Effects of empagliflozin on progression of chronic kidney disease: a prespecified secondary analysis from the empa-kidney trial

BACKGROUND

Sodium-glucose co-transporter-2 (SGLT2) inhibitors reduce progression of chronic kidney disease and the risk of cardiovascular morbidity and mortality in a wide range of patients. However, their effects on kidney disease progression in some patients with chronic kidney disease are unclear because few clinical kidney outcomes occurred among such patients in the completed trials. In particular, some guidelines stratify their level of recommendation about who should be treated with SGLT2 inhibitors based on diabetes status and albuminuria. We aimed to assess the effects of empagliflozin on progression of chronic kidney disease both overall and among specific types of participants in the EMPA-KIDNEY trial.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA), and included individuals aged 18 years or older with an estimated glomerular filtration rate (eGFR) of 20 to less than 45 mL/min per 1·73 m2, or with an eGFR of 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher. We explored the effects of 10 mg oral empagliflozin once daily versus placebo on the annualised rate of change in estimated glomerular filtration rate (eGFR slope), a tertiary outcome. We studied the acute slope (from randomisation to 2 months) and chronic slope (from 2 months onwards) separately, using shared parameter models to estimate the latter. Analyses were done in all randomly assigned participants by intention to treat. EMPA-KIDNEY is registered at ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and then followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroups of eGFR included 2282 (34·5%) participants with an eGFR of less than 30 mL/min per 1·73 m2, 2928 (44·3%) with an eGFR of 30 to less than 45 mL/min per 1·73 m2, and 1399 (21·2%) with an eGFR 45 mL/min per 1·73 m2 or higher. Prespecified subgroups of uACR included 1328 (20·1%) with a uACR of less than 30 mg/g, 1864 (28·2%) with a uACR of 30 to 300 mg/g, and 3417 (51·7%) with a uACR of more than 300 mg/g. Overall, allocation to empagliflozin caused an acute 2·12 mL/min per 1·73 m2 (95% CI 1·83-2·41) reduction in eGFR, equivalent to a 6% (5-6) dip in the first 2 months. After this, it halved the chronic slope from -2·75 to -1·37 mL/min per 1·73 m2 per year (relative difference 50%, 95% CI 42-58). The absolute and relative benefits of empagliflozin on the magnitude of the chronic slope varied significantly depending on diabetes status and baseline levels of eGFR and uACR. In particular, the absolute difference in chronic slopes was lower in patients with lower baseline uACR, but because this group progressed more slowly than those with higher uACR, this translated to a larger relative difference in chronic slopes in this group (86% [36-136] reduction in the chronic slope among those with baseline uACR <30 mg/g compared with a 29% [19-38] reduction for those with baseline uACR ≥2000 mg/g; ptrend<0·0001).

INTERPRETATION

Empagliflozin slowed the rate of progression of chronic kidney disease among all types of participant in the EMPA-KIDNEY trial, including those with little albuminuria. Albuminuria alone should not be used to determine whether to treat with an SGLT2 inhibitor.

FUNDING

Boehringer Ingelheim and Eli Lilly.

Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial

BACKGROUND

The EMPA-KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained ≥40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62-0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16-1·59), representing a 50% (42-58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1).

INTERPRETATION

In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease.

FUNDING

Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council.

Environmental DNA metabarcoding for benthic monitoring: A review of sediment sampling and DNA extraction methods

Environmental DNA (eDNA) metabarcoding (parallel sequencing of DNA/RNA for identification of whole communities within a targeted group) is revolutionizing the field of aquatic biomonitoring. To date, most metabarcoding studies aiming to assess the ecological status of aquatic ecosystems have focused on water eDNA and macroinvertebrate bulk samples. However, the eDNA metabarcoding has also been applied to soft sediment samples, mainly for assessing microbial or meiofaunal biota. Compared to classical methodologies based on manual sorting and morphological identification of benthic taxa, eDNA metabarcoding offers potentially important advantages for assessing the environmental quality of sediments. The methods and protocols utilized for sediment eDNA metabarcoding can vary considerably among studies, and standardization efforts are needed to improve their robustness, comparability and use within regulatory frameworks. Here, we review the available information on eDNA metabarcoding applied to sediment samples, with a focus on sampling, preservation, and DNA extraction steps. We discuss challenges specific to sediment eDNA analysis, including the variety of different sources and states of eDNA and its persistence in the sediment. This paper aims to identify good-practice strategies and facilitate method harmonization for routine use of sediment eDNA in future benthic monitoring.

Derivation of the clinical grade human embryonic stem cell line RCe013-A (RC-9)

The human embryonic stem cell line RCe013-A (RC-9) was derived under quality assured compliance with UK regulation, European Union Directives and International guidance for tissue procurement, processing and storage according to Good Manufacturing Practice (GMP) standards. The cell line was derived from a failed to fertilise oocyte voluntarily donated as unsuitable and surplus to fertility requirements following informed consent. RCe013-A (RC-9) shows normal pluripotency marker expression and differentiation to the three germ layers in vitro and in vivo. It has a normal 46XY male karyotype and microsatellite PCR identity, HLA and blood group typing data are available.

In vivo biocompatibility, clearance, and biodistribution of albumin vehicles for pulmonary drug delivery

The development of clinically acceptable albumin-based nanoparticle formulations for use in pulmonary drug delivery has been hindered by concerns about the toxicity of nanomaterials in the lungs combined with a lack of information on albumin nanoparticle clearance kinetics and biodistribution. In this study, the in vivo biocompatibility of albumin nanoparticles was investigated following a single administration of 2, 20, and 390 μg/mouse, showing no inflammatory response (TNF-α and IL-6, cellular infiltration and protein concentration) compared to vehicle controls at the two lower doses, but elevated mononucleocytes and a mild inflammatory effect at the highest dose tested. The biodistribution and clearance of ¹¹¹In labelled albumin solution and nanoparticles over 48 h following a single pulmonary administration to mice was investigated by single photon emission computed tomography and X-ray computed tomography imaging and terminal biodistribution studies. ¹¹¹In labelled albumin nanoparticles were cleared more slowly from the mouse lung than ¹¹¹In albumin solution (64.1 ± 8.5% vs 40.6 ± 3.3% at t = 48 h, respectively), with significantly higher (P < 0.001) levels of albumin nanoparticle-associated radioactivity located within the lung tissue (23.3 ± 4.7%) compared to the lung fluid (16.1 ± 4.4%). Low amounts of ¹¹¹In activity were detected in the liver, kidneys, and intestine at time points > 24 h indicating that small amounts of activity were cleared from the lungs both by translocation across the lung mucosal barrier, as well as mucociliary clearance. This study provides important information on the fate of albumin vehicles in the lungs, which may be used to direct future formulation design of inhaled nanomedicines.

Identifying viable regulatory and innovation pathways for regenerative medicine: a case study of cultured red blood cells

The creation of red blood cells for the blood transfusion markets represents a highly innovative application of regenerative medicine with a medium term (5-10 year) prospect for first clinical studies. This article describes a case study analysis of a project to derive red blood cells from human embryonic stem cells, including the systemic challenges arising from (i) the selection of appropriate and viable regulatory protocols and (ii) technological constraints related to stem cell manufacture and scale up to clinical Good Manufacturing Practice (GMP) standard. The method used for case study analysis (Analysis of Life Science Innovation Systems (ALSIS)) is also innovative, demonstrating a new approach to social and natural science collaboration to foresight product development pathways. Issues arising along the development pathway include cell manufacture and scale-up challenges, affected by regulatory demands emerging from the innovation ecosystem (preclinical testing and clinical trials). Our discussion reflects on the efforts being made by regulators to adapt the current pharmaceuticals-based regulatory model to an allogeneic regenerative medicine product and the broader lessons from this case study for successful innovation and translation of regenerative medicine therapies, including the role of methodological and regulatory innovation in future development in the field.

Threshold and subthreshold post-traumatic stress disorder in bulimic patients: prevalences and clinical correlates

OBJECTIVE

Post-traumatic stress disorder (PTSD) is believed to impact the clinical presentation and treatment response in bulimia nervosa (BN), but available data do not clarify the clinical implications of subthreshold forms of PTSD, believed to affect a sizable proportion of bulimic women.

METHOD

In 78 women with BN and 61 women who ate normally, we assessed lifetime rates of threshold and subthreshold PTSD, and examined clinical correlates.

RESULTS

Among bulimic women, rate of threshold PTSD was 17.9% and rate of a formally-defined, subthreshold PTSD syndrome was 41.0%. Bulimic women with subthreshold PTSD did not differ from women with threshold PTSD on any clinical indices (except generalized anxiety disorder) and both groups with a PTSD-spectrum syndrome displayed worse psychiatric symptoms than did bulimic women without PTSD symptoms.

DISCUSSION

Threshold and subthreshold variants of PTSD occur substantially more frequently among bulimic women than they do among normal-eater women. Intriguingly, bulimic women with subthreshold PTSD appear to be at similar risk for psychiatric morbidity as are those with threshold PTSD. The preceding suggests that formal, categorical concepts of PTSD may not fully reflect important trauma correlates seen in women with BN.

Antimicrobial potential of bioactive bone cements

Poly(methyl methacrylate) (PMMA) based bone cement is widely used to anchor artificial joints. In recent years, antibiotics have been incorporated in bone cements and administered systemically to either prevent or reduce the severity of infections. Certain antibiotics, such as tobramycin or vancomycin antibiotics have been incorporated at high concentrations into PMMA bone cements when dealing with infected hip joints, however, the inclusion of some antibiotics adversely affect the mechanical properties of the cement. Furthermore, studies have indicated that the incorporation of gentamicin in PMMA cements does not have a statistically significant effect on the biofilm formation of species such as Staphylococcus aureus (S. aureus). Bioactive glasses have been shown to have numerous applications in the biomedical field because of their properties in bonding to both hard and soft tissues. Bioglass(R) undergoes surface dissolution in a physiological environment forming a hydroxycarbonate apatite layer and, in addition, exhibits the anti-inflammatory properties. Recent studies have shown that two paste bioactive bone cement systems that use Bioglass(R) as filler exhibit physical and mechanical properties comparable to PMMA cements with low polymerization exotherm and better mechanical properties with improved adhesion to bone and implant surfaces. In this study, Bioglass(R) containing two paste bone cements were investigated for their potential bacteriostatic properties and compared with PMMA cements with and without antibiotics. The results of this study indicated that the PMMA cement containing the antibiotic, gentamycin and the Bioglass(R) containing cements both pre- and post-immersion in simulated body fluid (SBF) for brief periods showed the inhibition zones were not statistically significantly different in their average size for any of the three bacterial species, namely Pseudomonas aeruginosa, S. aureus and Staphylococcus epidermidis. However, the PMMA cement without any antibiotic, namely gentamycin (CMW1) did not show any inhibition zones around the specimens for any of the three bacterial species. It was also noted that both Bioglass(R) filled bioactive cements immersed in SBF showed statistically significant increases in inhibition zones for all three specimens compared to specimens that were not immersed (p<0.001).

Tuberculosis in an indigenous young white south Wales population

Concerns about tuberculosis in young people in two linked deprived non-metropolitan communities triggered an investigation into local disease incidence and control measures. A pragmatic case-finding exercise, epidemiological enquiry and DNA genotyping were carried out to establish incidence and connections between cases over a five-year period. Of the 91 cases identified, 88 were from the white indigenous population. Approximately one third of cases were aged under thirty. Eight disease clusters were identified. Epidemiological investigation found spurious links between these, and DNA genotyping was necessary to clarify links. Seven cases and several contacts had been in prisons throughout the United Kingdom. Index cases under thirty generated more contacts, more contacts needing prophylaxis and more secondary cases than older patients. The workload resulting from tuberculosis control in younger cases was considerable. Tuberculosis remains an important problem in this population.

Increased presence of eosinophilic granulocytes expressing transforming growth factor-beta1 in collagenous colitis

BACKGROUND

Collagenous colitis is a disease characterized by chronic watery diarrhea, and on microscopic examination of colonic tissue, a typical thickening of the subepithelial collagen layer is seen. The etiology and pathophysiology behind this disease state are largely unknown.

METHODS

We have used in situ hybridization and immunohistochemistry to study the expression of transforming growth factor (TGF) -beta1, a growth factor with the capacity to cause accumulation of collagen in tissues, in collagenous colitis. Colonic pinch biopsy specimens from a total of 34 patients were investigated: 17 patients with collagenous colitis and 17 controls.

RESULTS

In patients with collagenous colitis there was increased expression of the TGF-beta1 gene compared with controls, as visualized by in situ hybridization. The vast majority of the TGF-beta1-expressing cells were eosinophils, both in collagenous colitis and controls, but there were also scattered fibroblastic and histiocytic stromal cells. Immunohistochemistry showed the presence of TGF-beta1, mainly in eosinophils, in the colonic mucosa. Morphometric quantification showed 603 +/- 192 eosinophils/mm2, (mean +/- standard error of the mean) in the colonic mucosa of patients with collagenous colitis compared with 30 +/- 7 eosinophils/mm2 in the controls.

CONCLUSIONS

The present results suggest that eosinophils expressing TGF-beta1 may be of pathophysiologic importance in the connective tissue remodeling seen in collagenous colitis.

Anorexia in rats infected with the nematode, Nippostrongylus brasiliensis: experimental manipulations

Nippostrongylus brasiliensis induces a biphasic anorexia in laboratory rats, the first phase coincident with lung invasion (ca day 2) and the second when the worms mature in the intestine (ca day 8). Using the anthelminthic, mebendazole (MBZ), N. brasiliensis infections of the rat were eliminated between the first and second anorexic episodes. This intervention prevented the expression of the second phase of anorexia. Rats exposed to a second infection with N. brasiliensis, 3 weeks after the primary infection, exhibited only a first phase anorexic response which was not influenced by MBZ termination of the primary infection. The lower cumulative food intake and weight gain of all infected rats after 8 days of infection were accompanied by elevated plasma insulin and, in some individuals, by elevated plasma leptin, compared with uninfected controls and previously-infected MBZ-treated rats. Messenger RNA levels for neuropeptide Y were higher in the hypothalamic arcuate nucleus of 8-day infected rats than in recovering MBZ-treated animals. Inoculation of rats with heat-killed N. brasiliensis larvae failed to induce anorexia and did not alter the severity of biphasic anorexia on subsequent injection of viable larvae. The first anorexic episode is therefore dependent upon viable migrating larvae. The second phase of anorexia clearly requires the continuing presence of the parasite beyond the lung phase. Viable migrating larvae are also required to confer 'resistance' to reinfection.

Characterization and distribution of ferritin binding sites in the adult mouse brain

Studies on iron uptake into the brain have traditionally focused on transport by transferrin. However, transferrin receptors are not found in all brain regions and are especially low in white matter tracts where high iron concentrations have been reported. Several lines of research suggest that a receptor for ferritin, the intracellular storage protein for iron, may exist. We present, herein, evidence for ferritin binding sites in the brains of adult mice. Autoradiographic studies using 125I-recombinant human ferritin demonstrate that ferritin binding sites in brain are predominantly in white matter. Saturation binding analyses revealed a single class of binding sites with a dissociation constant (K(D)) of 4.65 x 10(-9) M and a binding site density (Bmax of 17.9 fmol bound/microg of protein. Binding of radiolabeled ferritin can be competitively displaced by an excess of ferritin but not transferrin. Ferritin has previously been shown to affect cellular proliferation, protect cells from oxidative damage, and deliver iron. The significance of a cellular ferritin receptor is that ferritin is capable of delivering 2,000 times more iron per mole of protein than transferrin. The distribution of ferritin binding sites in brain vis-à-vis transferrin receptor distribution suggests distinct methods for iron delivery between gray and white matter.

Nigrothalamic projections and nigrothalamocortical pathway to the medial agranular cortex in the rat: single- and double-labeling light and electron microscopic studies

Although the rat medial agranular cortex (AGm) has been implicated in a variety of motor functions, the source of the afferents impinging upon thalamic neurons projecting to the AGm is not directly known. The main purpose of this study was to determine whether the AGm is a major recipient of the nigrothalamocortical pathway. This issue was addressed by two sets of experiments. First, the organization of the nigrothalamic projections was studied by light and electron microscopy following injections of the anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHA-L) into the pars reticulata of the substantia nigra (SNR). The major finding of this study was the disclosure of a heretofore unknown projection to the rostromedial part of the ventral anterior-ventral lateral complex (VAL). This projection originates exclusively from the ventral portion of the SNR and is comparable in strength to the well-known nigrothalamic projection to the ventromedial nucleus (VM). Electron microscopic examination revealed differences in the synaptic organization of nigral terminals in the VAL and the VM. A large proportion of the labeled terminals in the VAL was involved in axosomatic synapses, whereas, in the VM, the axosomatic synapses were rare, and 67% of nigral terminals were found in contact with thin dendrites. To assess a possible disynaptic nigrothalamocortical pathway to the AGm, a double-labeling strategy combining PHA-L injections in the SNR and pressure injections of the retrograde tracer, cholera toxin subunit B (CTB) in the AGm was employed. The greatest density of CTB-labeled neurons was found in the rostral and central portion of the VAL, coincident with the nigrothalamic labeling originating from the ventral SNR. Electron microscopic analysis confirmed that some of the PHA-L-labeled terminals established synaptic contacts with the CTB-labeled cell bodies and large dendrites. In conclusion, our findings indicate that there exist two different nigrothalamocortical pathways through the motor thalamus in the rat. The SNR-VAL-AGm cortical projection may play a role in oculomotor functions, whereas the SNR-VM-cortical pathway has been implicated in arousal mechanisms.

Human patched (PTCH) mRNA is overexpressed consistently in tumor cells of both familial and sporadic basal cell carcinoma

Recently, a human homologue of the Drosophila patched gene, PTCH, was identified as a putative tumor suppressor mutated in both hereditary and sporadic basal cell carcinomas. Because PTCH controls its own transcription, inactivating mutations in PTCH may lead to overexpression of mutant PTCH mRNA due to loss of autoregulation. The present study is aimed at evaluating whether deregulation of PTCH mRNA expression is a general feature of BCCs of varying histological growth pattern and malignant potential. Irrespective of histological subtype, PTCH mRNA was overexpressed consistently as determined by in situ hybridization in all of the sporadic (n = 16) and hereditary (n = 20) tumors examined. PTCH expression was found in all of the tumor cells but appeared stronger in the peripheral palisading cells. PTCH mRNA was not detected in adjacent nontumor epidermal cells or in other parts of the epidermis. In the majority of tumors (20 of 36), nuclear immunostaining for p53 was found in scattered cells, whereas seven tumors completely lacked p53 immunoreactivity. Our finding of an up-regulation of PTCH mRNA levels in all of the BCCs analyzed indicates that deregulation of the PTCH signaling pathway constitutes an early rate-limiting event in BCC development.

Collagenase-3 (MMP-13) is expressed during human fetal ossification and re-expressed in postnatal bone remodeling and in rheumatoid arthritis

To explore possible physiologic functions for the metalloproteinase collagenase-3, we have examined its temporal and spatial expression during human fetal development. Except for mesenchymal cells in the umbilical cord at 4 weeks of gestation, signal for collagenase-3 mRNA was confined to mineralizing skeletal tissue and detected in hypertrophic chondrocytes and osteoblastic cells involved in ossification beginning at 10 weeks and continuing through gestation. These cells were also immunoreactive with collagenase-3 antiserum, indicating their ability to produce collagenase-3 protein. In osteoblastic cells, the expression of membrane-type 1 metalloproteinase and 72-kd gelatinase mRNA, which have the capacity to activate collagenase-3 in vitro, colocalized with that of collagenase-3. In postnatal tissues, collagenase-3 was re-expressed in processes involving skeletal remodeling, such as bone cysts and ectopic bone and cartilage formation. Multinucleated osteoclasts were consistently negative for collagenase-3. Furthermore, in patients with seropositive rheumatoid arthritis, expression of collagenase-3 was prominent in articular cartilage, and collagenase-3 protein was detected by immunoblotting in synovial fluids. Consistent with its substrate specificities, a plausible function for collagenase-3 in these processes is to preferentially degrade type II collagen, thus serving a role during primary ossification, in skeletal remodeling, and in destructive joint disease.

Description of a novel plasmid replicative origin from a genetically distinct family of conjugative plasmids associated with phytosphere microflora

A novel replicative origin (oriV) from a conjugative, mercury resistance plasmid (pQBR11, 304 kbp) has been cloned and sequenced. Homology to the pQBR11 oriV-containing 3.55 kbp BamHI fragment (pCV1200) was restricted to one of five genetically distinct classes (group I) of narrow host range, mega-plasmids that persist as a genetic component of the pseudomonad community indigenous to the microflora of sugar beet. The oriV of pQBR11 was located within a unique sequence of 300 bp which initiated the replication of pUC derived suicide vectors in Pseudomonas putida UWC1. The limited size of the DNA sequence required to initiate replication, and the presence of two 15/16 bp directly repeated motifs, indicate that this group of mega-plasmids contain a single origin of replication, which initiates replication via a host-polymerase dependent rolling circle mechanism.

Regulation of cellular Mg2+ by Saccharomyces cerevisiae

Regulation of cellular Mg2+ by S. cerevisiae was investigated. The minimal concentration of Mg2+ that results in optimal growth of S. cerevisiae is about 30 microM and a half-maximum growth rate is attained at about 5 microM Mg2+. Since the plasma membrane has an electrical potential greater than 100 mV, passive equilibration of Mg2+ across the plasma membrane would provide sufficient cytosolic Mg2+ (0.1-1 mM). The total cellular Mg2+ of cells grown in synthetic medium containing 1 mM Mg2+ is about 400 nmol/mg protein, most of which is bound to polyphosphate, nucleic acids, and ATP. Total cellular Mg2+ decreases to about 80 nmol/mg protein as the Mg2+ in synthetic growth medium is reduced to 0.02 mM, but remains relatively constant in growth medium containing 1 to 100 mM Mg2+. Cells shifted into Mg(2+)-free medium continue to grow by utilizing the vacuolar Mg2+ stores. Mg(2+)-starved cells replenish vacuolar Mg2+ stores with a halftime of 30 min. following the addition of 1 mM Mg2+ to the growth medium. The data indicate that cytosolic Mg2+ is maintained by the regulation of Mg2+ fluxes across both the vacuolar and plasma membranes.

Stromelysin-3 mRNA associated with myofibroblasts is overexpressed in aggressive basal cell carcinoma and in dermatofibroma but not in dermatofibrosarcoma

Stromelysin-3 is produced in the stroma of various malignant tumors, and in breast carcinoma there seems to be a positive correlation between aggressive disease and intensity of stromelysin-3 expression, suggesting that stromelysin-3 participates in the tumor spread. In basal cell carcinoma, previous findings on stromelysin-3 have been inconclusive in this respect. Our study was undertaken to determine the pattern of stromelysin-3 production in relation to different histologic subtypes and stromal reactions in basal cell carcinoma. By in situ hybridization, stromelysin-3 mRNA was detected in stromal fibroblastic cells in 51/56 samples. Furthermore, there was a significant correlation between strong signal for stromelysin-3 mRNA and infiltrative tumor growth. In all tumors, there was ongoing collagen synthesis as shown by a signal for procollagen I mRNA; this signal co-localized with stromelysin-3 around tumor nests. Our findings suggest a link between stromelysin-3 and fibrotic stromal response, which prompted us to evaluate the expression of stromelysin-3 in other fibrotic skin tumors. Interestingly, stromelysin-3, co-localizing with procollagen I mRNA, was consistently expressed in lesional cells in dermatofibromas (19/19), but not in dermatofibrosarcomas (0/7). Thus, our results indicate that in addition to being a marker for malignant disease, stromelysin-3 is produced by fibroblastic cells associated with benign fibrosis. A subset of cells producing stromelysin-3 appears to be myofibroblasts as demonstrated by immunoreactivity for alpha smooth muscle actin in both basal cell carcinoma and dermatofibroma.

Visualization of G1 chromosomes: a folded, twisted, supercoiled chromonema model of interphase chromatid structure

We have used light microscopy and serial thin-section electron microscopy to visualize intermediates of chromosome decondensation during G1 progression in synchronized CHO cells. In early G1, tightly coiled 100-130-nm "chromonema" fibers are visualized within partially decondensed chromatin masses. Progression from early to middle G1 is accompanied by a progressive uncoiling and straightening of these chromonema fibers. Further decondensation in later G1 and early S phase results in predominantly 60-80-nm chromonema fibers that can be traced up to 2-3 microns in length as discrete fibers. Abrupt transitions in diameter from 100-130 to 60-80 nm along individual fibers are suggestive of coiling of the 60-80-nm chromonema fibers to form the thicker 100-130-nm chromonema fiber. Local unfolding of these chromonema fibers, corresponding to DNA regions tens to hundreds of kilobases in length, reveal more loosely folded and extended 30-nm chromatin fibers. Kinks and supercoils appear as prominent features at all observed levels of folding. These results are inconsistent with prevailing models of chromosome structure and, instead, suggest a folded chromonema model of chromosome structure.

Notes on a light and electron microscopic double-labeling method combining anterograde tracing with Phaseolus vulgaris leucoagglutinin and retrograde tracing with cholera toxin subunit B

Investigations of monosynaptic connections in the central nervous system have been hindered by the lack of compatible markers that can be used at both light and electron microscopic levels. In attempts to determine synaptic contacts between fibers originating in the substantia nigra and neurons projecting to the spinal cord, we have developed a double immunolabeling technique using anterograde transport of Phaseolus vulgaris leucoagglutinin (PHA-L) and retrograde transport of unconjugated cholera toxin subunit B (CTB). In this report, we describe technical modifications which consistently produced superior labeling together with adequate ultrastructural preservation of the tissue and discuss the advantages of the two tracers.

Quantitation of medullary astrogliosis in sudden infant death syndrome

One of the few relatively consistent pathologic observations in sudden infant death syndrome (SIDS) is astrogliosis of the brain stem. Astrogliosis is a nonspecific reactive process and its cause in SIDS, although still uncertain, is postulated to be hypoxia-ischemia. In this study, the distribution of reactive astrocytes throughout the rostral-caudal extent of the medulla has been determined. Although astrogliosis was present throughout the length of the medulla, it reached a maximum at levels 50-75% of total length, with 0% at the pontomedullary junction. Counting every reactive astrocyte through serial sections of the medulla seems unwarranted in view of the nonspecificity of the astrocytic response. This report proposes a practical approach to the quantitation of reactive astrocytes in SIDS by examining a representative sample of medulla midway through its length.

Rehabilitation of the disabled adolescent: experience with a local authority assessment centre

School leavers and young adults who are severely physically disabled pose particular problems for habilitation and rehabilitation. A local authority unit, the Fourways Assessment Centre, has been providing a comprehensive service to this group of people for the past 10 years. Rather than operating as an independent self contained unit it has been closely integrated with the local authority social services and educational services.