Cryopreservation of porcine embryos by vitrification: A study of in vitro development

Until recently, attempts to preserve porcine embryos have been unsuccessful. Vitrification has been developed as a method of cryopreserving mammalian embryos by avoiding ice crystal formation, assuring a cryopreserved glass state during storage in liquid nitrogen. Vitrification may be a useful method of overcoming the deleterious effects of chilling injury when pig embryos are cryopreserved using conventional slow freezing procedures. In this study, we applied vitrification procedures for rodent and/or bovine embryos to cryopreserve porcine embryos. Following warming, survival was defined as normal development of embryos in culture, namely the formation or reexpansion of the blastocoelic cavity. Experiment 1 tested the relative toxicity of 3 vitrification procedures on Day-5, 6 and 7 porcine embryos. Embryos equilibrated in vitrification solution (VS3a) continued to develop in vitro at rates comparable to that of untreated control embryos. Experiment 2 was designed to evaluate embryonic development following cryopreservation by vitrification in VS3a. Day-5 porcine embryos did not survive cryopreservation while Day-6 and Day-7 embryos survived and continued development in vitro. In Experiment 3, we evaluated a period of culture prior to vitrification and its effect on cryosurvivability of porcine embryos. A 3-h culture period prior to vitrification had no effect on cryosurvivability over that of freshly recovered, immediately vitrified embryos. These studies indicate, for the first time, that porcine embryos can be successfully cryopreserved by vitrification based on morphology and subsequent development in vitro. However, survival following cryopreservation appears to depend upon embryonic age or stage of development.

Successful gamete intrafallopian transfer (GIFT) in the porcine

Gamete intrafallopian transfer (GIFT) was successfully established in the pig. In Experiment 1 (6 replicates) 234 oocytes (39 +/- 5.5 per recipient) plus spermatozoa (4000 to 8000 per oocyte) were transferred bilaterally into the oviducts of synchronized gilts, and embryos were recovered 48 h thereafter. The recovery rate was 50.4% and 50% of the recovered oocytes were fertilized. A total of 55 embryos was cultured in vitro in NCSU-medium for 48 h and 63.6% developed to morula or blastocyst stages. In Experiment 2 (5 replicates) 220 oocytes (44 +/- 4.9 per recipient) plus spermatozoa (4000 per oocyte) were transferred to 5 recipients which were allowed to go to term. Three gilts delivered 16 (n = 3, 5, 8) piglets. In Experiment 3 (5 replicates) 183 oocytes (36.6 +/- 1.2 per recipient) plus flow cytometry gender sorted spermatozoa (4000 per oocyte) were transferred to 5 recipients. The recovery rate was 47.8%, and 27.6% of the oocytes were fertilized. From all cleaved oocytes 45.8% developed to expanded blastocysts, with the number of blastomeres varying from 20 to 85 (38.3 +/- 22.5). These results indicate that the GIFT procedure can be used successfully in pigs, and can be a valuable tool for the study of gamete interaction as well as in the continued development of biotechnological procedures such as sex pre-determination.

Aerobes isolated in fecal microflora of infants in the intensive care nursery: relationship to human milk use and systemic sepsis

BACKGROUND

Staphylococcus epidermidis is a leading cause of nosocomial sepsis in the intensive care nursery. The relationship between rates of gastrointestinal colonization and the incidence of systemic sepsis with S. epidermidis in hospitalized neonates is under investigation.

METHODS

In this study, we enrolled 46 infants consecutively admitted to the intensive care nursery (mean +/- standard deviation, birth weight 1300 +/- 337 gm, gestational age 29.4 +/- 2.2 weeks). At the time of enrollment, infants had been fed enterally for at least 1 week (28 were fed formula and 18 received their own mothers' frozen milk). Stool samples were collected when infants were 2 to 3 weeks of age (16.3 +/- 7.4 days).

RESULTS

Aerobic stool flora were present in 65% of all patients. Human milk use was associated with a significant increase in the presence of aerobic stool flora (78% vs 46%, p = 0.035), as well as more frequent isolation of S. epidermidis. The incidence of S. epidermidis sepsis was 33% in those infants whose stool specimens grew S. epidermidis and 3.5% in those whose stool specimens did not (p < 0.01).

CONCLUSIONS

These findings suggest the gastrointestinal tract as a possible site of entry for S. epidermidis in the hospitalized preterm infant. In addition, frozen human milk may be a vehicle for gastrointestinal S. epidermidis colonization.

Gender preselection in humans? Flow cytometric separation of X and Y spermatozoa for the prevention of X-linked diseases

Human X- and Y-chromosome-bearing spermatozoa were separated based on their DNA content, using modified flow cytometric cell sorting technology. The resulting separation purity of the X-bearing from Y-bearing spermatozoa was evaluated using in-situ hybridization with alpha satellite DNA probes for the X- and Y-chromosomes. In the putative X-enriched-sorted populations, an average of 82% of the spermatozoa showed a hybridization signal with the X probe. Similarly, in the Y-sorted population 75% gave a signal with the Y probe. Sorted X- and Y-bearing spermatozoa were found to maintain their viability for several hours after sorting. These results demonstrate that the human sperm sex ratio can be significantly shifted to favour the selection of female-producing (X) spermatozoa or male-producing (Y) spermatozoa when spermatozoa are flow cytometrically sorted on the basis of DNA content. We propose that flow cytometrically sorted human spermatozoa, used in conjunction with in-vitro fertilization or intra-oviductal insemination, could be used by families who are at risk for X-linked diseases to preferentially produce female offspring. Sorted spermatozoa could also be used to pre-select for male offspring if that were medically indicated.

Magnetic resonance imaging of overall and regional body fat, estrogen metabolism, and ovulation of athletes compared to controls

The association of menstrual dysfunction of athletes with changes in body composition has been controversial, because most estimations of body fatness have been indirect. Using magnetic resonance imaging, we quantified the sc and internal fat over a specific volume from the fifth thoracic vertebra to femoral fat in the upper thigh and at 4 other anatomical landmarks of 17 athletes (13 oarswomen and 4 runners) compared to that in 11 nonathletic controls. The magnetic resonance imaging data were also analyzed for the athletes and controls in relation to ovulatory status, which was determined by assay of urinary pregnanediol glucuronide, and in relation to the extent of 2-hydroxylation of estradiol to a nonpotent metabolite, 2-hydroxyestrone, which was evaluated by radiometric analysis. We found that 1) the relative and absolute body fat values of the athletes were significantly less (P < 0.05) than those of the controls overall and at each of the six regional sites, although the body weights of the rowers were significantly heavier than those of the controls, and the runners did not differ from the controls; 2) the ratio of sc fat to internal fat was 80%:20% among both athletes and controls, even though the athletes had significantly less fat; 3) the extent of estradiol 2-hydroxylation was significantly (P = 0.005) inversely related to total fat as a percentage of the total volume and to sc fat as a percentage of the total volume (P = 0.004) overall and at each of the regional fat depots; 4) athletes with menstrual disorders had significantly decreased sc and internal fat overall and at all regional sites compared to controls; and 5) a subgroup of ovulatory rowers had an apparent increase or lack of decrease in internal fat at the level of vertebrae lumbar 4, sacral 1, and sacral 4, compared to controls, whereas their sc fat was decreased at these sites compared to that in controls. Changes in regional fat deposits of both sc and internal fat may be involved in the menstrual dysfunction of the athletes in addition to their decreased overall fatness. The body weight and body mass index of well trained athletes can be a misleading index of body composition.

Experimental murine chronic hepatitis: results following intrahepatic inoculation of human uveitis mycoplasma-like organisms

Mycoplasma-like organisms (MLO) are non-cultivated intracellular cell-wall deficient pathogenic bacteria with a distinctive ultrastructural appearance. Diagnosis of MLO disease depends on finding the organisms in parasitized cells using a transmission electron microscope. MLO are a well studied cause of transmissible chronic plant disease responsive to antibiotics. MLO have recently been found to cause human chronic uveitis, orbital, and retinal disease with autoimmune features. Ophthalmic leucocytes in these patients display MLO parasitization. Inoculation of human uveitis MLO into mouse eyelids produced chronic uveitis. MLO also disseminated to produce randomly distributed lethal systemic disease including chronic hepatitis. MLO parasitized leucocytes were present in all disease sites. Direct intrahepatic inoculation of human hepatic pathogens is a simple and efficient technique to produce murine hepatitis. This report describes the delayed onset widespread inflammatory liver disease produced by direct intrahepatic inoculation of human chronic uveitis MLO in 12 of 20 mice versus 0 in 40 controls (P < 0.05). The liver disease was accompanied by elevated serum SGOT levels, splenomegaly, and accelerated mortality. All 12 inflamed livers displayed MLO parasitized leucocytes versus 0 of 10 control livers. The resemblance of human chronic active hepatitis, massive hepatic necrosis, and post-necrotic cirrhosis to the MLO induced murine liver disease, the role of molecular biologic techniques in the detection and classification of those bacteria, and in therapy of MLO disease are discussed.

Binding of anti-H-Y monoclonal antibodies to separated X and Y chromosome-bearing porcine and bovine sperm

Studies designed to answer the question whether or not H-Y antigen is preferentially expressed on Y chromosome bearing sperm have resulted in conflicting results. This is probably due to the absence of reliable methods for estimating the percentage of X and Y chromosome bearing sperm in fractions, enriched or depleted for H-Y antigen positive sperm. In recent years a reliable method for separating X and Y chromosome bearing sperm has been published. With this method, separation is achieved by using a flow cytometer/cell sorter, which detects differences in DNA content. This technique provided the first opportunity for testing anti-H-Y antibody binding to fractions enriched for X and Y chromosome bearing sperm, directly. A total of 7 anti-H-Y monoclonal antibodies were tested using sorted porcine sperm and in one experiment also sorted bovine sperm. All monoclonal antibodies bound only a fraction of the sperm (20 to 50%). However, no difference in binding to the X and Y sperm enriched fractions was found. Therefore, the present experiments do not yield evidence that H-Y antigen is preferentially expressed in Y chromosome bearing sperm.

Relaxation of imprinted genes in human cancer

Genomic imprinting, or parental allele-specific expression of genes, has been demonstrated at the molecular level in insects and mice but not in man. Imprinting as a potential mechanism of human disease is suggested by paternal uniparental disomy of 11p15 in Beckwith-Wiedemann syndrome and by maternal uniparental disomy of 15q11-12 in Prader-Willi syndrome. Beckwith-Wiedemann syndrome is characterized by multiorgan overgrowth and predisposition to embryonal tumours such as Wilms' tumour of the kidney. A loss of heterozygosity of 11p15 is also frequently found in a wide variety of tumours, including Wilms' tumour and lung, bladder, ovarian, liver and breast cancers; 11p15 also directly suppresses tumour growth in vitro. Two genes in this band, H19 and insulin-like growth factor-II (IGF2) undergo reciprocal imprinting in the mouse, with maternal expression of H19 (ref. 13) and paternal expression of IGF2 (ref. 14). Here we find that both of these genes show monoallelic expression in human tissues and, as in mouse, H19 is expressed from the maternal allele and IGF2 from the paternal allele. In contrast, 69% of Wilms' tumours not undergoing loss of heterozygosity at 11p showed biallelic expression of one or both genes, suggesting that relaxation or loss of imprinting could represent a new epigenetic mutational mechanism in carcinogenesis.

Tumor cell growth arrest caused by subchromosomal transferable DNA fragments from chromosome 11

A fundamental problem in the identification and isolation of tumor suppressor and other growth-inhibiting genes is the loss of power of genetic complementation at the subchromosomal level. A direct genetic strategy was developed to isolate subchromosomal transferable fragments (STFs) from any chromosome, each containing a selectable marker within the human DNA, that could be transferred to any mammalian cell. As a test of the method, several overlapping STFs from 11p15 were shown to cause in vitro growth arrest of rhabdomyosarcoma cells. This activity mapped between the beta-globin and insulin genes.

MR quantification of cerebral ventricular volume using a semiautomated algorithm

PURPOSE

A semiautomated border identification algorithm, insensitive to user bias, is evaluated for accuracy and speed in the measurement of ventricular volumes from three-dimensional MR images.

METHODS

A three-dimensional gradient-echo technique was implemented on a Signa clinical imaging system. Data from phantoms and patients were analyzed for volume using a segmentation algorithm designed with: 1) correction for partial volume averaging; 2) insensitivity to user bias; and 3) speed. Accuracy, precision, and intra- and interobserver variability were determined.

RESULTS

Average error for phantom studies was 4% to 6%, or 1 to 2 cc across the volumes, which ranged from normal to mild hydrocephalus (< 60 cc). Patient studies showed intra- and interobserver error of 2.3% and 7.8%, respectively. The correction for partial volume averaging resulted in a threefold decrease in error. Data were acquired and reconstructed within 7 minutes. Experienced radiologists required less than 15 minutes to perform each analysis.

CONCLUSIONS

This algorithm allows accurate measurement of ventricular volumes in an efficient, minimally supervised manner.

Mycoplasma-like organisms and ophthalmic disease

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Analysis of variance of parameter estimates: F tests and t tests

The problem of comparing and pooling experimentally independent estimates of a parameter such as a Michaelis constant (K) has been treated as a simple analysis of variance of "within" and "between" set deviations from the fitted variable (v). As applied to assessing the reproducibility of multiple estimates of the same K, this is identical to the procedure of Duggleby (Anal. Biochem. 189, 84-87, 1990). However, the theory developed here shows that applying Duggleby's procedure to the comparison of two experiments (each consisting of multiple data sets) depends critically on the assumption of equal errors within and between the individual sets, i.e., Fvb vw = s2wv/s2bv is close to 1. Application of the method when this is not the case will underestimate the common error (s2rv), overestimate its associated degrees of freedom (vr = vb+vw), and may suggest apparently significant differences where there are none. The theory also shows that this situation is an instance of the Fisher-Behrens problem and shows how Welch's solution can be applied. This gives the between set error s2bv as the corrected estimate of the common error and the corrected degrees of freedom as a simple function of vb, vw, and Fvb vw. When the nine prephenate dehydratase data sets which originally showed three apparently significant differences were reanalyzed in this way, all the variations in K were found to be within the range of the experimental error.

A novel general strategy for cloning tumor suppressor genes using radiation-reduced chromosomal superfragments

To identify the tumor suppressor gene on human chromosome 11p15, we generated mouse microcell hybrids containing small transferable chromosome 11p15 fragments, which we have termed "DNA superfragments". These hybrids will be used to identify which fragments contain a tumor suppressor gene by direct transfer of the fragments to tumor cells via microcell fusion.

Multiple tumor suppressor genes in multistep carcinogenesis

One of the most exciting areas of molecular oncology is the convergence of two independent lines of evidence suggesting involvement of multiple tumor suppressor genes in a given type of cancer. First, epidemiology and somatic cell genetics indicate the presence of multiple tumor suppressor genes in each of several malignancies. Second, cancers often lose multiple chromosomal regions during tumor progression. We will use two tumors, colorectal cancer and Wilms tumor, to illustrate the questions that multiple tumor suppressor genes raise.

Two-dimensional electrophoresis and densitometric analysis of solubilized bovine sperm plasma membrane proteins detected by silver staining and radioiodination

Bovine sperm plasma membranes were extracted with deoxycholate and subjected to two-dimensional gel electrophoresis. Proteins were visualized either by silver staining or autoradiography using 125I. When 1.5-2.0 micrograms of protein extract was applied to the first-dimension get, 250 spots could be detected by autoradiography. Thirty micrograms of protein was required to obtain spot visualization using silver strain, revealing more than 500 spots on the gel. These data establish the limit under which two-dimensional electrophoresis can be used in conjunction with flow cytometric sorting of sperm for the analysis of possible sex-specific membrane differences. The necessity of orienting sperm as they past the laser in the cell sorting system reduces throughput; thus, the number of sperm sorted within a given time is limited. It is suggested that autoradiography will allow the flow cytometer to be used in a time-efficient manner. Longer sorting times would be required to obtain sufficient sample to analyze total protein composition.

Serum free thyroxine levels respond inversely to changes in levels of dietary iodine in the domestic cat

Because of a perceived increase in the incidence of toxic multinodular goitres in cats in recent years, we investigated the iodine content of three varieties of commercial canned cat foods and studied the acute effects of 'ingestion of these preparations on urinary iodine excretion and serum free thyroxine levels in young, healthy cats. Ten castrated male cats were fed from a common source. The type of food was changed every 2 weeks. Urine and blood specimens were obtained weekly. Serum free thyroxine levels were determined and iodine concentrations in urine were assayed. The iodine content of the cats' food was also assayed. Food varieties of high, intermediate and low iodine content were fed for 2-week periods. There was a consistent, reciprocal relationship between the mean urinary iodine concentration and the mean serum free thyroxine level for each 2-week period. The difference in the mean serum free thyroxine concentrations for the high and low iodine intake periods was highly significant (p<0.01). When the serum free thyroxine level and the urinary iodine level for each cat at each collection throughout the 12-week study were analysed (66 paired results), a strong inverse correlation (r=0.59, p<0.01) was found. We concluded that the serum free thyroxine level in cats, as measured by a kit designed for human serum, is acutely responsive to changes in iodine intake.

Degradation of triglycerides by a pseudomonad isolated from milk: molecular analysis of a lipase-encoding gene and its expression in Escherichia coli

Psychrotrophic lipolytic bacteria represent a significant problem in the storage of refrigerated dairy products. A lipase-encoding gene has been cloned and characterized from a highly lipolytic strain of Pseudomonas. The nucleotide sequence of the gene predicts a polypeptide of M(r) 49,905, which was identified when the gene was expressed in Escherichia coli.

Iodine content of commercially-prepared cat foods

Twenty-eight varieties of commercially-available cat food (23 canned, 5 dried) were analysed for iodine. The iodine concentration varied from less than 0.37 micromol/kg to 41.8 pmol/kg, wet weight (less than 1.48 micromol/kg to 167 micromol/kg, dry weight). Excessive or insufficient iodine intake or wide swings in iodine intake over prolonged periods may contribute to thyroid disorders in cats.

Quantitative chemical shift imaging of vertebral bone marrow in patients with Gaucher disease

To evaluate extent of bone marrow involvement and disease severity in Gaucher patients, results of modified Dixon quantitative chemical shift imaging (QCSI) of the lumbar spine were correlated with quantitative analysis of marrow triglycerides and glucocerebrosides and with quantitative determination of splenic volume at magnetic resonance (MR) imaging. High-field-strength MR spectra of surgical marrow specimens were dominated by a single fat and a water peak, validating use of QCSI. QCSI showed average vertebral marrow fat fractions of 10% +/- 8 in Gaucher patients (normal adult averages, 29% +/- 6). Relaxation times for lipid and water approximated normal averages; bulk T1 values were significantly longer, reflecting decreased marrow fat. Glucocerebroside concentrations were higher in Gaucher marrow and inversely correlated with triglyceride concentrations. Extent of marrow infiltration determined by fat fraction measurements correlated with disease severity measured by splenic enlargement. These results show that as Gaucher cells infiltrate bone marrow and displace normal marrow adipocytes, bulk T1 increases due to the higher T1 of water compared with that of fat. QCSI provides a sensitive, noninvasive technique for evaluating bone marrow involvement in Gaucher disease.