Partial urethral obstruction of rabbit urinary bladder: stereological evidence that the increase in muscle content is mostly driven by changes in number, rather than size, of smooth muscle cells

The effects of partial urethral obstruction on the detrusor muscle of rabbit urinary bladder were investigated using stereological sampling and estimation tools. Twelve female Norfolk rabbits (2.5-3.0 kg body weight) were divided into four groups: 3, 7 and 12 weeks after surgical intervention to produce a standard partial obstruction and unobstructed controls. Following removal, bladder axes (craniocaudal, dorsoventral and laterolateral) and organ weights were recorded. Bladders were prepared for light microscopy by multistage random sampling procedures. Stereological methods were used to estimate the volume of muscle and the packing density and total number of myocyte nuclei in each bladder. We also estimated mean myocyte volume and the mean cross-sectional area and length of myocytes. Group comparisons were made by one-way analysis of variance. Changes in bladder axes were mainly laterolateral and craniocaudal. Mean bladder weight increased roughly six-fold by 3 weeks and 17-fold by 12 weeks and was accompanied, on average, by 12- and 33-fold increases in total muscle volume. These variables did not differ at 3 and 7 weeks post-obstruction. Increases in muscle content were not accompanied by changes in packing densities but were associated with increases in the total numbers of myocyte nuclei (13-fold by 3 weeks, 28-fold by 12 weeks). Mean myocyte volume did not vary significantly between groups but cells in obstructed groups were shorter and wider. These findings support the notion that partial outflow obstruction leads to an increase in the number, but not mean volume, of myocytes. If due solely to myocyte mitosis, the total of 43 x 10(8) cells found at 12 weeks could be generated by the original complement of 15 x 10(7) cells if an average of only 2.1 x 10(6) new cells was produced every hour. In reality, even this modest proliferation rate is unlikely to be achieved because myocyte proliferation rates are very low and it is possible that new myocytes can arise by differentiation of mesenchymal or other precursor cells.

Evaluation of a double-setting alpha-tricalcium phosphate cement in eviscerated rabbit eyes

Purpose: To evaluate the macroscopy, microstructure, and tissue reaction of a double-setting a-tricalcium phosphate bone cement used as an intraocular implant in rabbits.Methods: the internal and external surface of the double-setting a-tricalcium phosphate implant was analyzed macroscopically and by scanning electron microscopy. Twelve New Zealand rabbits received 12-mm implants made of double-setting alpha-tricalcium phosphate cement after unilateral evisceration. Clinical evaluation was performed daily for the first 15 days after surgery and at 15-day intervals until the end of the study period. For histopathologic analysis, 3 animals per experimental period were submitted to enucleation at 15, 45, 90, and 180 days.Results: on gross inspection, the external surface of the implant was solid, smooth, and compact. The microarchitecture was characterized by the formation of columns of hexagonal crystals with interconnecting channels forming micropores. No wound dehiscence, signs of infection, or implant extrusion were observed in any animal throughout the study period. Histologic examination revealed the formation of fibrovascular tissue surrounding the implants, and there were signs of minimal integration of the surface limiting the fibrocellular cap with the space previously occupied by the implant.Conclusions: the double-setting alpha-tricalcium phosphate implant behaved as an inert and nonintegratable material. The lack of incorporation of this material by fibrovascular tissue is related to its characteristics of compactness and high resistance.

Sulfation of intrinsic glycoproteins of the rabbit vitreous

The experiments reported here were designed to characterize the intrinsic vitreous glycoproteins and to understand the process of their sulfation. Rabbits were injected intravitreally with S-35-sodium sulfate and killed at several time intervals after injection. In another series of experiments, rabbits were injected either with S-35-sodium sulfate, H-3-fucose or H-3-tyrosine, associated or not associated with tunicamycin administration. Vitreous from the control eyes was also digested with N-glycosidase.. Furthermore, ciliary bodies, the putative source of the intrinsic vitreous glycoproteins, were incubated with S-35-sodium sulfate in the presence or absence of the protein synthesis inhibitor cycloheximide, and the culture media recovered for analysis. These and the vitreous samples of the other experiments were processed for sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and fluorography. Except for serum albumin, practically all polypeptide bands of the vitreous and culture media were labeled with radioactive sulfate and were shown to undergo renewal. The experiments using tunicamycin or enzyme treatment suggest that radioactive sulfate was incorporated not only into the carbohydrate side chains of the glycoproteins but also into the amino acid tyrosine of the polypeptide backbone of these glycoproteins. (C) 1998 Academic Press.

Chondroitin sulfate proteoglycans are structural renewable constituents of the rabbit vitreous body

Purpose: To characterize the vitreous intrinsic proteoglycans, investigate their dynamics, and examine their role in the supramolecular organization of the vitreous. Methods: Vitreous from normal rabbits was collected and processed for observation with the transmission electron microscope after treatment with glycosidases. Also, rabbits were injected intravitreally with [S-35]-sodium sulfate and sacrificed at several time intervals after the injection. Proteoglycans (PGs) were assayed in the vitreous supernatant or in whole samples extracted with guanidine hydrochloride by polyacrylamide or agarose gel electrophoresis, followed respectively by fluorography or autoradiography, and ion-exchange chromatography and gel-filtration chromatography, combined with glycolytic treatment of the samples. The sulfated glycosaminoglycans (GAGs) were characterized by agarose gel electrophoresis after treating vitreous samples with protease and specific glycosidases. Results: the electron microscopic study revealed a network with hyaluronic acid ( HA) as thin threads coating and connecting collagen fibrils. The elimination of the HA coat showed chondroitin sulfate granules (8-25 nm) arranged at regular intervals on the fibril surface. The chondroitinase ABC digestion, besides removing the granules, also caused the formation of thicker bundles of the collagen fibrils. The PG and GAG analysis indicated that there are three renewable PGs in the vitreous ( e. g., one heparan-and two chondroitin-sulfate ones). Conclusions: At least one of the chondroitin sulfate PGs is involved in the interactions that occur in the vitreous structure, mainly by providing adequate spacing between the collagen fibrils, a condition that is probably required for the transparency of the vitreous.

Atypical beta-adrenoceptor subtypes mediate relaxations of rabbit corpus cavernosum

This study was performed to characterize the beta-adrenoceptor population in rabbit isolated corpus cavernosum (RbCC) by using nonselective and selective beta-adrenoceptor agonists and antagonists in functional assays. Metaproterenol, ritodrine, fenoterol, and 8-hydroxy-5-[(1R)-1-hydroxy-2-[N-[(1R)-2-(rho-methoxy-phenyl)1-methylethyl] amino] ethyl] carbostyril (TA 2005) (3-100 nmol each) dose dependently relaxed the RbCC preparations. These relaxations were markedly reduced by N-omega-nitro-L-arginine methyl ester (L-NAME; 10 muM) and 1H-[1,2,4]-oxadiazolo-[4,3,-a]quinoxalin-1-one (ODQ) (10 muM), whereas the adenylyl cyclase inhibitor SQ 22,536 [9-(2-tetrahydrofuryl)adenine] (10 muM) had no effect. In contrast, neither L-NAME nor ODQ affected the isoproterenol-induced RbCC relaxations, but SQ 22,536 abolished this response. Sildenafil (1 muM) significantly potentiated the relaxations induced by beta(2)-agonists without affecting the isoproterenol-evoked relaxations. Rolipram (10 muM) enhanced the relaxations elicited by isoproterenol but had no effect on those induced by the selective beta(2) agonists. Propranolol and (+/-)-1-[2,3-(dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanolhydrochloride (ICI 118,551) determined a rightward shift in the concentration-response curves to isoproterenol in a noncompetitive manner with a reduction of maximum response at the highest antagonist concentration, with the slope values significantly different from unity. Propranolol and ICI 118,551 had no effect on the relaxations elicited by fenoterol, TA 2005, metaproterenol, and ritodrine. Atenolol and 1-[2-((3-carbamoyl-4-hydroxy)phenoxy) ethylamino]-3-[4-(1-methyl-4-trifluoromethyl-2-imidazolyl)-phenoxy]2-propanol methanesulfonate (CGP 20712A) (0.1-10 muM) failed to affect the relaxations induced by all tested beta-adrenoceptor agonists. Our study revealed the existence of two atypical beta-adrenoceptors in the rabbit erectile tissue. Isoproterenol relaxes the rabbit cavernosal tissue by activating atypical beta-adrenoceptors coupled to adenylyl cyclase pathway, whereas the selective beta2-adrenoceptor agonists relax the RbCC tissue through another atypical beta-adrenoceptor subtype coupled to nitric oxide release from the sinusoidal endothelium.

The development of a febrile response to pyrogen in the thyroid-deficient rabbit

The development of the febrile response to E. coli lipopolysaccharide (1.5 μg/kg, i.v.) in thyroid-deficient rabbits has been studied. Twenty-eight New Zealand White rabbits weighing 2.1-2.3 kg were used. Hypothyroidism was induced by treatment with propylthiouracil (100 or 200 mg/kg body wt./15 days). Thyroid-deficient animals showed a reduction in the febrile response to lipopolysaccharide, but the effect was significantly different (p<0.01) from the control only for rabbits treated with 200 mg/kg of propylthiouracil. Propranolol (2 mg/kg, i.p.) given 30 min before lipopolysaccharide also reduced (p<0.01) the fever response in control rabbits. The results of this experiment are consistent with the hypothesis that the reduction in the febrile response of thyroid-deficient rabbits is due to the reduced number of β-adrenergic receptors, or to a change in the availability of neurotransmitter in thermogenically active tissues, such as brown fat.

Rabbit antibody responses to experimental infestation with Dermatobia hominis.

The three larval stages of Dermatobia hominis (Linnaeus) have been evaluated for their immunogenicity by ELISA and immunodiffusion (ID) using sera from experimentally infested rabbits. During a primary infestation, first instar D. hominis were found to cause most reaction and allowed the earliest diagnosis by ELISA. An inhibition of the antibody response against second and third instars was observed. The inhibition disappeared after departure of the larvae from the host. In experimentally immunized hosts the antibody response, following challenge, was highest against second and third instar antigens. Antibody remained elevated during the infestation but fell immediately after the larvae had left the host.

Two-Way Selection for Daily Gain and Feed Conversion in a Composite Rabbit Population

We conducted a two-way selection experiment in a composite rabbit population to investigate the responses to selection for postweaning ADG and feed conversion (FC). Two generations of crossing, followed by four generations of random pair matings, preceded three generations of selection. Selection was practiced within four lines: high-feed conversion (HFC), low-feed conversion (LFC), high gain (HG), and low gain (LG). Data on 1,446 rabbits from the random mating and selection generations were fitted to an animal model to estimate heritabilities of and the genetic correlation between ADG and FC. The two-trait model included rabbit and common litter random effects and line, generation, and sex fixed effects. Estimates of heritability of ADG and FC were .48 and .29, respectively, and the genetic correlation between them was -.82. Common litter environmental effects accounted for a proportion of .11 and . 13 of the phenotypic variation of the two traits, respectively. For ADG (in g/d) the regressions of mean breeding values on generation number during the selection period were 1.23 ± .12 (P < .01) in the HG line and -.86 ± .12 (P < .01) in the LG line; the regressions for FC (in g feed/g gain) were -.07 ± .01 (P < .01) in the HFC line and .03 ± .01 (P < .05) in the LFC line. Selection for ADG was effective in improving ADG and FC.

A study of different calcification areas in newly formed bone 8 weeks after insertion of dental implants in rabbit tibias

In orofacial implantology there are many types of implants for the different systems. Among these is the implant surface type, e.g., a screw type, cylindrical and laminar. Furthermore, the implants are different in their dimensions, their metal composition, their surface condition, such as smooth, grit or layered surfaces and in their methods of application. Two different self-tapping implants, one smooth and the other grit-blasted, are screwed into the bone, and another one with a plasma of titanium coating, which is also in a screw form but with greater spaces between the screw threads are compared. The greatest amount of bone deposition in the bone/implant interface was encountered in the latter one, the smooth surfaced implant being in second place. All of these systems can alter the implant healing process and to demonstrate this, we injected bone markers in the rabbits over different periods of time so as to observe the different areas of bone deposition in the tibias where the implants had been inserted. The bone tracers used were Alizarin, Calcein and Xylenol-orange. The amount of deposition was calculated by using the method of surface morphometry.

Morphological aspects of rabbit masseter muscle after cervical sympathectomy

The objective of this paper was to study the effect of sympathetic innervation on morphological and histochemical aspects of skeletal muscle tissue. Rabbit masseter muscle was studied using histochemical and immunohistochemical methods for periods of up to 18 months post-sympathectomy. The morphological and enzymatic characteristics of control masseter muscles were similar on both the left and right sides. The main features were muscle fibres with a mosaic pattern and a predominance of type IIa fibres, followed by type I. Type IIb fibres showed very low frequency. Sympathectomized animals showed varying degrees of metabolic and morphological alterations, especially 18 months after sympathectomy. The first five groups showed a higher frequency of type I fibres, whilst the oldest group showed a higher frequency of type lib fibres. In the oldest group, a significant variation in fibre diameter was observed. Many fibres showed small diameter, atrophy, hypertrophy, splitting, and necrosis. Areas with fibrosis were observed. Thus cervical sympathectomy induced morphological alterations in the masseter muscles. These alterations were, in part, similar to both denervation and myopathy. These findings indicate that sympathetic innervation contributes to the maintenance of the morphological and metabolic features of masseter muscle fibres.