Milk feeding level and starter protein content: Effects on growth performance, blood metabolites, and urinary purine derivatives of Holstein dairy calves.

The objective of this study was to investigate the effects of milk allowances equal to 526 g/d as moderate (MOD) versus 790 g/d of milk dry matter as high (HI), and starter diets containing 18% or 23% crude protein (CP), on growth performance, blood metabolites, and purine derivative (PD) excretion in the urine of dairy calves. A total of 52 female Holstein dairy calves (40.8 kg of body weight) were randomly assigned to the experimental diets. The treatments were (1) moderate milk and 18% CP starter diet (MOD-18CP); (2) MOD and 23% CP starter diet (MOD-23CP); (3) high milk and 18% CP starter diet (HI-18CP); and (4) HI and 23% CP starter diet (HI-23CP). Calves had free access to a starter feed and water and were weaned on d 53 but remained in the study until d 73. Urine samples were collected during the preweaning period (for 6 consecutive days between d 35 and 40) and postweaning period (for 6 consecutive days between d 65 and 70) to investigate urinary excretion of PD. Starter feed intake, ß-hydroxybutyrate (BHB), and blood urea concentrations were reduced; however, average daily gain (ADG) and blood glucose levels increased in calves fed HI before weaning compared with MOD. During the preweaning period, high milk feeding increased total urinary PD excretion but decreased it after weaning. The 23CP diet resulted in higher feed intake and ADG before weaning and higher excretion of allantoin and total excretion of PD compared with the 18CP diet. The HI-23CP treatment resulted in the greatest withers and hip heights at weaning and final measurement, as well as the highest preweaning blood insulin concentrations. In terms of rumen development, MOD-23CP showed the greatest benefits based on starter intake, blood BHB concentration, and urinary excretion of PD. Based on the higher urinary excretion of PD found in HI-fed calves before weaning, it is possible that milk feeding overestimates estimated microbial yield. The results suggest that feeding starters with a higher proportion of CP may help maintain a more balanced ratio of CP to ME during high milk feeding, to avoid protein deficiency due to low starter intake. When calves are fed a high milk allowance, urine excretion of PD may be misinterpreted as a measure of estimated microbial growth and rumen development; this should be considered during calculations of estimated microbial yield in milk-fed calves.

The heart of an acrobatic bird.

The courtship behavior of some species of birds can be energetically demanding, but it is unknown if cardiovascular specializations enable such behaviors. While performing a highly acrobatic courtship dance, heart rate in male golden-collared manakins increases briefly to 1300 beats per minute, among the highest heart rates recorded in any bird or mammal. We hypothesize that male manakins have enhanced cardiovascular capabilities to meet these demands on the heart. Using histological and molecular techniques, we examined manakin heart structure as well as expression of genes involved in Ca2+ handling, action potential duration, steroidal signaling and cardiac growth. These measures were also made on the hearts of zebra finches, a similar-sized bird with limited cardiovascular demands. Compared to the zebra finch, the manakin had a significantly thicker left ventricular (LV) muscle (cross-sectional thickness of the free LV wall and septum) with a smaller LV chamber. In addition, compared to zebra finches, manakin hearts had significantly greater gene expression of ryanodine receptors as well as androgen receptors. Testosterone (T) treatment of non-breeding manakins (with low T) increased gene expression of the Ca2+ pump SERCA. These observations suggest that hearts of breeding male manakins require specialized Ca2+ handling and androgens may facilitate manakin cardiovascular function.

Novel WASP mutation in a patient with Wiskott-Aldrich syndrome: case report and review of the literature

BACKGROUND: The Wiskott-Aldrich syndrome (WAS) is a rare X-linked recessive immunodeficiency disorder, caused by mutations in the WAS protein (WASP) gene and characterised by thrombocytopenia, small platelets, eczema, and recurrent infections associated with increased risk of autoimmunity and malignancy disorders. The gene for WAS has been mapped to the short arm of the X chromosome at Xp 11.22-23 and early detection of patients and diagnosis of new mutation might reduce related complications and increase their life expectancy. Method and result: We found a novel mutation by sequence analysis of genomic DNA coding of a 9-month old boy suffering from WAS. The mutation was insertion G in exon 10 of WASP gene. The consequence of the G insertion is a premature stop immediately at amino acid 335 (N335X or p.G334GfsX1) and truncated protein. CONCLUSION: The mutation analysis is helpful for the diagnosis of WAS patients and also expanding the spectrum of WASP mutations for carrier detection and prenatal diagnosis

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Novel WASP mutation in a patient with Wiskott-Aldrich syndrome: Case report and review of the literature.

BACKGROUND: The Wiskott-Aldrich syndrome (WAS) is a rare X-linked recessive immunodeficiency disorder, caused by mutations in the WAS protein (WASP) gene and characterised by thrombocytopenia, small platelets, eczema, and recurrent infections associated with increased risk of autoimmunity and malignancy disorders. The gene for WAS has been mapped to the short arm of the X chromosome at Xp 11.22-23 and early detection of patients and diagnosis of new mutation might reduce related complications and increase their life expectancy. METHOD AND RESULT: We found a novel mutation by sequence analysis of genomic DNA coding of a 9-month old boy suffering from WAS. The mutation was insertion G in exon 10 of WASP gene. The consequence of the G insertion is a premature stop immediately at amino acid 335 (N335X or p.G334GfsX1) and truncated protein. CONCLUSION: The mutation analysis is helpful for the diagnosis of WAS patients and also expanding the spectrum of WASP mutations for carrier detection and prenatal diagnosis.

Study of SH2D1A gene mutation in paediatric patients with B-cell lymphoma

BACKGROUND: X-linked lymphoproliferative disease (XLP) is an often fatal inherited immunodeficiency disorder characterised by fulminant infectious mononucleosis, acquired haemophagocytic lymphohistiocytosis, dysgammaglobulinaemia and malignant lymphoma. Given the paucity of data on the genetic stratification of XLP gene mutations in paediatric patients diagnosed with B-cell lymphoma, we sought to determine the existence of such association in the present study. METHODS: We studied 20 male subjects diagnosed with non-Hodgkin B-cell lymphoma. RESULTS: Eleven patients had laboratory evidence of EBV infection by serology and quantitative PCR. The SH2D1A gene analysis was negative in all patients. CONCLUSIONS: This is the first study to analyse the SH2D1A gene mutations in Iranian paediatric patients diagnosed with lymphoma. Although we could not demonstrate such an association in our cohort of patients, larger, multi-centre studies are required to extend and confirm our early finding

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Study of SH2D1A gene mutation in paediatric patients with B-cell lymphoma.

BACKGROUND: X-linked lymphoproliferative disease (XLP) is an often fatal inherited immunodeficiency disorder characterised by fulminant infectious mononucleosis, acquired haemophagocytic lymphohistiocytosis, dysgammaglobulinaemia and malignant lymphoma. Given the paucity of data on the genetic stratification of XLP gene mutations in paediatric patients diagnosed with B-cell lymphoma, we sought to determine the existence of such association in the present study. METHODS: We studied 20 male subjects diagnosed with non-Hodgkin B-cell lymphoma. RESULTS: Eleven patients had laboratory evidence of EBV infection by serology and quantitative PCR. The SH2D1A gene analysis was negative in all patients. CONCLUSIONS: This is the first study to analyse the SH2D1A gene mutations in Iranian paediatric patients diagnosed with lymphoma. Although we could not demonstrate such an association in our cohort of patients, larger, multi-centre studies are required to extend and confirm our early findings.

Comparison of seminal oxidants and antioxidants in subjects with different levels of physical fitness.

The purpose of this study was to evaluate the seminal 8-Isoprostane, reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), catalase, total antioxidant capacity (TAC) in subjects with different level of physical fitness. A total of 161 semen samples were obtained from three groups of healthy males, including elite athletes (23.8 ± 5.2 years, n = 56) who had regular training (4-5 days per week), recreationally active men (24.2 ± 4.9 years, n = 52) who participated in educational or recreational physical activities for 4-5 h per week and non-active men (23.9 ± 5.0 years, n = 53) who did not participate in any exercise programmes for at least 6 months prior to the study. The results showed significantly higher levels of SOD, catalase and TAC as well as lower levels of 8-Isoprostane, ROS and MDA in recreationally active men compared with either elite athletes or non-active men (p < 0.001). Also, elite athletes revealed significantly higher seminal 8-Isoprostane, ROS and MDA as well as lower SOD, catalase and TAC levels compared with recreationally active and non-active men (p < 0.001). In conclusion, the results of the present study indicate that there are differences in seminal oxidants and antioxidants of elite athletes, recreationally active and non-active men. These differences are more likely related to indices that favour decrement of oxidative stress-induced peroxidative damage in spermatozoa from recreationally active men. Hence, recreationally active men seem to have a healthier semen production. The physiological significance of this observation is worthy of further investigation.

The comparison of treating Holstein dairy cows with progesterone, CIDR and GnRH after insemination on serum progesterone and pregnancy rates.

This experiment was conducted to investigate the effects of different exogenous progesterone sources administrated after artificial insemination (AI) on serum progesterone (P(4) ) concentration and pregnancy rates in Holstein lactating cows. Sixty-four lactating Holstein dairy cows were allocated to four different treatments (n = 16 per treatment): the cows 1) were injected with physiological saline on days 5 and 13 after AI (control group); 2) were injected with progesterone on days 5 and 13 after AI (P group); 3) received controlled internal drug releasing device (CIDR) for a period from day 5 to 19 after AI (CIDR group); and 4) were injected with gonadotropin-releasing hormone (GnRH) agonist on days 5 and 13 after AI (GnRH group). Blood samples were collected on days 0 (AI day), 5, 13, 16 and 19 after AI to determine serum P(4) concentration. The results revealed a significant difference among treatment groups for serum P(4) concentration on days 13, 16 and 19 with the lowest concentration of serum P(4) for the control group. The pregnancy rate was also positively affected by all the treatments with CIDR having the greatest effect on pregnancy rate. Overall, the results indicated that CIDR has the greatest effect on serum P(4) concentration and pregnancy rate, although the administration of P and GnRH during days after AI increased serum P(4) concentration in lactating dairy cows as well.

Effects of copper and superoxide dismutase content of seminal plasma on buffalo semen characteristics.

To investigate the effects of copper and superoxide dismutase (SOD) content of seminal plasma on buffalo semen characteristics, 54 semen samples collected from buffalo bulls by a bovine artificial vagina were used. Semen characteristics (motility, viability, morphology, concentration and volume) were recorded. Seminal plasma was harvested by centrifugation and kept frozen until analysis. Seminal plasma copper content was determined by atomic absorption procedure and SOD was measured by using a kit. The mean total copper value of seminal plasma was recorded as 2.51 +/- 0.04 mg kg(-1) (Mean +/- SEM) and the mean total SOD values was 39.02 +/- 0.81 IU mL(-1). To reduce the range of variability, the data were categorized according to their motility records in 3 groups of Excellent (Ex, >90% motile, n = 33), Good (Go, 80-89% motile, n = 15) and Moderate (Mo, < 79% motile, n = 6). The mean motility, viability, copper and SOD values in Ex group was recorded as 92.24 +/- 0.51%, 94.00 +/- 0.48%, 2.56 +/- 0.04 mg kg(-1) and 39.52 +/- 0.57 IU mL(-1), respectively. These values were 81.66 +/- 0.62%, 85.26 +/- 0.95%, 2.38 +/- 0.11 mg kg(-1) and 36.48 +/- 1.51 IU mL(-1) in Go group and 71.66 +/- 1.05%, 77.00 +/- 2.94%, 2.55 +/- 0.10 mg kg(-1) and 50.66 +/- 2.51 in Mo group, respectively. The mean copper value in Ex group was highly (r = 0.600) correlated with SOD and correlated with sperm motility (r = 0.372) and viability (r = 0.363), while, in Go group it was highly correlated (r = 0.945) with SOD and sperm viability (r = 0.652) and in Mo group it was correlated (r = 0.874) with semen volume only. The mean SOD values in Ex group was highly correlated with sperm motility (r = 0.492) and viability (r = 0.490) and mean copper values, in Go group, it was highly correlated whit sperm viability (r = 0.659) and mean copper values and in Mo group it had no significant correlations with semen parameters. These results suggest that copper and SOD content of the buffalo seminal plasma have an influence on the sperm motility and viability which are the most important factors in semen fertility.

An endoplasmic reticulum trafficking signal prevents surface expression of a voltage- and Ca2+-activated K+ channel splice variant.

Protein delivery to restricted plasma membrane domains is exquisitely regulated at different stages of the cell trafficking machinery. Traffic control involves the recognition of export/retention/retrieval signals in the endoplasmic reticulum (ER)/Golgi complex that will determine protein fate. A splice variant (SV), SV1, of the voltage- and Ca(2+)-activated K(+) channel alpha-subunit accumulates the channel in the ER, preventing its surface expression. We show that SV1 insert contains a nonbasic, hydrophobic retention/retrieval motif, CVLF, that does not interfere with proper folding and tetramerization of SV1. Localization of proteins in the ER by CVLF is independent of its position; originally, on the first internal loop, SV1 insert or CVLF perform equally well if placed at the middle or end of the alpha-subunit intracellular carboxyl terminus. Also, CVLF is able to restrict the traffic of an independently expressed transmembrane protein, beta 1-subunit. CVLF is present in proteins across species and in lower organisms. Thus, CVLF may have evolved to serve as a regulator of cellular traffic.

External pore collapse as an inactivation mechanism for Kv4.3 K+ channels.

Kv4 channels are thought to lack a C-type inactivation mechanism (collapse of the external pore) and to inactivate as a result of a concerted action of cytoplasmic regions of the channel. To investigate whether Kv4 channels have outer pore conformational changes during the inactivation process, the inactivation properties of Kv4.3 were characterized in 0 mM and in 2 mM external K+ in whole-cell voltage-clamp experiments. Removal of external K+ increased the inactivation rates and favored cumulative inactivation by repetitive stimulation. The reduction in current amplitude during repetitive stimulation and the faster inactivation rates in 0 mM external K+ were not due to changes in the voltage dependence of channel opening or to internal K+ depletion. The extent of the collapse of the K+ conductance upon removal of external K+ was more pronounced in NMG+-than in Na+-containing solutions. The reduction in the current amplitude during cumulative inactivation by repetitive stimulation is not associated with kinetic changes, suggesting that it is due to a diminished number of functional channels with unchanged gating properties. These observations meet the criteria for a typical C-type inactivation, as removal of external K+ destabilizes the conducting state, leading to the collapse of the pore. A tentative model is presented, in which K+ bound to high-affinity K+-binding sites in the selectivity filter destabilizes an outer neighboring K+ modulatory site that is saturated at approximately 2 mM external K+. We conclude that Kv4 channels have a C-type inactivation mechanism and that previously reported alterations in the inactivation rates after N- and C- termini mutagenesis may arise from secondary changes in the electrostatic interactions between K+-binding sites in the selectivity filter and the neighboring K+-modulatory site, that would result in changes in its K+ occupancy.

Remodeling of Kv4.3 potassium channel gene expression under the control of sex hormones.

Kv4.3 channels are important molecular components of transient K(+) currents (Ito currents) in brain and heart. They are involved in setting the frequency of neuronal firing and heart pacing. Altered Kv4.3 channel expression has been demonstrated under pathological conditions like heart failure indicating their critical role in heart function. Thyroid hormone studies suggest that their expression in the heart may be hormonally regulated. To explore the possibility that sex hormones control Kv4.3 expression, we investigated whether its expression changes in the pregnant uterus. This organ represents a unique model to study Ito currents, because it possesses this type of K(+) current and undergoes dramatic changes in function and excitability during pregnancy. We cloned Kv4.3 channel from myometrium and found that its protein and transcript expression is greatly diminished during pregnancy. Experiments in ovariectomized rats demonstrate that estrogen is one mechanism responsible for the dramatic reduction in Kv4.3 expression and function prior to parturition. Furthermore, the reduction of plasma membrane Kv4.3 protein is accompanied by a perinuclear localization suggesting that cell trafficking is also controlled by sex hormones. Thus, estrogen remodels the expression of Kv4.3 in myometrium by directly diminishing its transcription and, indirectly, by altering Kv4.3 delivery to the plasma membrane.

GABA concentration sets the conductance of delayed GABAA channels in outside-out patches from rat hippocampal neurons.

GABAA channels were activated by GABA in outside-out patches from rat cultured hippocampal neurons. They were blocked by bicuculline and potentiated by diazepam. In 109 of 190 outside-out patches, no channels were active before exposure to GABA (silent patches). The other 81 patches showed spontaneous channel activity. In patches containing spontaneous channel activity, rapid application of GABA rapidly activated channels. In 93 of the silent patches, channels could be activated by GABA but only after a delay that was sometimes as long as 10 minutes. The maximum channel conductance of the channels activated after a delay increased with GABA concentration from less than 10 pS (0.5 microm GABA) to more than 100 pS (10 mm GABA). Fitting the data with a Hill-type equation gave an EC50 value of 33 microm and a Hill coefficient of 0.6. The channels showed outward rectification and were chloride selective. In the presence of 1 microm diazepam, the GABA EC50 decreased to 0.2 microm but the maximum conductance was unchanged. Diazepam decreased the average latency for channel opening. Bicuculline, a GABA antagonist, caused a concentration-dependent decrease in channel conductance. In channels activated with 100 microm GABA the bicuculline IC50 was 19 microm. The effect of GABA on channel conductance shows that the role of the ligand in GABAA receptor channel function is more complex than previously thought.

A novel MaxiK splice variant exhibits dominant-negative properties for surface expression.

We identified a novel MaxiK alpha subunit splice variant (SV1) from rat myometrium that is also present in brain. SV1 has a 33-amino acid insert in the S1 transmembrane domain that does not alter S1 overall hydrophobicity, but makes the S0-S1 linker longer. SV1 was transfected in HEK293T cells and studied using immunocytochemistry and electrophysiology. In non-permeabilized cells, N-terminal c-Myc- or C-terminal green fluorescent protein-tagged SV1 displayed no surface labeling or currents. The lack of SV1 functional expression was due to endoplasmic reticulum (ER) retention as determined by colabeling experiments with a specific ER marker. To explore the functional role of SV1, we coexpressed SV1 with the alpha (human SLO) and beta1 (KCNMB1) subunits of the MaxiK channel. Coexpression of SV1 inhibited surface expression of alpha and beta1 subunits approximately 80% by trapping them in the ER. This inhibition seems to be specific for MaxiK channel subunits since SV1 was unable to prevent surface expression of the Kv4.3 channel or to interact with green fluorescent protein. These results indicate a dominant-negative role of SV1 in MaxiK channel expression. Moreover, they reveal down-regulation by splice variants as a new mechanism that may contribute to the diverse levels of MaxiK channel expression in non-excitable and excitable cells.

Bicuculline, pentobarbital and diazepam modulate spontaneous GABA(A) channels in rat hippocampal neurons.

Spontaneously opening, chloride-selective channels that showed outward rectification were recorded in ripped-off patches from rat cultured hippocampal neurons and in cell-attached patches from rat hippocampal CA1 pyramidal neurons in slices. In both preparations, channels had multiple conductance states and the most common single-channel conductance varied. In the outside-out patches it ranged from 12 to 70 pS (Vp=40 mV) whereas in the cell-attached patches it ranged from 56 to 85 pS (-Vp=80 mV). Application of GABA to a patch showing spontaneous channel activity evoked a rapid, synchronous activation of channels. During prolonged exposure to either 5 or 100 microM GABA, the open probability of channels decreased. Application of GABA appeared to have no immediate effect on single-channel conductance. Exposure of the patches to 100 microM bicuculline caused a gradual decrease on the single-channel conductance of the spontaneous channels. The time for complete inhibition to take place was slower in the outside-out than in the cell-attached patches. Application of 100 microM pentobarbital or 1 microM diazepam caused 2 - 4 fold increase in the maximum channel conductance of low conductance (<40 pS) spontaneously active channels. The observation of spontaneously opening GABA(A) channels in cell-attached patches on neurons in slices suggests that they may have a role in neurons in vivo and could be an important site of action for some drugs such as benzodiazepines, barbiturates and general anaesthetics.

Pentobarbital modulates gamma-aminobutyric acid-activated single-channel conductance in rat cultured hippocampal neurons.

We examined the effect of a range of pentobarbital concentrations on 0.5 microM gamma-aminobutyric acid (GABA)-activated channels (10 +/- 1 pS) in inside-out or outside-out patches from rat cultured hippocampal neurons. The conductance increased from 12 +/- 4 to 62 +/- 9 pS as the pentobarbital concentration was raised from 10 to 500 microM and the data could be fitted by a Hill-type equation. At 100 microM pentobarbital plus 0.5 microM GABA, the conductance seemed to reach a plateau. The pentobarbital EC(50)(0.5 microM GABA) value was 22 +/- 4 microM and n was 1.9 +/- 0.5. In 1 mM pentobarbital plus 0.5 microM GABA, the single-channel conductance decreased to 34 +/- 8 pS. This apparent inhibition of channel conductance was relieved by 1 microM diazepam. The channel conductance was 64 +/- 6 pS in the presence of all three drugs. The channels were open more in the presence of both GABA and pentobarbital than in the presence of either drug alone. Pentobarbital alone (100 microM) activated channels with conductance (30 +/- 2 pS) and kinetic properties distinct from those activated by either GABA alone or GABA plus pentobarbital. Whether pentobarbital induces new conformations or promotes conformations observed in the presence of GABA alone cannot be determined from our study, but the results clearly show that it is the combination of drugs present that determines the single-channel conductance and the kinetic properties of the receptors.

Hippocampal GABA(A) channel conductance increased by diazepam.

Benzodiazepines, which are widely used clinically for relief of anxiety and for sedation, are thought to enhance synaptic inhibition in the central nervous system by increasing the open probability of chloride channels activated by the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). Here we show that the benzodiazepine diazepam can also increase the conductance of GABAA channels activated by low concentrations of GABA (0.5 or 5 microM) in rat cultured hippocampal neurons. Before exposure to diazepam, chloride channels activated by GABA had conductances of 8 to 53pS. Diazepam caused a concentration-dependent and reversible increase in the conductance of these channels towards a maximum conductance of 70-80 pS and the effect was as great as 7-fold in channels of lowest initial conductance. Increasing the conductance of GABAA channels tonically activated by low ambient concentrations of GABA in the extracellular environment may be an important way in which these drugs depress excitation in the central nervous system. That any drug has such a large effect on single channel conductance has not been reported previously and has implications for models of channel structure and conductance.

Expression of SPARC in normal and fibrotic livers.

SPARC (secreted protein, acidic and rich in cysteine)--also known as osteonectin, BM-40, and 43K glycoprotein--is secreted by endothelial cells and fibroblasts in response to culture shock. SPARC has been found in association with tissues undergoing cell proliferation, migration, and extracellular matrix remodeling. We demonstrate that normal livers from humans, rats, and mice express substantial levels of SPARC messenger RNA (mRNA). Moreover, when compared with control specimens, significantly increased levels of SPARC mRNA were found in fibrotic livers from two animal models of liver disease: murine schistosomiasis and carbon tetrachloride-induced fibrosis in rats. Fibrotic human livers also had markedly increased levels of SPARC mRNA in comparison with normal livers. We also detected an increased production of SPARC protein in the liver of animals treated with carbon tetrachloride. By immunocytochemical analysis, SPARC protein was apparent in freshly isolated Ito cells. Hybridization studies showed Ito cells to be the main source of SPARC mRNA. Extracts from a Kupffer-endothelial cell fraction exhibited traces of SPARC transcript, but expression of SPARC mRNA was absent in extracts from freshly isolated hepatocytes. These studies demonstrate the increased expression of SPARC--a protein that modulates cell shape and disrupts cell-matrix interactions--during the initial stages of hepatic fibrosis.

Gender-specific differences in expression of mRNAs for functional and structural proteins in rat ventricular myocardium.

Sex-related differences in predisposition to heart diseases have long been recognized. The molecular and cellular bases for this difference are unknown. In this study we have compared expression of genes for various structural and functional proteins of muscle and interstitial compartments of the myocardium in the adult and neonatal, male and female rat heart. We have also compared cultured cardiac fibroblasts from male and female hearts with regards to gene expression and proliferative capacity. We showed that in the adult rats, the abundance of mRNAs for contractile proteins alpha- and beta-myosin heavy chain (MHC) is higher in the heart of female rats than in that of age-matched male rats. However, the difference in mRNA level for alpha-MHC was more drastic (736%, P < 0.001) than that for beta-MHC (469%, P < 0.001). mRNA levels for sarcomeric actin in the female heart were greater by 79% (P < 0.001). Collagen type I had a significantly higher (303%, P < 0.01) mRNA level in the female heart compared with the male heart. mRNAs for TGF-beta 1, cytoskeletal actin and connexin 43 were also higher (150%, P < 0.01; 130%, P < 0.01, and 150%, P < 0.01, respectively) in the female heart compared with age-matched male heart. There were no significant sex-related differences at the mRNA levels for the above proteins in ventricular tissue from neonatal male and female littermates. At the cellular level, cardiac fibroblasts obtained from adult and neonatal hearts of both sexes were comparable with respect to the abundance of mRNAs for collagen type I, TGF-beta 1 or cytoskeletal actin. However, DNA synthesis, as measured by [3H]thymidine incorporation, was higher (328%, P < 0.01) in cells from adult female heart compared with that in cells from adult male rat heart. This difference was even more pronounced in cardiac fibroblasts obtained from newborn female rats (933%, P < 0.001) compared with that in cells obtained from newborn male rat hearts. Together, these findings show that there are sex-related differences in gene expression for most major proteins in heart tissue and that this phenomenon is associated with the post-pubertal period. These findings further suggest that sex-related differential gene expression and DNA synthesis in cardiac cells are due to the regulatory effects of male- and female-specific hormones.