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Biomedical subjects

A Tomita

Publications and source records attributed to A Tomita.

At least 19 recordsLinked to original sources
PubMed1992

[Bone mineral content in premenopausal women treated with gonadotropin-releasing hormone analogue].

To assess bone metabolism during treatment with gonadotropin-releasing hormone analogue (GnRHa), serum osteocalcin (BGP), alkaline phosphatase (ALP), parathyroid hormone (PTH), calcitonin (CT), calcium (Ca) and phosphorus (P) were determined before and after 6 months of GnRHa treatment in 15 premenopausal women with clinically diagnosed endometriosis. The bone mineral content (BMC) of the lumbar spine (L3) was measured by single energy quantitative computed tomography in 9 women, and in 6 of these 9 women microdensitometry was performed simultaneously during the treatment. BMC decreased significantly to 92.5 +/- 6.8% (mean +/- SD) of the pretreatment value after 6 months of treatment. On the other hand, microdensitometry revealed no significant change during treatment. Serum BGP and ALP were significantly higher after 6 months of treatment than before treatment, indicating an increase in bone formation. These data indicate that the GnRHa treatment induces an increase in bone turnover and a significant bone loss.

Adult↗
PubMed1991

Aggravation of subclinical diabetes insipidus during pregnancy.

BACKGROUND: Transient polyuria and polydipsia during pregnancy are rare, and their cause is not entirely clear. Possible explanations include the exacerbation of preexisting abnormalities in the secretion or action of vasopressin and abnormally large increases in plasma vasopressinase activity. METHODS: We studied two women in whom overt polyuria and polydipsia developed during the third trimester of pregnancy and disappeared after delivery. The secretion and action of vasopressin were studied both when the women had polyuria and polydipsia and later, when their water intake and urine volume were normal. RESULTS: One patient had partial nephrogenic diabetes insipidus. She had little increase in urine osmolality in response to water deprivation, hypertonic-saline infusion, and vasopressin injection and no response to desmopressin acetate (1-deamino-8-D-arginine vasopressin) during the immediate postpartum period. Her basal and stimulated plasma vasopressin concentrations were high (16.5 to 203.4 pmol per liter) before and during hypertonic-saline infusion 30 months post partum. The other patient had partial neurogenic diabetes insipidus. She had subnormal basal plasma vasopressin concentrations, a subnormal increase in the plasma vasopressin level and a subnormal decrease in urine flow in response to the administration of vasopressin, and a normal response to desmopressin. After pregnancy, when her urine volume was normal, she had no increase in plasma vasopressin in response to hypertonic-saline infusion, but she had a normal rise in the plasma vasopressin level and a normal renal response to vasopressin administration. CONCLUSIONS: Pregnancy may unmask subclinical forms of both nephrogenic and neurogenic diabetes insipidus. This exacerbation may result from both increased vasopressinase activity and diminished renal responsiveness to vasopressin.

Adult↗
PubMed1991

Comparative studies of decay-accelerating factor and HLA-DR within the CD8-brightly positive population.

Decay-accelerating factor (DAF) is a membrane protein that inhibits C3 convertase activity of autologous complement at the cell surface. We found that DAF+ cells and DAF- (DAFlow, if any) cells are clearly separated from each other among CD8-brightly positive (CD8bright) cells. Using three-color fluorescence flow cytometry, we found that whereas the CD8bright DAF- population express HLA-DR (class II major histocompatibility complex antigens, and an activated T cell marker), the CD8bright DAF+ population does not. Therefore, among the CD8bright T cells, DAF and HLA-DR are mutually exclusive. In addition, the CD8bright DAF+ population proliferates in the presence of recombinant interleukin 2 (rIL2) while the CD8bright DAF- population does not. After a 4-day cultivation of peripheral blood lymphocytes in the presence of rIL2, expression of HLA-DR increased in the CD8bright DAF- population and expression of IL 2Rp55 (alpha chain, the receptor for IL2, and a marker of T cell activation) occurred in the CD8bright DAF+ population. Furthermore, C3 deposition occurred in the CD8bright HLA-DR+ population which lacks DAF when lymphocytes, that had been cultured for 3 days in the presence of rIL2, were incubated with fresh autologous serum. This result suggests that the absence of DAF on CD8bright HLA-DR+ T cells might play a role in permitting complement reaction on the cells in vivo and may be related to the regulation of T cell activation.

Adult↗
PubMed1991

Mouse targets undergo double-strand DNA fragmentation when exposed to syngeneic or xenogeneic LAK cells whereas human targets undergo single-strand breaks.

A number of recent studies have shown that mouse target cells (TC) of hematopoietic origin, when exposed to cytotoxic lymphocytes, undergo double-stranded DNA fragmentation. The cause and relevance of the fragmentation remain controversial. In this study we generated a number of mouse (M-LAK) and human LAK (H-LAK) cells and exposed them to a variety of mouse and human TC. YAC and SP/2, 2 mouse TC underwent rapid and extensive fragmentation when lysed by either human or mouse LAK whereas K562 and Daudi, 2 human TC, under the same conditions did not. All 4 TC, however, were killed quite efficiently. Next we labeled TC with 125I-deoxyuridine, exposed them to LAK cells for up to 18 h and loaded the LAK:TC mixtures over an alkaline linear sucrose gradient. After lysing the cells with a lysis buffer containing Triton X-100 we showed that K562 that had been in contact with LAK cells for more than 1 h exhibited single-strand nicks. However, whereas double-strand fragmentation preceded chromium release (lytic activity), the appearance of single-strand nicks did not. Finally, protein synthesis was not required for either type of fragmentation. In summary, we have demonstrated that: (1) the ability to undergo DNA fragmentation is a property of the TC rather than the effector cells that mediated their death, and (2) K562 and Daudi, 2 human TC, undergo single-strand nicks when lysed by LAK cells whereas SP/2 and YAC, 2 mouse TC undergo double-strand fragmentation when exposed to the same syngeneic or xenogeneic effector cells.

Animals↗
PubMed1991

[Bone mass and biochemical parameters in metabolic bone diseases].

We studied the relationship between the bone mass and biochemical parameters in 175 normal premenopausal, 72 normal postmenopausal and osteoporotic postmenopausal women, between 20 and 88 years old, and in 40 patients with hyperthyroidism, and 23 patients with primary hyperparathyroidism, between 13 and 64 years old. The bone mineral density (BMD) of the spine (L2-L4) and proximal femur (femoral neck) was measured by dual-energy X-ray absorptiometry using a QDR-1000, Hologic. The bone mineral content (BMC) of the radius was measured by single photon absorptiometry (SPA) using a model 2780, Norland. Serum PTH, BGP and calcitonin (CT) were determined by radioimmunoassay. The BMD of the spine (L2-L4), and the proximal femur in postmenopausal women were negatively correlated with age. The mean BMD in patients with postmenopausal osteoporosis was significantly lower than that in normal postmenopausal women. In postmenopausal women, age was positively correlated with BGP, PTH, CT and negatively correlated with P. In patients with osteoporosis, the BMD of the spine was negatively correlated with serum BGP. The BMC of radius in patients with hyperthyroidism decreased significantly compared with that in the controls, and was negatively correlated with F-T3. The BMC of the radius in patients with primary hyperparathyroidism was significantly lower than that in the controls, and was negatively correlated with serum BGP and serum calcium. The measurements of biochemical parameters such as serum BGP, ALP and PTH may be useful in the assessment of metabolic bone diseases.

Adolescent↗
PubMed1990

Osmoregulation of plasma vasopressin in myxedema.

We studied osmoregulation of plasma vasopressin (AVP) in eight patients with untreated myxedema due to primary hypothyroidism. All patients had severe thyroid hormone deficiency due to chronic thyroiditis and had been receiving no medication at the time of this study. AVP release was defined by 5% hypertonic saline infusion test in all patients, and urinary diluting capacity was estimated by the iv water-loading tests in five patients. Plasma AVP was measured by sensitive and specific RIA. The mean basal plasma AVP level in the patients (0.5 +/- 0.1 pmol/L) was significantly lower (P less than 0.01) than that in normal adults (2.5 +/- 0.5 pmol/L). During hypertonic saline infusion, the rise in plasma AVP was normal or subnormal in all patients. In two patients who showed mild to moderate hyponatremia in the basal state and mild urinary diluting defect during water loading, plasma AVP was appropriately suppressed in each case. These results indicate that inappropriate elevation of plasma AVP is not common in myxedema, and that impaired water excretion is due mainly to AVP-independent mechanisms.

Adult↗
PubMed1990

Effect of metyrapone pretreatment on adrenocorticotropin secretion induced by corticotropin-releasing hormone in normal subjects and patients with Cushing's disease.

To examine the influence of endogenous cortisol on the ACTH response to CRH, we compared ACTH secretion during CRH tests before and after metyrapone administration in 9 normal subjects and 12 patients with Cushing's disease. The administration of 4.5 g metyrapone (750 mg, orally, every 4 h) resulted in a decrease in basal (pre-CRH) plasma cortisol levels and an increase in basal plasma ACTH levels in both normal subjects and Cushing's patients. The pretreatment with metyrapone significantly blunted the increase in plasma cortisol levels and markedly enhanced ACTH secretion after iv injection of 100 micrograms human CRH. The peak ACTH levels during CRH test before and after metyrapone administration were 8 +/- 1 and 58 +/- 8 pmol/L, respectively, in normal subjects (P less than 0.01) and 26 +/- 5 and 50 +/- 11 pmol/L, respectively, in Cushing's patients (P less than 0.05). Although the basal and peak ACTH levels as well as delta ACTH (peak ACTH - basal ACTH) during the CRH test before metyrapone administration were significantly higher in Cushing's disease patients than in normal subjects (P less than 0.01), no such difference was observed between the 2 groups after metyrapone administration. The results clearly indicate that the endogenous cortisol levels greatly influence the ACTH response to CRH, and that the CRH test as commonly performed does not allow a correct evaluation of potential responsiveness of normal pituitaries and Cushing's adenomas to CRH.

Adolescent↗
PubMed1990

[Lumbar bone density and serum osteocalcin in pre- and postmenopausal women].

The bone mineral density of the lumbar spine (L3) and serum osteocalcin (OC) were measured in 31 pre- and 25 postmenopausal women. Bone density was measured by single energy quantitative computed tomography (QCT value). A significant inverse correlation between the QCT value and age was demonstrated in postmenopausal women but no correlation was found in premenopausal women. Mean QCT value was significantly lower in postmenopausal women than in premenopausal women. Serum OC increases with advancing age and mean serum OC was significantly higher in postmenopausal women than in premenopausal women. A significant inverse correlation between the QCT value and serum OC was demonstrated. These data suggest that there is an association between menopause and accelerated loss of lumbar bone density and that the serum OC level may be useful in evaluating the bone mass.

Adolescent↗
PubMed1989

Human PTH(1-34) infusion test in differential diagnosis of various types of hypoparathyroidism: an attempt to establish a standard clinical test.

To introduce a simple procedure and reliable diagnostic criteria for parathyroid hormone (PTH) infusion test, 128 patients with either pseudo- (PsH) or idiopathic hypoparathyroidism (IdH) and 25 normocalcemic controls were studied. Incremental responses of urinary cyclic AMP and phosphate to 20 micrograms (67 U) or 30 micrograms (100 U) of human PTH(1-34) were assessed by using simple parameters of urinary excretion rates of the two substances. The results are summarized as follows. (1) PTH dose-cyclic AMP response relation suggests that 100 U of PTH is more appropriate than 67 U as a standard test dose for adults. (2) By presenting the magnitude of cyclic AMP response as either net increase or fold increase during 1 h after 100 U of PTH infusion, we can differentiate PsH type I from others without overlap. (3) Differentiation between PsH and IdH or normocalcemic subjects by phosphaturic response is less clearcut than that made by cyclic AMP response whatever indices and criteria are used. Thus it seems difficult to diagnose PsH type II merely based on the discrepancy between cyclic AMP and phosphaturic responses to exogenous PTH. (4) The test results are essentially similar in the examinations performed before and during vitamin D therapy. However, when the magnitude of phosphaturic response is expressed as net increase during 2 h after PTH, it tends to be enhanced after vitamin D therapy in patients with PsH compared to the response before therapy.

Adolescent↗
PubMed1989

Neurohypophyseal function in postpartum hypopituitarism: impaired plasma vasopressin response to osmotic stimuli.

We studied neurohypophyseal function in 12 women with postpartum hypopituitarism (Sheehan's syndrome) by measuring plasma arginine vasopressin concentrations during 5% hypertonic saline infusions. All patients had a history of obstetric shock or massive bleeding, and were receiving cortisol and/or L-T4 replacement therapy. None had any symptoms of diabetes insipidus. The mean basal plasma vasopressin level in the patients [0.6 +/- 0.1 (+/- SE) pmol/L] was significantly lower (P less than 0.01) than that in normal adults (2.5 +/- 0.5 pmol/L; n = 12), whereas mean plasma osmolality values were similar in the two groups. During hypertonic saline infusion, the 10 hypopituitary patients had varying degrees of subnormal arginine vasopressin responses to the increase in plasma osmolality. Urine-concentrating ability after dehydration also was lower in the patients, although overt polyuria was absent at the time of this study. These results indicate that the osmoregulation of arginine vasopressin secretion is frequently impaired in postpartum hypopituitarism, suggesting neurohypophyseal damage.

Adult↗