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Biomedical subjects

R M Boyar

Publications and source records attributed to R M Boyar.

At least 19 recordsLinked to original sources
PubMed1990

A light and scanning electron microscopic study of enamel decalcification in children living in a water-fluoridated area.

Eleven children, each having one or two pairs of premolars to be extracted for orthodontic purposes, participated in the study. The model involved placement of a special orthodontic band that allowed the accumulation of plaque in a defined area between the band and the buccal enamel. Examination of enamel changes was carried out in experimental teeth that had been exposed to local plaque accumulation for one, two, four, eight or 14 days. The specimens were examined under the light (LM) and the scanning electron microscope (SEM). All teeth had signs of very mild dental fluorosis. No indications of demineralization were noted after one day. SEM examination showed signs of crystal dissolution in some of the two-day specimens. Six of eight four-day specimens exhibited surface dissolution. All eight- and 14-day specimens showed signs of surface demineralization in the LM as well as in the SEM. These observations documented that undisturbed bacterial deposits are capable of initiating enamel demineralization within short time periods, even in children living in a water-fluoridated area.

Adolescent↗
PubMed1989

The microflora associated with the development of initial enamel decalcification below orthodontic bands in vivo in children living in a fluoridated-water area.

Thirty-four caries-free teeth destined for orthodontic extraction were banded to provide a protected area for the accumulation of plaque. The teeth were extracted at one, two, four, eight, and 14 days after being banded, and samples of the flora below the band were analyzed for the presence of Streptococcus sanguis, Streptococcus 'mitior', 'mutans streptococci', Actinomyces viscosus, Actinomyces naeslundii, Actinomyces odontolyticus, Lactobacillus species, and Veillonella. After plaque sampling, the teeth were sent to the Royal Dental College (Copenhagen) for histological analysis. The results showed that S. mutans could colonize the area below the band after one day, but that colonization was only 100% at 14 days. Lactobacillus was only isolated from 2/8 samples at four days and from 4/8 samples at 14 days. S. sanguis and 'S. mitior' were regularly isolated at all banding times, and Veillonella was isolated from all samples. A. viscosus was the most commonly isolated Actinomyces. The numbers of Streptococcus and Veillonella were significantly higher at day 1 than at day 14 (p less than 0.05). S. mutans and A. viscosus were isolated more frequently at day 14 than at day 1 (p less than 0.01). Histological examination revealed that dissolution of the enamel below a band could occur after two days, but that even after 14 days dissolution could be questionable. Dissolution was detected in areas where S. mutans was not isolated (8/34), but S. mutans was also present in samples showing dissolution (12/34). There was no relationship between dissolution and the numbers of S. mutans; however, the isolation frequency of S. mutans was associated with dissolution (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomyces↗
PubMed1985

Influence of pH and fluoride on properties of an oral strain of Lactobacillus casei grown in continuous culture.

A freshly isolated oral strain, Lactobacillus casei RB1014, was grown in continuous culture to compare the effects of pH and fluoride on growth and metabolism. The cells were grown at pH 7.0 to 3.2 in the absence of fluoride and from pH 7.0 to 5.4 with 20 mM NaF. Cell numbers varied from 3 X 10(9) to 30 X 10(9)/ml on blood agar during alterations in the growth pH from 7.0 to 4.27. Only when the culture was stressed by lowering the pH to 3.2 were cell numbers drastically reduced. Cells growing at pH 7.0 without fluoride were unable to grow when plated on fluoride agar (10.5 mM) at pH 5.5; however, when the growth pH was allowed to decrease to 4.94, cells grew on the fluoride plates in numbers equal to those growing on blood agar. This fluoride tolerance trait appeared rapidly once pH control was removed and was lost when the culture was returned to pH 7.0. The addition of 20 mM NaF to the culture medium did not adversely affect growth, provided that the pH was maintained at 6.0 or above; cells tolerant to 10.5 and 16 mM NaF appeared on pH 5.5 plates during this phase. In cells removed from the chemostat throughout the experiment and incubated at the pH of growth in a pH stat, glycolytic activity was optimum at pH 5.5 in the absence of NaF. Fluoride stimulated glycolytic activity by cells incubated at pH 7.0 and by cells growing with 20 mM NaF, provided that the pH of growth remained at or above 6.0. A more detailed examination of the adaptation to fluoride tolerance during shifts to acidic pH values revealed that cells capable of growth on acidic fluoride agar plates appeared within 2 h of the start of the fall in pH of the chemostat culture. Estimation of the intracellular pH during the period of the initial pH fall revealed that the intracellular pH was identical to the extracellular pH (i.e., no pH gradient [delta pH]), indicating that fluoride would not be transported into the cells to inhibit metabolism. However, once the pH of the medium was stabilized, delta pHs were generated, with the delta pH increasing as the pH declined. The inhibition of glycolysis by fluoride increased in proportion to the delta pH. Cells grown at pH 5.5 generated larger delta pHs than did cells grown at pH 7.0, although the values were normally small (approximately 0.9 U). The data suggest that the inherent fluoride tolerance of L. casei RB1014 was associated with relatively small delta pHs.

Fluorides↗
PubMed1982

The 24-hour secretory pattern of LH and the response to LHRH in transsexual men.

Ten separate aspects of hypothalamic and pituitary function were studied in 13 male-to-female transsexuals and compared to the results of 7 heterosexual adult men. In 4 of 5 transsexuals, the 24-hour mean serum concentration of LH, the LH pulse frequency or amplitude, or the apparent half-life of disappearance of serum LH were greater than the 95% confidence limit of normal men. The maximum concentration of LH or FSH following the administration of 100 micrograms LHRH, the area under the response curve of LH or FSH following LHRH, or both were significantly greater than normal in 5 of 13 male-to-female transsexuals. The response of LH following the administration of LHRH was repeated in 3 subjects during estrogen therapy, and in one there was a paradoxical increase in the response of LH. Transsexualism may be associated with a neuroendocrine defect in the hypothalamus or pituitary that is characterized by high-frequency, high-amplitude pulsatile secretion of pituitary LH.

Adolescent↗
PubMed1981

Daily rhythms in cortisol and melatonin in primate cerebrospinal fluid. Effects of constant light and dark.

Cerebrospinal fluid was continuously collected from the cisternal-cervical subarachnoid space of chair-restrained rhesus monkeys. The concentrations of melatonin and cortisol were measured in the cerebrospinal fluid. Under diurnal lighting (light:dark, 12:12 h) melatonin concentrations were elevated during darkness and low during illumination. The melatonin rhythm persisted in constant darkness but was suppressed in constant illumination. Under diurnal lighting, cortisol concentrations were elevated in the early portion of the light period. This daily rhythmicicty of cortisol secretion was not altered by constant illumination or constant darkness. The differential response of the two hormones to constant light suggest that the daily fluctuation of melatonin secretion was not responsible for the daily rhythmicity of cortisol secretion in the rhesus monkey.

Animals↗
PubMed1980

Gonadal function in trisomy 21.

Endocrinologic evaluation of 39 patients with trisomy 2 and associated hypogonadism demonstrated elevations of follicle-stimulating hormone and luteinizing hormone; consequently, it can be concluded that both germinal and Leydig cell function are affected. A negative correlation between testicular size and plasma follicle-stimulating hormone was documented. Plasma testosterone levels were found to be normal in male patients as were estradiol levels in female patients with trisomy 21. On the basis of these findings, the simplest and most practical diagnostic approach to evaluate germinal cell function appears to be a single plasma follicle-stimulating hormone determination supplemented by an accurate measurement of testicular volume in males.

Down Syndrome↗
PubMed1979

Circadian cortisol secretory rhythms in Cushing's disease.

Plasma cortisol was measured at 20-min intervals for 24 h in eight patients with Cushing's disease and ACTH-secreting pituitary tumors. The 24-h mean (+/- SD) cortisol level was 25.6 +/- 11.3 microgram/dl (range, 15.5--40.6), which was significantly higher than the level of normal control subjects (P less than 0.01). The 24-h mean ACTH level varied between 22--107 pg/ml, with a mean +/- SD of 63.4 +/- 27.2. The mean ACTH level was higher than that of the control subjects but the difference was not statistically significant. The 24-h cortisol secretory pattern was characterized by an absence of the normal circadian variation and a failure of the plasma cortisol level to fall to less than 2 microgram/dl between 2300--0300 h. The coefficient of variation, an expression of the amplitude of cortisol secretory episodes, was significantly decreased in patients with Cushing's disease compared to normal control subjects; there was no significant difference in the number of cortisol secretory episodes in the patients vs. control subjects. Three of the patients were restudied after successful resection of their ACTH-secreting pituitary tumors. Two showed normalization of their 24-h circadian cortisol patterns and normal metyrapone responses. In the third, the 24-h mean cortisol level was normal, but the circadian cortisol rhythm remained abnormal. This patient had diminished ACTH reserve, demonstrated by a subnormal response to metyrapone. Additional studies will be required to determine if normalization of the circadian cortisol rhythm occurs in all patients with Cushing's disease who are cured after transsphenoidal microsurgery and who also show normal ACTH reserve.

Adrenocorticotropic Hormone↗
PubMed1979

[Melatonin and LH secretion patterns in pubertal boys (author's transl)].

Plasma melatonin and LH were measured at 20 minute intervals for 24 hours in four normal pubertal boys. All four subjects showed a significant augmentation of LH and melatonin during noctural sleep. There was also a significant correlation between the LH and melatonin levels (p less than 0.001). There were periods of episodic secretion of melanin during the diurnal waking period which seemed related to "stress". These data indicate that the peripheral concentrations of melatonin which occur during sleep are insufficient to prevent spontaneous LH secretion during puberty.

Adolescent↗
PubMed1978

The effect of oral contraceptive treatment on the serum concentration of dehydroisoandrosterone sulfate.

Dehydroisoandrosterone sulfate (DS), the major C19-steroid in the human circulation, was measured in serum obtained from blood samples collected daily (8 to 10 A.M.) throughout the menstrual cycles of eight normal, presumably ovulatory women and daily throughout the treatment cycles in four women taking an oral contraceptive (norethindrone, 1 mg., plus mestranol, 80 mcg.). The serum concentrations of DS in the ovulatory women ranged from 1,025 to 4,200 ng. per milliliter; mean, 2,062 +/- 137 ng. per milliliter (mean and standard error; n = 213). Serum DS concentrations during the follicular and luteal phases of the menstrual cycles of these women were similar. In women taking the oral contraceptive, the plasma DS concentrations ranged from 475 to 1,400 ng. per milliliter (mean, 895 +/- 83; n = 119). The 24 hour secretory pattern of DS was evaluated in one subject during a nontreatment cycle and again after 20 days of oral contraceptive treatment. In this subject, the mean serum DS level was 34 per cent lower during oral contraceptive treatment than the level before treatment. The decrease in the serum concentration of DS during oral contraceptive treatment likely results from a reduction in adrenal DS secretion since DS secretion by the normal human ovary is negligible and ovarian dehydroisoandrosterone secretion is small. Therefore, it is likely that the reduced serum DS levels in women taking oral contraceptives are the consequence of reduced adrenal secretion of DS resulting from reduced release of adrenocorticotropic hormone.

Adrenal Cortex↗
PubMed1978

Analysis of secretory patterns of prolactin and gonadotropins during twenty-four hours in a lactating woman before and after resumption of menses.

Twenty-four hour secretory patterns of prolactin, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were obtained on two separate occasions from a woman with late physiologic lactation. The studies were performed 26 and 34 months after her child's birth. During the initial study, she had amenorrhea, and her child suckled 13 per cent of the 24 hour period (Study 1). At the time of the second study, she had resumed regular menses and her child suckled for 7 per cent of the 24 hour period (Study 2). The average concentrations of prolactin during Studies 1 and 2 were 40 +/- 1.0 (mean and standard error; No. = 72) and 31 +/- 1.4 ng. per milliliter, respectively. The mean plasma prolactin concentration in Study 1 was significantly greater than that in Study 2 (p less than 0.001). The plasma concentrations of LH and FSH were significantly less in Study 1 than in Study 2 (p less than 0.001 and less than 0.01, respectively). It is concluded that hyperprolactinemia and hypogonadotropinemia were endocrinologic correlates of the amenorrhea of late physiologic lactation in this woman.

Adult↗
PubMed1978

Regulation of gonadotropin secretion in Turner's syndrome.

To determine the role of body fat in regulating secretion of luteinizing hormone and follicle-stimulating hormone, we measured both at 20-minute intervals for 24 hours in eight children with Turner's syndrome. The 24-hour mean luteinizing hormone levels varied from 20.2 to 70.5 mlU per milliliter. Total body weight, total body fat and percentage of body fat showed a significant negative correlation with the 24-hour mean luteinizing hormone concentrations (P less than 0.01). The 24-hour mean follicle-stimulating hormone concentrations ranged from 60.4 to 229 mlU per milliliter, with a significant negative correlation between total body fat and percentage body fat and the 24-hour mean concentrations (P less than 0.05). These negative correlations were not mediated by estrogens or androgens.

Adipose Tissue↗
PubMed1978

Endocrine studies in primary hypogonadism.

Two 15-year-old boys with primary hypogonadism had evaluation of their hypothalamic-pituitary-gonadal axis. Testicular biopsies and chromsomal studies were also performed. Both patients presented with delayed puberty and short stature and had prepubertal LH, FSH and testosterone concentrations. Serial 24-hour frequent-interval blood studies over a 2-year period in one patient (R.F.) showed a gradual progression from a normal early pubertal LH secretory pattern to one characteristic of 'primary' testicular failure. The testicular biopsies showed prepubertal tests with no significant germinal cell maturation. Although both patients had some somatic stigmata of Noonan's syndrome, they had different karyotypes (XY and xyq-). These studies show that elevated levels of LH and FSH in primary hypogonadism syndrome may not become apparent until after the onset of CNS puberty.

Adolescent↗