Estrogen stimulates the transient association of calmodulin and myosin light chain kinase with the chicken liver nuclear matrix.

Previous work has demonstrated that estrogen administration to immature chickens results in a rapid but transient increase in nuclear estrogen receptor content, a large portion of which is associated with the nuclear matrix. The present studies were undertaken to determine whether estrogen produced a more generalized change in the protein composition of the nuclear matrix. High-resolution two-dimensional gel analysis of the matrix revealed a very complex protein pattern, but several major qualitative differences were observed after estrogen treatment. To simplify the number of proteins evaluated, we examined the effects of estrogen on a subset of matrix proteins, namely, calmodulin and its binding proteins. Calmodulin was measured by radioimmunoassay and the binding proteins were detected by interaction of 125I-calmodulin with matrix proteins distributed on one-dimensional polyacrylamide gels. Calmodulin and two specific Ca2+-dependent calmodulin-binding proteins were found to be associated with matrix preparations. The two binding proteins exhibited apparent Mr of 200,000 and 130,000. The Mr 130,000 protein was identified as myosin light chain kinase on the basis of enzymatic activity and immunoreactivity with a specific antibody to this enzyme. Estrogen treatment of immature chickens did not alter the hepatic content of calmodulin. However, the steroid did result in an enrichment of the proportion of calmodulin and its two binding proteins associated with the nuclear matrix within 4 h after injection. The time course of these changes paralleled those previously documented for estrogen receptor. Taken together, these data are compatible with a role for calmodulin and myosin light chain kinase in the response of chicken liver cells to steroid hormones.

Autoantibodies to zona pellucida: a possible cause for infertility in women.

Human and pig ovaries were tested by agar gel diffusion and found to contain several cross-reacting (common) antigens. At least one common antigen was located in the zona pellucida as determined by indirect immunofluorescence. Serum samples from 22 infertile women were tested on pig eggs by immunofluorescence, and six of these samples produced strong and nine produced moderate reactions with the zona pellucida. The autoantibodies may be responsible for infertility in these women.

Molecular cloning and expression of an abundant rabbit ovarian protein with 20 alpha-hydroxysteroid dehydrogenase activity.

An abundant 37-kDa protein, which comprises up to 30% of the soluble proteins of the ovary, has been found to have 20 alpha-hydroxysteroid dehydrogenase (20 alpha HSD) activity. The steroidogenic enzyme 20 alpha HSD regulates the conversion of progesterone to 20 alpha-hydroxyprogesterone in many mammalian species. Complimentary DNA clones encoding a unique and abundant 20 alpha HSD were isolated from a mature rabbit ovary library using guinea pig antisera generated to the purified 37-kDa protein and from a 5' EcoRI fragment from the initial positive clone. A full-length cDNA clone of 1217 basepairs encoding a 323-amino acid protein with an estimated mol wt of 37 kilodaltons was obtained. Amino acid sequence data indicate a similarity to human chlordecone reductase, bovine lung prostaglandin F synthase, human aldose reductase, human aldehyde reductase, and frog lens rho-crystallin, placing rabbit ovarian 20 alpha HSD in the aldo-keto reductase family of proteins. Northern blot analysis demonstrated a 1.2-kilobase mRNA in the interstitial tissue of mature rabbit ovaries and, to a lesser extent, in corpora luteal tissue. 20 alpha HSD was expressed in bacteria as a recombinant protein and was shown to possess enzymatic activity, preferring NADP as a cofactor. These studies demonstrate that an abundant ovarian protein belonging to the superfamily of NADP-dependent aldo-keto reductases has 20 alpha HSD activity. This is the first example of an abundant crystallin-related protein with known enzymatic activity in a tissue other than the lens.

Synergistic roles of bone morphogenetic protein 15 and growth differentiation factor 9 in ovarian function.

Knockout mouse technology has been used over the last decade to define the essential roles of ovarian-expressed genes and uncover genetic interactions. In particular, we have used this technology to study the function of multiple members of the transforming growth factor-beta superfamily including inhibins, activins, and growth differentiation factor 9 (GDF-9 or Gdf9). Knockout mice lacking GDF-9 are infertile due to a block in folliculogenesis at the primary follicle stage. In addition, recombinant GDF-9 regulates multiple cumulus granulosa cell functions in the periovulatory period including hyaluronic acid synthesis and cumulus expansion. We have also cloned an oocyte-specific homolog of GDF-9 from mice and humans, which is termed bone morphogenetic protein 15 (BMP-15 or Bmp15). To define the function of BMP-15 in mice, we generated embryonic stem cells and knockout mice, which have a null mutation in this X-linked gene. Male chimeric and Bmp15 null mice are normal and fertile. In contrast to Bmp15 null males and Gdf9 knockout females, Bmp15 null females (Bmp15(-/-)) are subfertile and usually have minimal ovarian histopathological defects, but demonstrate decreased ovulation and fertilization rates. To further decipher possible direct or indirect genetic interactions between GDF-9 and BMP-15, we have generated double mutant mice lacking one or both alleles of these related homologs. Double homozygote females (Bmp15(-/-)Gdf9(-/-)) display oocyte loss and cysts and resemble Gdf9(-/-) mutants. In contrast, Bmp15(-/-)Gdf9(+/-) female mice have more severe fertility defects than Bmp15(-/-) females, which appear to be due to abnormalities in ovarian folliculogenesis, cumulus cell physiology, and fertilization. Thus, the dosage of intact Bmp15 and Gdf9 alleles directly influences the destiny of the oocyte during folliculogenesis and in the periovulatory period. These studies have important implications for human fertility control and the maintenance of fertility and normal ovarian physiology.

Identification and characterization of an abundant ovarian interstitial gland protein associated with sexual maturity in rabbits.

An abundant ovarian protein with a relative mol wt (Mr) of 37K and an apparent pI of 8, associated with the onset of sexual maturity in the rabbit, has been identified. Ovaries from sexually mature (greater than 6 months old) rabbits contain large quantities of this 37K protein, while none can be detected in ovaries of immature (1 and 2 months) animals. Analysis of polyacrylamide gel electrophoresis (PAGE) gels of mature ovarian homogenates demonstrates that this protein is more abundant than actin in these preparations. It appears to be tissue specific, since it was not detected in 16 other rabbit tissues tested. Autoradiographic analysis of proteins labeled with 35S in ovarian organ culture demonstrates that a protein of identical Mr and charge to the 37K protein is synthesized in this tissue. Polyclonal sheep antiserum has been produced to the two-dimensional PAGE-purified protein. Immunoblotting of two-dimensional PAGE gels shows specific recognition of this protein and two slightly more acidic proteins of the same Mr by this antiserum. These three protein species also stain identical colors with a silver-based color stain, further suggesting that these are charge variants of the same protein. This protein is not present in corpora lutea isolated form sexually mature ovaries and is present in interstitial cell-enriched ovaries of rabbits which have been actively immunized with zona pellucida proteins. Immunocytochemical localization studies further demonstrate that this protein is localized in the interstitial gland cells. These findings suggest that this 37K protein is not associated with either follicular or luteal cells, but, rather, is linked with the 20 alpha-hydroxyprogesterone-secreting interstitial gland cell population.

Immunization with zona pellucida proteins results in abnormal ovarian follicular differentiation and inhibition of gonadotropin-induced steroid secretion.

Changes in rabbit ovarian hormonal responses and cellular differentiation of ovarian follicles after immunization with porcine zona pellucida (ZP) have been examined. Steroid and peptide hormone levels were monitored after immunization to evaluate ovulation and pseudopregnancy cycles in immunized and control animals. All immunized rabbits developed serum antibodies to specific ZP antigens and failed to form functional corpora lutea in response to hCG administration, as evidenced by the absence of elevated serum progesterone concentrations. This is in contrast to control rabbits, which had elevated progesterone levels 8-9 days after hCG administration. Furthermore, all immunized animals showed greatly increased serum levels of FSH and LH compared to those of control animals. These effects on ovarian function were apparent within 20 weeks of the primary immunization. Follicular development was analyzed by light and electron microscopies. The numbers of primary, secondary, and tertiary follicles in ovaries of immunized animals were markedly reduced within 7 weeks compared with control values. By 23 weeks, few if any growing follicles were present. Although numerous distinct clusters of cells with ultrastructural properties that resemble those of normal follicular cells were present in immunized animals, they contained no oocytes. These studies suggest that antibodies to ZP glycoprotein alter ovarian function by interfering with cells during the stage of follicle differentiation at which the ZP proteins are being synthesized and secreted. This system should provide an excellent model with which to study the early events associated with ovarian follicular cell differentiation and subsequent hormonal responsiveness.

The heterogeneity of porcine 32,000 Mr inhibin alpha-subunit: a gel electrophoresis and immunoblot study.

Porcine 32,000 Mr inhibin is a glycoprotein with one asparagine-linked glycosylation site on the alpha-subunit. The presence of carbohydrate on the alpha-subunit was visualized by periodate-Schiff (PAS) staining. This stain for carbohydrate also verified that the beta-subunit of 32,000 Mr porcine inhibin does not contain carbohydrate. When analyzed by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (1D-PAGE) under reducing conditions, the inhibin alpha-subunit consistently existed as a doublet, and by the PAS stain, both bands of the doublet were glycosylated. Analysis by two-dimensional (2D) PAGE further revealed the presence of charge isoforms of the alpha-subunit. The alpha-subunit of inhibin could be deglycosylated by N-glycanase, but not by endoglycosidase F, endoglycosidase D, or endoglycosidase H. When the N-glycanase-treated inhibin was analyzed by either 1D-PAGE or 2D-PAGE, the molecular size of the alpha-subunit was reduced by 3500 Mr. Each doublet band observed with reducing conditions in 1D-PAGE or 2D-PAGE for the alpha-subunit became a single band (spot) in the deglycosylated alpha-subunit. However, the charge heterogeneity detected by 2D-PAGE was retained, indicating that only a portion of this heterogeneity is attributable to the carbohydrate moiety. The in vitro biological activity of the deglycosylated inhibin was not different from the control sample. The composition of the carbohydrate in inhibin was investigated with the Dionex carbohydrate analyzer. Inhibin contains fucose, glucosamine, galactose, mannose, and glucose. Colorimetric analysis revealed the presence of sialic acid. Taken together, this implies some aspect of the peptide portion of the molecule is involved in charge heterogeneity. Inhibin may have an unusual carbohydrate component, as evidenced by the detection of glucose in inhibin samples. The absence of glucose in the carbohydrate moiety of another glycoprotein fraction that accompanied the inhibin through all the same fractionation procedures argues against the artifactual introduction of glucose in the fractionation medium per se.

Localization of a carbohydrate antigen associated with growing oocytes and ovarian surface epithelium.

We used a monoclonal antibody (PS1) to a carbohydrate antigen to study the development of the oocyte and follicle during early stages of differentiation in several mammalian species. This antigen has been shown to localize within the cytoplasm of oocytes in primordial follicles as well as in growing oocytes. It is also localized within distinct layers of the zona pellucida (ZP) of developing follicles. Although this antibody was made against a specific ZP glycoprotein, the antigen also appears to be abundant in cells of the ovarian surface epithelium (OSE). The localization of this carbohydrate moiety has been observed in ovaries of rabbits of different ages as well as in the ovarian surface epithelium of other mammalian species including cat, cynomolgus monkey, baboon, and human. These studies demonstrate that there is an abundant carbohydrate antigenic determinant which is associated with both the mammalian oocyte and the ovarian surface epithelium but which is not apparent in other ovarian cell types or in non-ovarian secretory epithelium. This antibody probe should provide a valuable tool for studying the development and differentiation of the ovary, since this antigen is associated with two highly differentiated but distinct cell types.

A specific radioimmunoassay for evaluation of serum antibodies to zona pellucida antigens.

A radioimmunoassay procedure has been developed for detecting antibodies to porcine zonae pellucidae antigens using Staphylococcus aureus Protein A cells (Pansorbin) as the immunoadsorbent. This method offers a rapid and reproducible procedure for detecting specific antibodies to zona antigens. The zona antigens detected by antibodies in this assay were found not to cross-react with antigens in 11 other tissues. Immune serum produced against a variety of other antigens, including protein hormones, steroid hormones, porcine serum and red blood cells, did not bind to any zonae components in this assay. This assay is compared with other methods which have been used to detect antibodies to zona antigens and has been found to be more specific than immunofluorescence methods and more sensitive than either immunofluorescence or immunoelectrophoresis methods.

Use of immunoaffinity purified antibodies to zona pellucida to compare alloimmunization of male and female rabbits.

In order to study the immunogenicity as well as tissue specificity of zona pellucida (ZP) antigens, the present studies have been designed to examine the effects of alloimmunization of male and female rabbits with rabbit zonae pellucidae. These studies are the first to demonstrate that high titers of antibodies to homologous ZP antigens are developed in male rabbits while no detectable antibodies are developed in females. As demonstrated using the ELISA assay, the antibodies from these males immunized with rabbit ZP, have a greater reactivity against rabbit ZP antigens than do antibodies from female rabbits heteroimmunized with porcine ZP. The antibodies from the male rabbits immunized with rabbit ZP also recognize antigenic determinants of porcine ZP. Methods for the immunoaffinity purification of antibodies from serum were developed to determine whether low levels of antibodies against ZP are present in sera of alloimmunized female rabbits. They also allow more detailed analysis of antibodies used to detect antigenic determinants which are cross-reactive between different mammalian species. Although this method was effective in isolating low levels of antibodies from male alloimmunized rabbits or from female rabbits heteroimmunized with porcine ZP proteins, no specific antibodies could be isolated from the serum of females alloimmunized with rabbit ZP. These studies more clearly demonstrate that zona pellucida antigens are specific to the ovary in that female rabbits do not develop significant antibody levels against rabbit ZP antigens, even following active immunization with adjuvant, while male rabbits develop high titers of antibodies.

Antibody reactivity with porcine zona pellucida.

A comparative study on anti-zona antibody activities in the sera from clinically defined categories of patients registered at the WHO Reference Bank for Reproductive Immunology was performed at five different laboratories with different detection methods. Considerably higher incidences of positive reactions were detected by immunofluorescence on porcine zonae in infertile women (16.3%) than in control subjects (7.1%). A similar proportion of positives was found by radioimmuno-binding assay (RIBA) using porcine zona antigen preparation in the infertile group (13.0%) but not in the female control group (0%), giving an indication of the specificity of this test. It is noteworthy that high incidences of positives were observed by RIBA with sera from male subjects with unexplained sterility, vasectomy and aspermatogenesis. A test system of passive hemagglutination reaction (PHAR) using purified porcine zona substance as antigen gave a low but slightly higher incidence of positives in infertile (3.1%) than in control sera (0.9%). No positive reactions were observed with infertile and control sera by another PHAR or by radioimmunoassay using an antigen preparation common to the two test systems. Anti-zona activities in these sera were therefore seen to vary, depending largely upon the detection systems and the antigen preparations.

Human sperm-oocyte recognition and infertility.

The incidence of infertility related to both male and female factors continues to rise despite many advances in reproductive technologies. Some abnormalities in human gamete interaction have been shown to be due to defects in the sperm, and others have been attributed to defects in the zona pellucida (ZP). Our lack of understanding of molecular mechanisms involved in the interaction of human sperm with the ZP in fertile as compared with infertile females and males has been limited because of the unavailability of human oocytes and ethical restraints on experimental studies. It is becoming increasingly apparent that improved clinical assays are necessary for evaluating sperm-ZP interaction in order to assess the optimal procedures for successful fertilization and pregnancy. With advances in molecular biology, the genes encoding the three major human ZP proteins have been identified and complementary DNAs are available to begin to better evaluate the molecular basis of sperm-ZP interaction.

Immunization of monkeys with recombinant complimentary deoxyribonucleic acid expressed zona pellucida proteins.

OBJECTIVE: To evaluate the effects of immunization with zona pellucida (ZP) proteins produced by recombinant complementary DNA (cDNA) technology for the elicitation and antibodies that inhibit sperm binding without altering ovarian function in the nonhuman primate. DESIGN: Controlled nonhuman primate study. SETTING: Controlled environment with individual housing of monkeys in facility approved by National Institutes of Health (NIH) guidelines. PARTICIPANTS: Monkeys housed and treated according to NIH regulations. INTERVENTIONS: Monkeys immunized and boosted at regular intervals with ZP proteins produced using recombinant cDNA techniques. MAIN OUTCOME MEASURE: Urinary estrogen, P, serum antibody levels, sperm-ZP binding, and ovarian morphology. RESULTS: Monkeys immunized with a recombinant rabbit 75-kd ZP protein expressed from a partial cDNA in the pEX bacteria expression system produce antibodies that interfere with ovarian follicular development and ovarian cyclicity. On the contrary, monkeys immunized with a recombinant rabbit 55-kd ZP protein develop antibodies that inhibit homologous sperm binding but do not affect ovarian follicular development or subsequent ovarian hormonal cyclicity. CONCLUSION: Monkey antibodies to the rabbit 75-kd ZP recombinant protein can be generated that inhibit ovarian cyclicity as desired for animal sterilization vaccines. Antibodies to the 55-kd ZP recombinant protein inhibit homologous monkey sperm binding to the ZP without altering ovarian endocrine function or morphology as is desired for human immunocontraception.

Use of a synthetic peptide adjuvant for the immunization of baboons with denatured and deglycosylated pig zona pellucida glycoproteins.

Baboons were immunized using a synthetic peptide adjuvant with two purified pig zona pellucida glycoproteins. The major zona pellucida glycoprotein (ZPI) was purified by preparative isoelectric focusing, and the 80 K deglycosylated zona pellucida protein (ZPIII) was purified by preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis. The immunogenicity as well as the antigenicity of these proteins were evaluated by characterizing antibodies using the enzyme-linked immunoassay and by immunoblotting of zona pellucida proteins separated by high-resolution two-dimensional polyacrylamide gel electrophoresis. Both groups of animals developed antibodies that recognize the major zona pellucida glycoprotein, (ZPI) and immunoblotting procedures provide evidence that two of the major porcine zona pellucida glycoprotein families (ZPI and ZPIII) contain shared antigenic determinants. The animals immunized with ZPI showed decreased levels of estrogen throughout their menstrual cycles, and two of the animals ceased ovulation. All animals in the group immunized with ZPIII had a significant reduction in the numbers of antral follicles as compared with control animals. Although ovarian cyclicity was not altered significantly within a few months after immunization, two of the five animals in this group became amenorrheic by 8 months. Histologic analysis of ovarian tissue shows that follicles were absent or frequently abnormal in animals of both groups following long-term immunization. These studies demonstrate that the synthetic adjuvant is effective in inducing antibodies (to purified zona pellucida glycoproteins) that recognize antigenic determinants to either denatured or deglycosylated zona pellucida glycoproteins, and that some of these antibodies may interfere with normal ovarian function.

The ovary as an immune target.

The ovary does not have a distinct morphologic barrier between the immune system and the developing gametes. This is in contrast to the testis in which the junctional complexes between the Sertoli cells form the blood-testis barrier. Whereas there are numerous factors, including genetic ones, associated with ovarian dysfunction, the immune factors have frequently been implicated in ovarian dysfunction. Much of our knowledge used to evaluate the immune system of the ovary has come from studies on the expression of the zona pellucida (ZP) proteins during ovarian development. Initial studies by Dunbar and colleagues demonstrated that immunization of rabbits with porcine ZP proteins (but not rabbit ZP proteins) would result in the generation of antibodies that inhibit sperm binding to the ZP and interfere with normal ovarian follicular development. In contrast to the rabbit and primate models, immunization of mice or rats with porcine ZP proteins does not have an effect on fertility or ovarian function although immunization of certain strains of mice with mouse ZP peptides and immune activator systems has been shown to result in ovarian pathology. Whereas immune inflammatory reactions have been observed in the mouse models, no such immune reactions have been observed in rabbit, guinea pig, or nonhuman primate models. Subsequent observations in nonhuman primates have shown that immunization of primates with ZP proteins expressed from cDNAs coding for the mouse and rabbit ZP2 (the mouse homologue has 60% amino acid identity with human ZP2) or the mouse ZP3 (the mouse protein has 67% amino acid identity with human ZP3) causes ovarian dysgenesis. In contrast, immunization of primates with recombinant rabbit ZP1 protein (the mouse homologue has 39% amino acid identity with human ZP1) does not affect nonhuman primate ovarian function or follicular development but will elicit antibodies that inhibit sperm binding to the primate ZP. These studies have collectively provided important information concerning the immunologic status of the ovary and demonstrate the species variations in immune responses to different ovarian immunogens.

Identification of a meiotically expressed carbohydrate antigen in ovarian carcinoma: I. Immunohistochemical localization.

A monoclonal antibody developed against a meiotically expressed porcine oocyte carbohydrate antigen has been shown to recognize an antigen in ovarian surface epithelial cells. Immunohistochemical studies of ovaries demonstrated that this antigen is present in the ovarian surface epithelia (OSE) of numerous mammalian species, including the non-human primate and the human (1). Although most of the ovarian surface epithelial cells are lost during aging in the human, a few cells may remain in ovarian crypts. In view of theories that most ovarian carcinomas are derived from the OSE cells in aging women, the PS1 antibody has been used to evaluate ovarian tumors using immunocytochemistry to detect the PS1 antigen in paraffin embedded pathology tissues. The present study found that the PS1 antigen is abundant in a number of malignant ovarian tumors, but is not expressed in a non-malignant Brenner's (ovarian) tumor or granulosa cell tumors. This antibody therefore appears to have great potential for the histopathological and immunochemical analysis of ovarian tumors.

Identification of a meiotically expressed carbohydrate antigen in ovarian carcinoma: II. Association with proteins in tumors and peritoneal fluid.

A monoclonal antibody developed against a meiotically expressed porcine oocyte carbohydrate antigen has been shown to recognize an antigen in ovarian surface epithelial cells (OSE) of numerous mammalian species, including the non-human primate and the human (1). Although most of the ovarian surface epithelial cells are lost during aging in the human, a few cells may remain in ovarian crypts. Because the majority of ovarian carcinomas are thought to be derived from the OSE cells in aging women the PS1 antibody has been used to evaluate ovarian tumors. The secretory origin of this carbohydrate antigen in meiotic cells prompted further analyses of peritoneal fluid collected from gynecological surgery patients including those diagnosed with ovarian cancer. The present study demonstrates that ovarian tumor proteins separated on SDS PAGE include an antigen having a heterogeneous molecular weight (> 100 kDa) typical of glycosylated proteins. Additional studies show that peritoneal fluid from 19 patients not having cancer contain PS1 associated glycoproteins. However, of 14 cancer patients, only one had detectable levels of the carbohydrate antigen. These observations suggest that either the secretion of this glycoprotein is altered in ovarian carcinoma or that glycosidases or other proteolytic enzymes are involved in the degradation of these glycoproteins.

The mammalian zona pellucida: its biochemistry, immunochemistry, molecular biology, and developmental expression.

Many studies of the molecular and biochemical aspects of mammalian fertilization have focused on the interaction of the spermatozoa with the zona pellucida (ZP). The zona pellucida, a unique extracellular matrix surrounding the mammalian oocyte, is formed during ovarian follicular development. Following ovulation of the mature ovum, the spermatozoa must bind to and penetrate this matrix before the fertilization process is completed and the male and female genetic information combine. Although numerous models for this interaction have been proposed, the complete process has yet to be elucidated. The precise mechanisms by which these interactions occur also vary markedly among different mammalian species, making it more difficult to establish a unified model. To a great extent, the study of the molecules involved in these interactions have been limited because small numbers of female gametes are available for these studies. The recent development of techniques to isolate large numbers of zonae pellucidae as well as advances in immunological and molecular biology techniques have permitted the detailed characterization of ZP proteins. Although there is a paucity of information on the post-translational modification and extracellular processing of these molecules which result in matrix formation, a number of properties have been elucidated allowing better correlation between the structure and function of different ZP proteins among species. This review reflects these studies in relation to protein nomenclature and the molecular complexity of ZP antigens.

Large-scale isolation of equine zonae pellucidae.

A simple and rapid method is described for the large-scale isolation of cumulus cell-free, zona pellucida-intact equine oocytes. Aspiration of palpable antral follicles present on frozen-thawed equine ovaries was accomplished using a constant vacuum source. The resultant follicular fluid, oocytes, and particulate matter were then filtered through a series of nylon screens of alternating mesh openings in combination with sodium citrate-containing buffer to a final volume of approximately 20 ml. This fluid was transferred to scored Petri dishes and a stereomicroscope was used to locate the oocytes for futher processing or storage. The methodology described is inexpensive, time-efficient, and the recovery rate is similar to or better than other methods previously described for equine oocyte recovery. Collected oocytes are adequate for biochemical evaluation of the equine zona pellucida (EZP) as well as sperm-egg binding assays.

Omega 3 and omega 6 fatty acids in human and animal health: an African perspective.

Lipids are essential for plant and animal development, growth and nutrition and play critical roles in health and reproduction. The dramatic increase in the human population has put increasing pressure on human food sources, especially of those sources of food which contain adequate levels of polyunsaturated fatty acids (PUFAs) and more importantly, sources of food which have favorable ratios of the n-3 (18-carbon, α-linolenic acid, ALA) to n-6 (18-carbon linoleic acid, LA) PUFAs. Recent studies have demonstrated the beneficial effects of the n-3 PUFAs in diets as well as potentially negative effects of excessive levels of n-6 PUFAs in diets. This review discusses these human health issues relating to changes in diets based on environmental and industrial changes as well as strategies in East Africa for improving lipid composition of food using indigenous sources.