Praphulla K. Bajpai

Osteoconductive Composite Grouts for Orthopedic Use

A composite of HA particulate and calcium sulfate hemihydrate has been developed. When this dry material is mixed with either sterile saline or water, the resulting mixture begins to gel. While in the gel or dough state, the composite can be manually inserted or injected under pressure into a bone defect where it sets in situ. The calcium sulfate acts as a binder to hold the HA particles in place. The subsequent resorption of the calcium sulfate leaves controlled porosity for bone ingrowth and attachment to the nonresorbable HA particulate. The combination of calcium sulfate and HA results in a composite with handling properties superior to those of HA alone. Calcium sulfate has a long history of medical use as an implant material. The biocompatibility of the material has been clearly established. The combination of HA and calcium sulfate is likewise extremely compatible as demonstrated in the present studies. Bone ingrowth concomitant with resorption occurs rapidly with efficient conduction of bone from particle to particle. Based on the experiments presented herein, the composite of HA and calcium sulfate may be a useful alternative or adjunct to autogenous bone grafting. Many questions, however, remain regarding long-term tissue response and bone remodeling as well as the efficacy of this material relative to bone grafting.

The Delivery of Testosterone and Dihydrotestosterone by ALCAP Ceramic Implants in Rats

The objectives of this investigation were to evaluate the release of testosterone (T) and dihydrotestosterone (DHT) from nonimpregnated and polylactic acid (PLA) impregnated ALCAP ceramic reservoirs implanted in rats, and to study the effects of delivered androgens on the reproductive system of male rats. A total of 120 Sprague-Dawley albino male rats were distributed equally into three groups Two ALCAP capsules, one nonimpregnated and the other impregnated with PLA, were implanted into each rat in groups I and II. Capsules implanted into group I rats were loaded with a mixture of 20 mg T and 20 mg DHT. Group II rats were implanted with two empty capsules (sham group), and group III animals served as unimplanted controls. Eight rats from each group were euthanized at the end of 3, 6, 9, and 12 months following the implantation of the ceramics. No significant change in the weights of vital organs of rats was observed among any of the three different groups. Vas deferens and epididymal fluid were devoid of normal spermatozoa within 3 months of implanting the steroid-containing ceramics. Testicular weights decreased significantly in the rats implanted with ALCAP containing steroids and the seminiferous tubules became oligospermic after 1 month and azoospermic after 3 months. The data collected in this study suggest that (1) ALCAP ceramic capsules are capable of delivering T and DHT in combined form, and (2) T and DHT delivered by ALCAP capsules can be used effectively to regulate spermatogenesis in rats.

Development of Tricalcium Phosphate Ceramic Cements

Slowly resorbable and relatively nonresorbable bone cements have been developed to repair various types of defects in bone. A relatively fast-resorbing, porous, biocompatible beta tricalcium phosphate (TCP) cement would be ideal for replacing bone lost as a result of nonresorptive processes. In this investigation the following materials were tested as setting agents for developing a resorbable TCP cement: bovine serum albumin, Carbopol, Hespan, monomers of low-molecular-weight carboxylic acids, orthophosphoric acid, polyvinyl pyrrolidone, and water. Initial experiments consisted of determining the amounts of setting agent or water or both required to gel the TCP powder. The gel time was monitored at 30-s intervals. The setting hardness was determined by mixing the optimal proportions of TCP and setting agent or water, or both, and monitoring the hardness at 15-min intervals at room temperature for 105 min. Mixtures of TCP and monomers of low-molecular-weight carboxylic acids yielded the most efficient cements. By varying the quantity of acid or combining different acids, or combining both methods, setting times from 30 s to 8 min were achieved for the TCP/polyfunctional acid cements. These cements have been used successfully to repair experimentally traumatized tibiae and femora in rabbits and rats, respectively.

The Effects of Long-Term Sustained Delivery of Dihydrotestosterone by Poly(lactic acid) Impregnated and Noncoated Biodegradable Ceramic Devices in Male Rodents

The objectives of this investigation were to evaluate the release of dihydrotestosterone (DHT) from nonimpregnated and poly(lactic acid) (PLA) impregnated ALCAP ceramic reservoirs implanted in male rats, and to study the effects of delivered DHT on the reproductive system of male rats. A total of 120 Sprague-Dawley male albino rats were distributed equally into three groups. Two ALCAP capsules, one nonimpregnated and the other impregnated with PLA, were implanted in each rat in groups I and II. Capsules implanted in group I rats were loaded with 40 mg DHT each. Group II rats were implanted with two empty capsules (sham group), and group III animals served as un implanted controls. Eight rats from each group were euthanized at the end of the one, three, six, nine, and twelve months following the implantation of the ceramics. No significant changes in the weights of vital organs of rats were observed among any of the three different groups. Vas deferens and epididymal fluid were devoid of normal spermatozoa within three months of implanting the steroid-containing ceramics. Testes weights decreased significantly in the rats implanted with ALCAP ceramics containing DHT and the seminiferous tubules became oligospermic after one month and azoospermic after three months. The data collected in this study suggest that: (1) ALCAP ceramic cap sules are capable of delivering DHT for one year at a sustained manner; (2) DHT delivered by ALCAP capsules can be used effectively to regulate sperma togenesis in rats.

Successful antidote of multiple lethal infections using sustained delivery of difluoromethylornithine by means of ceramic drug delivery devices

The objectives of this study were (1) to cure multiple infections of trypanosomiasis in rats by the sustained release of DFMO from biodegradable tricalcium phosphate (TCP) and aluminum-calcium-phosphorous oxide (ALCAP) delivery systems, and (2) to determine if the side effects associated with oral administration of DFMO can be avoided by using TCP and ALCAP capsules. Sixty-eight SD male albino rats (235-270 g) were divided randomly into five groups. Each rat in group I (n = 16) was implanted subcutaneously (s.c.) with four TCP capsules (two large TCP (L-TCP), one PLA-impregnated large TCP (IL-TCP) and one thin TCP capsule (TN-TCP)). Rats in group II (n = 16) were implanted s.c. with four ALCAP ceramics (two large ALCAP (L-ALCAP), one PLA-impregnated large ALCAP (IL-ALCAP) and one thin ALCAP capsule (TN-ALCAP)). Rats in groups III (n = 16), IV (n = 4) and V (n = 16) were left without implants. Rats in group III (n = 16) were given 4% (w/v) DFMO (pH 7) in drinking water at the day of inoculation and continued up to 7 days postinoculation. Rats in group IV (n = 4) served as a nontreated group. Rats in group V (n = 16) served as normal controls. The results showed that all rats implanted with with TCP or ALCAP implants had no intoxications symptoms or side effects such as diarrhea during the treatment period. In contrast, rats given DFMO in drinking water exhibited foul-smelling diarrhea during the treatment period. Microscopic evaluation of blood smears collected from rats receiving DFMO chemotherapy showed an occasional or limited number of stumpy shape (SS) trypanosomes. This study suggests that (1) ceramic drug delivery systems are capable of delivering DFMO in a sustained manner for two months, and were able to cure repeated infections of trypanosomiasis; (2) the use of ceramic implants avoided widely fluctuating, irregular levels of DFMO in the body by keeping sustained levels above minimal effective concentrations; (3) ceramic drug delivery systems provide a pharmacological potentiality for drugs such as DFMO which have been withheld from the market because of severe side effects when administered using conventional methods of drug administration; and (4) DFMO-filled ceramic devices can be implanted subcutaneously in animals that face a threat of lethal protozoal infections in highly infested areas of the world.

Sustained delivery of difluoromethylornithine (DFMO) by means of implantable ceramic devices.

A total of 25 Sprague-Dawley albino male rats were assigned to five groups, each group consisting of five rats. Polylactic acid-impregnated ALCAP capsules filled with 40 mg DFMO were implanted subcutaneously (sc) or intraperitoneally (ip) in group I and II rats, respectively. Rats in group III were implanted with empty ALCAP capsules (ALCAP control). Group IV rats were administered orally 3% DFMO in drinking water. Rats in group V served as control. Blood samples were collected every week for six weeks via the tail artery. The concentration of DFMO was determined by a modified ninhydrin hydrindantin method. Data obtained in this investigation showed that the levels of DFMO in the serum of rats in groups I and II were 41.87 +/- 6.8 and 237.62 +/- 13.3 micrograms/mL, respectively. Body, spleen, liver, prostate, seminal vesicles, and testicular weights of the controls and DFMO treated rats were not significantly different (p less than 0.05) over the entire duration of this study. The diarrhea often noted in rats treated orally with DFMO was not observed in rats implanted with ALCAP capsules filled with DFMO. The results of this study suggest that (1) polymer-impregnated ALCAP ceramic capsules can be used to deliver DFMO in a sustained manner for long durations of time, (2) side effects associated with oral administration of DFMO can be avoided by using DFMO-filled ALCAP ceramic implants, and (3) a ceramic system can be designed to deliver DFMO and drugs such as DFMO in a sustained manner over long periods of time in humans.

Effect of anti-sperm gamma globulins on metabolism of human spermatozoa

Abstract Rabbits were immunized with saline extracts of human spermatozoa Presence of antibodies to spermatozoa was confirmed by Ouchterlony gel diffusion, microscopic sperm agglutination, and immunofluorescent techniques. Anti-sperm gamma globulin significantly decreased the average oxygen consumption of 10 8 washed human spermatozoa. Sperm incubated in the presence of anti-sperm gamma globulin had a significantly lower rate of lactic acid accumulation than sperm incubated in normal rabbit gamma globulin. It appears that anti-sperm antibodies can influence both aerobic respiration and glycolysis of washed human spermatozoa.

Resorbable Porous Aluminum-Calcium-Phosphorus Oxide (ALCAP) Ceramics

A porous aluminum-calcium-phosphorus oxide (ALCAP) ceramic has been developed for potential use in corrrecting bone defects. The material is at least partly resorbed and appears to have acceptable biocompatibility and toxicity characteristics for its intended applications. ALCAP ceramics are fabricated by calcining mixtures of aluminum, calcium, and phosphorus oxide powders and sintering the compressed blocks from calcined particles of the desired size. By varying the dimensions of the die, particle size, sintering time, and temperature, ALCAP ceramics have been fabricated that may be useful for repairing a wide variety of bone defects. The fate of ALCAP ceramics in both in vitro and in vivo environments has been studied by means of chemical analysis of tissues, chemical and enzyme analysis of implants, radiography, radioactive isotope uptake, scanning electron microscopy, energy-dispersive X-ray analysis, and histology. ALCAP ceramics were implanted in experimentally induced defects in long bones of rats and mandibles of rabbits. Results of these studies suggest that the ALCAP ceramics resorb and allow ingrowth of new bone.