Chronic disseminated Trichosporon asahii infection in a leukemic child.

We report a case of chronic disseminated Trichosporon asahii infection in a leukemic child. Administration of amphotericin B lipid complex resulted in rapid control and improvement of the initial infection but failed to prevent the development of chronic disseminated disease. Cure was achieved after treatment was changed to a 20-month course of itraconazole. This case report demonstrates that Trichosporon species can cause chronic disseminated disease with a pattern similar to that of disease caused by Candida species.

Delayed union of femoral fractures in older rats:decreased gene expression.

BACKGROUND: Fracture healing slows with age. While 6-week-old rats regain normal bone biomechanics at 4 weeks after fracture, one-year-old rats require more than 26 weeks. The possible role of altered mRNA gene expression in this delayed union was studied. Closed mid-shaft femoral fractures were induced followed by euthanasia at 0 time (unfractured) or at 1, 2, 4 or 6 weeks after fracture in 6-week-old and 12-15-month-old Sprague-Dawley female rats. mRNA levels were measured for osteocalcin, type I collagen alpha1, type II collagen, bone morphogenetic protein (BMP)-2, BMP-4 and the type IA BMP receptor. RESULTS: For all of the genes studied, the mRNA levels increased in both age groups to a peak at one to two weeks after fracture. All gene expression levels decreased to very low or undetectable levels at four and six weeks after fracture for both age groups. At four weeks after fracture, the younger rats were healed radiographically, but not the older rats. CONCLUSIONS: (1) All genes studied were up-regulated by fracture in both age groups. Thus, the failure of the older rats to heal promptly was not due to the lack of expression of any of the studied genes. (2) The return of the mRNA gene expression to baseline values in the older rats prior to healing may contribute to their delayed union. (3) No genes were overly up-regulated in the older rats. The slower healing response of the older rats did not stimulate a negative-feedback increase in the mRNA expression of stimulatory cytokines.

MRNA expression of Phex in mice and rats: the effect of low phosphate diet.

Phex is the gene whose mutation is the cause of X-linked hypophosphatemia in humans and mice. The organs expressing Phex in normal animals, and their possible sensitivity to stimulation by low phosphate diets, are unknown. In this study, Phex expression was measured in 6-wk-old normal B6C3H male and female mice and in 135 g Sprague-Dawley rats fed a normal phosphate diet or a low phosphate diet with deionized water ad libitum for 7 d. The animals were then anesthetized, and a variety of organs were collected and frozen in liquid nitrogen. Phex mRNA expression was measured in each organ by reverse transcription-polymerase chain reaction (RT-PCR) with primers specific for both Phex and glyceraldehyde-3-phosphate dehydrogenase (G3PDH). Southern blots were prepared, hybridized with 32P-labeled internal oligonucleotides, and quantified with a phosphor imager. The Phex/G3PDH ratio was computed, and the data were compiled as the mean +/- SEM. In these growing animals, the highest Phexexpression levels were found in the gonads, brain, and lung. In contrast, Phex expression in calvaria and femur was markedly less. Two significant changes were found in animals that were fed a low phosphate diet. Spleen showed a significant decrease in Phex mRNA levels on low phosphate diet (60+/-10% of normal P diet, n = 12/group, p = 0.002). The pituitary gland showed a significant increase in Phex expression with low phosphate diet (851+/-127% of G3PDH) over normal P diet (569+/-78%, n = 24 - 25/group, p = 0.03). No significant change was found in femur, calvaria, or a variety of soft tissues. In summary, Phex mRNA was found in most tissues examined. Expression levels varied by two orders of magnitude from highest to lowest with more in gonads, brain, and lung and with less in bone. Increased Phex mRNA was found in the pituitary gland of animals that were fed a low phosphate diet.

Effect of age on the expression of Pex (Phex) in the mouse.

Pex is a newly discovered gene (also called Phex) whose mutation is the cause of X-linked hypophosphatemia. Other members of this gene family encode endopeptidases that activate or inactivate endocrine and paracrine factors. Though embryonic bone expresses mRNA for the Pex gene at relatively high levels, we have found Pex expression to be widespread in adult organs and to be poorly expressed in adult bone. This led to the hypothesis that Pex mRNA expression changes with age. To test this, genetically normal mice of the B6C3H hybrid strain were studied at 0 (newborn), 2, 3, 10, and 72 weeks of age. Organs known to express Pex were collected, and RNA was extracted from them. Following reverse transcription, cDNA was amplified by the polymerase chain reaction with primers for Pex and G3PDH, a housekeeping gene. The amplimers were separated by electrophoresis, blotted onto nylon membranes, and hybridized with radioactively labeled internal oligonucleotide probes. The radioactivity was quantified, and the data were analyzed as the Pex/G3PDH ratio. The brain samples had high levels of Pex mRNA expression that rose slightly with age. Calvaria, kidney, and lung samples had the highest Pex mRNA expression at birth. In these organs Pex mRNA expression fell with age to undetectable or barely detectable levels. Thymus, heart, and skeletal muscle samples had low Pex mRNA expression at birth that did not change with age. Some organs showed a decline in G3PDH levels with age, but Pex expression decreased more, leading to a reduced Pex/G3PDH ratio. The widespread expression of mRNA for Pex suggests a role beyond that of phosphate homeostasis. The high level of expression in newborn animals suggests a role in growth and development. This seems to occur in addition to its role for the endocrine regulation of phosphate homeostasis by as yet unknown humoral agents that must occur throughout life. In summary, Pex mRNA expression is high in brain and bone at birth. Expression remains high in brain with age but falls with age in bone, kidney, and lung.

Magnesium deficiency-induced osteoporosis in the rat: uncoupling of bone formation and bone resorption.

Magnesium (Mg) intake has been linked to bone mass and/or rate of bone loss in humans. Experimental Mg deficiency in animal models has resulted in impaired bone growth, osteopenia, and increased skeletal fragility. In order to assess changes in bone and mineral homeostasis that may be responsible, we induced dietary Mg deficiency in adult Simonsen albino rats for 16 weeks. Rats were fed either a low Mg diet (0.002 percent) or a normal control Mg diet (0.063 percent). Blood was obtained at baseline, 4 weeks, 8 weeks, 12 weeks and 16 weeks in both groups for serum Mg, calcium, PTH, and 1.25(OH)2-vitamin D determinations. Femora were harvested at 4 weeks and 16 weeks for mineral analysis and histomorphometry. Serum Mg fell in the Mg depleted group to 0.6 mg/dl (mean) by 16 weeks (controls = 2.0 mg/dl). The serum calcium (Ca) concentration was higher in the Mg depleted animals at 16 weeks, 10.8 mg/dl (controls = 8.9 mg/dl). Serum PTH concentration fell progressively in the Mg deficient rats to 30 pg/ml by week 16 (control = 96 pg/ml). Serum concentration of 1.25(OH)2-vitamin D also fell progressively in the Mg deficient animals by 16 weeks to 14 pg/ml (control = 30 pg/ml). While the percent ash weights of Ca and phosphorus in the femur were not different at any time point, the percent ash weight of Mg progressively fell to 0.54 percent vs control (0.74 percent) by 16 weeks. The percent ash weight of potassium also fell progressively in the Mg deficient group to approximately 30 percent of control by 16 weeks. Histomorphometric analyses showed a significant drop in trabecular bone volume in Mg deficient animals by 16 weeks (percent BV/TV = 13.2 percent vs 17.3 percent in controls). Evaluation of the endosteal bone surface features showed significantly greater bone resorption in the Mg depleted group as reflected in increased number of tartrate-resistant positive osteoclasts/mm bone surface (7.8 vs 4.0 in controls) and an elevated percent of bone surface occupied by osteoclasts (percent OcS/BS = 12.2 percent vs 6.7 percent in controls. This increased resorption occurred in the presence of an inappropriate lowered bone forming surface relative to controls; a decreased number of osteoblasts per mm bone surface (0.23 vs 0.94 in control) and a decrease in percent trabecular surface lined by osteoid (percent OS/BS = 0.41 vs 2.27 percent in controls) were also noted. Our findings demonstrate a Mg-deficiency induced uncoupling of bone formation and bone resorption resulting in a loss of bone mass. While the fall in PTH and/or 1.25(OH)2-D may explain a decrease in osteoblast activity, the mechanism for increased osteoclast activity is unclear. These data suggest that Mg deficiency may be a risk factor for osteoporosis.

Isoproterenol increases renal tubular reabsorption of phosphate in X-linked hypophosphatemic (Hyp) mice.

Hypophosphatemic (Hyp) mice have a reduced renal retention of phosphate. The beta-adrenergic agonist isoproterenol reverses phosphaturia induced by parathyroid hormone in the rat. This study determined whether isoproterenol could raise the renal tubular maximum transport of phosphate (TmP) in Hyp mice. Male 10- to 12-week-old normal and Hyp mice were infused with (3)H-inulin and isoproterenol (0.0, 0.25, 0.5 and 1.0 microg/kg/min) in 0.9% NaCl. Glomerular filtration rate, plasma phosphate, urinary phosphate excretion, TmP, urinary sodium excretion, and urinary cyclic adenosine monophosphate were measured. As expected, Hyp controls (0.0 dose) had a TmP which was significantly below that of normal controls: 1.15+/-(SEM) 0.6 (n = 9) versus 2.13+/-0.10 (n = 11) micromol P/ml glomerular filtrate (p<0.001). Isoproterenol at doses of 0.5 and 1.0 microg/kg/min elevated the TmP of Hyp mice to the level of normal controls: 1.94+/-0.19 (n = 7) and 1.98+/-0.10 (n = 9) micromol P/ml glomerular filtrate, respectively. These results indicate that the low tubular reabsorption of phosphate in Hyp mice is not due to a fixed low level of phosphate transport, but to decreased stimulation of phosphate transporters, since Hyp mouse kidneys increase phosphate reabsorption with suitable stimulus.

Evaluation of Lunar small animal software for measuring bone mineral content in excised rat bones.

The purpose of this study was to evaluate software from Lunar Corporation (Madison, WI) designed for the measurement of bone mineral content ([BMC],g) in excised rat femurs using dual-energy X-ray absorptiometry (DXA). Femurs were harvested from intact 2- to 12-mo-old female Sprague-Dawley rats, stripped of soft tissues, wrapped in saline-soaked gauze, and frozen at -20 degrees F. Thawed bones were scanned in air on a 1.7-cm-thick Lucite plate that was laid on the manufacturer's supplied Delrin platform. Bones were in an anteroposterior position and scanned in a proximal-to-distal manner. Small animal software version 1.0d was used with a Lunar DPX-L densitometer. Regions of interest (ROIs) were the middle one-third of the diaphysis, a small central area of the distal metaphysis, and the total bone. Precision (n = 6 femurs) was calculated for each region of interest. After DXA scanning, one group of bones (n = 10 femurs) was dried and incinerated in a muffle furnace to obtain bone ash. The ash was then digested in acid and aliquots assayed for calcium using atomic absorption spectrophotometry. This group of bones was used to correlate BMC with ash weight and areal bone mineral density (BMD) with calcium concentration. A second group of bones (n = 14 femurs) was used to correlate BMC with maximal load to failure (N), a biomechanical variable that provides information about bone strength. Precision of repetitive measurements for the three ROIs was 1.2, 3.0, and 0.65%, respectively. Total femur BMC and total femur ash weights were significantly correlated (r = 0.974, p <0.0001). Total femur area BMD (g/cm2) was significantly correlated with calcium concentration (microM) of the bone hydrolysate (r = 0.686, p = 0.029). Total femur BMC and maximum load to midshaft fracture were also significantly correlated (r = 0.914, p<0.0001). The greatest problem with the software was with edge detection: operator intervention was necessary to place edges manually during scan analyses. We conclude that the small animal software from Lunar Corporation accurately and precisely measured BMC in excised rat femurs. However, poor edge detection resulted in tedious and time-consuming analyses.

Magnesium deficiency induces bone loss in the rat.

Disorders in which magnesium (Mg) depletion is common have an associated high incidence of osteoporosis. Mg depletion in humans results in hypocalcemia, low serum parathyroid hormone (PTH) and 1, 25(OH)2-vitamin D levels, as well as PTH and vitamin D resistance which may serve as mechanisms for the development of osteoporosis. In order to determine if isolated Mg depletion will result in bone loss, we have induced dietary Mg deficiency in the rat. Adult (290 g) female rats were given either a low-Mg diet (2 mg/100 g chow; n = 6) or a normal control Mg diet (63 mg/100 g chow; n = 6). Dietary calcium (Ca) was normal in both groups (592 mg/100 g chow). At 12 weeks, blood was obtained for serum Mg, Ca, PTH, 1,25(OH)2-vitamin D, and osteocalcin determinations. The rats were then euthanized and the femurs obtained for mineral analysis and histomorphometry. Serum Mg in the low-Mg group was less than control (0.4 +/- 0.2 vs. 1.9 +/- 0.2 mg/dl, p < 0.001; mean +/- SD) while serum Ca was higher (11. 7 +/- 0.5 vs. 9.3 +/- 0.4 mg/dl, p < 0.001). PTH was suppressed in the Mg-deficient group (36 +/- 16 vs. 109 +/- 30 pg/ml in controls, p < 0.002). Serum 1,25(OH)2-vitamin D was also suppressed in the Mg-deficient animals (7.1 +/- 4.8 vs. 28.5 +/- 8.2 pg/ml in controls, p < 0.002). Serum osteocalcin levels were not different (19.8 +/- 2.5 ng/ml in Mg-deficient rats vs. 15.3 +/- 3.4 ng/ml in controls). While the ash weight of Ca and phosphorus in the femur did not change, the ash weight of Mg fell (low-Mg group 0.55 +/- 0.01%, controls 0.65 +/- 0.02%, p < 0.001). Histomorphometry demonstrated reduction in bone mass; the trabecular bone volume in the femur of the low-Mg group was reduced from control (7.7 +/- 0.2 vs. 13.7 +/- 1.9%, p < 0.002). A surprising new observation was an increase in osteoclast (OC) bone resorption with Mg depletion. The number of OC per millimeter bone surface was 16.9 +/- 1.3 in the low-Mg group versus 7.8 +/- 1.5 in controls (p < 0.001). The percentage of bone surface occupied by OC was 38.3 +/- 3.7 in the low-Mg group versus 17.7 +/- 2.4 in controls (p < 0.001). This increased resorption occurred with an inappropriate non-altered bone-forming surface relative to control (% osteoid surface: low-Mg group 2.4 +/- 0.7 vs. controls 2.6 +/- 0.4; % osteoid volume: low-Mg group 0.25 +/- 0.09 vs. controls 0.38 +/- 0.06; number of osteoblasts per millimeter bone surface: low-Mg group 0.9 +/- 0.3 vs controls 1.3 +/- 0.3). No increase in bone-forming surface or osteoblast number despite an increase in OC-resorbing surface and OC number strongly suggests impaired activation of osteoblasts and an uncoupling of bone formation and bone resorption. Our data demonstrate that Mg depletion in the rat alters bone and mineral metabolism which results in bone loss.

Partial deletion of both the spermine synthase gene and the Pex gene in the X-linked hypophosphatemic, gyro (Gy) mouse.

Gy, along with Hyp, is a dominant mutation of the normal gene Pex causing X-linked hypophosphatemia in the mouse. Hemizygous Gy male mice, however, have greater defects in survival, bodily growth, skeletal mineralization, and neurological function than those found in heterozygous Gy females or in Hyp mice. Since the gene for spermine synthase is immediately upstream of the homologous human gene PEX, we compared the effects of the Gy and Hyp mutations on both the spermine synthase gene and the Pex gene. Barely detectable levels of spermine (< 5% of normal) with elevated levels of its precursor, spermidine, were found in organs of Gy male mice compared to normal male littermates. Neither Gy females nor Hyp male mice were significantly affected. Four missing introns of the spermine synthase gene were identified in Gy male mice, suggesting extensive gene disruption. A pseudogene for spermine synthase was also identified in the mouse genome. Pex mRNA was found in several but not all tissues studied in adult normal mice. Pex mRNA was altered in both Gy and Hyp mice. All male Hyp mice were lacking the 3' end of the Pex message, whereas all male Gy mice were deficient at the 5' end. In summary, the Gy mutation is associated with a recessively expressed mutation of the spermine synthase gene, leading to spermine deficiency, and a dominantly expressed mutation of the Pex gene, leading to hypophosphatemia. Alterations in two contiguous genes in Gy may explain the additional phenotypic abnormalities present in the Gy male mouse.

Family, work, and access to health insurance among mature women.

We use a life course approach to address much ignored variation in access to health insurance. Using data from the National Longitudinal Survey of Mature Women, we reinterpret the role of both family and employment characteristics in shaping coverage. Mature women are more likely to be insured as wives than as workers, but that safety net is only available to married women. As a result, unmarried women are two to three times as likely to be uninsured or to rely on public programs such as Medicaid. And because they are significantly less likely to be married to a covered worker, Black women are two to three times more likely to be uninsured or to rely on public programs. Given rising instability in employment and marital status across the life course, stable health insurance coverage can only be attained by universal rather than employment-based or family-based schemes.

Renal expression of Na+-phosphate cotransporter mRNA and protein: effect of the Gy mutation and low phosphate diet.

The X-linked Gy mutation is closely linked, but not allelic, to Hyp and is characterized by rickets, hypophosphatemia, decreased renal tubular maximum for phosphate (Pi) reabsorption (TmP) and a specific reduction in renal brush-border membrane (BBM) Na+-Pi cotransport. Gy mice, like their normal littermates, respond to a low-Pi diet with an increase in BBM Na+-Pi cotransport, but fail to show an adaptive increase in Tmp. Using an antibody raised against the NH2 terminal peptide of the rat renal-specific Na+-Pi cotransporter (NaPi-2) and a NaPi-2 cDNA probe, we examined the effect of the Gy mutation and low-Pi diet (0.03% Pi) on NaPi-2 protein and mRNA abundance. The reduction in BBM Na+-Pi cotransport in Gy mice (51 +/- 5% of normal, P < 0.05) was associated with a decrease in NaPi-2 protein (46 +/- 12% of normal, P < 0.05) and mRNA abundance (76 +/- 5%, P < 0.05). The low-Pi diet elicited a two- to three-fold increase in Na+-Pi cotransport in both normal and Gy mice that was accompanied by a large increase in NaPi-2 protein (10.2-fold in normal and 16.9-fold in Gy mice) and a modest increase in NaPi-2 mRNA (1.3-fold in both mouse strains, P < 0.05). The present data demonstrate that (1) the renal defect in BBM Pi transport in Gy mice can be ascribed to a deficit in NaPi-2 protein and mRNA abundance, (2) both normal and Gy mice respond to low Pi with an adaptive increase in NaPi-2 protein that exceeds the increase in Na+-Pi cotransport activity and NaPi-2 mRNA, (3) the adaptive increase in NaPi-2 protein and mRNA are not sufficient for the overall increase in TmP following Pi restriction.

Effects of altered diet on serum levels of 1,25-dihydroxyvitamin D and parathyroid hormone in X-linked hypophosphatemic (Hyp and Gy) mice.

X-linked hypophosphatemia is a metabolic bone disease occurring in both humans and mice. In mice, two different mutations (Hyp and Gy), occurring at separate but closely linked loci, have been proposed as models for this disease. Varying reports of the Vitamin D status of these two mutants has led us to reexamine the influence of diet on circulating calcitrophic hormones and mineral metabolism in both mutants. Hyp and Gy mice were raised on the B6C3H background, and both normal females and heterozygous mutant females were studied at 10 weeks of age. Animals were fed one of three diets at random: high (1.5% Ca and 1.0% P); medium (0.6% Ca and 0.6% P); or low (0.0% Ca and 0.6% P). After 3 days, serum and urine samples were collected. In comparison to mutant mice fed the high diet, both Hyp and Gy mice fed the low diet had decreased serum calcium levels, and further elevations in both serum alkaline phosphatase and serum parathyroid hormone (PTH). Serum 1,25-dihydroxyvitamin D levels were elevated by both the medium and low diets in all groups of mice over values obtained with the high diet. Mutant mice were significantly higher in serum PTH on all diets compared to normal mice fed the same diet. Mutant mice were not elevated in serum 1,25-dihydroxyvitamin D over normal mice when fed the high diet. However, both Hyp and Gy mice fed the medium and low diets were elevated in serum 1,25-dihydroxyvitamin D over normal mice. Serum PTH levels were correlated to serum 1,25-dihydroxyvitamin D levels with Hyp and Gy mice lying on the same line (r = 0.86; p < 0.0001). In summary, when Hyp and Gy mice are studied on the same genetic background and fed the same diet, similar responses are seen in PTH levels and 1,25-dihydroxyvitamin D levels. Both mutants should be useful in elucidating the pathophysiology of this poorly understood human disease.

Femoral abnormalities and vitamin D metabolism in X-linked hypophosphatemic (Hyp and Gy) mice.

X-linked hypophosphatemia is a genetic bone disease in humans and mice. Two closely linked mutations in mice, Hyp and Gy, cause low plasma phosphate and a rachitic and osteomalacic bone disease. Because of the controversy as to whether Gy is a good model for X-linked hypophosphatemia, the phenotypic severity of these two mutations was compared in both sexes and on two genetic backgrounds. The depression in plasma levels of phosphate was similar in all 10-week-old mutant mice. Male Hyp mice and heterozygous female Hyp mice were affected with similar severity in terms of reduced tail growth, shortened femora, reduced femoral mineral content, and abnormal mineral composition of the femoral matrix. In contrast, male Gy mice did not survive on the C57BL/6J background and were more severely affected than female Gy mice on the B6C3H background. The hybrid B6C3H background ameliorated the bone disease compared with the inbred C57BL/6J background for both mutant strains. There was no evidence of change in the plasma levels of 1,25-dihydroxyvitamin D, duodenal level of vitamin D-dependent calcium-binding protein, or urinary level of calcium in these adult mutant mice. In summary, Gy mice have a sexual dimorphism not present in Hyp mice. These two genes may indicate the presence of multiple gene loci in the human disease, with multiple proteins involved in the pathophysiology of the bone disease.

Response of jejunal phosphate absorption to 1,25-dihydroxyvitamin D(3) stimulationin vivo in young X-linked hypophosphatemic (Hyp) mice.

YoungHyp mice malabsorb phosphate from the jejunum at 4 weeks of age. This has been attributed to both low plasma levels of 1,25-dihydroxyvitamin D and to intestinal resistance to stimulation by 1,25-dihydroxyvitamin D. To differentiate between these two hypotheses, 4 week old normal andHyp mice were treated with 0, 17, 50, or 150 ng/kg/day of 1,25-dihydroxyvitamin D(3) by Alzet osmotic mini pumps (n=10-12/group). After 4 days, the jejunum was isolated by sutures and 0.5 ml 2 mM Na(2)HPO(4) in 150MM: NaCl with 1.0 µCi(32)PO(4) was injected into the lumen. After 8 min, plasma, jejunal tissue and lumenai contents were measured for(32)P content. Absorption was measured as counts removed from the lumen. Both normal andHyp mice responded to the 1,25-dihydroxyvitamin D(3) with increased absorption, increased tissue(32)P and increased plasma(32)P.Hyp mice responded less than normal mice to the 50 ng/kg/day dose in plasma(32)P levels (significant dose by genotype interaction,P<0.05). Plasma was pooled by genotype and dose for the measurement of plasma 1,25-dihydroxyvitamin D. This yielded 13 samples (7 normal and 6Hyp). Absorption of(32)P (r=0.75, p=0.002) and jejunal tissue content of(32)P (r=0.66, p=0.02) were correlated to plasma 1,25-dihydroxyvitamin D. Analysis of covariance revealed a significant difference in phosphate absorption between normal andHyp mice (p=0.02). In conclusion, there is a partial resistance of intestinal phosphate absorption to 1,25-dihydroxyvitamin D stimulation.

X-linked hypophosphatemic Gy mice: renal tubular maximum for phosphate vs. brush-border transport after low-P diet.

We examined the effect of the X-linked hypophosphatemic Gy mutation on the maximal renal tubular reabsorption of phosphate (TmP) and compared the effects of phosphate deprivation on both TmP and Na(+)-dependent phosphate transport in renal brush-border membrane vesicles (BBMV). Adult female normal and Gy mice were fed a control (1.0% P) or low-phosphate (0.03% P) diet for 5 days. For TmP measurement, anesthetized mice were infused intravenously with [3H]inulin and increasing increments of phosphate (0, 0.27, 0.54, and 1.08 mumol/min). TmP was significantly reduced in Gy mice on the control diet. Normal mice responded to the low-phosphate diet by raising their TmP [2.35 +/- 0.12 (n = 9) vs. 3.71 +/- 0.16 (n = 9) mumol/ml glomerular filtrate, mean +/- SE, P < 0.001], whereas in Gy mice, the change was not significant [1.46 +/- 0.10 (n = 10) vs. 1.70 +/- 0.11 (n = 10)]. In contrast, Gy mice did respond to phosphate restriction by increasing the initial-rate Na(+)-dependent phosphate transport in the renal BBMV [314 +/- 11 (n = 5) vs. 1,105 +/- 157 (n = 5) pmol.mg protein-1.6 s-1, P < 0.01] as did normal mice [583 +/- 64 (n = 5) vs. 1,692 +/- 203 (n = 5) pmol.mg protein-1.6 s-1, P < 0.01]. In conclusion, the adaptive increase in Na(+)-phosphate cotransport in the brush-border membrane of the proximal tubule is not sufficient for the overall increase in TmP in the whole kidney in response to dietary phosphate deprivation.

Intestinal malabsorption of 45calcium in young Gy mice, a second model for X-linked hypophosphatemia.

X-linked hypophosphatemia, a common metabolic bone disease in humans and mice (the Hyp and Gy mutations), is characterized by decreased plasma phosphate, decreased renal tubular reabsorption of phosphate, rickets, and osteomalacia. The question of whether intestinal malabsorption of calcium contributes to the bone disease is controversial. Intestinal absorption of 45Ca was studied in three different mouse colonies: Gy on B6C3H background, Hyp on B6C3H background, and Hyp on C57BL/6J background, all at 4 weeks of age. The duodenum was isolated by sutures, and 45Ca in a 150 mM NaCl and 2 mM CaCl2 solution at pH 7.2 was injected into the lumen. Absorption was measured by the amount of 45Ca remaining in the lumen and by the plasma isotope level. The Gy and Hyp mice of both sexes significantly malabsorbed 45Ca at 4 weeks of age compared to normal littermates. Following the 4 week study, intestinal absorption was measured at 2, 7-8, and 12 weeks of age in normal and Gy mice on the B6C3H background. At 2 and 7-8 weeks of age, the Gy males significantly malabsorbed 45Ca compared to their normal littermates. Serum 1,25-dihydroxyvitamin D was not significantly altered in Gy males at 4 weeks of age. This suggests the possibility of resistance of the intestine to stimulation. Malabsorption of calcium in young Gy and Hyp mice may exacerbate the low mineralization in their rachitic bone disease.

Creatinine assay by the fuller's earth procedure or by enzymatic determination is adequate for urine but not plasma of mice.

1. Mouse plasma creatinine measured by fuller's earth (15.1 +/- 0.5(41) microM, mean +/- SE) exceeded the same pools read by HPLC [7.5 +/- 0.2(41); P < 0.001]. 2. For mouse urine, the fuller's earth method (3.26 +/- 0.21 mM) slightly exceeded the HPLC method (2.65 +/- 0.18; P < 0.001) with good correlation (r = 0.915, P < 0.001). 3. An enzymatic method (creatinine PAP, Boehringer-Mannheim Diagnostics) for plasma creatinine (5.2 +/- 0.3 microM) was equivalent to HPLC (6.1 +/- 0.1, NS) but with poor correlation (r = 0.23, NS). 4. Creatinine in the urine agreed closely between HPLC (2.84 +/- 0.12 mM) and the enzymatic procedure (2.95 +/- 0.17, NS) with good correlation (r = 0.845, P < 0.001).

Renal phosphate transport and vitamin D metabolism in X-linked hypophosphatemic Gy mice: responses to phosphate deprivation.

Two closely linked, nonallelic genes, Gy and Hyp, result in X-linked hypophosphatemia in mice. The present studies in Gy mice were undertaken to determine whether renal brush-border membrane Na(+)-phosphate cotransport kinetics and adaptive responses of renal phosphate transport and vitamin D metabolism to phosphate deprivation are comparable in the two mutant strains. Transport studies in purified brush-border membrane vesicles over a phosphate concentration range of 10-500 microM demonstrated that the apparent maximum velocity of the high affinity transport system is significantly decreased in Gy mice (420 +/- 110 vs. 710 +/- 100 pmol/mg protein.6 sec, Gy vs. normal; mean +/- SE; P less than 0.05), whereas the affinity of the cotransporter for phosphate is unchanged (apparent Km, 25 +/- 3 vs. 27 +/- 2 microM; NS). Feeding a low phosphate diet results in a significant fall in plasma phosphate and an increase in brush-border membrane Na(+)-phosphate cotransport in both normal (568 +/- 40 to 1416 +/- 139 pmol/mg protein.6 sec; P less than 0.01) and Gy mice (407 +/- 27 to 1236 +/- 132 pmol/mg protein.6 sec; P less than 0.01). While the low phosphate diet elicited a rise in plasma 1,25-dihydroxyvitamin D in normal mice (51 +/- 12 to 158 +/- 12 pM; P less than 0.01), a fall in plasma hormone levels was evident in phosphate-deprived Gy mice (90 +/- 22 to 23 +/- 11 pM; P less than 0.01). Phosphate deprivation decreased 25-hydroxyvitamin D-24-hydroxylase (24-hydroxylase), the first enzyme in the renal vitamin D catabolic pathway, in normal mice (117 +/- 21 to 69 +/- 8 fmol/mg protein.min), but increased enzyme activity in Gy mice (172 +/- 14 to 240 +/- 18 fmol/mg protein.min; P less than 0.05). Moreover, under both dietary conditions, 24-hydroxylase activity was significantly elevated in Gy mice. The present results demonstrate that hypophosphatemia in Gy mice can be attributed to a decrease in the maximum velocity of the high affinity Na(+)-phosphate cotransport process in renal brush-border membranes. Our results also show that while renal brush-border membrane phosphate transport is appropriately modulated by phosphate in Gy mice, phosphate regulation of vitamin D metabolism is apparently impaired in the mutant strain. The present findings provide evidence for phenotypic similarities between murine Gy and Hyp mutations.

Falling into the Medicaid gap: the hidden long-term care dilemma.

This study describes the income, health, and functional capacity of older Florida residents who fall into the Medicaid gap--those whose incomes are too high to obtain eligibility for Medicaid yet too low to cover the cost of nursing home care as private pay patients--and examines the strategies adopted by their primary caregivers. Our findings suggest that few strategies succeed in alleviating this all but unresolvable problem, that those caught in the gap receive inadequate medical care, and that their primary caregivers face tremendous financial and emotional burdens with little hope for relief.

Assuring quality of care: nursing home resident councils.

Increasing concern over the quality of care in nursing homes has prompted the National Institute of Medicine to recommend that residents have regular input into nursing home administration, primarily through the development of resident councils. Yet little is known of the effectiveness of resident councils. The literature is divided in its assessment of the potential of the institutionalized to represent themselves. Rather than suggesting either that resident councils are impotent or that they are a cure-all, these data, which examine the activities and effectiveness of existing resident councils, suggest that resident councils are successful in accomplishing some but not all of their objectives, that their success is maximized when professional organizers are available to help residents overcome the many barriers they face, and that there are many institutional factors that resident councils are seldom in any position to control.