Biomedical subjects

T G Smith

Publications and source records attributed to T G Smith.

At least 19 recordsLinked to original sources

PubMed2005

PCDD/F and PCB concentrations in Arctic ringed seals (Phoca hispida) have not changed between 1981 and 2000.

Concentrations of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) and of non-ortho-, mono-ortho- and di-ortho-substituted polychlorinated biphenyls (NO-CB, MO-CB and DO-CB) were measured in blubber of ringed seals sampled at Holman, NWT, in 1981, 1991, 1996 and 2000. Total PCDD and PCDF concentrations were usually below approx. 10 and 5 pg/g wet wt., respectively, and did not change significantly between 1981 and 2000, although there were sporadic temporal differences in some congeners. Total NO-CB, MO-CB and DO-CB concentrations were below approx. 1 ng/g, 250 ng/g and 1 microg/g wet wt. respectively; none of the total PCB concentrations changed significantly over the sampling period. Neither PCDD nor PCDF concentrations differed between males and females, nor did they increase with age in male samples. MO-CB and DO-CB concentrations increased with age in males, but not in females, and concentrations of total MO-CB and DO-CB were usually lower in females than in males. Changes in the distribution of PCB congeners between the 1980s and the 1990s are consistent with atmospheric transport processes becoming increasingly important in the introduction of PCBs to the Arctic in recent years.

Adipose Tissue↗

PubMed2005

PCDD/F and PCB in harbour seals (Phoca vitulina) from British Columbia: response to exposure to pulp mill effluents.

Blubber of harbour seals (Phoca vitulina) sampled from the Strait of Georgia, BC, in 1991 and 1992 contained higher concentrations of polychlorinated dibenzo-p-dioxins and furans (PCDD/F) than did samples from Quatsino Sound on western Vancouver Island. The higher proportions of 1,2,3,6,7,8-hexachlorodibenzodioxin and 2,3,7,8-tetrachlorodibenzofuran in the Strait of Georgia samples probably reflect contamination arising from the discharge of effluents from bleached kraft mills. Higher concentrations of non-ortho- and mono-ortho substituted polychlorinated biphenyls were also found in the Strait of Georgia samples, probably as a result of general industrial activity in the region. Principal components analysis showed that residues were distributed differently between males and females. Within males, concentrations of PCDD, PCDF and PCBs appeared to increase with age. Toxic equivalents (TEQ) to 2,3,7,8-tetrachlorodibenzodioxin in the Quatsino Sd. samples were close to the working guidelines for edible fish used by Health Canada; TEQ calculated for the Strait of Georgia samples exceeded these guidelines by up to a factor of five.

Adipose Tissue↗

PubMed2001

Renal parenchymal injury after standard and mini percutaneous nephrostolithotomy.

PURPOSE: Mini percutaneous nephrostolithotomy was developed for use in children and in adults with a reduced renal reserve to minimize the morbidity and renal parenchymal damage presumed to occur with traditional percutaneous nephrostolithotomy. We compared the extent of renal injury incurred by different sized nephrostomy tracts in female farm pigs undergoing 11 or 30Fr percutaneous nephrostomy. MATERIALS AND METHODS: Bilateral percutaneous nephrostomy was attempted via a mid or lower pole calix under fluoroscopic guidance in 6 pigs. In 2 pigs the procedure was unsuccessful on 1 side, leaving 5 successfully established nephrostomy tracts on each side. In each pig the right percutaneous tract was dilated with a 28Fr dilating balloon and a 30Fr Amplatz working sheath (Cook Urological, Spencer, Indiana) was positioned in the collecting system. On the left side an 11Fr sheath (Cook Urological) was placed. The sheaths were removed after 1 hour and nephrostomy tubes (22Fr on the right and 8Fr on the left side) were left in place overnight and then removed. Six weeks later the pigs were sacrificed and the kidneys were harvested. The nephrostomy tracts were identified grossly and examined microscopically, and the fibrotic scar was measured using digital analysis. The volume of scar was estimated using the calculated volume of a cylinder. RESULTS: At kidney harvest all 10 kidneys appeared grossly normal. No intra-abdominal urine collection or perirenal hematoma was noted. Mean estimated scar volume of the 30 and 11Fr tracts was 0.29 and 0.40 cc, which translates into a mean fractional loss of parenchyma of 0.63% and 0.91%, respectively (p not significant). CONCLUSIONS: Renal parenchymal damage resulting from the creation of a nephrostomy tract is small compared to overall renal volume regardless of the size of the nephrostomy tract. Consequently there is no advantage to the use of a small access sheath based on renal scarring alone.

Animals↗

PubMed2001

Laparoscopic radiofrequency thermal ablation of renal tissue with and without hilar occlusion.

PURPOSE: Few studies have evaluated the effect of radiofrequency thermal ablation on renal tissue, although it has been used clinically to treat small renal masses. We studied the size and histology of lesions created with radiofrequency thermal ablation administered via the laparoscopic approach with and without hilar occlusion in a porcine model. MATERIALS AND METHODS: The lower pole of each kidney was exposed laparoscopically in 11 farm pigs. In each kidney a 7-electrode dry radiofrequency thermal ablation probe was inserted at an identical location and deployed to a diameter of 2 cm. Energy was applied for 8 minutes at an average temperature of 100C. The left renal hilum of each pig was clamped during radiofrequency thermal ablation. Two pigs were sacrificed immediately, and 3 each were sacrificed at 24 hours, 2 and 4 weeks. The size and shape of the lesions created were measured and examined histologically. RESULTS: There were no intraoperative or postoperative complications. Laparoscopic ultrasound confirmed probe placement but did not monitor lesion progression. Acutely lesions were firm and white with a small adjacent hemorrhagic zone. Histological evaluation revealed preserved renal architecture but the loss of distinct cytoplasmic features. Nicotinamide adenine dinucleotide staining demonstrated no viable cells within the lesions. In surviving animals pelvicaliceal integrity was preserved. In the 2 and 4-week survival groups kidneys treated with hilar occlusion had larger lesions than nonoccluded kidneys but the differences were not significant at 4 weeks (3.2 x 2.7 x 2.5 cm. and 3.5 x 1.7 x 2.0, respectively, p >0.05). Histologically untreated parenchyma of hilar occluded kidneys demonstrated changes consistent with chronic pyelonephritis. In 1 kidney radiofrequency thermal ablation with hilar occlusion resulted in complete lower pole loss at 4 weeks. CONCLUSIONS: In the porcine model renal radiofrequency thermal ablation creates rapid and completely devitalized lesions of consistent size and shape. Hilar occlusion may result in slightly larger lesions but risks damage to the whole renal unit.

Animals↗

PubMed2000

Sex allocation and population structure in apicomplexan (protozoa) parasites.

Establishing the selfing, rate of parasites is important for studies in clinical and epidemiological medicine as well as evolutionary biology Sex allocation theory offers a relatively cheap and easy way to estimate selfing rates in natural parasite populations. Local mate competition (LMC) theory predicts that the optimal sex ratio (r*; defined as proportion males) is related to the selfing rate (s) by the equation r* = (1-s)/2. In this paper, we generalize the application of sex allocation theory across parasitic protozoa in the phylum Apicomplexa. This cosmopolitan phylum consists entirely of parasites, and includes a number of species of medical and veterinary importance. We suggest that LMC theory should apply to eimeriorin intestinal parasites. As predicted, data from 13 eimeriorin species showed a female-biased sex ratio, with the sex ratios suggesting high levels of selfing (0.8-1.0). Importantly, our estimate of the selfing rate in one of these species, Toxoplasma gondii, is in agreement with previous genetic analyses. In contrast, we predict that LMC theory will not apply to the groups in which syzygy occurs (adeleorins, gregarines and piroplasms). Syzygy occurs when a single male gametocyte and a single female gametocyte pair together physically or in close proximity, just prior to fertilization. As predicted, data from four adeleorin species showed sex ratios not significantly different from 0.5.

Animals↗

PubMed2000

Adrenal masses are associated with familial adenomatous polyposis.

PURPOSE: Although its defining feature is the development of multiple large-bowel polyps, familial adenomatous polyposis is a generalized disorder of tissue growth regulation, with a range of manifestations. An association between adrenal neoplasms and familial adenomatous polyposis has been suggested, but not prospectively documented. Patients with familial adenomatous polyposis were therefore screened to determine the frequency of adrenal masses. METHODS: Patients with familial adenomatous polyposis underwent spiral abdominal CT scan reported by two radiologists specialized in cross-sectional imaging. RESULTS: One hundred seven individuals were examined (median age, 36 (interquartile range, 30-48) years; 57 male). Fourteen (13 percent) had an adrenal mass of 1 cm or greater (bilateral in one case); none had clinical evidence of endocrine disturbance or hypertension. Two lesions were histologically confirmed adrenocortical adenomas and one a phaeochromocytoma; the remaining 12 had CT appearances of nonhyperfunctioning adrenocortical adenoma. CONCLUSIONS: The prevalence of unsuspected adrenal masses in the general population is approximately three percent. This prospective study found a significantly higher frequency of 13 percent in patients with familial adenomatous polyposis (chi-squared = 6.973; df = 1; P = 0.008). There is no evidence that the histologic nature of these differs from that in the general population.

Adenomatous Polyposis Coli↗

PubMed2000

Commitment to sexual differentiation in the human malaria parasite, Plasmodium falciparum.

The differentiation of the two sexes in the gametocytogenesis of Plasmodium falciparum was investigated using a plaque assay and antibodies specific for various stages and sexes of gametocytes. Immunofluorescence assays on plaques of cultured parasites grown in monolayers of erythrocytes revealed that the merozoites released from a single sexually-committed schizont became either all male or all female gametocytes. Thus, the commitment of this species to differentiate into one sex or the other is likely to occur prior to the nuclear division of the sexually-committed schizont. The characteristic female-biased gametocyte sex ratio observed for many Plasmodium species is manifested in P. falciparum by a greater percentage of schizonts that produce female gametocytes (67-71%) than those that yield males. From the plaque assay, it was determined that the number of gametocytes produced per sexually-committed schizont was similar for both sexes, indicating that allocation of parasite resources was equal for each sex of gametocyte. The timing of sexual differentiation and features of the gametocyte sex ratio is discussed in relation to previous observations on P. falciparum and related malaria parasites.

Animals↗

PubMed2000

Role of adrenergic receptors in veratridine-stimulated amylase secretion from rabbit pancreatic lobules.

Sympathetic inhibition of pancreatic enzyme secretion has been attributed to vasoconstriction and direct inhibition of acinar cells. We observed both adrenergic inhibition and facilitation of cholinergic transmission in rabbit pancreatic ganglia, which innervate acini. Here we used pancreatic lobules to determine whether adrenergic receptors also regulate synaptic transmission between pancreatic nerves and acini. Stimulation of pancreatic nerve terminals with veratridine (Ver), an activator of voltage-dependent Na+ channels, resulted in a 102% increase in amylase secretion, which was unaffected by alpha and beta receptor antagonists but inhibited 65% by atropine. At a concentration of 10 microM, norepinephrine inhibited (38%) and epinephrine potentiated (40%) Ver-stimulated secretion. At the same concentration, the alpha2 agonist clonidine (Clon) inhibited (39%), whereas the nonselective beta agonist isoproterenol (Iso) and the selective beta3 agonist BRL 37344 potentiated (71 and 67%, respectively) nerve-stimulated secretion. The effects of Clon and Iso and BRL 37344 were antagonized by yohimbine and propranolol, respectively. Phenylephrine, dobutamine, and terbutaline had no effect. Neither basal, bethanechol-stimulated, nor noncholinergic nerve-stimulated secretion was significantly altered by Clon or Iso. Thus, cholinergic nerve terminals innervating pancreatic acini exhibit both inhibitory alpha2 and atypical facilitatory beta adrenergic receptors. The apparent lack of adrenergic innervation suggests that adrenergic receptors on the nerve terminals of cholinergic pancreatic neurons are under hormonal control by circulating catecholamines. These results provide further evidence that intrinsic pancreatic neurons, which supply most, if not all, of the cholinergic innervation of acini, are important sites of sympathetic regulation of pancreatic exocrine secretion.

Adrenergic Agonists↗

PubMed2000

Intraerythrocytic development of species of Hepatozoon infecting ranid frogs: evidence for convergence of life cycle characteristics among apicomplexans.

Intraerythrocytic development of the adeleorin apicomplexans Hepatozoon clamatae and Hepatozoon catesbianae were investigated in the bullfrog, Rana catesbeiana, the green frog, Rana clamitans melanota, and the Northern leopard frog, Rana pipiens. Merozoites emerging from hepatic meronts penetrated erythrocytes and underwent 1-3 rounds of binary fission to produce 2-8 merozoites. Following their release from infected erythrocytes, individual merozoites entered new cells and transformed into gamonts. Although this is the first report of intraerythrocytic development for a fully described species of Hepatozoon, a phylogenetic reanalysis of 11 species of Hepatozoon, 6 species representative of the 5 other hemogregarine taxa, 2 species of dactylosomatids, and 2 species of piroplasms, indicates that asexual reproduction of parasites within blood cells of vertebrates has arisen at least 3 times in the apicomplexan lineage that includes adeleorins and piroplasms. This method of asexual development, which is also observed in species of hemospororin genera such as Plasmodium, is discussed in the context of the evolution of apicomplexan life cycles. In addition to supporting the paraphyly of the genus Hepatozoon determined in an earlier study, this phylogenetic analysis featured a monophyletic group, consisting of the sister taxa Hemolivia and Karyolysus, that was the sister group to a clade consisting of the more derived hemogregarines, the dactylosomatids, and the piroplasms.

Animals↗

PubMed2000

Direct modulation of basal and angiotensin II-stimulated aldosterone secretion by hydrogen ions.

Disturbances in acid-base balance in vivo are associated with changes in plasma aldosterone concentration, and in vitro changes in extracellular pH (pH(o)) influence the secretion of aldosterone by adrenocortical tissue or glomerulosa cells. There is considerable disparity, however, as to the direction of the effect. Furthermore, the mechanisms by which pH(o) independently affects aldosterone secretion or interacts with other secretagogues are not defined. Thus, bovine glomerulosa cells maintained in primary monolayer culture were used to examine the direct effects of pH(o) on cytosolic free calcium concentration ([Ca(2+)](i))( )and aldosterone secretion under basal and angiotensin II (AngII)-stimulated conditions. pH(o) was varied from 7.0 to 7.8 (corresponding inversely to changes in extracellular H(+) concentration from 16 nM to 100 nM). Whereas an elevation of pH(o) from 7.4 to 7.8 had no consistent effect, reductions of pH(o) from 7.4 to 7.2 or 7.0 caused proportionate increases in aldosterone secretion that were accompanied by increases in transmembrane Ca(2+) fluxes and [Ca(2+)](i). These effects were abolished by removal of extracellular Ca(2+). A decrease in pH(o) from 7.4 to 7.0 also enhanced AngII-stimulated aldosterone secretion. This effect was more pronounced at low concentrations of AngII and was manifested as an increase in the magnitude of the secretory response with no effect on potency. In contrast to its effect on AngII-stimulated aldosterone secretion, a reduction of pH(o) from 7.4 to 7.0 inhibited the Ca(2+) signal elicited by low concentrations (</=1x10(-10) M) of AngII, but did not affect the increase in [Ca(2+)](i) caused by a maximal concentration (1x10(-8) M) of AngII. These data suggest that pH(o) (i.e. H(+)) has multiple effects on aldosterone secretion. It independently increases aldosterone secretion through a mechanism involving Ca(2+) influx and an increase in [Ca(2+)](i). Also, it modulates the action of AngII by both decreasing the magnitude of the AngII-stimulated Ca(2+) signal and increasing the sensitivity of a more distal site to intracellular Ca(2+). The latter action appears to be a more important determinant in the effects of pH(o) on AngII-stimulated aldosterone secretion.

Aldosterone↗

PubMed1999

Phylogenetic relationships among Hepatozoon species from snakes, frogs and mosquitoes of Ontario, Canada, determined by ITS-1 nucleotide sequences and life-cycle, morphological and developmental characteristics.

The molecular biological characteristics of Hepatozoon species infecting various species of snakes, frogs and mosquitoes were investigated by determining the nucleotide sequences of the first internal transcribed spacer region. A phylogenetic analysis was performed on seven isolates of Hepatozoon infecting snakes, including Hepatozoon sipedon and four morphologically similar but not identical forms, and two isolates of Hepatozoon catesbianae infecting Green frogs (Rana clamitans melanota). This analysis, which utilised data from first internal transcribed spacer nucleotide sequences, morphological and morphometric features of gamonts, oocysts and sporocysts, and previously determined life-cycle and host-specificity characteristics, revealed that H. sipedon is a polymorphic species with a wide host and geographic range. Four synapomorphies. including two nucleotide substitutions and two morphological character state changes, supported a monophyletic group of six isolates of H. sipedon from the central region of Ontario which was the sister group for an isolate (HW1) from the southern part of the province. Based on the results of this study, an evaluation of which criteria are useful for describing species of Hepatozoon is presented, with the intent of curtailing the practice of naming species based on morphological features of gamonts or on incomplete life-cycle data.

Animals↗

PubMed1999

Veratridine-stimulated amylase secretion from rabbit pancreatic lobules: role of cholinergic and noncholinergic receptors.

Stimulation of pancreatic nerves results in marked increases in exocrine secretion. However, the neurotransmitters and pre- and postsynaptic receptors, which determine synaptic transmission between nerves and acinar cells, are poorly defined. We used rabbit pancreatic lobules, which contain nerve terminals and secrete independently of the influences of vascular perfusion or gastrointestinal hormones, to study the role of cholinergic and noncholinergic nerves in regulating amylase secretion. Pancreatic nerves were stimulated by veratridine (Ver; 50-200 microM), an activator of voltage-dependent sodium channels, in a concentration-dependent and tetrodotoxin-sensitive manner, resulting in an increase of 138+/-15% in amylase secretion above basal at 100 microM. This stimulation was unaffected by either hexamethonium (100 microM) or the combination of phentolamine and propranolol (10 microM). Atropine (5 microM) inhibited Ver-stimulated secretion by approximately 65-70%. Bethanechol (Bch; 0.01-100 microM) increased amylase secretion in a concentration-dependent manner (EC50, 6.2 microM), with a maximal stimulation of 177+/-15% above basal. Antagonism of Bch-stimulated secretion with 4-diphenylacetoxy-N-methyl-piperidine, pirenzepine (Pzp), or methoctramine (Met) resulted in IC50 values of 7.9 nM, 282 nM, and 79.8 microM, respectively. Ver-stimulated secretion was unaffected by Pzp (0.1 and 1 nM) or Met (1 and 100 nM) at concentrations that had no significant effect on Bch-stimulated secretion. Thus cholinergic nerves, activating postsynaptic M3 receptors, provided the predominant stimulatory innervation of rabbit pancreatic acini. Nonadrenergic, noncholinergic nerves also made a significant contribution to secretion. Adrenergic nerves did not appear to innervate acini or the excitatory cholinergic nerves directly.

Adrenergic Antagonists↗

PubMed1998

Identification and progression of a desmoid precursor lesion in patients with familial adenomatous polyposis.

BACKGROUND: Desmoid tumours occur in about 10 per cent of patients with familial adenomatous polyposis (FAP), and are an important cause of morbidity and death. The natural history of desmoids was investigated by documenting prospectively the prevalence and progression of possible precursor lesions. METHODS: A group of patients with FAP and controls were examined at laparotomy. Another group, with FAP and no clinical evidence of desmoid, and a group of controls, underwent abdominopelvic computed tomography. RESULTS: At laparotomy 13 of 42 patients with FAP had fibromatous mesenteric plaques; seven of these had not had surgery. Seven had more extensive mesenteric fibromatosis and had undergone significantly more laparotomies than the rest. Of 103 patients scanned, two had desmoid tumours and 22 (21 per cent) had mesenteric fibromatosis. On follow-up both desmoid tumours grew rapidly; mesenteric fibromatosis was unchanged in eight and resolved in four of the 12 patients rescanned. CONCLUSION: A model of desmoid tumour development is suggested, analogous to the adenoma-carcinoma sequence, in which a less benign phenotype emerges as molecular genetic abnormalities accumulate: mesenteric plaque-like desmoid precursor lesions arise in many patients with FAP before surgery as a result of abnormal fibroblast function; some, perhaps stimulated by surgery, progress to mesenteric fibromatosis; these in turn can give rise to desmoid tumours.

Adenomatous Polyposis Coli↗

PubMed1998

The life history and host specificity of Hepatozoon clamatae (Apicomplexa: Adeleorina) and ITS-1 nucleotide sequence variation of Hepatozoon species of frogs and mosquitoes from Ontario.

The life cycle of an intraerythrocytic hemogregarine, Hepatozoon clamatae, was studied in green frogs (Rana clamitans melanota), bullfrogs (Rana catesbeiana), northern leopard frogs (Rana pipiens), and in the mosquito, Culex territans. Gametogenesis, fertilization, and sporogony occurred within cells of the Malpighian tubules of laboratory-reared Cx. territans that had fed on naturally infected frogs. Mature oocysts containing hundreds of sporocysts were observed in mosquitoes 30 days postfeeding. Each sporocyst enclosed 4 sporozoites. Merozoites appeared in the peripheral circulation of laboratory-reared bullfrogs, green frogs and leopard frogs that had been fed sporocysts 35-70 days previously. Attempts to infect American toads (Bufo americanus) and blue-spotted salamanders (Ambystoma laterale) were not successful. Gamonts of this parasite induced nuclear fragmentation or segmentation in host erythrocytes. The life cycle, morphological, and morphometric features of H. clamatae are compared with H. catesbianae, a similar species that also infects ranids. Nucleotide sequence analysis of the internal transcribed spacer region (ITS-1) of these sympatric species revealed that only 6 nucleotide sites of the 129 base pairs of this region were variable among 4 isolates of H. clamatae and 2 isolates of H. catesbianae. A redescription of H. clamatae is presented based on data from this study and from the original description by Stebbins in 1905.

Animals↗

PubMed1997

L-arginine and superoxide dismutase prevent or reverse cerebral hypoperfusion after fluid-percussion traumatic brain injury.

To determine whether treatment with L-arginine or superoxide dismutase (SOD) would prove effective in reducing cerebral hypoperfusion after traumatic brain injury (TBI), we measured cerebral blood flow (CBF) using laser Doppler flowmetry (LDF) in rats treated before or after moderate (2.2 atm) fluid-percussion (FP) TBI. Rats were anesthetized with isoflurane and prepared for midline FP TBI and then for LDF by thinning the calvaria using an air-cooled drill. Rats were then randomly assigned to receive sham injury, sham injury plus L-arginine (100 mg/kg, 5 min after sham TBI), TBI plus 0.9% NaCl, TBI plus L-arginine (100 mg/kg, 5 min post-TBI), TBI plus SOD (24,000 U/kg pre-TBI + 1600 units/kg/min for 15 min after TBI), or TBI plus SOD and L-arginine. A second group of rats received TBI plus saline, L-, or D-arginine (100 mg/kg, 5 min after-TBI). After treatment and TBI or sham injury, CBF was measured continuously using LDF for 2 h and CBF was expressed as a percent of the preinjury baseline for 2 h after TBI. Rats treated with saline or D-arginine exhibited significant reductions in CBF that persisted throughout the monitoring period. Rats treated with L-arginine alone or in combination with SOD exhibited no decreases in CBF after TBI. CBF in the SOD-treated group decreased significantly within 15 min after TBI but returned to baseline levels by 45 min after TBI. These studies indicate that L-arginine but not D-arginine administered after TBI prevents posttraumatic hypoperfusion and that pretreatment with SOD will restore CBF after a brief period of hypoperfusion.

Animals↗

PubMed1996

Fractal methods and results in cellular morphology--dimensions, lacunarity and multifractals.

This paper discusses the concepts of fractal geometry in a cellular biological context. It defines the concept of the fractal dimension. D, as a measure of complexity and illustrates the two different general ways of quantitatively measuring D by length-related and mass-related methods. Then, these several Ds are compared and contrasted. A goal of the paper is to find methods other than length-related measures that can distinguish between two objects that have the same D but are structurally different. The mass-related D is shown potentially to be such a measure. The concept of lacunarity, L, is defined and methods of measuring L are illustrated. L is also shown to be a potentially distinguishing measure. Finally, the notion of multifracticality is defined and illustrated to exist in certain individual nerve and glial cells.

Cell Size↗

PubMed1996

The genus Hepatozoon (Apicomplexa: Adeleina).

Hemogregarines of the genus Hepatozoon are intraerythrocytic apicomplexan parasites that have been described from all groups of tetrapod vertebrates. Gametogenesis, fertilization, and sporogonic development, which culminates in the formation of polysporocystic oocysts, occur in the gut or hemocoel of a hematophagous arthropod definitive host. Merogonic development occurs in the internal organs of vertebrate hosts after they ingest these infected arthropods. The presence of cystic stages, observed for many Hepatozoon species, increases life cycle complexity and exploits the feeding behavior of vertebrate hosts. The inconsistency of morphological characteristics of these parasites, especially those associated with gamont structure, coupled with low host specificity of the parasites for their invertebrate and vertebrate hosts, have rendered species differentiation difficult. A systematic review of the hemogregarine complex has resulted in the expansion of the genus Hepatozoon to include all members of the genus Haemogregarina that infect amphibians, snakes, lizards, crocodilians, birds, and mammals.

Animals↗

PubMed1995

beta-Cyclodextrin: 52-week toxicity studies in the rat and dog.

A 52-wk toxicity study by dietary administration was performed in Sprague-Dawley rats and in pure-bred beagle dogs with beta-cyclodextrin, a starch derivative that acts as a molecular inclusion agent. Doses of 0 (control), 12,500, 25,000 and 50,000 ppm were selected for the rat study, and 0 (control), 6200, 12,500 and 50,000 ppm were selected for the dog study. The liver and kidney were identified at the histopathological examination as target organs for toxicity in the rat at doses of 50,000 and 25,000 ppm, with the hepatic changes associated with increased plasma liver enzyme and reduced plasma triglyceride concentrations. In the dog study, there was no pathological evidence of systemic toxicity, although there were minor changes in urinalysis and biochemical parameters and a slightly higher incidence of liquid faeces. These changes were considered to be of no toxicological importance. The results in these studies, therefore, indicate that the non-toxic effect level was 12,500 ppm in the rat (equivalent to 654 or 864 mg/kg/day for males or females, respectively) and 50,000 ppm in the dog (equivalent to 1831 or 1967 mg/kg/day for males or females, respectively).

Analysis of Variance↗