Measurement of isolated myocyte volume using the Coulter models Z2 and ZM/C256: a comparison of instrument function

Histologically measured cardiomyocyte hypertrophy correlates with body height as strongly as with body mass index

Cardiac myocytes are presumed to enlarge with left ventricular hypertrophy (LVH). This study correlates histologically measured myocytes with lean and fat body mass. Cases of LVH without coronary heart disease and normal controls came from forensic autopsies. The cross-sectional widths of myocytes in H&E-stained paraffin sections followed log normal distributions almost to perfection in all 104 specimens, with constant coefficient of variation across the full range of ventricular weight, as expected if myocytes of all sizes contribute proportionately to hypertrophy. Myocyte sizes increased with height. By regression analysis, height^2.7 as a proxy for lean body mass and body mass index (BMI) as a proxy for fat body mass, exerted equal effects in the multiple correlation with myocyte volume, and the equation rejected race and sex. In summary, myocyte sizes, as indexes of LVH, suggest that lean and fat body mass may contribute equally.

Performance evaluation of the Z2 coulter counter for WBC and RBC counting

The Z2 Coulter Counter (Z2) is a new, single-channel semi-automated electronic counter using the Coulter principle, providing both count and concentration results of cells, as well as providing size distribution of the cell population. The Z2 was evaluated according to guidelines published by the International Committee for Standardisation in Haematology. The results demonstrated excellent linearity for WBC and RBC (r > 0.999). The Z2 showed excellent precision, with a within-run, between-run and overall coefficient of variance less than 2%. Carryover was generally acceptable (<1%). WBC and RBC were stable after blood storage for 48 h at 4 degrees C and room temperature. There was almost no interference for WBC, RBC at high concentrations of bilirubin (178.5 mumol/l) or triglyceride (14.8 mmol/l) (P > 0.05). The bias of coincidence correction in WBC and RBC counting with the Z2 was less than 1%. Correlation between the Z2 and Sysmex F-820 or SE-9500 was excellent (r > 0.996) for WBC and RBC counting. Our results indicate that the Z2 has good features of precision, accuracy, linearity and good comparison with other haematology analysers, and could be used as a calibrating instrument for WBC and RBC counting.

Cell hydration as the primary factor in carcinogenesis: A unifying concept

The paper discusses the unifying concept that cell hydration is the primary factor in the mechanism of carcinogenesis. The concept includes the following hypotheses: (1) Increased cell hydration causes cancer not only by promoting cell division and oncogene expression, but also by inactivating genes inducing cell differentiation, and by preventing apoptosis. Conversely, factors that reduce cell hydration prevent cancer by inhibiting cell division and oncogene expression, while activating genes inducing cell differentiation, and by promoting apoptosis. The unique ability of cell hydration to have these opposite effects on cell behavior and gene expression can account for its postulated role as the primary factor in both the promotion and prevention of cancer. (2) A progressive increase in cell hydration, induced by successive mutations and/or epigenetic changes, is the basic mechanism of multi-step carcinogenesis, the degree of malignancy increasing with the degree of cell hydration. (3) The increased hydration of cancer cells accelerates their respiration rate, thereby enhancing their ability to compete for nutrients with their normal counterparts. This effect may play a major role in promoting tumor growth and in the postulated mechanism of multi-step carcinogenesis. (4) Increased cell hydration is also proposed as an alternative or additional explanation of the carcinogenetic effect of inflammatory agents and of hormones. A survey of the literature provides evidence consistent with these hypotheses, but suggestions are included for further investigations to test their validity and their implications. From a clinical perspective, the abnormally high water content of cancer cells permits the use of microwave technology for tumor detection and treatment. Also of considerable therapeutic significance is the increased sensitivity if cancer cells to desiccation, postulated to result from genetic changes induced by increased hydration. This may well be the achilles heel of cancer, and recent investigations indicate that it may be exploited very effectively in the treatment of the disease. In conclusion, I suggest that the need for studies on the molecular biology of cancer to be supplemented by more information on environmental effects on gene expression and on the biochemical and physiological factors that mediate genetic effects at the cellular level. This approach might also be used to assess the validity of the postulated role of cell hydration as a factor of particular significance.

The CRM1 nuclear export receptor controls pathological cardiac gene expression

Diverse pathological insults trigger a cardiac remodeling process during which myocytes undergo hypertrophy, with consequent decline in cardiac function and eventual heart failure. Multiple transcriptional regulators of pathological cardiac hypertrophy are controlled at the level of subcellular distribution. For example, prohypertrophic transcription factors belonging to the nuclear factor of activated T cells (NFAT) and GATA families are subject to CRM1-dependent nuclear export but are rapidly relocalized to the nucleus in response to cues for hypertrophic growth. Here, we demonstrate that the antihypertrophic chromatin-modifying enzyme histone deacetylase 5 (HDAC5) is shuttled out of the cardiomyocyte nucleus via a CRM1-mediated pathway in response to diverse signals for hypertrophy. CRM1 antagonists block the agonist-mediated nuclear export of HDAC 5 and repress pathological gene expression and associated hypertrophy of cultured cardiomyocytes. Conversely, CRM1 activity is dispensable for nonpathological cardiac gene activation mediated by thyroid hormone and insulin-like growth factor 1, agonists that fail to trigger the nuclear export of HDAC5. These results suggest a selective role for CRM1 in derepression of pathological cardiac genes via its neutralizing effects on antihypertrophic factors such as HDAC5. Pharmacological approaches targeting CRM1-dependent nuclear export in heart muscle may have salutary effects on cardiac function by suppressing maladaptive changes in gene expression evoked by stress signals.

Preservation of base-line hemodynamic function and loss of inducible cardioprotection in adult mice lacking protein kinase C epsilon

Signaling pathways involving protein kinase C isozymes are modulators of cardiovascular development and response to injury. Protein kinase C epsilon activation in cardiac myocytes reduces necrosis caused by coronary artery disease. However, it is unclear whether protein kinase C epsilon function is required for normal cardiac development or inducible protection against oxidative stress. Protein kinase C delta activation is also observed during cardiac preconditioning. However, its role as a promoter or inhibitor of injury is controversial. We examined hearts from protein kinase C epsilon knock-out mice under physiological conditions and during acute ischemia reperfusion. Null-mutant and wild-type mice displayed equivalent base-line morphology and hemodynamic function. Targeted disruption of the protein kinase C epsilon gene blocked cardioprotection caused by ischemic preconditioning and alpha(1)-adrenergic receptor stimulation. Protein kinase C delta activation increased in protein kinase C epsilon knock-out myocytes without altering resistance to injury. These observations support protein kinase C epsilon activation as an essential component of cardioprotective signaling. Our results favor protein kinase C delta activation as a mediator of normal growth. This study advances the understanding of cellular mechanisms responsible for preservation of myocardial integrity as potential targets for prevention and treatment of ischemic heart disease.

Myocyte growth and cardiac repair

Introduced several decades ago, the dogma persists that ventricular myocytes are terminally differentiated cells and cardiac repair by myocyte regeneration is completely inhibited shortly after birth. On the basis that cardiac myocytes are unable to divide in the adult heart, myocyte growth under physiologic and pathologic conditions is believed to be restricted to cellular hypertrophy. Evidence is presented to indicate that this old paradigm has to be changed to include myocyte replication as a significant component of the cellular processes of ventricular remodeling. Importantly, myocyte death, apoptotic and necrotic in nature, has to be regarded as an additional critical variable of the multifactorial events implicated in the alterations of cardiac anatomy and myocardial structure of the decompensated heart. Methodologies are currently available to recognize and measure quantitatively the contribution of myocyte size, number and death to the adaptation of the overloaded heart and its progression to cardiac failure.

c-Myc enhances protein synthesis and cell size during B lymphocyte development

Members of the myc family of nuclear protooncogenes play roles in cell proliferation, differentiation, and apoptosis. Moreover, inappropriate expression of c-myc genes contributes to the development of many types of cancers, including B cell lymphomas in humans. Although Myc proteins have been shown to function as transcription factors, their immediate effects on the cell have not been well defined. Here we have utilized a murine model of lymphomagenesis (Emu-myc mice) to show that constitutive expression of a c-myc transgene under control of the Ig heavy-chain enhancer (Emu) results in an increase in cell size of normal pretransformed B lymphocytes at all stages of B cell development. Furthermore, we show that c-Myc-induced growth occurs independently of cell cycle phase and correlates with an increase in protein synthesis. These results suggest that Myc may normally function by coordinating expression of growth-related genes in response to mitogenic signals. Deregulated c-myc expression may predispose to cancer by enhancing cell growth to levels required for unrestrained cell division.