Mosaicism with a normal cell line and an unbalanced structural rearrangement

Mosaicism with a normal cell line (N) and an unbalanced autosomal structural rearrangement (UASR) is rare. This report describes a case of a newborn female with a karyotype of 46,XX,der(4)t(4;15)(q35;q22)/46,XX. Molecular cytogenetic analysis confirmed the origin of the derivative chromosome 4. Here we discuss this case as well as other cases of mosaic karyotypes involving N/UASR.

Metal working fluid-associated hypersensitivity pneumonitis: an outbreak investigation and case-control study

Occupational exposure to bacterial or fungal antigens has been associated with hypersensivity pneumonitis (HP), an immunologically-mediated pulmonary disease. Between August 1995 and April 1996, 34 employees working in machining and assembly areas of an engine manufacturing plant were clinically diagnosed with HP. Of these, 20 employees met an epidemiologic case definition. In a case-control study, no exposure variables, including duration and intensity of metal working fluid (MWF) exposure, were statistically associated with an increased risk of disease. Neither cases nor controls demonstrated precipitin reactivity against unused samples of the seven MWF and two biocides used in the plant. HP cases had a significantly higher prevalence of positive precipitin reactions to used oil soluble and synthetic MWFs. Reactivity to used but not unused MWF suggests a biocontaminant, probably bacteria or fungi, is the causative antigen in the development of HP in this setting.

The inherited long QT syndrome: from ion channel to bedside

The inherited long QT syndrome is caused by mutations of at least 5 ion channel genes. Mutations of the cardiac sodium ion channel gene and 3 potassium channel genes have been identified to this time. A genetic locus on chromosome 4 has been identified, but no gene has been discovered as of yet. More than 120 mutations of the genes have been discovered. The majority of cases are inherited by autosomal dominant transmission. Syncope occurs in approximately two-thirds of gene carriers, with sudden death in 10% to 15% of untreated patients. The primary electrophysiologic disturbance is delayed recovery of the action potential, because of diverse physiologic perturbations dependent upon the specific ion channel and mutation. The delayed recovery predisposes individuals to the development of early afterdepolarizations and initiation of torsade de pointes arrhythmias. The torsade produces the syncope and sudden death. Patients with self-terminating torsade have syncope, whereas those whose torsade degenerates to ventricular fibrillation experience sudden death. The torsade maintenance appears to be because of complex reentry or repetitive triggered beats, both of which have been proposed as capable of explaining the unique and characteristic QRS morphology of torsade. It is proposed that the degree of dispersion of recovery at the time of torsade determines whether the torsade degenerates to ventricular fibrillation or self-terminates. The signs of long QT syndrome are prolongation of the QT interval on the electrocardiogram and abnormalities of T wave morphology. QTc values average 0.49 seconds and vary somewhat by genotype. Approximately 12% of long QT gene carriers have a normal QTc, < or =0. 44 seconds. Thus, a normal QTc interval does not exclude long QT syndrome. T wave morphology is relatively characteristic for each genotype. Diagnosis is likely with a QTc > or =0.48 seconds in females and > or =0.47 seconds in males. Values between 0.41 and 0.46 seconds require additional evaluation, as the disorder can neither be excluded nor made with those QTc intervals. Diagnosis is enhanced by identification of T wave abnormalities consistent with long QT syndrome. The principal treatment is beta-blocker therapy. Appropriate dosing, with ascertainment of efficacy and compliance with administration, are the key elements in therapeutic success. Molecular physiology-based strategies are being considered, including the use of sodium channel blockers in LQT3 and potassium administration in LQT1 patients.

Naturally occurring GM2 gangliosidosis in two Muntjak deer with pathological and biochemical features of human classical Tay-Sachs disease (type B GM2 gangliosidosis)

Two juvenile sibling male Muntjak deer (Muntiacus muntjak) with histories of depression, ataxia, circling and visual deficits were studied. Cerebrospinal fluid analyses revealed vacuolated macrophages that contained long parallel needle-like intracytoplasmic inclusions. Light microscopically, nerve cell bodies throughout the brain, ganglion cells within the retina and neurons in the myenteric plexuses were variably swollen and had pale granular to finely vacuolated eosinophilic cytoplasm. Neuronal cytoplasm stained specifically with sudan black and Luxolfast blue stains. Within the brain there were occasional axonal spheroids, foci of astrogliosis and scattered microglial cells with abundant pale foamy cytoplasm. Electron microscopy of the brain and retina revealed numerous neurons and ganglion cells, respectively, with multiple membrane-bound structures that contained compact electron-dense membranous whorls and fewer parallel membranous stacks. Thin layer chromatography of total lipid extracts of the cerebral cortex of both cases revealed massive accumulation of G(M2) ganglioside. Crude kidney extracts of the two affected deer were able to hydrolyze 4-methylumbelliferyl beta-GlcNAc, but not 4-methylumbelliferyl beta-GlcNAc-6-sulfate, indicating the defect of beta-hexosaminidase A. Cellogel electrophoresis of the kidney extracts also revealed the deficiency of beta-hexosaminidase A in the two deer. It is concluded that these two deer had the biochemical lesion identical to that of human type B G(M2) gangliosidosis (classical Tay-Sachs disease).

Evidence for a genetic basis for hyperandrogenemia in polycystic ovary syndrome

Our preliminary family studies have suggested that some female first-degree relatives of women with polycystic ovary syndrome (PCOS) have hyperandrogenemia per se. It was our hypothesis that this may be a genetic trait and thus could represent a phenotype suitable for linkage analysis. To investigate this hypothesis, we examined 115 sisters of 80 probands with PCOS from unrelated families. PCOS was diagnosed by the combination of elevated serum androgen levels and Collapse

Key Words Collapse

MESH Headings

• Adolescent
• Adult
• Child
• Female
• Genetic Linkage
• Genetic Predisposition to Disease
• Humans
• Hyperandrogenism/genetics
• Middle Aged
• Polycystic Ovary Syndrome/genetics

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Grants

• M01 RR010732 NCRR NIH HHS
• MO1 RR10732 NCRR NIH HHS
• R01 DK40605 NIDDK NIH HHS
• R01 DK040605 NIDDK NIH HHS
• U54 HD034449 NICHD NIH HHS
• KO8 HD0118 NICHD NIH HHS

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Genome scan of human systemic lupus erythematosus: evidence for linkage on chromosome 1q in African-American pedigrees

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by production of autoantibodies against intracellular antigens including DNA, ribosomal P, Ro (SS-A), La (SS-B), and the spliceosome. Etiology is suspected to involve genetic and environmental factors. Evidence of genetic involvement includes: associations with HLA-DR3, HLA-DR2, Fcgamma receptors (FcgammaR) IIA and IIIA, and hereditary complement component deficiencies, as well as familial aggregation, monozygotic twin concordance >20%, lambdas > 10, purported linkage at 1q41-42, and inbred mouse strains that consistently develop lupus. We have completed a genome scan in 94 extended multiplex pedigrees by using model-based linkage analysis. Potential [log10 of the odds for linkage (lod) > 2.0] SLE loci have been identified at chromosomes 1q41, 1q23, and 11q14-23 in African-Americans; 14q11, 4p15, 11q25, 2q32, 19q13, 6q26-27, and 12p12-11 in European-Americans; and 1q23, 13q32, 20q13, and 1q31 in all pedigrees combined. An effect for the FcgammaRIIA candidate polymorphism) at 1q23 (lod = 3.37 in African-Americans) is syntenic with linkage in a murine model of lupus. Sib-pair and multipoint nonparametric analyses also support linkage (P < 0.05) at nine loci detected by using two-point lod score analysis (lod > 2.0). Our results are consistent with the presumed complexity of genetic susceptibility to SLE and illustrate racial origin is likely to influence the specific nature of these genetic effects.

Stimulation of calcitonin secretion by calcium receptor activators: evaluation using a new, highly sensitive, homologous immunoradiometric assay for rat calcitonin

Current rat calcitonin immunoassays use human calcitonin antisera, and suffer from poor sensitivity, long incubation periods, nonspecific interferences, and unreliability. The homologous immunoradiometric assay (IRMA) for rat calcitonin described here overcomes these problems. Overnight incubation yields a detection limit of 0.4 pg/mL, a standard curve that is linear to >1800 pg/mL, and intra- and interassay coefficients of variation of <7%. Gel filtration chromatography of rat plasma and rat medullary thyroid carcinoma 44-2 cell media showed that the vast majority of immunoreactivity coeluted with calcitonin standard. In 44-2 cells, increasing extracellular Ca2+ concentration or incubation with the calcimimetic compound NPS R-467 markedly increased calcitonin secretion. Plasma calcitonin levels were elevated in rats anesthetized with ketamine/xylazine and in conscious rats with chronic renal insufficiency. Calcitonin levels decreased following EGTA-induced hypocalcemia and were undetectable after thyroparathyroidectomy. In normal conscious rats, plasma calcitonin levels averaged 3-5 pg/mL and increased up to 100-fold following calcium (Ca) infusion or NPS R-467 administration. The assay also quantified calcitonin in plasma of normal and Ca-injected mice. This assay has revealed that plasma calcitonin levels in normal rats are much lower than the detection limits of most existing assays, but can increase by 100-fold on activation of the C-cell Ca2+ receptor.

Decision support and disease management: a logic engineering approach

This paper describes the development and application of PROforma, a unified technology for clinical decision support and disease management. Work leading to the implementation of PROforma has been carried out in a series of projects funded by European agencies over the past 13 years. The work has been based on logic engineering, a distinct design and development methodology that combines concepts from knowledge engineering, logic programming, and software engineering. Several of the projects have used the approach to demonstrate a wide range of applications in primary and specialist care and clinical research. Concurrent academic research projects have provided a sound theoretical basis for the safety-critical elements of the methodology. The principal technical results of the work are the PROforma logic language for defining clinical processes and an associated suite of software tools for delivering applications, such as decision support and disease management procedures. The language supports four standard objects (decisions, plans, actions, and enquiries), each of which has an intuitive meaning with well-understood logical semantics. The development toolset includes a powerful visual programming environment for composing applications from these standard components, for verifying consistency and completeness of the resulting specification and for delivering stand-alone or embeddable applications. Tools and applications that have resulted from the work are described and illustrated, with examples from specialist cancer care and primary care. The results of a number of evaluation activities are included to illustrate the utility of the technology.

Enterohepatic Helicobacters: natural and experimental models

The genus Helicobacter now includes at least 18 formally named species as well as several novel helicobacters that have not been formally named. Eleven Helicobacter spp. colonize the intestinal tract of mammals and birds. In addition, a number of the intestinal helicobacters can colonize the biliary tract and liver, induce hepatitis and one in particular, Helicobacter hepaticus, can cause liver cancer in susceptible strains of mice. Further studies are needed to ascertain whether these helicobacters are also responsible for enterohepatic diseases in humans.

The Wisconsin Firearm-Related Injury Surveillance System

CONTEXT

Firearm-related injuries rank second only to motor vehicle-related injuries as a cause of injury death in Wisconsin.

OBJECTIVE

To evaluate the attributes of the Wisconsin Firearm-Related Injury Surveillance System.

DESIGN

A structured surveillance system evaluation using predetermined criteria.

SETTING

A passive surveillance system linking administrative data from existing state-funded inpatient hospitalization and mortality databases.

PARTICIPANTS

State health department.

MAIN OUTCOME MEASURES

Attributes assessed included simplicity, flexibility, acceptability, sensitivity, predictive value positive, representativeness, timeliness, resources, and data quality.

RESULTS

The use of two existing state databases simplifies data acquisition and linkage. However, hospital discharge and vital records databases are not sufficiently flexible to collect perpetrator and circumstance information. Acceptability is high because of state-mandated reporting to both databases. For firearm-related injuries requiring hospitalization, the system's predictive value positive is 97% when E codes are compared with data from chart reviews. The system is considered timely because annual data from the hospital discharge and vital records systems can be obtained, linked, analyzed, and reported by September of the subsequent year. The system is sustainable largely because existing software is used for annual evaluations, which requires less than 2 weeks of staff time.

CONCLUSIONS

With minimal resources and time, the Wisconsin Firearm-Related Injury Surveillance System uses existing state government databases to describe and report the burden of firearm-related injuries. Additional information on circumstances, perpetrators, and weapons involved are available but additional resources are needed to integrate this information with existing data.

Disseminating medical knowledge: the PROforma approach

Medical knowledge is traditionally disseminated via the publication of documents and through participation in clinical practice. Information technology offers to extend both modes of dissemination, via electronic publishing and virtual reality training, for example. AI promises even more radical changes through the possibility of publishing clinical expertise in the form of expert systems, which assist patient care through active decision support and workflow management. PROforma is a knowledge representation language that is designed to support this new mode of dissemination. It is based on an intuitive model of the processes of care and well-understood logical semantics. This paper provides a description of the language and associated software tools, and discusses its potential roles in, and implications for, medical knowledge publishing.

Disparate effects of mild, moderate, and severe secondary hyperparathyroidism on cancellous and cortical bone in rats with chronic renal insufficiency

The subtotally nephrectomized rat has often been used to investigate the etiology and treatment of secondary hyperparathyroidism (secondaryHPT), but it has been used less frequently to study the effects of secondaryHPT on bone. The recent development of a reliable and specific rat parathyroid hormone (PTH) immunoradiometric assay has provided an opportunity for a thorough investigation of the relationship between circulating, biologically active PTH, and the skeletal abnormalities that occur in chronic renal insufficiency (CRI). Rats were 5/6 nephrectomized (Nx) or sham operated and fed diets with varying levels of Ca and P for 12-14 weeks to induce differing magnitudes of secondaryHPT. Parathyroid gland volume increased by 80%-90% in 5/6 Nx rats in the mild and moderate secondaryHPT groups (2.3- and 7.7-fold higher PTH levels, respectively) and by 3.3-fold in the severe secondaryHPT group (12-fold increase in PTH). The increases in gland volume were caused primarily by cell hyperplasia. Mild secondaryHPT resulted in a 12% decrease in bone mineral density (BMD) across the entire femur, increased osteoclast numbers (N.Oc), unchanged osteoblast numbers (N.Ob), and decreased cancellous bone volume (Cn.BV) in the tibial metaphysis but, apart from increased marrow area, no major changes in cortical bone at the tibio-fibular junction. Moderate secondaryHPT was associated with no changes in femoral BMD, or in tibial Cn.BV, but N.Ob and bone formation rate (BFR) were markedly elevated. Increased periosteal, intracortical, and endocortical BFR and turnover were evident, and contributed to increased cortical porosity (Ct.Po). The changes were exaggerated in the severe secondaryHPT group; BMD was lower in the proximal, but higher in the distal femur, and Cn.BV, N.Ob, N.Oc, and BFR were increased by six-, seven-, three-, and 30-fold, respectively. Endocortical BFR was elevated 31-fold and the extensive Ct.Po (10%) decreased bone strength. However, Ct.Po was not apparent until PTH levels exceeded 500 pg/mL. Thus, in rats with CRI of similar magnitude, progressive secondaryHPT is associated with dramatically different effects on bone. Mild secondaryHPT caused loss of cancellous and endocortical bone, and moderate secondaryHPT tended to maintain both types of osseous tissue, whereas PTH levels >500 pg/mL resulted in substantial cortical bone loss, but cancellous bone gain.

Regulation of murine fetal-placental calcium metabolism by the calcium-sensing receptor

The calcium-sensing receptor (CaSR) regulates PTH secretion to control the extracellular calcium concentration in adults, but its role in fetal life is unknown. We used CaSR gene knockout mice to investigate the role of the CaSR in regulating fetal calcium metabolism. The normal calcium concentration in fetal blood is raised above the maternal level, an increase that depends upon PTH-related peptide (PTHrP). Heterozygous (+/-) and homozygous (-/-) disruption of the CaSR caused a further increase in the fetal calcium level. This increase was modestly blunted by concomitant disruption of the PTHrP gene and completely reversed by disruption of the PTH/ PTHrP receptor gene. Serum levels of PTH and 1, 25-dihydroxyvitamin D were substantially increased above the normal low fetal levels by disruption of the CaSR. The free deoxypyridinoline level was increased in the amniotic fluid (urine) of CaSR-/- fetuses; this result suggests that fetal bone resorption is increased. Placental calcium transfer was reduced, and renal calcium excretion was increased, by disruption of the CaSR. These studies indicate that the CaSR normally suppresses PTH secretion in the presence of the normal raised (and PTHrP-dependent) fetal calcium level. Disruption of the CaSR causes fetal hyperparathyroidism and hypercalcemia, with additional effects on placental calcium transfer.

Homologous up-regulation of vitamin D receptors is tissue specific in the rat

1,25-dihydroxyvitamin D3 (1,25(OH)2D3) receptors (VDR) are expressed in multiple tissues within the body. VDR levels are increased by 1,25(OH)2D3 in intestine and kidney and in numerous cell models. The ability of 1,25(OH)2D3 to affect VDR levels in other target tissues in vivo was studied by assessing VDR levels by the 3H-1,25(OH)2D3 binding assay under varied physiological conditions in the rat. When compared with vitamin D-deficient (-D) controls, rats raised on a normal vitamin D-sufficient (+D) diet showed elevated VDR levels in kidney (391 +/- 53 vs. 913 +/- 76 fmol/g of tissue;p < 0.05), but not in testis, heart, or lung. Up-regulation of the VDR also occurred in kidney of +D rats 1 day after a single 100-ng dose of 1,25(OH)2D3 (454 +/- 43 vs. 746 +/- 113 fmol/mg of DNA; p < 0.05), but no changes were seen in intestine, testis, or lung. Because 1,25(OH)2D3-induced hypercalcemia may independently affect VDR regulation, 1,25(OH)2D3 was infused into -D rats, and normocalcemia was maintained by reduced dietary calcium intake. In this model, the renal VDR was again up-regulated (446 +/- 115 vs. 778 +/- 58 fmol/mg of DNA; p < 0.05), but VDR levels in testis and lung were unaffected. Scatchard analysis and tests of 1,25(OH)2D3 dose (1-100 ng/day for 7 days) and temporal (100 ng/day for 1-7 days) responsiveness further supported the tissue-specific nature of the homologous VDR regulation. Assay of VDR levels by L-1-tosylamido-2-phenylethyl chloromethyl ketone-3H-1,25(OH)2D3 exchange assay ruled out differences in endogenous 1,25(OH)2D3 occupancy as the basis for the observed differences in VDR regulation. Finally, coidentity of the VDR-like sites in kidney versus testis was confirmed by competitive binding analysis comparing their relative affinities for 25(OH)D3 versus 1,25(OH)2D3 (30.5 +/- 6.4 vs. 35.6 +/- 3.6 in kidney and testis, respectively) and by immunoblot analysis using a highly specific monoclonal anti-rat VDR antibody. Thus, under a wide variety of experimental conditions, homologous up-regulation of the VDR occurs in the rat kidney in vivo, but not in several other target tissues which do not regulate plasma calcium homeostasis. Moreover, this differential VDR regulation did not result from secondary changes in plasma calcium, from differential 1,25(OH)2D3 responsiveness in the various tissues, nor from differences in endogenous 1,25(OH)2D3 occupancy of the VDR. These studies thus establish that, in contrast to observations in vitro, the widely described phenomenon of homologous VDR up-regulation in kidney and intestine is not a universal property of 1,25(OH)2D3 target tissues in vivo in the rat.

NPS R-568 halts or reverses osteitis fibrosa in uremic rats

Osteitis fibrosa is a common bone injury associated with secondary hyperparathyroidism (2(o)HPT). NPS R-568 is a phenylalkylamine derivative that acts as an agonist at the cell-surface Ca2+ receptor ("calcimimetic") and inhibits parathyroid hormone (PTH) secretion. In the present study, we tested whether NPS R-568 could ameliorate osteitis fibrosa in partially nephrectomized (Nx) rats with 2(o)HPT. Six months after surgery, Nx rats had developed mild but progressive 2(o)HPT and osteitis fibrosa. Two groups of Nx rats received NPS R-568 (3 and 30 mg/kg body wt x day) by daily gavage for 30 days, which led to a dose-related decrease in serum PTH levels and to a marked reduction in peritrabecular fibrosis (0.96 +/- 0.49% to < 0.1%). Furthermore, 2(o)HPT was associated with decreases in volumetric cortical bone mineral density (vCtBMD) and in cortical bone stiffness at the femoral midshaft. NPS R-568 significantly restored the deficits in vCtBMD and stiffness. These results indicate that NPS R-568 has beneficial effects on bones with osteitis fibrosa by normalizing serum PTH levels.

The effect of dietary enrichment with fish-oil on urinary excretion of N-acetyl-beta-D-glucosaminidase and renal function in proteinuric patients with primary glomerulopathies

The rate of progression of renal disease depends on many factors including serum lipids and tubulo-interstitial injury. Aim of the study was to see whether fish-oil therapy may affect serum lipids and NAG excretion with urine (a marker of tubular cell damage) in humans with renal disease. The effects of dietary fish-oil fatty acids on the serum lipids, NAG urinary excretion and serum arachidonic acid concentration were examined in thirteen primary glomerulonephritic patients with proteinuria and normal renal function. The regular diet enriched with 1650 mg n-3 polyunsaturated fatty acids (18%: 20:5; n-3 EPA and 12%: 22:5; n-3 DHA) was ingested for three months. At the end of fish-oil enriched diet neither creatinine clearance nor urinary protein excretion changed significantly. But serum concentration of HDL and arachidonic acid increased (48.0 +/- 15 vs. 52.0 +/- 14; p < 0.05), (0.47 +/- 0.13 vs. 0.72 +/- 0.29; p < 0.01), respectively. Simultaneously urine NAG excretion and serum LDL decreased (11.2 +/- 7.1 vs. 10.3 +/- 7.3; p < 0.05), (163.0 +/- 57 vs. 149.0 +/- 51, p < 0.01), respectively. We presume that fish-oil supplementation may have a beneficial effect on renal tubular cells in humans and it could be linked with arachidonic acid metabolism.

Evaluation of computer support for prescribing (CAPSULE) using simulated cases

OBJECTIVE

To evaluate the potential effect of computer support on general practitioners' prescribing, and to compare the effectiveness of three different support levels.

DESIGN

Crossover experiment with balanced block design.

SUBJECTS

Random sample of 50 general practitioners (42 agreed to participate) from 165 in a geographically defined area of Oxfordshire.

INTERVENTIONS

Doctors prescribed for 36 simulated cases constructed from real consultations. Levels of computer support were control (alphabetical list of drugs), limited support (list of preferred drugs), and full support (the same list with explanations available for suggestions).

MAIN OUTCOME MEASURES

Percentage of cases where doctors ignored a cheaper, equally effective drug; prescribing score (a measure of how closely prescriptions matched expert recommendations); interview to elicit doctors' views of support system.

RESULTS

Computer support significantly improved the quality of prescribing. Doctors ignored a cheaper, equally effective drug in a median 50% (range 25%-75%) of control cases, compared with 36% (8%-67%) with limited support and 35% (0-67%) with full support (P < 0.001). The median prescribing score rose from 6.0 units (4.2-7.0) with control support to 6.8 (5.8 to 7.7) and 6.7 (5.6 to 7.8) with limited and full support (P < 0.001). Of 41 doctors, 36 (88%) found the system easy to use and 24 (59%) said they would be likely to use it in practice.

CONCLUSIONS

Computer support improved compliance with prescribing guidelines, reducing the occasions when doctors ignored a cheaper, equally effective drug. The system was easy to operate, and most participating doctors would be likely to use it in practice.

PROforma: a general technology for clinical decision support systems

The need for flexible and well understood knowledge representations which are capable of capturing clinical guidelines and protocols for decision support systems is widely recognised. The PROforma method for specifying clinical guidelines and protocols comprises a graphical notation for their design, and a formal knowledge representation language to enable them to be executed by a computer to support the management of medical procedures and clinical decision making. PROforma technology consists of a graphical knowledge editor for the creation of guidelines, and an enactment engine for testing and executing them. This paper provides an overview of the motivation and structure of PROforma, and illustrates its use in the development of clinical applications.

Plasma levels of parathyroid hormone that induce anabolic effects in bone of ovariectomized rats can be achieved by stimulation of endogenous hormone secretion

Parathyroid hormone (PTH) administration increases bone mass in normal and osteopenic animals. However, this treatment currently requires the daily injection of large amounts of PTH, and the relationship of these doses to plasma levels of PTH that are achievable physiologically is unknown. We determined in ovariectomized (ovx) rats: 1) the plasma PTH levels that occur after the subcutaneous injection of graded doses of rat PTH, 2) whether similar PTH levels can be achieved by stimulation of endogenous PTH secretion, and 3) whether a plasma PTH profile that is achievable physiologically is anabolic on bone. Injection of 1, 5, or 25 micrograms/kg rat PTH-(1-34) increased plasma PTH by 46, 164, or 520 pg/mL, respectively, above basal levels within 60 min. Infusion of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid for 2 h reduced plasma Ca2+ by 0.36 mmol/L and produced a total plasma PTH response (area under the plasma PTH curve) similar to that with the 5 micrograms/kg rat PTH injection. Then, 1, 5, or 25 micrograms/kg doses of rat PTH-(1-34) were injected subcutaneously daily for 28 days in 19-week-old rats that were ovx 7 weeks earlier. The 5 and 25 micrograms/kg doses significantly increased bone mineral density in the distal femur and trabecular bone area and average trabecular thickness in the proximal tibia. All doses of PTH significantly increased indices of trabecular connectivity and cancellous bone formation, including double-labeled surface, mineralizing surface, and surface-referent bone formation rate. In conclusion, anabolic effects on bone can be achieved with a plasma PTH profile similar to that attained following stimulation of the parathyroid gland by induced hypocalcemia. These data suggest that agents that transiently increase endogenous PTH secretion may represent a novel means to promote anabolic effects in skeletal tissues.

Base transitions dominate the mutational spectrum of a transgenic reporter gene in MSH2 deficient mice

Tumors derived from individuals with hereditary nonpolyposis colorectal cancer syndrome frequently demonstrate mutations in both alleles of hMSH2, a key gene in DNA mismatch repair (MMR). Sporadic tumors also frequently exhibit MMR deficiency. In keeping with the role of MMR in the maintenance of genome integrity, mice deficient in MSH2 via gene targeting demonstrate a high incidence of thymic lymphomas and small intestinal adenocarcinomas. To investigate the effects of MSH2 deficiency in normal tissues, mice containing a retrievable transgenic lacI reporter gene for mutation detection were crossed with MSH2-/- mice. Mice homozygous for MSH2 deficiency revealed 4.8, 11.0 and 15.2-fold elevations in spontaneous mutation frequency in DNA obtained from brain, small intestine, and thymus, respectively, as compared to heterozygous or wild-type mice. Mutations most frequently recovered from MSH2-/- mice were single base substitutions (77%), particularly base transitions (64%). Frameshifts occurred less frequently (19%) and fell within very short (3-5 bp) mononucleotide runs. Thus the number of key growth control genes potentially impacted by MMR deficiency extends beyond those containing repetitive sequences. These results highlight the capacity for MSH2 deficiency to serve as a potent driving force during the multi-step evolution of tumors.