PubMed Health⌕ Search

Biomedical subjects

K C Richardson

Publications and source records attributed to K C Richardson.

At least 19 recordsLinked to original sources
PubMed1998

Evaluation of pulmonary volumetric morphometry at the light and electron microscopy level in several species of passerine birds.

The lungs of 3 small passerine species, having similar body mass but different diurnal activity patterns, were analysed morphometrically to assess the relationship between diurnal activity and pulmonary volumetry at the light and electron microscope levels. The percentage volumes of the major lung and exchange tissue components of the 3 species--an aerial insectivore, a foliage gleaner/nectarivore and a ground forager--were strikingly similar, and consistent with literature values for other passerine species. The only significant difference found was exchange tissue plasma volume and pulmonary haematocrit, with the ground-foraging, low activity Malurus splendens having significantly lower values than the other 2 species. This may indicate that cardiovascular parameters are more important determinants of metabolic activity in small passerines than aspects of pulmonary anatomy.

Animals↗
PubMed1997

Reference ranges for biochemical and haematological values in farmed saltwater crocodile (Crocodylus porosus) yearlings.

OBJECTIVE: To determine reference ranges for healthy yearling farmed saltwater crocodiles by performing routine biochemical and haematological laboratory tests on blood samples. DESIGN: A clinico-pathological study. PROCEDURE: Blood samples were collected from 120 healthy yearlings from four Northern Territory crocodile farms and body weight and length were measured. All animals had been fasted for 2 days before sample collection. Routine biochemical analytes were determined on 120 samples and haematological values determined on 30 samples (from one farm). RESULTS: Reference ranges for biochemical and haematological values were determined for farmed yearling saltwater crocodiles in the Northern Territory. CONCLUSION: The results were comparable with published reference ranges for other crocodilian species. Other published results of haematological values from saltwater crocodiles were from very young (6-week-old) hatchlings and older (2- to 4-year-old) crocodiles. Differences in values were presumed to be caused by age-related factors.

Aging↗
PubMed1996

Retinal photoreceptor fine structure in the Australian galah (Eolophus roseicapillus) (Aves).

The retinal photoreceptors of the galah (Eolophus roseicapillus), an Australian cockatoo, consist of rods, single cones and double (unequal) cones present in a ratio of about 1:3:3 respectively. The rods are long slim cells which are believed to undergo retinomotor movements. The rod inner segment displays an ellipsoid of mitochondria, much rough endoplasmic reticulum (RER), numerous polysomes and some autophagic vacuoles. No hyperboloid of glycogen was noted. Single cones show a slightly tapered outer segment, no oil droplet but a prominent ellipsoid at the apex and glycogen scattered throughout the inner segment. Double cones consist of a chief member which displays a heterogeneous oil droplet but no paraboloid of glycogen and an accessory cone with no oil droplet but a prominent paraboloid. All cones show below the ellipsoid plentiful polysomes, RER, Golgi zones and autophagic vacuoles. Cones are not felt to undergo retinomotor movements. In the light-adapted state the pigment-laden apical processes of the retinal epithelium (RPE) cells surround all photoreceptor types down to the inner segments. Along the length of the contiguous membranes between the two members of the double cones are membrane densifications that are presumed to be junctions. All cone photoreceptors are relatively small in diameter and hence closely packed. Rods and cones (both types) display both invaginated (ribbon) and superficial (conventional) synaptic sites.

Adaptation, Ocular↗
PubMed1996

Fine structure of the pecten oculi in the Australian galah (Eolophus roseicapillus) (Aves).

The pecten oculi of the Australian galah (Eolophus roseicapillus) has been examined by both light and electron microscopy. In this species the pecten is large relative to the size of the eye and is of the pleated type. It consists of 20-25 accordion folds that are joined apically by a bridge of tissue which holds the pecten in a fan-like shape widest at its base. Within each fold are many melanocytes, numerous capillaries as well as larger supply and drainage vessels. The capillaries are extremely specialized for transport functions and display extensive microfolds on both their luminal (inner) and abluminal (outer) borders. Except for the nuclear region which also contains most of the organelles, the endothelial cell bodies are extremely thin. These capillaries are surrounded by thick fibrillar basal laminae which are felt to be structurally important. Pericytes are a common feature within the basal lamina of capillaries. The numerous pleomorphic melanocytes which more or less surround the capillaries are also presumed to be important in structural support of the pecten. The pecten represents a supplementary retinal circulation and is comparable to the falciform process of some teleosts, the conus papillaris of reptiles, the supraretinal vessels of amphibians and some teleosts and the intraretinal vessels of mammals, all of which are felt to be alternative methods of bringing nutrients to the inner retina.

Adaptation, Ocular↗
PubMed1996

Retinal pigment epithelial fine structure in the Australian Galah (Eolophus roseicapillus) (Aves).

As part of a comparative morphological study, the fine structure of the retinal epithelium (RPE), choriocapillaris and Bruch's membrane (complexus basalis) has been investigated by light and electron microscopy in the galah (Eolophus roseicapillus), an Australian cockatoo. The RPE consists of a single layer of low cuboidal cells joined basally by a series of zonulae occludentes. Basally (sclerally) the retinal epithelial cells display numerous deep infoldings while apically (vitreally) microvillar processes interdigitate with photoreceptor outer segments. Internally the RPE cells show a large vesicular nucleus, plentiful smooth endoplasmic reticulum (SER) and numerous polysomes but very little rough endoplasmic reticulum (RER). Numerous mitochondria are located basally. In the light-adapted specimens studied, the melanosomes of the RPE are almost exclusively located within the apical processes indicating that retinomotor movement of this pigment probably occurs. Phagosomes and lysosome-like bodies are present as are myeloid bodies which may show ribosomes on their outer surface. The choriocapillaris endothelium is thin but only minimally fenestrated facing Bruch's membrane. Most fenestrations of the choriocapillaris display a single-layered diaphragm while the remainder have a double-layered diaphragm. Bruch's membrane (complexus basalis) is typical of avian species in that it is pentalaminate with the central lamina densa displaced towards the choriocapillaris.

Animals↗
PubMed1995

Cephalic morphology of the honey possum, Tarsipes rostratus (Marsupialia: Tarsipedidae); an obligate nectarivore.

The sharply tapering skull of the honey possum is delicately constructed and has only a few, minute teeth; its mandible is reduced to a thin, flexible rod. The mandibular fossa has been displaced caudally to the caudomedial corner of the squamosal. Head skeletons of the feathertail glider and western pygmy-possum, omnivores that are closely related to the honey possum, bear greater resemblance to the distantly related carnivorous fat-tailed dunnart than to the honey possum. Selected muscles associated with the jaws, hyoid, and tongue of these four mouse-sized (9-22 g) marsupials are described for the first time. The honey possum is characterized by a greatly reduced temporalis that is almost completely hidden by the eye. Its digastric consists of a single belly that inserts onto the caudal margin of the mylohyoid. The lateral pterygoid is relatively long as it extends caudally to insert onto the elongated mandible. The stylohyoid originates high up on the caudal surface of the tympanic bulla; it curves around the caudal and ventral surfaces of the bulla to reach the basihyoid. The insertion of the genioglossus is restricted to the caudal quarter of the tongue. Homologous muscles of the feathertail glider and western pygmy-possum are more similar to those of the fat-tailed dunnart. In addition to the very different musculoskeletal system, the honey possum has an unusual tongue that tapers to a fine point.

Animals↗
PubMed1994

Distribution of heat-stable enterotoxin/guanylin receptors in the intestinal tract of man and other mammals.

The human intestinal tract, as well as that of several eutherian and metatherian mammals, was examined for the distribution of heat-stable enterotoxin (ST)/guanylin receptors. These receptors were confined to the intestinal epithelium lining the lumen and forming the intestinal glands throughout the length of both the small intestine and colon of all species examined. In man and most other mammalian species, there appeared to be a decrease in receptor density distally along the longitudinal axis of the small intestine. ST/guanylin receptors were not observed in other strata forming the gut wall. Along the vertical axis of the human small intestine (villus/crypt unit), as well as that of most other mammals, receptor density was greatest in enterocytes located near the base of villi and in those forming the proximal portion of the intestinal glands. ST/guanylin receptors were for the most part confined to the region of the plasmalemma forming the microvillus border. In the colon of man and the other species examined, receptor density was greatest in enterocytes forming the proximal region of the intestinal glands. Receptors were present in the intestinal epithelium lining the lumen of the colon, but generally were fewer in number. The distribution of cellular cGMP accumulation responses to E. coli ST and guanylin in the opossum (Didelphis virginiana) and raccoon (Procyon lotor) revealed that proximal small intestine had greater magnitudes of cGMP responses than did the distal small intestine. Proximal colon had greater cGMP responses than distal colon, which had no significant cGMP responses to either ST or guanylin.

Animals↗
PubMed1993

Heterogeneity of motilin-immunoreactive cells in the duodenum and pyloric region of several avian species.

Immunohistochemical characterizations of motilin-immunoreactive cells were examined in gastric and duodenal mucosae of nine species of birds from seven orders using five different region-specific motilin antisera. Motilin-immunoreactive cells appeared as open-type cells in the mucosal epithelium and showed varying immunoreactivities to antisera used in all the birds examined except for the cormorant and penguin, which did not show any kinds of immunoreactivity to motilin. Motilin-immunoreactive cells of the emu duodenum were detected by all the motilin-antisera used. The present results suggest that there is a wide range of heterogeneity between motilin molecules among avian species, or perhaps alternatively the existence of a family of motilin-like peptide. Furthermore, the present results should prove useful for a molecular biological study on the evolution of avian motilin.

Animals↗
PubMed1993

An immunohistochemical study on the gastrointestinal endocrine cells of three honeyeaters: singing honeyeater (Meliphaga virescens), spiny-cheeked honeyeater (Acanthogenys rufogularis) and brown honeyeater (Lichmera indistincta).

The gastrointestinal endocrine cells of the singing honeyeater (Meliphaga virescens), spiny-cheeked honeyeater (Acanthogenys rufogularis) and brown honeyeater (Lichmera indistincta) were studied immunohistochemically with special reference to their degree of dependency upon nectar. The nine types of immunoreactive endocrine cells were detected in their gastrointestinal mucosa. Coexistence of motilin and serotonin in the same cells was confirmed in the pyloric region. In the duodenum and jejunum, a few peptide tyrosin tyrosin (PYY)-immunoreactive cells were detected. The clear difference in the distribution and frequency of the gastrointestinal endocrine cells among three types of honeyeaters, which differ in the degree of dependency upon the nectar, could not be confirmed. However, some differences were found that serotonin-, somatostatin- and gastrin-releasing peptide (GRP)-immunoreactive cells in the gizzard, gastrin-immunoreactive cells in the duodenum and jejunum, enteroglucagon-immunoreactive cells in the caeca and in the colon, and pancreatic glucagon-immunoreactive cells in the ileum of brown honeyeaters were more numerous (p < 0.05) than other two species.

Animals↗
PubMed1993

A qualitative analysis of the kidney structure of Meliphagid honeyeaters from wet and arid environments.

The qualitative ultrastructural renal anatomy was examined in 4 species of honeyeater (parvorder Corvi) inhabiting 2 distinctly different environments. The kidneys of the wet zone New Holland honeyeater Phylidonyris novaehollandiae and little wattlebird Anthochaera lunulata were compared with those of the arid zone white-fronted honeyeater Phylidonyris albifrons and spiny-cheeked honeyeater Acanthogenys rufogularis. The size and structure of glomeruli were similar between species. In all species, except in P. novaehollandiae, the proximal tubule cells contained wide intercellular spaces filled with basolateral cell membrane interdigitations. Medullary nephron tubules were arranged in a sequential manner in all species. Thick and thin limbs of Henle were separated by the collecting ducts and extended the entire length of the medulla, a situation not found in muscicapid passerines. This tubular arrangement is not entirely consistent with the proposed single-effect countercurrent multiplier theory. The thin limb of Henle consisted of only one epithelium type, which had wide intercellular spaces. The thick limb of Henle consisted of 2 types of epithelial cells, each having narrow intercellular spaces, but with varying degrees of cell membrane infoldings. The ultrastructural morphology of the limbs of Henle in honeyeaters differed from those of muscicapid passerines. The ultrastructure of the distal nephron was similar in each species studied. All of the above nephron characteristics are considered to enable honeyeaters to absorb a large proportion of solutes and water from the glomerular filtrate.

Animals↗
PubMed1992

A stereological analysis of kidney structure of honeyeater birds (Meliphagidae) inhabiting either arid or wet environments.

Stereology was used to quantify components within the kidney of honeyeater birds. Arid zone and wet zone inhabiting 'matched' body mass pairs of birds were examined. The kidney structure of the arid zone white-fronted honeyeater, Phylidonyris albifrons (16.9 g), was compared with that of the wet zone New Holland honeyeater, Phylidonyris novaehollandiae (21.9 g), and that of the arid zone spiny-cheeked honeyeater, Acanthogenys rufogularis (42.5 g), with that of the wet zone little wattlebird, Anthochaera lunulata (62.0 g). Both arid zone honeyeaters had a significantly higher (P less than 0.001) percentage of medulla in the kidneys, while the wet zone birds had a significantly higher (P less than 0.001) percentage of cortex. There were few differences between arid and wet zone honeyeaters in the percentage of nephron components in the cortex and medulla. Both arid zone bird species had a significantly larger volume of medulla, a feature characteristic of a high ability to conserve water by producing a concentrated urine. Both wet zone species had a higher volume of cortex but the difference was not significant. Few differences were found in the volumes and surface areas of tubules within the nephron. Differences that did occur were not always consistent with a high ability to conserve either ions or water more efficiently. The volume and surface area of brush border in the proximal tubule were significantly higher in the little wattlebird. This characteristic may lead to a greater capacity of its kidneys to absorb both water and ions.

Animals↗
PubMed1991

The relative sizes and asymmetry of kidneys in passerine birds from Australia and North America.

Despite their close taxonomic affinities, nectar-feeding passerine birds from Australia had smaller kidneys, on average, than sympatric passerines of equivalent weight that fed entirely upon insects. Insectivorous passerines from North America had larger kidneys, on average, than comparable insect-feeding passerines from the separate endemic radiation in Australia. Dietary and other environmental differences, rather than phylogenetic origins, may account for these differences. The left kidney of Australian passerines was significantly longer, on average, than the right. Kidney widths showed no lateral asymmetry.

Animals↗
PubMed1990

An immunohistochemical study of endocrine cells of the alimentary tract of the King's skink (Egernia kingii).

The gastrointestinal tract of the King's skink (Egernia kingii) was examined for the presence of fifteen regulatory peptides, two proteinases and an amine by immunohistochemical methods. Immunoreactivity was detected for somatostatin, gastrin, motilin, bovine pancreatic polypeptide, pepsinogen and serotonin, but not for avian pancreatic polypeptide, gastric inhibitory peptide, secretin, cholecystokinin, enteroglucagon, pancreatic glucagon, gastrin-releasing polypeptide, neurotensin, vasoactive inhibitory polypeptide, leu-enkephalin or chymosin. The six peptides detected in E. kingii have been previously found in the gastrointestinal tract of squamate reptiles; however, immunoreactivity for other peptides previously detected in squamates, in particular another skink, was not observed. In addition, chromogranin was found to be effective in the detection of endocrine cells though its specificity was unknown.

Animals↗
PubMed1989

An immunohistochemical study of gastrointestinal endocrine cells in a nectarivorous marsupial, the honey possum (Tarsipes rostratus).

The distribution and relative frequency of occurrence of gastrointestinal endocrine cells exhibiting immunoreactivity to eleven peptides and one amine were examined immunohistochemically in the gastrointestinal mucosa of the adult honey possum which feeds almost exclusively on nectar and pollen. Seven types of endocrine cells, immunoreactive for serotonin, somatostatin, gastrin, motilin, enteroglucagon, neurotensin and gastric inhibitory peptide (GIP), were detected in the gastrointestinal mucosa of the honey possum. In the cardiac gland region, including the diverticulum, endocrine cells were very scarce, and few serotonin- and somatostatin-immunoreactive cells were identified in 4 out of 8 honey possums. Moderate numbers of serotonin- and a few somatostatin-immunoreactive cells were found in the fundic glands. In the pyloric glands, moderate numbers of gastrin-immunoreactive cells and a few serotonin- and somatostatin-immunoreactive cells were detected. Along the length of the small intestine, serotonin-immunoreactive cells were the dominant endocrine cell type but small numbers of somatostatin-, gastrin-, motilin-, enteroglucagon-, neurotensin- and GIP-immunoreactive cells, all with different distribution patterns and relative frequencies of occurrences, were also found. In the large intestine, a small number of serotonin- and enteroglucagon-immunoreactive cells were found in all animals, but a few somatostatin- and neurotensin-immunoreactive cells were detected in some animals.

Animals↗
PubMed1988

Anaesthesia in two species of large Australian skink.

The use of ketamine hydrochloride and sodium pentobarbitone in the anaesthesia of two species of Australian skink was examined. The effects of ketamine at ambient temperatures of 15 degrees C and 30 degrees C were studied. Ketamine produced consistent responses up to and including anaesthesia at dose rates of 170 to 230 mg/kg at 30 degrees C. The effect of temperature on the anaesthetic dose, respiratory and cardiac rates, muscle relaxation, analgesia and the onset and duration of anaesthesia was examined. Respiration in both species was depressed but heart rate was increased in Bobtail skinks (Tiliqua rugosa) and depressed in King's skinks (Egernia kingii). Muscle relaxation was good when anaesthetic doses were given. Generally, the onset and duration of anaesthesia were extended at 15 degrees C while the dose rates required for this effect were reduced. Although there was individual variation in the response to ketamine, it was found to be a useful and practical agent for the anaesthesia of large skinks. Pentobarbitone was found to be unsuitable as an anaesthetic agent because it produced inconsistent results and several fatalities.

Anesthesia↗
PubMed1983

Electromyographic events in the stomach and small intestine of a small kangaroo, the Tammar wallaby (Macropus eugenii).

The extracellular electrical activity of the stomach and small intestine of a macropodid marsupial was studied using chronically implanted bipolar electrodes. Recordings from the elongate, tubular, haustrated stomach showed triphasic slow waves with a frequency of 5.5/min, an amplitude of 120 microV and an aborad propagation rate of 3 mm/sec. Action potentials were recorded only from the pylorus. These occurred as bursts of six to fourteen consecutive spikes. Shortly after the period of regular spike activity occurred in the adjacent duodenum action potentials in the pylorus ceased, leaving only the slow wave present for up to 20 min. Both slow waves and action potentials were recorded from the small intestine. There was no decrease in the frequency of the slow wave from the duodenum to the ileum. The slow wave frequency was 26/min on the duodenum and 25/min on the ileum. These frequencies were not affected by fasting the animals. Migrating myoelectric complex activity of the small intestine comprising three distinct electrical patterns, occurred at regular intervals. This was only slightly affected by feeding.

Action Potentials↗