The role of sunlight and DNA repair in melanoma and nonmelanoma skin cancer. The xeroderma pigmentosum paradigm

BACKGROUND AND DESIGN

The frequency of melanoma and nonmelanoma skin cancer is increasing rapidly in the United States. However, the linkage of these cancers to sun exposure has been questioned because of differences in anatomic site distribution. To obtain insights into the development of these skin cancers, we examined reports of 132 patients with xeroderma pigmentosum (XP), an inherited cancer-prone, DNA repair-deficient disorder with marked clinical and laboratory UV hypersensitivity.

RESULTS

Malignant skin neoplasms were present in 70% of the patients with XP at a median age of 8 years, which is 50 years earlier than in the US white population. Fifty-seven percent of the patients had basal cell or squamous cell carcinoma, and 22% had melanoma. The frequency of melanomas, like the frequency of nonmelanoma skin cancers (basal cell and squamous cell carcinomas), anterior eye cancers, and tongue cancers, but unlike that of internal neoplasms, was increased 1000-fold or more in patients with XP who were younger than 20 years. As in the general population, the anatomic distribution of melanomas was different from that of nonmelanomas in the patients with XP.

CONCLUSIONS

These data suggest that (1) DNA repair plays a major role in the prevention of cutaneous cancers in the general population and (2) sunlight exposure is responsible for the induction of melanoma as well as nonmelanoma skin cancer in patients with XP, although acting by different mechanisms for the two types of skin cancer.

Cell-substrate adhesion and metastatic potential of cultured mesothelioma cells induced by asbestos

Cell-substrate adhesion was quantified for two cultured mesothelioma cell lines (epitheliomatous and sarcomatous) on glass, fibronectin and laminin substrates. Interference reflection microscopy (IRM) was used to image the adhesion patterns of cells and a grey level analysis was employed to quantify adhesion. Sarcomatous cells demonstrated marked adhesion to glass and fibronectin-coated substrates but not to laminin-coated substrate, with the greatest adhesion occurring on the fibronectin-coated surface. This adhesion was accompanied by cytoplasmic spreading. By contrast, epitheliomatous cells showed little tendency to adhere to any of the substrates and only showed significant spreading when in contact with the laminin substrate (P < 0.01). A bioassay was used to determine the metastatic potential of each of the cell lines. Via the intravenous route, the sarcomatous cells killed the host rats in 24.7 +/- 1.5 (S.D.) days compared to 27.3 +/- 0.9 (S.D.) days for the epitheliomatous cells (P < 0.01). After subcutaneous inoculation of tumour cells, the sarcomatous cells killed the host rats in 54.7 +/- 0.7 (S.D.) days compared to 48.5 +/- 0.5 (S.D.) days for the epitheliomatous cells (P < 0.01). We conclude that the results of the metastasis bioassays were consistent with the predicted behavior of these cell lines based on their ability to adhere to substrates in the in vitro adhesion assays.

A semiquantitative dietary history questionnaire for Chinese Americans

An 84-item, semiquantitative dietary history questionnaire was developed for epidemiologic studies of diet and diseases in Chinese Americans. The questionnaire is a 30-minute, face-to-face administered instrument designed especially for assessing mixed dishes; it consists of a food list and requires information on frequency of consumption and portion estimation. A nutrient database was compiled from many sources, but mostly from US Department of Agriculture publications. The relative validity of this food frequency questionnaire was tested among 74 Chinese women between the ages of 30 and 60 years living in the San Francisco Bay area against a 1-day recall deemed a typical day's diet. Correlation coefficients of nutrients from both methods ranged from 0.2 for total fat to 0.7 for calcium and were all statistically significant at less than the 0.001 level. Agreement between these two methods was assessed by the percentage of misclassification of quartile distributions. Around 10% were grossly misclassified and 50% were correct estimates of intake in the same highest quartile, while 73% were correctly placed in the two highest quartiles. This food frequency questionnaire can reasonably estimate the usual dietary intakes among Chinese Americans for epidemiologic studies, but further validation would be needed.

The interrelationship between impaired glucose tolerance and other risk factors for cardiovascular disease: is it a predictor for cardiovascular disease?

Glucose intolerance and cardiovascular risk factors were assessed among 215 subjects aged 27-86 years in Ho-long, Taiwan. An oral glucose tolerance test (OGTT) was normal in 107 subjects, impaired in 41 subjects, and abnormal in 67 subjects (as noninsulin dependent diabetes mellitus, NIDDM). Body fatness, blood pressure, carbohydrate and lipid metabolic factors were examined. One-way ANCOVA was used to compare age- and/or BMI-adjusted differences among these groups. Male subjects with NIDDM and impaired glucose tolerance (IGT) had higher systolic (SBP) and diastolic (DBP) blood pressures, plasma insulin (fasting and 1-hour after OGTT), serum triglycerides (TG), heavier body weight, and larger BMI than normal. IGT subjects were also found to have higher TG, insulin (2-hour) and larger insulin area under curve (IAUC) after OGTT than NIDDM. In females, subjects with NIDDM had higher TG, insulin (fasting and 1-hour after OGTT), and larger IAUC than normal. Moreover, female IGT subjects were also found to have significantly higher SBP, DBP, insulin (1-and 2-hour after OGTT), and larger IAUC than both normal and NIDDM subjects. These results suggest that adverse cardiovascular risk factors are present not only in NIDDM subjects, but also in IGT subjects.

Variant angina complicating ergot therapy of migraine

A 55-year-old man demonstrated typical reflux esophagitis, not esophageal spasm, by esophageal manometry, although he demonstrated classic migraine, positive Raynaud's scan, and proven coronary artery spasm. He suffered from severe chest pain by medication of ergotamine tartrate. Ergot alkaloids should be avoided in patients with symptomatic coronary artery spasm.

Developmental changes in mullerian inhibiting substance in the cynomolgus monkey, Macaca fascicularis

Mullerian inhibiting substance (MIS) is a glycoprotein hormone produced in Sertoli cells of the fetal and postnatal testis, and granulosa cells of the pubertal ovary. We examined MIS expression in a nonhuman primate, the cynomolgus macaque monkey (Macaca fascicularis), to define an animal model for studying MIS gene regulation. Changes in testicular MIS mRNA with age were assessed by in situ hybridization of prepubertal to adult testes, Northern analysis of pubertal and adult specimens, and determination of serum MIS concentrations from infancy to adulthood. We found that MIS expression was highest in the youngest animals and decreased progressively with increasing age. Serum MIS concentrations correlated inversely with increasing age (r = -0.74), body weight (r = -0.79), and testicular volume (r = -0.73), but not with testosterone levels (r = -0.35). The mean MIS concentrations +/- SEM for the four developmental age groups were 270.6 +/- 23.8 (infants), 195.5 +/- 18.5 (juveniles), 102.7 +/- 28.4 (peripubertals), and 51.6 +/- 7.1 (adults). This study confirms that nonhuman primate and human MIS are highly homologous and have similar developmental patterns. The normative data for serum MIS concentrations in cynomolgus monkeys at different ages and developmental stages will be invaluable for further work examining MIS regulation.

Association of abnormal nipple aspirate cytology and mammographic pattern and density

The pattern and density of mammograms have been shown to be associated with proliferative histopathology and an increased risk of breast cancer. We recently found that epithelial atypia in nipple aspirate fluid obtained 10-18 years earlier was associated with an increased risk of breast cancer. In the present study we examined the association between the cytology of nipple aspirate fluid and mammographic patterns in 588 volunteers recruited from the mammography clinic at the University of California. Nipple aspirate fluid cytology was classified according to the most severe epithelial change present and mammograms were classified by the Wolfe method and the percentage area of density. A direct relationship was found between mammographic density and cytological abnormality. When controlled for age, body mass index, previous biopsy, and calcification, the odds ratios of high density mammograms (over 50%) with nipple aspirate fluid cytological atypia was 4.4 (95% confidence interval, 0.9-21.5; P = 0.08) when normal cytology was the referent. These preliminary findings indicate that highly dense mammograms are associated with cytological atypia and are consistent with studies reporting an association of histological hyperplasia and atypical hyperplasia with severe mammographic findings. If confirmed by further studies, nipple aspirate cytology may be a useful adjunct to mammographic patterns in the prediction of breast cancer risk, especially among premenopausal women.

A human DNA segment encompassing leucine and methionine tRNA pseudogenes localized on chromosome 6

A human genomic clone, designated LHtlm8, that strongly hybridized to a mammalian leucine tRNA(IAG) probe, was found to encompass a pair of tRNA pseudogenes that are transcribed in a homologous cell extract. A leucine tRNA(AAG) pseudogene (TRLP1) is 2.1-kb upstream and of opposite polarity to a methionine elongator tRNA(CAU) pseudogene (TRMEP1). TRLP1 has three nucleotide variations (97% identity) from its cognate leucine tRNA(IAG), while TRMEP1 has a 78% identity with its cognate tRNA. Similar to a number of other eukaryotic tRNA pseudogenes, presumptive precursor tRNA transcripts are generated from the two pseudogenes in vitro, but possibly due to their aberrant and unstable secondary and tertiary structures, no detectable mature tRNA products are observed. The two tRNA pseudogenes are encompassed within a 9.6-kb EcoRI fragment that has been assigned to the chromosomal locus, 6pter-q13, by Southern blot hybridization of human-rodent somatic cell hybrid DNAs with probes derived from the cloned tRNA pseudogenes and flanking sequences. A 4.4-kb EcoRI fragment also harbored in clone LHtlm8 was mapped to human chromosome 11, suggesting that the two EcoRI fragments were inadvertantly ligated together during construction of the genomic library.

Relation of pulmonary venous flow to mean left atrial pressure in mitral stenosis with sinus rhythm

To determine whether pulmonary venous flow measured by transesophageal Doppler echocardiography can be used to estimate mean left atrial pressure (LAP), we prospectively studied 12 consecutive patients with sinus rhythm undergoing percutaneous mitral balloon commissurotomy for their severe mitral stenosis (mitral valve area < 1.5 cm2). We correlated Doppler variables of pulmonary venous flow and the mean LAP measured by left atrial catheterization. Among the variables of the pulmonary venous flow, the systolic fraction (i.e., the systolic velocity-time integral expressed as a fraction of the sum of systolic and early diastolic velocity-time integral) correlated significantly with mean LAP (r = -0.71, p < 0.05) and mitral valve area (r = 0.64, p < 0.05). Peak velocity and velocity-time integral in systole also significantly correlated with mean LAP (r = -0.66, r = -0.67 respectively, p < 0.05). We conclude that the more severe the degree of mitral stenosis in patients with sinus rhythm, the less systolic pulmonary venous flow in severe mitral stenosis.

Gross cystic disease fluid protein in nipple aspirates of breast fluid of Asian and non-Asian women

Gross cystic disease fluid protein 15 (GCDFP-15) is universally present in the apocrine metaplastic epithelium of cystic breast disease and breast cancer, but it is rarely found in normal breast epithelium. Therefore GCDFP-15 detected in nipple aspirates of breast fluid (NAF) could serve as a biochemical marker of the presence and possibly extent of apocrine metaplasia within the breast. GCDFP-15 levels were measured in NAF from 37 Asian and 78 non-Asian women using radioimmunoassay. GCDFP-15 (range, 0-81,643 micrograms/ml) was found in the NAF of all but 1 woman and was highly correlated between right and left breasts. Mean concentrations of GCDFP-15 were significantly lower in NAF from Asian compared with non-Asian women. Markedly reduced levels of GCDFP-15 were found in the 17 women who had been parous in the previous 2 years. In women not parous within the prior 2 years, no relationship was found between GCDFP-15 levels and age, weight, age at menarche, first-degree family history of breast cancer, parity, oral contraceptive use, or smoking history. High concentrations of GCDFP-15 were found in the NAF of women with a history of a benign breast biopsy. Because similarly high levels of GCDFP-15 were found in NAF in over 40% of women without a history of benign breast biopsy, and because GCDFP-15 in the breast is produced only by apocrine metaplastic epithelium, we infer that the breasts of these women likely contain a significant degree of apocrine metaplasia.(ABSTRACT TRUNCATED AT 250 WORDS)

A study of surface property changes in rat mesothelial cells induced by asbestos using aqueous two-phase polymer solutions

Intraperitoneal (i.p.) injection of crocidolite asbestos was used to induce mesotheliomas in rats. The morphological changes of the mesothelial cells were studied by light and electron microscopy and by cytologic examination of peritoneal washings. After injection, the asbestos fibres stimulated an acute inflammatory response and were rapidly phagocytosed by the mesothelial cells and incorporated into the submesothelial tissues. At 7 days, the normal microvillous surface of the mesothelium was replaced with a syncytium of proliferating mesothelial cells showing extensive loss of microvilli. Nine months or so later, multifocal mesothelial tumours arose within the peritoneal cavity. The surface thermodynamic properties of normal, asbestos-stimulated mesothelial cells and of mesothelial tumour cells in culture were studied using an aqueous two-phase system containing 4% Dextran T-2000 and 4% poly (ethylene glycol) (PEG) w/w. After asbestos stimulation, there was a significant (P < 0.01) increase in contact angle between the dextran-rich phase and the mesothelial cell surface. These changes were even greater for the mesothelial tumours. The results indicate that the work of adhesion for asbestos-stimulated mesothelial cells and mesothelial tumours is lower than in normal tissue. These findings may be relevant to the process of tumour spread in the serosal cavities and to the development of distant metastases.

Müllerian inhibiting substance is present in embryonic testes of dogs with persistent müllerian duct syndrome

Müllerian Inhibiting Substance (MIS) causes regression of the Müllerian ducts during a critical period in embryonic development in male mammals. In Persistent Müllerian Duct Syndrome (PMDS), an autosomal recessive trait in humans and dogs, the Müllerian ducts fail to regress in otherwise normal males. Previously we reported that PMDS-affected dogs produce bioactive testicular MIS postnatally. The purpose of the present study was to determine whether PMDS-affected canine embryos appropriately express MIS mRNA and protein during the critical period for Müllerian duct regression. Homozygous (PMDS-affected) and normal canine embryos were removed from timed pregnancies. Gonadal sex and the degree of Müllerian duct regression were determined from histologic sections. Positive immunohistochemical staining for MIS was found in testis sections of PMDS-affected and normal male embryos. A 1.8-kb MIS mRNA transcript was detected in testes of PMDS-affected males and normal male embryos and neonates. Furthermore, equal amounts of MIS mRNA transcript were detected in testes of PMDS-affected embryos and normal male littermates during the critical period for Müllerian duct regression. These data support a hypothesis of target organ resistance, such as an abnormality in the putative MIS receptor, as the etiology of the defect in this dog model.

Breast cancer risk associated with abnormal cytology in nipple aspirates of breast fluid and prior history of breast biopsy

The authors previously reported an increased risk of breast cancer in women from the San Francisco Bay Area first enrolled between 1973 and 1980 with proliferative cytologic findings (hyperplasia, moderate hyperplasia, and atypia) compared with women with normal cytologic findings in breast fluids obtained by nipple aspiration and with women from whom breast fluid could not be obtained. To look for factors which might modify the risks associated with cytology, the authors examined several standard breast cancer risk factors: parity, age at first pregnancy, age at menarche, family history of breast cancer, and prior history of breast biopsy. Among women aged 30 years or over, only prior biopsy modified the effect of proliferative cytologic findings on the risk of breast cancer (p < 0.10). For those women with no prior biopsy, breast cancer incidence was 5% (47 of 985) among women with normal cytology and 5% (13 of 277) among women with proliferative findings, whereas among those women with normal cytology and 18% (11 of 62) among women with proliferative cytology. Age-adjusted as well as multivariate-adjusted relative risks indicated that the increased risk of breast cancer associated with proliferative cytologic findings was largely confined to women who had a prior history of breast biopsy.

Mullerian inhibiting substance: a gonadal hormone with multiple functions

Mullerian inhibiting substance (MIS) is the gonadal hormone that causes regression of the Mullerian ducts, the anlagen of the female internal reproductive structures, during male embryogenesis. MIS is a member of the large transforming growth factor-beta (TGF beta) multigene family of glycoproteins that are involved in the regulation of growth and differentiation. The proteins in this gene family are all produced as dimeric precursors and undergo posttranslational processing for activation, requiring cleavage and dissociation to release bioactive C-terminal fragments. Similarly, the 140 kilodalton (kDa) disulfide-linked homodimer of MIS is proteolytically cleaved to generate its active C-terminal fragments. The sexually dimorphic expression of MIS in Sertoli cells of the testis and granulosa cells of the ovary is critical for normal differentiation of the internal reproductive tract structures. A number of extra-Mullerian functions such as control of germ cell maturation and gonadal morphogenesis, induction of the abdominal phase of testicular descent, suppression of lung maturation, and growth inhibition of transformed cells have also been proposed for this growth-inhibitory hormone and will be discussed. This article will summarize the current understanding of the biology and multiple functions of MIS including its activation, regulation, and mechanism of action and discuss areas of interest in ongoing research.

Müllerian inhibiting substance in the diagnosis and management of intersex and gonadal abnormalities

Müllerian inhibiting substance (MIS), a gonadal hormone important in sexual differentiation, is high (10 to 70 ng/mL) in human male serum postnatally for several years before declining during the peripubertal period, but is undetectable in female serum until the onset of puberty. The sexually dimorphic secretion of MIS suggested possibilities for its use in several clinical settings. Thirty-one patients with intersex and gonadal anomalies from 17 institutions were therefore evaluated between 1989 and 1992 with an MIS enzyme-linked immunosorbent assay (ELISA). Serum MIS levels correlated with the presence of testicular tissue in two patients with suspected anorchia, five patients with male pseudohermaphroditism, and eight other intersex patients with undescended testes, dysgenetic gonads, or ovotestes. In these latter patients, serial MIS values were also helpful to confirm complete removal of gonadal tissue postoperatively. MIS may be a more sensitive marker for the presence of testicular tissue than serum testosterone levels, both before and after the neonatal androgen surge, and, consequently, may obviate the need for human chorionic gonadotropin stimulation in the evaluation of certain intersex disorders. In values were useful in differentiating the underlying etiology of the disorder. Four patients with undetectable levels have presumptive MIS gene mutations, while 7 others with MIS values of 2 to 45 ng/mL may have bioinactive hormone of MIS receptor defects. Finally, two young girls with ovarian granulosa cell tumors had elevated MIS values that fell from 18 to 2 ng/mL and from 6.5 to 1 ng/mL during postoperative follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

The reappraisal of the association of glycosylated hemoglobin A1c (HbA1c) and blood pressure: a hypertension and diabetes study in a Taiwan rural area

The association of age, body weight, body mass index (BMI) and glycosylated hemoglobin A1c (HbA1c) to blood pressure in the general population of the Ho-long area in Taiwan was examined. A total of 1341 subjects, 746 men and 595 women, aged 40-90 years, were studied. Sex-specific multiple regression analyses were carried out on variables both univariately and significantly associated with blood pressure. Results show HbA1c to be significantly associated with SBP in both males and females before age, weight and/or BMI are adjusted (p < 0.05). After controlling for these confounders, the strength of SBP-HbA1c association was slightly reduced in males, but remained significant. In contrast, there was no significance in females. Moreover, no significant relationship in DBP-HbA1c was found in either sex group. These findings suggest that although a positive correlation was found between HbA1c and SBP, HbA1c or glucose status appeared to be a less important contributing factor in hypertension than age or body weight.

Type I glycogen storage disease: nine years of management with cornstarch

Long-term effects of cornstarch (CS) therapy on biochemical values and physical growth in children with type I glycogen storage disease (GSD I) were compared to those of children receiving continuous nocturnal nasogastric glucose feedings (CNG). Only patients who had received more than 5 years of dietary therapy (either CS or CNG) were evaluated. Six patients (five female, age 13.5 years +/- 1.3, range 11.7-16.5 years) received CS (1.75-2.5 g/kg, four times daily) and seven patients (five female, age 9.6 +/- 2.5 years, range 7.3-14.8 years) received CNG. Blood glucose, lactate, cholesterol and triglyceride levels were not significantly different between the two methods of treatment. All patients maintained linear growth rates normal for their age. The standard deviation score of height after 6.7 +/- 1.6 years (range 5-9 years) of CS treatment was -1.29 +/- 0.59 and after 8.8 +/- 2.4 years (range 7-14 years) of CNG was -1.24 +/- 0.63. These values did not differ significantly from each other or from the target height, an estimate of genetic potential for height as determined from parental heights. With the exceptions of diarrhea, increased flatulence and excess weight gain, there were no adverse effects of CS after 9 years of treatment. Our data suggests that cornstarch is a simple, effective and safe therapy for GSD I.

Foods predictive of nutrient intake in Chinese diet in Taiwan: I. Total calories, protein, fat and fatty acids

Dietary consumption data obtained by food weighing for 539 households in Taiwan in 1980-1981 were used to search for foods predictive of nutrient intake. The average per capita nutrient intake in each household was calculated for total calories, protein, fat and fatty acids (saturated fatty acids, oleic acid and unsaturated fatty acids). Stepwise multiple regression analysis was carried out to reveal the relative importance of each of 405 food items in the dietary survey data for predicting nutrient intake. We found that as few as seven to 20 food items could account for a large proportion of the variability of macronutrient intake in this population. These lists of foods were the minimum needed to categorize an individual's nutrient intake for epidemiological studies in Taiwan. The types and amounts of cooking oils (important predictors of fat and calories) added to the dishes were found to vary from family to family, and should be considered in designing dietary questionnaires for Chinese in other societies.

Foods predictive of nutrient intake in Chinese diet in Taiwan: II. Vitamin A, vitamin B1, vitamin B2, vitamin C and calcium

Dietary consumption data obtained by food weighing for 539 households in Taiwan in 1980-1981 were used to search for predictor foods of individual intake of several vitamins and calcium. Stepwise multiple regression analysis was carried out on food items that were univariately and significantly associated with nutrient intakes, to screen for the important predictors. Less than ten foods were enough to explain more than 90% of the interperson variation for vitamin A, vitamin B1, and vitamin B2. For vitamin C and calcium, 20 food items could explain only 87% of the variation. Salt, brown sugar, and soy bean sauce were selected among calcium predictors. The information on foods predictive of nutrient intake is useful in designing food frequency questionnaires and materials for nutrition education. Although this paper provides such information for Chinese living in Taiwan, some issues described (such as the need to assess spices) may have been overlooked and could be generalized to populations using stir-frying as a major cooking method.

Red cell membrane elasticity as determined by flow channel technique

The elasticity of red cell membrane was determined in a rectangular flow channel under controlled shear flow. The relation between shear stress and cell extension ratio (lambda) has been analyzed with the use of Evans' two-dimensional model. The deformed cell shapes observed experimentally agreed well with the model with lambda up to 1.4. The best correlation was found at lambda = 1.2. The analysis suggests a nonlinear extensional membrane modulus in the low stress range encountered in the flow channel. In terms of an appropriate strain parameter, the elastic modulus is shown to rise toward the level encountered in micropipette aspiration experiments. The implications of the present findings in modeling of cell mechanics and in cell hemolysis are discussed.

Reliability of recalled physical activity, cigarette smoking, and alcohol consumption

Reliability of recalled measures of physical activity and alcohol and tobacco use was examined in a cohort of 873 men and women in three California communities. In personal interviews in 1972, participants provided baseline data on these three habits. In repeat interviews in 1983, they recalled their habits in 1972 and reported their current habits. On average, recalled physical activity levels significantly exceeded those originally reported (1899 kcal/d versus 1345 kcal/d, P < 0.001) and were similar to current reported levels (1822 kcal/d). Similarly, recalled alcohol and cigarette consumption was higher than the original reports (alcohol: 126 versus 119 g/wk; cigarettes: 8.5 versus 6.2/d). By contrast, current reported alcohol (103 g/wk) and cigarette consumption (4.6/d) were lower than at baseline. Analysis of variance was used to partition the variation in recalled and original habits into components due to interpersonal variation in true measures, errors in recall, and residual reporting error. Interpersonal variation accounted for only 20% of the total variation in physical activity, but for 48 to 60% of total variation in cigarette smoking and alcohol consumption. These results suggest that inconsistencies among studies of chronic disease and physical activity may arise from either large random measurement errors in individual assessments or from homogeneity of activity levels among the populations studied.

Mullerian inhibiting substance messenger ribonucleic acid expression in granulosa and Sertoli cells coincides with their mitotic activity

In males, Mullerian inhibiting substance (MIS) mRNA was first detected on the medial aspect of the urogenital ridge early on the morning of day 13 of gestation before testicular differentiation was evident, and localized to the more obvious Sertoli cells later on embryonic day 13. MIS transcripts remained at maximal levels between 14.5 and 17.5 days gestation, while the Mullerian duct involutes, and remained high until birth. MIS gene expression decreased progressively after birth and, as germ cell meiosis increased, became barely detectable in the Sertoli cells of the seminiferous tubules. In female rats, MIS mRNA was first detected in the single layer of cuboidal granulosa cells surrounding larger primary follicles 3 days after birth, coincident with the initiation of follicular growth. As follicular growth progressed, MIS mRNA expression was high in preantral and small antral follicles, especially in those granulosa cells closest to the oocyte. MIS mRNA expression decreased gradually in larger antral follicles, remaining prominent only in the cumulus cells and the dividing population of granulosa cells closest to the lumen. MIS gene expression was absent in follicles with features of atresia and in the larger antral follicles. The expression of MIS mRNA in actively dividing Sertoli and granulosa cells correlates with the stages of germ cell division. These findings are suggestive of a role for MIS in the control of germ cell maturation.

The association of dietary fat with ability to obtain breast fluid by nipple aspiration

The ability to obtain breast fluid by nipple aspiration was examined in relation to self-reported dietary fat intake in 1347 white and 153 black women. Study participants were between 20 and 59 years of age, were not pregnant or breastfeeding, and had no history of breast cancer. The proportion of women from whom nipple aspirate fluid was obtained increased with increasing dietary fat consumption; the odds ratio for obtaining breast fluid was 1.4 (95% confidence interval, 1.0-1.8) in white women who consumed over 90 g of fat/day compared with those who consumed less than 50 g of fat/day, adjusting for age, smoking, and parity. Among black women, the association was much stronger; the odds ratio for obtaining nipple aspirate fluid in those who consumed over 90 g of fat/day was 3.6 (95% confidence interval, 1.3-10.1) compared with those who consumed less than 50 g of fat/day. In both blacks and whites, the associations were most pronounced in women aged 30-44 years. These findings suggest a relationship between dietary fat consumption and breast secretion.

Augmented growth hormone (GH) secretory burst frequency and amplitude mediate enhanced GH secretion during a two-day fast in normal men

Serum GH concentrations are increased in fasted or malnourished human subjects. We investigated the dynamic mechanisms underlying this phenomenon in nine normal men by analyzing serum GH concentrations measured in blood obtained at 5-min intervals over 24 h on a control (fed) day and on the second day of a fast with a multiple-parameter deconvolution method to simultaneously resolve endogenous GH secretory and clearance rates. Two days of fasting induced a 5-fold increase in the 24-h endogenous GH production rate [78 +/- 12 vs. 371 +/- 57 micrograms/Lv (Lv, liter of distribution volume) or 0.24 +/- 0.038 vs. 1.1 +/- 0.16 mg/m2 (assuming a distribution volume of 7.9% body weight), P = 0.0001]. This enhanced GH production rate was accounted for by 2-fold increases in the number of GH secretory bursts per 24 h (14 +/- 2.3 vs. 32 +/- 2.4, P = 0.0006) and the mass of GH secreted per burst (6.3 +/- 1.2 vs. 11 +/- 1.6 micrograms/Lv, P = 0.002). The latter was a result of increased secretory-event amplitudes (maximal rates of GH release attained within a burst) with unchanged secretory burst durations. GH was secreted in complex volleys composed of multiple discrete secretory bursts. These secretory volleys were separated by shorter intervals of secretory quiescence in the fasted than fed state (respectively, 88 +/- 4.2 vs. 143 +/- 14 min, P = 0.0001). Similarly, within volleys of GH release, constituent individual secretory bursts occurred more frequently during the fast [every 33 +/- 0.64 (fasted) vs. every 44 +/- 2.0 min (fed), P = 0.0001]. The t1/2 of endogenous GH was not significantly altered by fasting [18 +/- 2.2 (fasted) vs. 20 +/- 1.5 min (fed), P = 0.47]. Serum insulin-like growth factor I concentrations were unchanged after 56 h of fasting. In conclusion, the present data suggest that starvation-induced enhancement of GH secretion is mediated by an increased frequency of GHRH release, and longer and more pronounced periods of somatostatin withdrawal.