the cups and is then directed outwards to form the shell and that secondly, the VCL may contain an evolutionary, calcified cuticular layer. These observations serve as a baseline for studies investigating the effect of shell structure and strength on hatchling trauma and the influence of maternal diet.

Animals↗
PubMed2000

The optical microscope--en route to extinction?

Change in medical curricula is a worldwide trend. Concomitant with this is a change in the role of the microscope and its contribution to a student's career. In this questionnaire-based study the perceptions of medical, dental and veterinary students to microscopy and alternative forms of histology tuition, as well as the role of microscopy in their future careers, was assessed. Veterinary students indicate a strong preference for the microscope and microscopy training due to the importance of the microscope in their chosen career, whilst medical and dental students are somewhat ambivalent. However, the students would not choose to eliminate the microscope entirely from their studies.

Attitude of Health Personnel↗
PubMed1998

Microscopical localization on adenylate cyclase: a historical review of methodologies.

The histochemistry technique for localizing adenylate cyclase has been developed over the past two decades. Early efforts were directed at overcoming the criticism of the lead capture technique, the inhibition of the enzyme by fixation, and problems associated with the substrate. The introduction of alternative metal ions, strontium and cerium, offered solutions to the criticism of the lead capture technique. The inhibition of the enzyme by the various fixation methods used has been rarely overcome satisfactorily and the use of non-fixed material during incubation is one of the alternatives that has been suggested. The introduction of adenylate (beta-gamma-methylene) diphosphate as an alternative substrate offers a solution to the problems associated with commercially available adenylyl imidodiphosphate. Although no standard medium or method has been accepted by all researchers, the histochemical technique still has a place in the arsenal of the modern cell biologist. The technique localizes the active enzyme, as opposed to the protein, active and nonactive, by immunocytochemistry and the precursors of the protein by in situ hybridization methods.

Adenosine Triphosphate↗
PubMed1998

Immunocytochemical localization of adenylyl cyclase in human myometrium.

The enzyme adenylyl cyclase (AC) plays a pivotal role in smooth muscle relaxation. Biochemical evidence suggests that AC is predominantly located in the outer layers of the myometrium; however, neither immunocytochemical nor histochemical studies have been undertaken to demonstrate the specific cellular distribution of the enzyme in this tissue. As part of an ongoing study of the human myometrium, a polyclonal antibody against types V and VI AC was used to detect the presence of these isoforms in sections of formalin-fixed, wax-embedded myometrial tissue. A positive reaction was seen in the cytoplasm of the smooth muscle cells with the midmyometrial area having the greatest number of positive cells, when compared to the subserosal and subendometrial areas. It is hypothesized that AC isoform type VI is the predominant isoform present in the myometrium and that the percentage distribution of positive cells reflects the area of highest myometrial activity during parturition.

Adenylyl Cyclases↗
PubMed1998

Detection of rotavirus in children under five years of age presenting with diarrhoea at Mapulaneng Hospital at Bushbuckeridge, Republic of South Africa.

OBJECTIVE: To determine the incidence of Rotavirus infection in children under five years of age presenting with diarrhoea. DESIGN: Cross sectional study. SETTING: Mapulaneng Hospital, Bushbuckridge, Republic of South Africa. SUBJECTS: 50 children under five years of age presenting with diarrhoea. MAIN OUTCOME MEASURES: Rotavirus seroprevalence. RESULTS: Out of 50, 24 (48%) had detectable Rotavirus particles in their stools. The highest incidence of infection was observed among the seven to 12 months age group. Out of the 245 positive subjects 22 (91.7%) were breast fed. CONCLUSION: This study shows that diarrhoea in children under five years of age is probably caused by Rotavirus in Bushbuckridge. We therefore recommend that all children presenting with diarrhoea should be screened for Rotavirus.

Cross-Sectional Studies↗
PubMed1997

Some observations on fluorescence in situ hybridization evaluation of chronic myelocytic leukemia.

Cosmid probes specific for the major BCR/ABL rearrangement (commercially available probes) were employed by us to evaluate 134 patients with the clinical diagnosis of chronic myelocytic leukemia (CML). The following represent our main observations: 1) No significant statistical difference regarding a false positive fusion signal was seen in the distribution pattern between the Ph negative (-) cases (110) and the normal controls (3.23 +/- 1.97 vs 2.8 +/- 1.92, respectively). 2) The mean percentage of cells with a positive fusion signal in the Ph positive (+) CML cases at presentation was 70 +/- 12.3 in bone marrow samples (12 cases) and 45 +/- 12.4 in blood samples (3 cases). 3) A significant discrepancy was seen between the interphase FISH and cytogenetics data in the monitoring of four out of eight patients post-therapy. The clinical significance of this observation needs to be clarified. 4) Three Ph(-) patients with significant leukocytosis had closely adjacent but not fused signals (20%, 16%, and 20% of cells, respectively, vs. the control: 4%). This may indicate a temporal and spatial association between chromosomes 9 and 22 prior to the BCR/ABL rearrangement (Ph chromosome formation).

Aged↗
PubMed1994

Cytochemical localization of adenylate cyclase in the sodium-transporting epithelium isolated from frog skin.

A modified cytochemical technique with 5'-adenylylimidodiphosphate as substrate, was used to examine the distribution of adenylate cyclase in cells comprising the transepithelial Na+ transport pathway in isolated frog skin epithelium. Particular attention was paid to the effects of fixation on the activity and localization of adenylate cyclase. Fixation in glutaraldehyde alone or in combination with paraformaldehyde reduced the amount of reaction product, while better results were obtained using unfixed tissues. Optimum results were obtained following stimulation of adenylate cyclase with forskolin and in the presence of specific metabolic inhibitors. Adenylate cyclase was localized in the basolateral membranes of the principal cells which constitute a functional syncytium for Na+ transport and was absent from the apical membranes of the outermost granulosum cells. This distribution is consistent with the transepithelial Na+ transport model and defines the functional morphology of the cells involved in Na+ transport across frog skin. The results are compatible with the process of Na+ re-absorption across other epithelial cells, verifying that frog skin is a convenient model-tissue to study Na+ transport mechanisms. Adenylate cyclase was also found in membranes of the mitochondria-rich cells, a minor and parallel Na+ transporting pathway.

Adenylyl Cyclases↗
PubMed1994

Towards a standard method to demonstrate adenylate cyclase activity at the electron microscopical level.

The ventral epidermis of the frog Rana fuscigula is a typical tight epithelium which acts as a functional syncytium in the active transepithelial transport of sodium ions. Transport across this epithelium is regulated by cyclic adenosine monophosphate (cAMP). This study was undertaken to formulate an optimal protocol for the localization, within this epithelium, of adenylate cyclase; the enzyme involved in cAMP synthesis. The ventral epithelium of R. fuscigula was collagenase treated and processed using five different fixation/incubation protocols. The components of a basal incubating medium were modified by changing the localizing agent, adding adenylate cyclase stimulators and inhibitors of other enzymes. Control incubations undertaken included a) leaving the substrate out, b) prior heat inactivation of the enzyme, c) specific blockers and d) incubation for alkaline phosphatase as an alternative enzyme. The samples were then processed for electron microscopy. Localization of adenylate cyclase was best obtained, when fixing the tissue after incubation for 30 min at 37 degrees C. The medium that gave the best and most consistent localization contained magnesium chloride; as a required ion, theophylline, dithiothreitol, ouabain, levamisole; as enzyme inhibitors, forskolin; as a stimulator of adenylate cyclase, lead nitrate; as the capture agent and column purified adenylyl imidodiphosphate; as the substrate.

Adenylyl Cyclase Inhibitors↗
PubMed1993

An ultrastructural study of melanocytes and melanosomes in the skin and hair bulbs of rufous albinos.

We have examined hair bulb and skin melanocytes of rufous albinos from Southern Africa to further characterize this form of albinism. In the skin melanocytes we find both eumelanosomes and pheomelanosomes at various stages of melanization and, in addition, there appeared to be many aberrant incompletely melanized melanosomes. On average, rufous melanosomes are 30% smaller than normal black skin melanosomes. In the keratinocytes, the melanosomes are packaged into distinct aggregations, whereas in normal black skin, they occur singly. We suggest that the reddish skin color of these albinos is a consequence of an increase in the pheomelanin synthesis resulting in a raised pheomelanin/eumelanin ratio and that the aggregation of melanosomes results in a skin color slightly lighter than normal. In hair bulb melanocytes, only eumelanosomes were seen and these were mostly incompletely melanized. These findings correlate with our visual observations that the hair color of Southern African albinos is very pale (light brown or ginger). Based on our observations, we speculate on the possible cause of rufous albinism.

Albinism, Oculocutaneous↗
PubMed1986

The antiemetic efficacy of secobarbital and chlorpromazine compared to metoclopramide, diphenhydramine, and dexamethasone. A randomized trial.

The efficacy of secobarbital sodium plus chlorpromazine (SC) in the prevention of cisplatin induced emesis was compared to the combination of metoclopramide, diphenhydramine, and dexamethasone (MDD). Twenty-three patients were entered onto protocol. Eighteen were evaluable. Good to excellent antiemetic prophylaxis was obtained in 72% with MDD versus 17% with SC (P less than 0.01). Sedation and anticholinergic side effects were more common with SC. Extrapyramidal reactions were more commonly seen with MDD. Significantly more patients preferred the combination of metoclopramide, diphenhydramine, and dexamethasone (P less than 0.05).

Adult↗
PubMedDate not supplied

The ultrastructure of fibromyomatous myometrium and its relationship to infertility.

The aim of this study was to determine whether the ultrastructure of the non-neoplastic myometrial portion (host myometrium) of fibromyomatous uteri is normal or abnormal when compared to that of fibromyomata and normal myometria. Myometrial samples from 23 normal and 54 fibromyomatous uteri were examined at the ultrastructural level using standard electron microscopy techniques. Ultrastructural abnormalities of certain cellular organelles were noted in myocytes of fibromyomata but not in those of normal or host myometria. The sarcolemmal dense bands of host myometrial myocytes were of significantly greater length than those of normal myometria, but not significantly different to those of fibromyomata. Consequently, the numbers of caveolae in host myometria and fibromyomata are conceivably decreased in comparison to normal myometria. Host myometria can be, therefore, considered to be structurally abnormal. The specific structural abnormality noted may affect calcium metabolism in these tissues by causing a decrease in the cellular calcium extrusion mechanism and thus raising intracellular calcium concentrations. Such an abnormality may provide an answer, in terms of contraction abnormalities, for the unexplained infertility that occurs in a small percentage of symptomatic myomatous patients.

Female↗