Effect of rabbit antiserum to ovine LH on reproductive organs in male hamsters and guinea-pigs

Administration of rabbit antiserum to ovine luteinizing hormone to immature hamsters and guinea-pigs resulted in a significant decrease in the weights of testes, seminal vesicle and ventral prostate. The author wishes to thank Prof. N.R. Moudgal for his interest and Family Planning Foundation for financial assistance.

The role of fsh and lh in the initiation of ovulation in rats and hamsters: a study using rabbit antisera to ovine fsh and lh

The relative rôles of FSH and LH in ovulation induction in immature and adult cycling rats and hamsters have been evaluated. Both heterologous purified pituitary hormones and homologous crude pituitary extracts have been used as ovulatory stimuli in immature animals primed with PMSG. Well-characterized FSH and LH antisera have been used in the above model systems to achieve specific neutralization of FSH and LH. The present study revealed that LH is the physiological trigger needed for induction of ovulation in both rats and hamsters and FSH cannot, by itself, induce ovulation in the total absence of LH.

Changes in testicular function following specific deprivation of LH in the adult male rabbit

Sexually mature male rabbits actively immunized against highly purified ovine LH (oLH) were used as a model system to study the effects of endogenous LH deprivation (and therefore testosterone) on spermatogenesis as well as pituitary FSH secretion. Immunization against oLH generated antibody titres capable of cross-reacting and neutralizing rabbit LH and this resulted in a significant reduction (P<0.01) in serum testosterone levels by 2-4 weeks of immunization. A significant increase in circulating FSH concentration (from a basal level of similar to 1 ng to 60-100 ng/ml; P<0.01) was observed within 4-6 weeks of immunization, perhaps a consequence of the negative feedback effect of the lack of testosterone. The effect of LH deprivation on spermatogenesis assessed by DNA flow cytometry and histological analyses of testicular biopsy tissue revealed that lack of testosterone primarily results in a rapid reduction and complete absence of round (1C) and elongated (HC) spermatids. The immediate effect of LH/testosterone deprivation thus appears to be at the step of meiotic transformation of primary spermatocytes (4C) to 1C. A significant reduction (>80%; P<0.01) in the 4C population and a relative accumulation (>90%; P<0.01) in spermatogonia (2C) was also observed, suggesting a need for testosterone during the transformation of 2C to 1C. In all but one of the rabbits, both qualitative and quantitative recovery in spermatogenesis occurred during the recovery phase, even at a time when only a marginal increase in serum testosterone (compared with the preimmunization) levels was observed as a result of a rapid decline in the cross-reactive antibody titres. These results clearly show that LH/testosterone deprivation in addition to primarily affecting the meiotic step also regulates the conversion of 2C to 4C during spermatogenesis.

Chemical approaches of penicillin allergy—III Isolation of the penicillin-free carrier receptor protein (CRP) on a polymeric 7-deoxy penicillin analogue template and its role in penicillin immunogeneses in rabbit and man

Specific penicillin-carrier receptor proteins (CRP) have been isolated from the sera of penicillin allergic rabbits and human subjects in the unconjugated native state in electrophoretically homogeneous form by employing a synthetic polymeric affinity template containing the 7-deoxy analogue of penicillin G. The synthesis of the 7-deoxy analogue has been described. In this affinity system the antipenicillin-antibody is desorbed by 0·9M thiourea and the CRP in 8M urea. The CRP after incubation with penicillin is converted into the full-fledged antigen. Studies on the origin of CRP and the nature of antibody as well as comparative studies on the properties of the rabbit antibody and those of antibodies elicited by a BSA-BPO conjugate are reported.

Chemical approaches to penicillin allergy—V. Nature of reaction between rabbit antigen (CRP-penicillin conjugate) and rabbit antipenicillin antibody

The availability of an electrophoretically homogeneous rabbit penicillin carrier receptor protein (CRP) and rabbit antipenicillin antibody afforded an idealin vitro system to calculate the thermodynamic parameters of the binding of14C benzyl penicillin CRP conjugate (antigen) to the purified rabbit antipenicillin antibody. The thermodynamic parameters of this antigen-antibody reaction has been studied by radio-active assay method by using millipore filter. Equilibrium constant (K) of this reaction has been found to be 2·853×109M−2 and corresponding free energy (ΔG) at 4°C and 37°C has been calculated to be −12·02 and −13·5 kcal/mole, enthalpy (ΔH) and entropy (ΔS) has been found to be 361 kcal/mole and +30 eu/mole respectively. Competitive binding studies of CRP-analogue conjugates with the divalent rabbit antibody has been carried out in the presence of14C-penicilloyl CRP. It was found that 7-deoxy penicillin-CRP complex and 6-amino penicilloyl CRP conjugate binds to the antibody with energies stronger than that with the14C-penicilloyl CRP. All the other analogue conjugates are much weaker in interfering with the binding of the penicilloyl CRP with the antibody. The conjugate of methicillin,o-nitro benzyl penicillin and ticarcillin with CRP do not materially interfere in the process.

Acute toxicity of methyl isocyanate in rabbit: In vitro and in vivo effects on rabbit erythrocyte membrane

Methyl isocyanate (MIC) interaction with the rabbit erythrocyte membrane increased the fluidity of the membrane and decreased the osmotic fragility of erythrocytes both in vitro and in vivo in rabbits intoxicated with MIC subcutaneously. MIC inhibited both acetylcholinesterase (AChE) and adenosine triphosphatase (ATPase) activities of erythrocytes dose-dependently in vitro, while in vivo a decreased trend in ATPase activity with unaltered AChE activity was observed. MIC also caused significant decrease in plasma sodium level with corresponding increase in potassium level in rabbits. The observed effects are due to MIC, per se, as the hydrolysis products of MIC, methylamine and N,Nprime-dimethylurea did not affect the erythrocyte fluidity and enzymes activities both in vitro and in vivo while they increased the osmotic fragility of erythrocytes in vivo in rabbits administered subcutaneously in equimolar concentration to MIC dosage. Inhibition of Na+-K+-dependent ATPase with altered permeability to cations and also probably water transport of plasma membrane due to MIC interaction are envisaged.

Early osseointegration of a strontium containing glass ceramic in a rabbit model

The most important property of a bone cement or a bone substitute in load bearing orthopaedic implants is good integration with host bone with reduced bone resorption and increased bone regeneration at the implant interface. Long term implantation of metal-based joint replacements often results in corrosion and particle release, initiating chronic inflammation leading onto osteoporosis of host bone. An alternative solution is the coating of metal implants with hydroxyapatite (HA) or bioglass or the use of bulk bioglass or HA-based composites. In the above perspective, the present study reports the in vivo biocompatibility and bone healing of the strontium (Sr)-stabilized bulk glass ceramics with the nominal composition of 4.5SiO(2)-3Al(2)O(3)-1.5P(2)O(5)-3SrO-2SrF(2) during short term implantation of up to 12 weeks in rabbit animal model. The progression of healing and bone regeneration was qualitatively and quantitatively assessed using fluorescence microscopy, histological analysis and micro-computed tomography. The overall assessment of the present study establishes that the investigated glass ceramic is biocompatible in vivo with regards to local effects after short term implantation in rabbit animal model. Excellent healing was observed, which is comparable to that seen in response to a commercially available implant of HA-based bioglass alone. (C) 2013 Elsevier Ltd. All rights reserved.

Better early osteogenesis of electroconductive hydroxyapatite-calcium titanate composites in a rabbit animal model

In view of the fact that bone healing can be enhanced due to external electric field application, it is important to assess the influence of the implant conductivity on the bone regeneration in vivo. To address this issue, this study reports the in vivo biocompatibility property of multistage spark plasma sintered hydroxyapatite (HA)-80 wt % calcium titanate (CaTiO3) composites and monolithic HA, which have widely different conductivity property (14 orders of magnitude difference). The ability of bone regeneration was assessed by implantation in cylindrical femoral bone defects of rabbit animal model for varying time period of 1, 4, and 12 weeks. The overall assessment of the histology results suggests that the progressive healing of bone defects around HA-80 wt % CaTiO3 is associated with a better efficacy with respect to (w.r.t) early stage neobone formation, which is histomorphometrically around 140% higher than monolithic HA. Overall, this study demonstrates that the in vivo biocompatibility property of HA-80 wt % CaTiO3 with respect to local effects after 12 weeks of implantation is not compromised both qualitatively and quantitatively, and a comparison with control implant (HA) points toward the critical role of electrical conductivity on better early stage bone regeneration. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 842-851, 2014.

In vitro osteogenic cell proliferation, mineralization, and in vivo osseointegration of injection molded high-density polyethylene-based hybrid composites in rabbit animal model

The present work reports the biocompatibility property of injection molded HDPE-HA-Al2O3 hybrid composites. In vitro cytocompatibility results reveal that osteogenic cell viability and bone mineralization are favorably supported in a statistically significant manner on HDPE-20% HA-20% Al2O3 composite, in comparison to HDPE-40 wt.% HA or HDPE-40 wt.% Al2O3. The difference in cytocompatibility property is explained in terms of difference in substrate wettability/surface energy and importantly, both the cell proliferation at 7 days or bone mineralization at 21 days on HDPE-20% HA-20% Al2O3 composite are either comparable or better than sintered HA. The progressive healing of cylindrical femoral bone defects in rabbit animal model was assessed by implantation experiments over 1, 4 and 12 weeks. Based on the histological analysis as well as histomorphometrical evaluation, a better efficacy of HDPE-20% HA-20% Al2O3 over high-density polyethylene (HDPE) for bone regeneration and neobone formation at host bone-implant interface was established. Taken together, the present study unequivocally establishes that despite the presence of 20% Al2O3, HDPE-based hybrid composites are as biocompatible as HA in vitro or better than HDPE in vivo.

Biocompatibility property of 100% strontium-substituted SiO2-Al2O3-P2O5-CaO-CaF2 glass ceramics over 26 weeks implantation in rabbit model: Histology and micro-Computed Tomography analysis

One of the desired properties for any new biomaterial composition is its long-term stability in a suitable animal model and such property cannot be appropriately assessed by performing short-term implantation studies. While hydroxyapatite (HA) or bioglass coated metallic biomaterials are being investigated for in vivo biocompatibility properties, such study is not extensively being pursued for bulk glass ceramics. In view of their inherent brittle nature, the implant stability as well as impact of long-term release of metallic ions on bone regeneration have been a major concern. In this perspective, the present article reports the results of the in vivo implantation experiments carried out using 100% strontium (Sr)-substituted glass ceramics with the nominal composition of 4.5 SiO2-3Al(2)O(3)-1.5P(2)O(5)-3SrO-2SrF(2) for 26 weeks in cylindrical bone defects in rabbit model. The combination of histological and micro-computed tomography analysis provided a qualitative and quantitative understanding of the bone regeneration around the glass ceramic implants in comparison to the highly bioactive HA bioglass implants (control). The sequential polychrome labeling of bone during in vivo osseointegration using three fluorochromes followed by fluorescence microscopy observation confirmed homogeneous bone formation around the test implants. The results of the present study unequivocally confirm the long-term implant stability as well as osteoconductive property of 100% Sr-substituted glass ceramics, which is comparable to that of a known bioactive implant, that is, HA-based bioglass. (c) 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 1168-1179, 2015.