Toxicologic update of dimethyl sulfoxide

Microwave Sensor for the Determination of DMSO Concentration in Water-DMSO Binary Mixture

This research aims to develop a microwave sensor to accurately measure the concentration of dimethyl sulfoxide (DMSO) in water-DMSO binary mixtures. The proposed sensor will utilize microwave frequency measurements to determine the DMSO concentration, providing a non-invasive and efficient method for analyzing DMSO solutions. The research will involve the design, fabrication, and testing of the sensor, as well as the development of an appropriate calibration model. The outcomes of this study will contribute to improved monitoring and quality control in various fields, including pharmaceuticals, chemical synthesis, and biomedical research. The binary mixtures of dimethyl sulfoxide (DMSO) and water with varying concentrations were investigated in the frequency range of 1 GHz to 5 GHz at room temperature using a microwave sensor. The proposed microwave sensor design was based on an interdigital capacitor (IDC) microstrip antenna loaded with a hexagonal complementary ring resonator (HCRR). The performance of the sensor, fabricated using the print circuit board (PCB) technique, was validated through simulations and experiments. The reflection coefficient (S₁₁) and resonance frequency (F_r) of binary mixtures of DMSO and water solutions were recorded and analyzed for DMSO concentrations ranging from 0% v/v to 75% v/v. Mathematical models were developed to analyze the data, and laboratory tests showed that the sensor can detect levels of DMSO/water binary mixtures. The sensor is capable of detecting DMSO concentrations ranging from 0% v/v to 75% v/v, with a maximum sensitivity of 0.138 dB/% for S₁₁ and ΔS₁₁ and 0.2 MHz/% for F_r and ΔF_r at a concentration of 50% v/v. The developed microwave sensor can serve as an alternative for detecting DMSO concentrations in water using a simple and cost-effective technique. This method can effectively analyze a wide range of concentrations, including highly concentrated solutions, quickly and easily.

Encapsulation of the Anti-inflammatory Dual FLAP/sEH Inhibitor Diflapolin Improves the Efficiency in Human Whole Blood

Diflapolin is a dual FLAP/sEH inhibitor with potent anti-inflammatory efficiency in cellular assays and experimental in vivo studies. Despite these outstanding characteristics, its high lipophilicity and plasma protein binding hamper the bioactivity in blood. To overcome these limitations, diflapolin was encapsulated in poly(lactic-co-glycolic acid) nanoparticles to develop an efficient and biocompatible drug delivery system. Two different cosolvent approaches were tested showing the possibility to exchange dimethyl sulfoxide in the organic phase by the sustainable 400 g/mol poly(ethylene glycol). A particle size of 220 nm and the amorphous encapsulation of diflapolin in high amounts rendered the nanoparticles appropriate for the intended application. Excellent biocompatibility of the nanoparticles was demonstrated in an ex ovo hen's egg model. The potent suppression of FLAP-dependent 5-lipoxygenase product formation by the nanoparticles in human whole blood, superior to the free drug, makes them to a promising drug delivery system to improve the bioactivity of diflapolin.

Effects of storage media, supplements and cryopreservation methods on quality of stem cells

Despite a vast amount of different methods, protocols and cryoprotective agents (CPA), stem cells are often frozen using standard protocols that have been optimized for use with cell lines, rather than with stem cells. Relatively few comparative studies have been performed to assess the effects of cryopreservation methods on these stem cells. Dimethyl sulfoxide (DMSO) has been a key agent for the development of cryobiology and has been used universally for cryopreservation. However, the use of DMSO has been associated with in vitro and in vivo toxicity and has been shown to affect many cellular processes due to changes in DNA methylation and dysregulation of gene expression. Despite studies showing that DMSO may affect cell characteristics, DMSO remains the CPA of choice, both in a research setting and in the clinics. However, numerous alternatives to DMSO have been shown to hold promise for use as a CPA and include albumin, trehalose, sucrose, ethylene glycol, polyethylene glycol and many more. Here, we will discuss the use, advantages and disadvantages of these CPAs for cryopreservation of different types of stem cells, including hematopoietic stem cells, mesenchymal stromal/stem cells and induced pluripotent stem cells.

Resveratrol and Its Analogs as Functional Foods in Periodontal Disease Management

Periodontitis is a common chronic inflammatory disease driven by the interaction between a dysbiotic oral microbiome and the dysregulated host immune-inflammatory response. Naturally derived nutraceuticals, such as resveratrol and its analogs, are potential adjunctive therapies in periodontal treatment due to their antimicrobial and anti-inflammatory properties. Furthermore, different analogs of resveratrol and the choice of solvents used may lead to varying effects on therapeutic properties. This review presents the current findings and gaps in our understanding on the potential utility of resveratrol and its analogs in periodontal treatment.

Cryopreservation in 95% serum with 5% DMSO maintains colony formation and chondrogenic abilities in human synovial mesenchymal stem cells

Background

Synovial mesenchymal stem cells (MSCs) are an attractive cell source for cartilage and meniscus regeneration. The optimum cryopreservation medium has not been determined, but dimethylsulfoxide (DMSO) should be excluded, if possible, because of its toxicity. The purposes of our study were to examine the possible benefits of higher concentrations of serum and the effectiveness of 100% serum (without DMSO) for the cryopreservation of synovial MSCs.

Methods

Human synovium was harvested from the knees of four donors with osteoarthritis during total knee arthroplasty. Synovial MSCs (8 × 10⁵ cells) were suspended in 400 μL medium and used as a Time 0 control. The same number of synovial MSCs was also suspended in 400 μL α-MEM medium containing 10% fetal bovine serum (FBS) (5% DMSO, and 1% antibiotic), 95% FBS (and 5% DMSO), or 100% FBS (no DMSO) and cryopreserved at − 80 °C for 7 days. After thawing, the cell suspensions (1.5 μL; 3 × 10³ cells) were cultured in 60 cm² dishes for 14 days for colony formation assays. Additional 62.5 μL samples of cell suspensions (1.25 × 10⁵ cells) were added to tubes and cultured for 21 days for chondrogenesis assays.

Results

Colony numbers were significantly higher in the Time 0 and 95% FBS groups than in the 10% FBS group (n = 24). Colony numbers were much lower in the 100% FBS group than in the other three groups. The cell numbers per dish reflected the colony numbers. Cartilage pellet weights were significantly heavier in the 95% FBS group than in the 10% FBS group, whereas no difference was observed between the Time 0 and the 95% FBS groups (n = 24). No cartilage pellets formed at all in the 100% FBS group.

Conclusion

Synovial MSCs cryopreserved in 95% FBS with 5% DMSO maintained their colony formation and chondrogenic abilities to the same levels as observed in the cells before cryopreservation. Synovial MSCs cryopreserved in 100% FBS lost their colony formation and chondrogenic abilities.

Electronic supplementary material

The online version of this article (10.1186/s12891-019-2700-3) contains supplementary material, which is available to authorized users.

DMSO induces drastic changes in human cellular processes and epigenetic landscape in vitro

Though clinical trials for medical applications of dimethyl sulfoxide (DMSO) reported toxicity in the 1960s, later, the FDA classified DMSO in the safest solvent category. DMSO became widely used in many biomedical fields and biological effects were overlooked. Meanwhile, biomedical science has evolved towards sensitive high-throughput techniques and new research areas, including epigenomics and microRNAs. Considering its wide use, especially for cryopreservation and in vitro assays, we evaluated biological effect of DMSO using these technological innovations. We exposed 3D cardiac and hepatic microtissues to medium with or without 0.1% DMSO and analyzed the transcriptome, proteome and DNA methylation profiles. In both tissue types, transcriptome analysis detected >2000 differentially expressed genes affecting similar biological processes, thereby indicating consistent cross-organ actions of DMSO. Furthermore, microRNA analysis revealed large-scale deregulations of cardiac microRNAs and smaller, though still massive, effects in hepatic microtissues. Genome-wide methylation patterns also revealed tissue-specificity. While hepatic microtissues demonstrated non-significant changes, findings from cardiac microtissues suggested disruption of DNA methylation mechanisms leading to genome-wide changes. The extreme changes in microRNAs and alterations in the epigenetic landscape indicate that DMSO is not inert. Its use should be reconsidered, especially for cryopreservation of embryos and oocytes, since it may impact embryonic development.

Review : Utilization of dimethyl sulfoxide for treating anthracycline extravasation

Objective. To review the literature available on the use of dimethyl sulfoxide (DMSO) to treat anthracy cline extravasation.

Data Sources. English-language literature was gathered using Medline, EMBASE International Phar maceutical Abstracts, CINAHL, and references from bibliographies.

Study Selection. Studies selected for review included controlled animal studies and any available human studies, including case reports and case series. All studies must have used DMSO in the treatment of an anthracycline extravasation.

Data Extraction. Data extracted from animal studies included the animal model used; method of doxorubicin and DMSO administration; ulcer out come ; and statistical significance. Individual case re ports and case series were abstracted for the anti neoplastic agent extravasated; associated symptoms; DMSO administration; concurrent therapies; and short- and long-term results (symptoms, functional damage).

Data Synthesis. One of six animal studies indi cated a significant difference in peak lesion size and area under the curve between DMSO and control. However, local cooling resulted in less toxicity as compared with DMSO, and the time to ulcer healing was actually prolonged in the DMSO-treated group. Clinical experience with DMSO has resulted in no surgical intervention and no residual function impair ment after anthracycline extravasation.

Conclusion. The controversial animal data and the lack of controlled clinical experience with DMSO should preclude its use as the sole initial therapy of anthracycline extravasations. A comparison study be tween topical DMSO and local cooling versus local cooling alone would aid in determining the true benefit of DMSO in the treatment of anthracycline extravasation.

Vehicle selection for nonclinical oral safety studies

INTRODUCTION

The development of poorly soluble or permeable new chemical entities within the pharmaceutical industry often requires the use of nonstandard enabling nonclinical oral formulations. Despite this, the toxicity profile of many commonly used nonclinical vehicles is poorly understood. This lack of data can lead to unexpected formulation-related effects being observed in critical oral safety studies.

AREAS COVERED

This article summarizes the key considerations for formulation selection for oral nonclinical safety studies, and provides a strategy for appropriate development-phase formulation selection. The industry's use of oral nonclinical vehicles is reviewed, based on data from the FDA's Orange Book. Finally, a summary of the repeat dose oral toxicity of commonly used vehicles is presented.

EXPERT OPINION

The rapid identification of a suitable nonclinical oral formulation is a critical step in small-molecule drug development. In order to maintain flexibility and address the needs of a diverse set of new chemical entities (NCEs) with widely varying physiochemical properties, a "tool belt" of multiple oral formulations is recommended. The appropriate formulation is identified based on the goals of the study, as well as exposure required, species, duration and therapeutic indication of the NCE.

Intraperitoneal exposure to nano/microparticles of fullerene (C₆₀) increases acetylcholinesterase activity and lipid peroxidation in adult zebrafish (Danio rerio) brain

Even though technologies involving nano/microparticles have great potential, it is crucial to determine possible toxicity of these technological products before extensive use. Fullerenes C₆₀ are nanomaterials with unique physicochemical and biological properties that are important for the development of many technological applications. The aim of this study was to evaluate the consequences of nonphotoexcited fullerene C₆₀ exposure in brain acetylcholinesterase expression and activity, antioxidant responses, and oxidative damage using adult zebrafish as an animal model. None of the doses tested (7.5, 15, and 30 mg/kg) altered AChE activity, antioxidant responses, and oxidative damage when zebrafish were exposed to nonphotoexcited C₆₀ nano/microparticles during 6 and 12 hours. However, adult zebrafish exposed to the 30 mg/kg dose for 24 hours have shown enhanced AChE activity and augmented lipid peroxidation (TBARS assays) in brain. In addition, the up-regulation of brain AChE activity was neither related to the transcriptional control (RT-qPCR analysis) nor to the direct action of nonphotoexcited C₆₀ nano/microparticles on the protein (in vitro results) but probably involved a posttranscriptional or posttranslational modulation of this enzymatic activity. Taken together these findings provided further evidence of toxic effects on brain after C₆₀ exposure.

Dimethyl sulfoxide: an effective penetration enhancer for topical administration of NSAIDs

Dimethyl sulfoxide (DMSO) is a molecule with a long history in pharmaceutics and is now well established as a penetration enhancer in topical pharmaceutical formulations. It is currently used for this purpose in diclofenac sodium topical solution (approved in the United States to treat signs and symptoms of osteoarthritis) and idoxuridine topical solution (approved in Europe for the treatment of herpes zoster). This article reviews the mechanism of action of DMSO as a pharmaceutical penetration enhancer, the characteristics of the molecule that facilitate transdermal drug delivery, and studies of efficacy and safety. The clinical use of pharmaceutical-grade DMSO as a penetration enhancer is supported by the robust data that have accumulated over the past 3 decades demonstrating the favorable safety and tolerability profile. Dimethyl sulfoxide is a safe and effective mechanism for facilitating the transdermal delivery of both hydrophilic and lipophilic medications to provide localized drug delivery.

Diclofenac sodium topical solution with dimethyl sulfoxide, a viable alternative to oral nonsteroidal anti-inflammatories in osteoarthritis: review of current evidence

Topical nonsteroidal anti-inflammatory drugs (NSAIDs) may offer a safer alternative to their oral counterparts for the management of osteoarthritis. Diclofenac sodium topical solution with dimethyl sulfoxide (TDiclo) was evaluated in five randomized, controlled trials and is indicated for treatment of the signs and symptoms associated with osteoarthritis of the knee. Three studies showed that TDiclo is superior to placebo and vehicle control with respect to pain, physical function, and perception of osteoarthritis symptoms. Two studies showed that benefits are similar to those of oral diclofenac, with one study demonstrating statistical equivalence. The most common adverse event associated with TDiclo in these studies was dry skin. Incidences of gastrointestinal adverse events and abnormal levels of liver enzymes were lower with TDiclo compared with oral diclofenac in active-controlled studies. Based on these studies, TDiclo represents a practical, evidence-based option for the management of osteoarthritis of the knee.

Cytotoxicity assessment of four pharmaceutical compounds on the zebra mussel (Dreissena polymorpha) haemocytes, gill and digestive gland primary cell cultures

Pharmaceutical compounds are considered the new environmental pollutants but at present few studies have evaluated their ecotoxicity on aquatic invertebrates. This study was aimed to investigate the in vitro cytotoxicity of four common drugs, namely atenolol (ATL), carbamazepine (CBZ), diclofenac (DCF) and gemfibrozil (GEM), on three different cell typologies from the zebra mussel (Dreissena polymorpha): haemocytes, gill and digestive gland cells. Results obtained by the Trypan blue exclusion test revealed that exposure to increasing concentrations (0.001; 0.01; 0.1; 1 and 10 mg L(-1)) of CBZ, DCF and GEM were able to significantly decrease the viability of each cell type, while the MTT (3(4,5-dimethyl-2thiazholyl)-2,5-diphenyl-2H-tetrazolium bromide) reduction assay highlighted only a slight reduction of mitochondrial activity of gill and digestive gland cells. Overall, DCF was the most cytotoxic drug for zebra mussel cells, followed by GEM, CBZ, while ATL has not a noteworthy toxic potential. Our preliminary results lay the groundwork for further in vitro evaluations, which will allow a better definition of the potential toxicity of these drugs.

The potential of nanoscale combinations of self-assembling peptides and amino acids of the Src tyrosine kinase inhibitor in acute lung injury therapy

Many newly discovered therapeutic agents require a delivery platform in order to translate them into clinical applications. For this purpose, a nanoscale formulation strategy was developed for the Src tyrosine kinase inhibitor PP2. The formulation utilizes the combination of the self-assembling peptides (EAK16-II) and amino acids to minimize the use of the toxic organic solvent DMSO; hence, the biocompatibility of the PP2 nanoformulations was significantly improved. They were found to be non-hemolytic and safe for intravenous and intratracheal administration; the formulations did not alter PP2 activity in Src inhibition on cultured cells. The PP2 nanoformulation was further evaluated on a lipopolysaccharide (LPS)-induced acute lung injury mouse model. Results revealed that the pretreatment of PP2 nanoformulation could decrease the inflammatory cell infiltration and the pro-inflammatory cytokine TNF-α production in the bronchoalveolar lavage fluid after LPS stimulation. The promising therapeutic efficacy and the formulation strategy developed in this work may help further translate PP2 and other hydrophobic therapeutic agents into clinical applications.

A long-term, open-label study to confirm the safety of topical diclofenac solution containing dimethyl sulfoxide in the treatment of the osteoarthritic knee

To assess the long-term safety of a topical solution of diclofenac sodium in a vehicle containing dimethyl sulfoxide (TDiclo), subjects with radiologically confirmed, symptomatic osteoarthritis of the knee(s) applied the clinical dose of TDiclo (40 drops, four times daily) to each painful knee for up to 52 weeks. Safety assessment included adverse events, skin irritation scores of the treated knee(s), ocular examinations, and routine laboratory tests. There were 793 subjects (mean age, 62.5 years) who applied TDiclo to one or both (72%) knees for an average of 204 days, including 463 subjects for 6 months and 144 for 1 year. The most frequent adverse events were at the application site with no increase in incidence with prolonged exposure: dry skin (25.3%), contact dermatitis without vesicles (13.0%) or with vesicles (9.5%). Skin irritation score was 0 (normal) in 61.0% of subjects, 0.5 (dryness or flaking) in 23.9%, 1 or 2 (erythema without or with induration) in 6.9%, and 3 or 4 (erythema with induration and vesicles/bullae) in 8.2%. Subject dropouts included 114 (14.4%) with an application site skin adverse event. Individual subject laboratory test shift to abnormal occurred for hemoglobin (3.2%), aspartate aminotransferase (6.4%), alanine aminotransferase (7.3%), and creatinine (4.2%), but few shifts (less than 0.3% per variable) were clinically significant. No increased risk of cardiovascular or cataract events was noted. This long-term study of TDiclo revealed a safety profile comparable to that shown in multiple, shorter, well-controlled, double-blind trials with the predominant adverse effect noted being an application site reaction.

Efficacy and safety of topical diclofenac containing dimethyl sulfoxide (DMSO) compared with those of topical placebo, DMSO vehicle and oral diclofenac for knee osteoarthritis

While topical non-steroidal anti-inflammatory drugs are considered safe, their long-term efficacy for osteoarthritis has been suspect. We conducted a 12-week, double-blind, double-dummy, randomized controlled trial of topical diclofenac (TDiclo) in a vehicle solution containing dimethyl sulfoxide (DMSO) in 775 subjects with radiologically confirmed, symptomatic primary osteoarthritis of the knee. This 5-arm study compared TDiclo with a placebo solution, the DMSO vehicle, oral diclofenac (ODiclo) and the combination of TDiclo+ODiclo for relieving the signs and symptoms of knee osteoarthritis. Subjects applied study solution, 40 drops four times daily, and took one study tablet daily for 12 weeks. Co-primary efficacy variables were WOMAC pain and physical function and a patient overall health assessment. Secondary variables were WOMAC stiffness and patient global assessment (PGA) of the knee osteoarthritis. TDiclo was superior to placebo for pain (-6.0 vs. -4.7, P=0.015), physical function (-15.8 vs. -12.3, P=0.034), overall health (-0.95 vs. -0.37, P<0.0001), and PGA (-1.36 vs. -1.01, P=0.016), and was superior to DMSO vehicle for all efficacy variables. No significant difference was observed between DMSO vehicle and placebo or between TDiclo and ODiclo. The commonest adverse event associated with TDiclo was dry skin (18.2%). Fewer digestive system and laboratory abnormalities were observed with TDiclo than with ODiclo. Addition of TDiclo to ODiclo did not increase the incidence of systemic adverse events. TDiclo in DMSO vehicle is an effective treatment option for knee osteoarthritis with efficacy similar to, but tolerability better than ODiclo. DMSO vehicle was no more efficacious than placebo.

Dimethyl sulfoxide (DMSO) produces widespread apoptosis in the developing central nervous system

Dimethyl sulfoxide (DMSO) is a solvent that is routinely used as a cryopreservative in allogous bone marrow and organ transplantation. We exposed C57Bl/6 mice of varying postnatal ages (P0-P30) to DMSO in order to study whether DMSO could produce apoptotic degeneration in the developing CNS. DMSO produced widespread apoptosis in the developing mouse brain at all ages tested. Damage was greatest at P7. Significant elevations above the background rate of apoptosis occurred at the lowest dose tested, 0.3 ml/kg. In an in vitro rat hippocampal culture preparation, DMSO produced neuronal loss at concentrations of 0.5% and 1.0%. The ability of DMSO to damage neurons in dissociated cultures indicates that the toxicity likely results from a direct cellular effect. Because children, who undergo bone marrow transplantation, are routinely exposed to DMSO at doses higher than 0.3 ml/kg, there is concern that DMSO might be producing similar damage in human children.

Teratology study of derivatives of tetramethylcyclopropyl amide analogues of valproic acid in mice

BACKGROUND

Although valproic acid (VPA) is used extensively for treating various kinds of epilepsies, it is well known that it causes neural tube and skeletal defects in both humans and animals. The amide and urea derivatives of the tetramethylcylcopropyl VPA analogue, N-methoxy-2,2,3,3-tetramethylcyclopropanecarboxamide (N-methoxy-TMCD) and 2,2,3,3-tetramethylcyclopropanecarbonylurea (TMC-urea), were synthesized and shown to have a more potent anticonvulsant activity than VPA. The objective of this study was to investigate the teratogenic effects of these compounds in NMRI mice.

METHODS

Pregnant NMRI mice were given a single subcutaneous injection of either VPA, N-methoxy-TMCD, or TMC-urea at 1.8 and 3.6 mmol/kg on gestation day (GD) 8. Cesarean section was performed on GD 18. First, the live fetuses were examined to detect any external malformations, then their skeletons were double-stained for bone and cartilage and subsequently examined.

RESULTS

Significant increases in fetal losses and neural tube defects were observed with administration of VPA at 3.6 mmol/kg when compared to the vehicle control. In contrast, upon cesarean section, there were no significant differences between either N-methoxy-TMCD or TMC-urea and the control groups for any parameter. Skeletal examination revealed that a number of the abnormalities were induced by VPA dose-dependently at high rates of incidence. These abnormalities were mainly at the axial skeletal level. However, lower frequencies of skeletal abnormality were observed with N-methoxy-TMCD and TMC-urea than with VPA.

CONCLUSIONS

In addition to their more potent antiepileptic activity, these findings clearly indicate that N-methoxy-TMCD and TMC-urea are distinctly less teratogenic than VPA in NMRI mice.

Amidic modification of valproic acid reduces skeletal teratogenicity in mice

BACKGROUND

The antiepileptic drug valproic acid (VPA) is well known to cause neural tube and skeletal defects in both humans and animals. The amidic VPA analogues valpromide (VPD) and valnoctamide (VCD) have much lower teratogenicity than VPA inducing exencephaly in mice. The objective of this study was to investigate the teratogenic effects of VPA, VPD, and VCD on the skeleton of NMRI mice.

METHODS

Pregnant NMRI mice were given a single subcutaneous injection of VPA (400 and 800 mg/kg), VPD (800 mg/kg), or VCD (800 mg/kg) on the morning of gestation day (GD) 8. Cesarean section was carried out on GD 18. Live fetuses were double-stained for bone and cartilage and their skeletons were examined.

RESULTS

Significant increases in fetal loss and exencephaly rate were observed with VPA at 800 mg/kg compared to the vehicle control. There were no significant differences between either VPD or VCD and the control groups for any parameter at cesarean section. A number of abnormalities were dose-dependently induced at high incidences by VPA in both the cartilage and bone of vertebrae, ribs and sternum. In contrast, lower frequencies of abnormality were exhibited with VPD and VCD than VPA in all skeletons affected by VPA.

CONCLUSIONS

These findings clearly indicate that VPD and VCD are distinctly less teratogenic than VPA in the induction of not only neural tube defects, but also skeletal abnormalities. A structure-teratogenicity relationship of VPA on the skeleton is suspected.

Rainbow trout primary epidermal cell proliferation as an indicator of aquatic toxicity: an in vitro/in vivo exposure comparison

Little or no work has been carried out on primary cell cultures in terms of cellular proliferation and toxicity studies. Cell proliferation represents one of the most relevant cellular functions. Anti-PCNA antibodies have aroused considerable interest recently as potential immunocytochemical markers of proliferation for use in toxicity studies. In this study, PCNA methodology, which was developed primarily for mammalian tissues, was adapted to rainbow trout (Oncorhynchus mykiss (R.)) primary cultured epidermal cells exposed in vivo i.e. whole animal exposures and in vitro for the study of the ecotoxicological potential of the aromatic amine, 2,4-dichloroaniline (2,4-DCA), a member of a little studied and widespread class of aquatic pollutants. There are many approaches to assess the proliferative activity of cells. Immunocytochemical methods offer a high sensitivity and specificity. The immunohistochemical avidin-biotin complex (ABC) method was used for the detection and quantification of PCNA, one of the best-known endogenous proliferation markers, applying the mammalian monoclonal antibody PC-10 to formalin-fixed primary cultures of rainbow trout skin. Here we describe our experience with the immunocytochemical detection and quantification of this proliferation marker. Results indicate that the antibody cross reacts with the corresponding rainbow trout epitope and that the alterations in PCNA labelling in the in vivo and in vitro exposed cultures followed similar patterns. This paper presents data on the validation of rainbow trout primary epidermal culture as an in vitro ecotoxicity model with epidermal proliferation as an endpoint. It can be concluded that cellular proliferation could be used as an indicator of the aquatic toxicity potential of xenobiotics. Correlations between cellular proliferation responses in primary cultures derived from in vivo exposed rainbow trout and primary cultures exposed in vitro were assessed. A dose-response was evidenced in both approaches, however the in vivo exposures appeared to be approximately two orders of magnitude more sensitive than the in vitro exposures. Responses in vitro occurred between 200 and 1000 micro M while in vivo responses were between 2 and 10 micro M. The good qualitative correspondence between the in vitro and in vivo results indicates that studies using trout epidermal cells allow the identification of xenobiotic effects in fish skin. However, further work is required before quantitative predictions i.e. effective concentrations in vivo, can be made from in vitro studies. This study suggests that the in vitro exposed rainbow trout primary cultured cell model with proliferation as an endpoint can be used as an alternative testing procedure to the whole animal assay.

Advances in male contraception

The methods devised for male contraception are meager. The authors review the various nonhormonal methods applied for contraception including vas deferens interference and heat. The former comprises the no-scalpel vasectomy, percutaneous vasal injection, the "Shug" method, and the argon laser vasal photocoagulation. Heat methods used wet heat, and artificial cryptorchidism was created by testicular suspension. The testicle was suspended in the superficial inguinal pouch close to the scrotal neck using 2 methods: stitch and ball. Two recently developed methods for male contraception--polyester-induced azoospermia and prolactin injection--are described. The azoospermic effect of the polyester sling seems to be due to (1) creation of an electrostatic field across the intrascrotal structures, and (2) disordered thermoregulation. Prolactin administration as a contraceptive method is efficient and safe and has the potential to be developed as a male contraceptive. The methods, especially testicular suspension and polyester suspensors, are simple and easily applicable and were well accepted by the subjects.

In vitro evaluation of the effect of dimethyl sulfoxide on equine articular cartilage matrix metabolism

OBJECTIVE

To evaluate the effects of dimethyl sulfoxide (DMSO) on equine articular cartilage matrix metabolism.

STUDY DESIGN

Using a cartilage explant culture system, proteoglycan (PG) synthesis, PG release, lactate metabolism, chondrocyte viability, and metabolism recovery were determined after cartilage exposure to DMSO.

SAMPLE POPULATION

Cartilage harvested from metacarpophalangeal and metatarsophalangeal joints of 12 horses (age range, 1 to 10 years).

METHODS

Explants were exposed to concentrations of DMSO (1% to 20%) for variable times (3 to 72 hours). PG synthesis and release were determined by a radiolabel incorporation assay and dimethylmethylene blue (DMMB) dye assay, respectively. Lactate released into culture media was measured, and chondrocyte viability was assessed using the Formizan Conversion Assay and a paravital staining protocol. Metabolism recovery was assessed in explants that were allowed to recover in maintenance media after exposure to DMSO.

RESULTS

PG synthesis and lactate metabolism were inhibited in a dose- and time-dependent manner after exposure to DMSO concentrations > or = 5%; there was no significant alteration in PG release. No change in chondrocyte viability was detected after incubation with DMSO. PG synthesis and lactate metabolism returned to baseline rates when allowed a recovery period after exposure to DMSO.

CONCLUSIONS

DMSO concentrations > or = 5% suppress equine articular cartilage matrix metabolism. Suppression of PG synthesis and lactate metabolism is reversible and does not appear to be the result of chondrocyte death.

CLINICAL RELEVANCE

Equine clinicians adding DMSO to intraarticular lavage solutions should be aware that DMSO may have deleterious effects on equine articular cartilage matrix metabolism.

Dimethyl sulfoxide enhances lipid synthesis and secretion by long-term cultures of adult rat hepatocytes

Dimethyl sulfoxide (DMSO) was tested for its effects on lipid metabolism of long-term cultures of adult rat hepatocytes. The addition of 1% DMSO to 3T3-hepatocyte cultures was not toxic to cells and in fact treated cultures maintained better their characteristic morphology for up to 14 days of exposure. DMSO treatment increased 2-3 fold the de novo synthesis of total lipids from[14C]acetate. The analysis by thin layer chromatography of cellular and secreted lipids revealed that DMSO increased the levels of cellular triglycerides, phospholipides and free and sterified cholesterol at 7 days of exposure while at 14 days there was also a 2-3-fold increase in medium secreted lipids. Additionally, DMSO increased the activity of glycerol-phosphate dehydrogenase, a marker enzyme of glycerolipid synthesis, by greater than 50% at either 7 or 14 days of exposure. These results show that 1% DMSO not only is not detrimental to cultured hepatocytes but also enhances lipid synthesis and secretion, both hepatic-differentiated functions.

Male mediated teratogenic potential evaluation of new antifertility compound SMA in rabbit (Oryctolagus cuniculus)

The male mediated teratogenic potential of a new antifertility compound, styrene maleic anhydride (SMA), was evaluated in rabbits. No teratogenic potential was observed at the doses of 1.25 mg, 2.5 mg and 5.0 mg used in our experiment.

Time-controlled injectable occlusion of the vas deferens

An injectable method of obtaining vas deferens occlusion is presented. The agent used is styrene maleic anhydride (SMA) with dimethyl sulphoxide as the solvent. The special feature of the approach is that after a period of time, spermatozoa passage is spontaneously reestablished. By varying the dose of SMA administered, the interval between injection and restoration of spermatozoa flow can be regulated from as short a period as about 3 months to more than five years.

Lack of ocular changes with dimethyl sulfoxide therapy of scleroderma

Eighty-four patients with scleroderma hand ulcers were treated 3 times daily for 3 months in a randomized, double-blind clinical trial by immersing their hands into bags of topical 70% dimethyl sulfoxide (DMSO), topical 2% DMSO, or 0.85% normal saline. Fifty-five of the patients completed the study, 46 of whom received blinded initial (0 days) and final (12 weeks) full ophthalmologic examinations. This evaluation included past ocular history, past drug history, family ocular history, pupillary examination, cycloplegic refraction, motility study, applanation tension, indirect dilated funduscopic examination, and slit-lamp examination. No statistical difference in these ocular variables, including visual acuity, lenticular changes, and cataract development, were noted among the three groups, and in no patients were the DMSO-related lenticular changes reported in numerous animal studies found. The maximum theoretical dosage of DMSO administered was 2.6 g/kg/day, which is comparable to those used in the animal studies.

Safety evaluation of a male injectable antifertility agent, styrene maleic anhydride, in rats

Injection of a polymer, styrene maleic anhydride (SMA), into the lumen of the vas deferens of rats, was observed to have effective and reversible contraception. The safety evaluation of the polymer, for 90 days, was carried out in Charles Foster male rats. There have been no significant changes in any of the toxicity parameters in the test animals as compared to the control animals. Hence, it is concluded that the compound is non-toxic to rodents.

Conventional chemotherapeutic agents combined with DMSO or DFMO in treatment of rat prostate carcinoma

Chemotherapy for prostatic carcinoma is usually reserved for those patients who have failed conventional therapy. These patients generally are in poor health and tolerate chemotherapy poorly. If doses of conventional agents could be decreased without altering cytotoxic activity, then conventional chemotherapy could become an attractive treatment modality. Dimethylsulfoxide and difluoromethylornithine have been shown to induce differentiation in some tumor systems. Growth alteration effects of these two agents were investigated individually and in association with conventional chemotherapeutic agents cyclophosphamide, cisplatin, and fluorouracil in an experimental prostatic cancer model. Copenhagen rats had subcutaneous tumors induced by injections of cells cultured in vitro from a subline of the Dunning rat prostatic tumor, MAT LyLu. Treatment with chemotherapeutic agents individually and associated with differentiation agents was initiated when tumors were palpable. Tumor growth rates and rat body weights were monitored in all groups. The differentiation agents used singly were not able to retard significantly tumor growth rates. In higher doses, each conventional agent used singly significantly retarded tumor growth. Used in combination, the differentiation agents induced cytodestructive properties of lower doses of conventional agents, but some combinations also increased host toxicity. These data suggest that differentiation agents may provide additional antineoplastic benefits when administered in combination with selected chemotherapeutic agents in the management of prostatic cancer.

Effect of DMSO and DFMO on rat prostate tumor growth

An anaplastic, metastatic subline of the Dunning rat tumor was exposed to non-cytodestructive doses of the cellular differentiation agents dimethylsulfoxide and difluoromethylornithine. Copenhagen rats hosting prostate tumors were evaluated by comparing solid tumor growth resulting from injection of treated cells with solid tumor growth of untreated control cells. Results showed significantly slower solid tumor growth after a 15 day in vitro exposure of cells to either agent, after oral treatment of host animals for 20 days with either agent before injection of untreated tumor cells, and after oral treatment of host animals with either agent initiated on the day of untreated tumor cell injection. Treatment of animals with established tumors with either agent also had an inhibitory effect on tumor growth, and the effect was related to the length of treatment. Thus, exposure of these highly malignant rat prostate carcinoma cells to non-cytotoxic doses of either agent induced slower tumor growth rates. Treatment with either agent could have selected for a slower growing population of tumor cells. Since a slowing of cell cycle transit times is an early indicator of cellular differentiation, these results could reflect an increase in the capacity of the malignant cells to differentiate.

Use of polar solvents in chemoprevention of 1,2-dimethylhydrazine-induced colon cancer

To examine the effect of the polar solvents on 1,2-dimethylhydrazine (DMH)-induced colon cancer, 100 male Sprague-Dawley rats were randomly allocated to a control and three treatment groups. Treated animals received N-methylformamide (NMF), dimethylsulfoxide (DMSO), or methylsulfonylmethane (MSM) added to drinking water 1 week before carcinogen injections commenced and for the duration of the experiment. Primary tumors were detected by serial laparotomy under ether anesthesia performed at 2-month intervals and commencing after carcinogen injections had been completed. The average time to tumor onset was significantly delayed in rats receiving NMF and MSM (P = 0.0141 and 0.0398 respectively, Mantel-Haenszel test). In addition, fewer poorly differentiated tumors were noted in treatment groups. No weight loss or toxicity was observed. These findings demonstrate that the polar solvents significantly reduce the latent period to tumor onset in DMH-induced colon cancer and indicate the need to further investigate such compounds as chemopreventive agents.

Medical management of spinal cord disease

In spinal cord disease of horses, a complete history, neurologic examination, and adjunctive diagnostic procedures are very helpful in establishing a tentative diagnosis; however, a definitive diagnosis may be difficult or impossible to establish antemortem. Medical management should be initiated with full consideration of possible etiologies and knowledge of the effects and consequences of medical therapies. This article discusses the drugs commonly used in the management of spinal cord disease and the rationale for their use.

Effect of organic vehicles on the pharmacokinetics of aminophylline administered intravenously to goats

Aminophylline dissolved in water, propylene glycol, or dimethyl sulfoxide was administered intravenously to goats in a randomized cross-over experiment. Model-dependent and model-independent pharmacokinetic parameters for theophylline were compared on the basis of the solvent used in the dosage form administered. No difference was found in any pharmacokinetic parameter. Thus, we found no evidence for the possibility that the organic solvents studied would confound pharmacokinetic investigations of theophylline and similar lipophilic drugs.

Dimethyl sulfoxide: lack of suppression of the humoral immune response in mice

Mice were injected intraperitoneally (i.p.) with 100% dimethyl sulfoxide (DMSO) or sterile saline (controls) for 36 days. The mice received 0.05 ml daily for one week, 0.025 ml every other day for the second week (because the DMSO-treated mice appeared weak), and 0.05 ml daily for 3 more weeks. All mice were immunized twice with sheep red blood cells (days 13 and 24), and bled twice by caudal incision (days 20 and 29). Hematocrits were significantly decreased (P less than or equal to 0.002) but still within the normal range. The primary and secondary antibody response to sheep red blood cells (SRBC), leukocyte counts, body weight, and the size of the heart, lungs, spleen, thymus, and kidneys were not affected. DMSO treatment resulted in significant liver enlargement (P = 0.02). It is concluded that this dose of DMSO is not deleterious to the humoral immune response in mice responding to a new antigen.

Prevention of granulocyte-mediated oxidant lung injury in rats by a hydroxyl radical scavenger, dimethylthiourea

Toxic, partially reduced metabolites of oxygen (toxic oxygen radicals) are increasingly implicated in acute leukocyte-mediated tissue injury. To further probe the roles of oxygen radicals in acute lung edema, I studied the effects of a recently described and very potent oxygen radical scavenger, dimethylthiourea (DMTU) (Fox, R. B., R. N. Harada, R. M. Tate, and J. E. Repine, 1983, J. Appl. Physiol., 55:1456-1459) on polymorphonuclear leukocyte (PMN) oxidant function and on two types of lung injury mediated by oxygen radicals and PMN. DMTU (10 mM) blocked 79% of hydroxyl radical (OH) production by PMN in vitro without interfering with other PMN functions, such as O-2 production, myeloperoxidase activity, chemotaxis, degranulation, or aggregation. When isolated rat lung preparations were perfused with PMN activated to produce OH, lung weights were increased from 2.3 +/- 0.2 to 11.2 +/- 0.8 g. DMTU (10 mM) prevented 70% of these increases (lung weights, 5.0 +/- 1.1 g, P less than 0.005). Finally, when intact rats were exposed to 100% O2 for 66 h, lung weight:body weight ratios were increased from 5.78 +/- 0.33 to 8.87 +/- 0.16 g. DMTU (500 mg/kg) prevented 83% of this hyperoxia-induced lung edema in vivo (lung:body weight ratios, 6.05 +/- 0.21, P less than 0.001). Pharmacokinetic studies showed that DMTU diffused effectively into lung interstitial fluids and had a relatively long half-life (25-35 h) in the circulation. Because a variety of oxygen radicals, such as superoxide (O-2), hydrogen peroxide (H2O2), or OH are produced by PMN, there is usually some uncertainty about which one is responsible for injury. However, in these studies, DMTU did not scavenge O-2 and scavenged H2O2 only very slowly while scavenging OH very effectively. Therefore, DMTU may be useful in the investigation of the roles of oxygen radicals, especially OH, in acute granulocyte-mediated tissue injury.