Transgenic animal models: new avenues in cardiovascular physiology

Coryneform bacteria and yeasts of 21 brick cheeses from six German dairies, produced by using undefined ripening cultures, were identified. Arthrobacter nicotianae, Brevibacterium linens, Corynebacterium ammoniagenes, Corynebacterium variabilis and Rhodococcus fascians were found in significant numbers. Out of 148 coryneform isolates 36 could not be identified at the species level. With the exception of a large rennet cheese, the coryneform microflora of rennet and acid cured cheeses were similar, but the cheeses had clearly different yeast populations. Debaryomyces hansenii and Galactomyces geotrichum prevailed in rennet cheeses while Kluyveromyces marxianus and Pichia membranaefaciens were the main species found in acid cured cheese. The dominance of Yarrowia lipolytica probably indicates an improper yeast population, resulting in poor cheese quality. Some of the species identified are potential candidates for designing a defined ripening culture for rennet red smear cheese.     

Transgenic models for eye malformations

Several lines of transgenic mice developing eye malformations have been described in the literature and appear to be of increasing interest for the study of eye teratology in humans, since gene expression and regulation can be studied in the developing animal. Transgenic applications are briefly described here and an overview of existing transgenic mouse models carrying different eye abnormalities is given according to the major diagnosis (e.g., cataract, microphthalmia, anterior segment dysgenesis, retinal dysplasia). Interestingly, many transgenic models exhibit pathological findings similar to those observed in human pediatric ophthalmology. Unfortunately, detailed embryological studies in transgenic mice bearing congenital eye malformations are not available for all lines. Thus, the importance of creating further transgenic models to study the function of morphogenes and growth factors in eye development is also discussed.     

Transgenic models of Huntington's disease

CAG/polyglutamine expansion has been shown to form the molecular basis of an increasing number of inherited neurodegenerative diseases. The mutation is likely to act by a dominant gain of function but the mechanism by which it leads to neuronal dysfunction and cell death is unknown. The proteins harbouring these polyglutamine tracts are unrelated and without exception are widely expressed with extensively overlapping expression patterns. The factors governing the cell specific nature of the neurodegeneration have yet to be understood. Upon a certain size threshold, expanded CAG repeats become unstable on transmission and a modest degree of somatic mosaicism is apparent. Similarly, the molecular basis of the instability and its tissue specificity has yet to be unravelled. Recent reports describing the first mouse models of CAG/polyglutamine disorders indicate that it will be possible to model both the pathogenic mechanism and the CAG repeat instability in the mouse. This has great potential and promise for uncovering the molecular basis of these diseases and developing therapeutic interventions.     

Dimercaptosuccinic acid distribution in renal tubular acidosis

A 99Tcm dimercaptosuccinic acid (DMSA) scan performed after a urinary tract infection demonstrated an unusual pattern of isotope uptake, promoting further investigations leading to a diagnosis of renal tubular acidosis secondary to nephropathic cystinosis. This is known to affect isotope imaging but a unique feature in this undiagnosed case was the uncorrected metabolic acidosis, which had further altered the distribution of the DMSA. It is noteworthy because other patients referred for imaging with renal disease may also have abnormalities of acid base balance.     

Regulating factors of renal tubular hypertrophy

Understanding the mechanisms of tubular hypertrophy is important because these cells simply represent the bulk of the nephron, and there is a convincing link between early tubular enlargement and the progression of renal disease. It seems reasonable to assume that cytokines and polypeptide growth factors including inhibitory factors such as TGF-beta induce in concert, rather than as single factors, tubular hypertrophy. The important observations that the activation of the intrarenal renin-angiotensin axis is altered in situations associated with renal growth, and that ACE inhibitors abolish compensatory hypertrophy in many models provided for us a basis for investigating the growth effects of ANG-II on cultured proximal tubular cells. ANG-II induces, as a single factor, tubular hypertrophy in vitro, and this growth effect has been studied in detail on a molecular levels. Endogenous induction of TGF-beta by ANG-II is important in the peptide-mediated hypertrophy. While some genes induced by ANG-II, such as immediate early genes, are engaged as part of a generalized activation of the nucleus, the hypertrophic effects may be mediated by a set of novel genes which may be part of an identifiable genetic program causing tubular enlargement. The identification of hypertrophy genes may offer new insight into the modulation of cytoplasmic enlargement and its interface with elements that control the cell cycle and may provide a tool for further therapeutic interventions.     

Transgenic mouse models for tumor suppressor genes

A 2-mo experiment with the white Sprague-Dawley (SD) rats was conducted to investigate the effect of the water extracts of black tea (BTWE) and green tea (GTWE) and the black tea leaves (BTF) and the green tea leaves (GTF) on the metabolism of mineral elements. One hundred eight 12-mo-old white SD rats were randomly divided into 13 groups; 6 of these drank the BTWE or GTWE in which the water extracts concentrations of black tea or green tea were, respectively, 0.6%, 1.2%, and 2.4%, and 6 of these had black tea leaves (BTF) and green tea leaves (GTF) added in which the contents of BTF or GTF were, respectively, 0.5%, 1.0%, and 2.0%, one of these was control. The teas and their water extracts could promote the absorption of manganese and copper. In GTF, BTF, GTWE, and BTWE, the apparent absorption rates of manganese were significantly increased. The manganese contents in the tibia were also elevated, and the differences between GTWE and GTF were significant. The apparent absorption rates of copper and the copper contents in the tibia were increased, but not significantly. The teas and their water extracts inhibited the absorption of calcium (p > 0.05) and iron (p < 0.05). The cerebrum calcium contents were significantly decreased, but the contents of calcium and iron in tibia were not significantly changed. Compared with the control, although the apparent absorption rates of aluminum in all experimental groups were not observed to be different, the aluminum contents in the tibia (p > 0.05) and cerebrum (p < 0.05) were increased. GTF and GTWE decreased the apparent absorption rates of zinc, but BTF and BTWE increased them; the zinc contents in tibia were a little improved, whereas its contents in the cerebrum were gradually decreased with the increase of tea leaves dose and tea concentration.     

Transgenic animals as models of neurodegenerative diseases in humans

Neurodegenerative diseases are of major socioeconomic importance and represent an enormous challenge for the scientific and medical communities. Advances in molecular genetics during the past decade have begun to provide approaches for the establishment of animal models for these disorders using transgenic technology. Their analysis will lead to better understanding of disease pathogenesis and will be invaluable for the identification of novel diagnostic and therapeutic agents. With the current pace of genomic research, the generation of transgenic animal models, reproducing in full the pathology and symptoms of even complex disorders such as Alzheimer's disease, must now be considered achievable.     

Molecular approaches to renal physiology and therapeutics

The relationship of long-term and heavy exposure of nonnarcotic analgesics to the risk of chronic renal disease (CRD) has been the object of intensive clinical, pharmacologic, toxicologic, and epidemiologic research for 4 decades. The clinical evidence of an increased risk has been suggestive but inconclusive. The experimental evidence in animal models has been inconsistent, and in any case it cannot be generalized to humans. The epidemiologic evidence has been unsatisfactory for the most part: most of the early studies had severe methodologic limitations; moreover, they related mainly to phenacetin-containing drugs and did not have useful information on other analgesics. Since 1980, 9 analytical epidemiologic studies have attempted to confirm that a causal relationship exists between phenacetin or other analgesics and CRD. In the aggregate, despite methodologic flaws, this work suggests that excessive use of phenacetin-containing analgesics probably causes renal papillary necrosis and interstitial nephritis. In contrast, there is no convincing epidemiologic evidence that nonphenacetin-containing analgesics (including acetaminophen, aspirin, and mixtures of these two compounds) or that nonsteroidal antiinflammatory drugs cause CRD. Moreover, the nature of dose-response relationships, the types of renal disease possibly caused by analgesics, and the cofactors that might be related both to analgesic use and to the development of CRD in humans are still uncertain, and the pathologic mechanisms of analgesic-induced CRD in humans remain unclear. It may take many years before all the outstanding issues are settled. Until they are, as a matter of good clinical judgment it would be prudent to consider all analgesics as potentially nephrotoxic and, as much as possible, to avoid excessive, protracted use.     

Effect of retabolil on renal tubular secretion

Chronic experiments on dogs and rats showed retabolil, an anabolic steroid (given in a dose of 2-5 mg/kg for 7 days) to produce an increase in renal tubular secretion of cardiotrast. Rats displayed a simultaneous elevation in the content of protein and RNA in the kidney cortex. The data obtained were interpreted from the aspect of protein nature of carriers taking part in the renal secretory transport.     

Distal renal tubular acidosis presenting with rhabdomyolysis

Severe hypokalemia is an uncommon cause of rhabdomyolysis. We describe a patient, 28-year-old woman, with distal renal tubular acidosis (DRTA) who developed severe hypokalemia and rhabdomyolysis. Muscle biopsy shows focal muscular necrosis mainly in type II muscle fibers and mild macrophagic reaction. After correcting the acidosis with oral administration of alkalinizing salts, clinical and laboratory improvement was seen. This clearly establish a causal relationship between the positive acid balance, hypokalemia and the muscular manifestation in DRTA.     

Transgenic mouse models of lipoprotein metabolism and atherosclerosis

Lipoprotein transport genes have either been added to the germ line of mice by transgenic techniques or knocked out by homologous recombination in embryonic stem cells. The resultant over- or underexpression of these genes has resulted in new insights about how these genes function in the body and their role in lipoprotein metabolism. Either singly or in combination, these genetic modifications can be used to engineer the mouse to make it a better model for human lipoprotein disorders and atherosclerosis.     

Verotoxins induce apoptosis in human renal tubular epithelium derived cells

We have developed an animal model to study human delayed-type hypersensitivity reactions. Previous studies in humans have shown after tuberculin injection the presence of a mononuclear cell infiltration, with almost no eosinophils, associated with a preferential Th-1-type cytokine profile. Human skin graft obtained from tuberculin-reactive donors was grafted onto the back of severe combined immunodeficient mice. After healing, mice were reconstituted intraperitoneally with peripheral mononuclear cells. Tuberculin and diluent were injected intradermally, and skin biopsies were performed 72 hours later. Skin grafts were divided into two parts, one for immunohistochemistry and one for in situ hybridization studies. Immunohistochemistry was performed on cryostat sections using the alkaline phosphatase anti-alkaline phosphatase technique. In the tuberculin-injected sites as compared with the diluent-injected sites, there were significant increases in the number of CD45+ pan leukocytes and CD4+, CD8+, CD45RO+ T cells but not in CD68+ monocytes/macrophages and EG2 or MBP+ eosinophils. The activation markers CD25 and HLA-DR were up-regulated in the tuberculin-injected sites. In situ hybridization was performed using 35S-labeled riboprobes for interleukin (IL)-2, interferon (IFN)-gamma, IL-4, and IL-5. After tuberculin injection, a preferential Th-1-type cytokine profile was observed with significant increases in the numbers of IL-2 and IFN-gamma mRNA-expressing cells. These results are similar to those reported after tuberculin-induced delayed-type hypersensitivity in humans, suggesting that this model might be useful to study cutaneous inflammatory reaction.     

Transgenic and knock-out mice: models of neurological disease

A sudden increase in the osmolarity of the environment is highly detrimental to the growth and survival of Escherichia coli and Salmonella typhimurium since it triggers a rapid efflux of water from the cell, resulting in a decreased turgor. Changes in the external osmolarity must therefore be sensed by the microorganisms and this information must be converted into an adaptation process that aims at the restoration of turgor. The physiological reaction of the cell to the changing environmental condition is a highly coordinated process. Loss of turgor triggers a rapid influx of K+ ions into the cell via specific transporters and the concomitant synthesis of counterions, such as glutamate. The increased intracellular concentration of K(+)-glutamate allows the adaptation of the cell to environments of moderately high osmolarities. At high osmolarity, K(+)-glutamate is insufficient to ensure cell growth, and the bacteria therefore replace the accumulated K+ ions with compounds that are less deleterious for the cell's physiology. These compatible solutes include polyoles such as trehalose, amino acids such as proline, and methyl-amines such as glycine betaine. One of the most important compatible solutes for bacteria is glycine betaine. This potent osmoprotectant is widespread in nature, and its intracellular accumulation is achieved through uptake from the environment or synthesis from its precursor choline. In this overview, we discuss the properties of the high-affinity glycine betaine transport system ProU and the osmotic regulation of its structural genes.     

Pathogenesis of renal calculi in distal renal tubular acidosis. Possible role of parathyroid hormone

Elevated circulating levels of immunoreactive parathyroid hormone (PTH), hypercalciuria and renal calculi were found in 3 patients with distal renal tubular acidosis (RTA). Treatment with alkali resulted in a fall of PTH toward normal and a reduction in urinary calcium, but the frequency of urolithiasis was unchanged. In one patient in whom prolonged follow-up was possible, a subtotal parathyroidectomy was performed. This was followed by virtual cessation of stone formation despite persistence of the acidification defect. This study suggests that RTA may be associated with secondary hyperparathyroidism and that the consequent elevation in PTH may play a contributory role in the pathogenesis of renal calculi.     

Prevalence of endemic distal renal tubular acidosis and renal stone in the northeast of Thailand

We have previously reported a large group of patients with endemic distal renal tubular acidosis (EdRTA) admitted to the hospitals in the northeast of Thailand. Since large number of patients were identified in a relatively short period of time, and in an area whose population is homogeneous, we were led to investigate the prevalence of the condition in the area. A survey was conducted in five villages (total population of 3,606) within the northeast of Thailand. 3,013 villagers were examined for urinary citrate concentration and short acid loading test was performed in those with low urinary citrate. 2.8% of the population (2.2-3.4%, 95% confidence interval) failed to lower their urine pH after acid loading; within this group, 0.8% of the population had serum potassium less than or equal to 3.5 mEq/l. In addition a large number of villagers were found to have low urinary citrate concentration and there was concurrent high prevalence of renal stone. The prevalence of EdRTA and renal stone was higher in villagers with poorer socioeconomic status, suggesting that environmental factors play a major role in their pathogenesis. Villagers with acidification defect have 2.4 times the chance of having renal stone and/or nephrocalcinosis. EdRTA is therefore one of the important factors responsible for the high prevalence of renal stone in the area. In conclusion we have confirmed the high prevalence of EdRTA in the northeast of Thailand and provided data showing high prevalence of renal stone and hypocitraturia in the same population.