A synergistic effect of extracellular hypocalcemic condition for hyperoxic reoxygenation injury in rat hepatocytes.

BACKGROUND: Calcium accumulation of cells and mitochondria during reperfusion or reoxygenation has been implicated as a potential factor in cell injury as the result of mitochondrial damage. The objective of this study was to disclose whether or not low extracellular calcium ion concentration ([Ca2+]ex) in the medium at the time of reoxygenation might prevent calcium accumulation and attenuate hepatocytes injury after severe hypoxia. METHODS: Isolated rat hepatocytes were incubated under a hyperoxic or hypoxic atmosphere for 60 min. During the ensuing 60-min hyperoxic reoxygenation, medium [Ca2+]ex was varied from 0.6 microM to 2.0 mM by altering total calcium and addition of chelators. RESULTS: Incubation in low [Ca2+]ex reduced total cellular calcium and mitochondrial calcium in both the hyperoxic and hypoxic group. Under hyperoxic/hyperoxic incubation (control), hepatocytes were able to maintain potassium balance when [Ca2+]ex was >3.0 microM (pCa=5.5) and cellular viability (% lactate dehydrogenase release) at all levels of extracellular calcium. Under hypoxic/hyperoxic incubation (reoxygenation), however, loss of the ability to restore potassium balance as well as apparent increase in lactate dehydrogenase release were observed at severely low [Ca2+]ex (<30 microM; pCa=4.5). This low [Ca2+]ex-induced exacerbation of hepatocytes viability could not be generated under mild reoxygenation such as normoxia. CONCLUSIONS: In normal isolated hepatocytes, very low [Ca2+]ex levels produce only very subtle changes in membrane permeability of isolated hepatocytes. After hypoxia, however, hypocalcemia acts synergistically with hyperoxic reoxygenation to produce more severe damage. These results suggested that [Ca2+]ex should be maintained on the physiological level to attenuate hepatocytes injury after severe hypoxia.

Expression pattern of heme oxygenase isoenzymes 1 and 2 in normal and stress-exposed rat liver.

Heme oxygenase (HO) catalyzes the oxidative cleavage of the alpha-mesocarbon of Fe-protoporphyrin-IX yielding equimolar amounts of biliverdin-IXa, iron, and carbon monoxide. The HO-system consists of two isoenzymes, namely HO-2 and the inducible isoform HO-1, also referred to as heat shock protein (hsp) 32. Although both parenchymal and non-parenchymal liver cells participate in heme metabolism, the expression pattern of the isoenzymes in normal and stress exposed liver is unknown. To study this, rats underwent either endotoxin (lipopolysaccharide [LPS]) challenge, hemorrhagic hypotension, glutathione (GSH) depletion, or cobalt chloride injection, all known to provoke oxidative stress. HO-2 messenger RNA (mRNA) and protein were constitutively expressed in hepatocytes, Kupffer/endothelial-, and stellate (Ito-) cell enriched fractions. Although both non-parenchymal cell fractions expressed HO-1 transcripts, HO-1 immunoreactive protein was restricted to Kupffer cells in the normal liver. In contrast to HO-2, a significant increase in HO-1 on the whole organ level was noted by hemorrhagic hypotension, GSH depletion, and cobalt chloride injection. However, the distinct stress models led to a strikingly different cell-type specific and sublobular expression pattern of HO-1 gene expression. HO-1 was inducible in sinusoidal lining cells (hemorrhagic hypotension, LPS challenge), in periportal (cobalt chloride), or pericentral (GSH depletion, hemorrhagic hypotension) hepatocytes. The blockade of protein translation before hemorrhage by cycloheximide reduced upregulation of HO-1/hsp32 mRNA significantly (65.4% reduction, P < .05), whereas the inducibility of hsp70 transcript was maintained. In addition to transcriptional regulation, HO-1 seems to be subject to posttranscriptional control in particular in non-parenchymal cells.

Hepatic intercellular communication in shock and inflammation.

The liver is well recognized as a target for injury during low flow or inflammatory states. Functionally, the result is both metabolic and host defense dysfunction. Although the liver is clearly responsive to changes in systemic levels of various mediators, it is becoming apparent that substantial changes occur within the liver that are not directly dependent on extrahepatic factors. This is the result of complex interactions among the various cell types that exist in a highly organized arrangement within the functional subunit of the liver. The purpose of this review is to summarize the structural relationships which form the basis for this system of cell-cell communication and their functional implications both in the normal liver and during both low-flow and normal-flow inflammatory states.

Maturational differences in hepatic microhemodynamics in rats.

Age-related changes in the hepatic microcirculation may contribute to the increased susceptibility of the immature liver to microvascular injury. We quantified sinusoidal and acinar diameters, sinusoidal red cell velocities (VRBC), and sinusoidal volume flows to characterize microhemodynamics of weanling and adult rat livers with and without hepatic artery (HA) ligation using intravital fluorescence videomicroscopy. Despite a 20% faster heart rate and a nearly 20% lower mean arterial and portal vein pressure in weanling rats relative to those in the adults, weanling periportal and pericentral sinusoidal velocities were approximately 30 and 25% faster, respectively, than those in adults. Furthermore, the HA was found to contribute more to maintenance of sinusoidal VRBC in the immature liver as demonstrated by a significant decrease in both periportal and pericentral VRBC following HA ligation. HA ligation had no effect on VRBC of either zone in adults. Zonal volume flow (HA intact), however, was maintained independent of age. These results suggest a lower extrasinusoidal resistance in the weanling. The 25% shorter acinar diameter that we found in weanling livers likely contributes to a lower extrasinusoidal resistance by allowing a higher ratio of inflow vessels to volume of tissue. Shorter sinusoidal pathways in weanling livers also decreases sinusoidal resistance 1.3-fold relative to that in the adult, countering the approximately 1.5 times increase in resistance due to the smaller caliber of sinusoidal vessels so that overall sinusoidal resistance is not age-dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effects of nonoxinol 9 on RFLP typing of postcoital vaginal smears]. / Auswirkungen von Nonoxinol 9 auf die RFLP-Typisierung postkoitaler Vaginalabstriche.

Nonoxinol 9 effectively inactivates high titres of HIV in vitro, which suggest its use for reducing HIV-transmission via sexual intercourse. Therefore, the suggestion has been made for the treatment of sexual assault victims with a topical anti-HIV agent such as nonoxinol 9 as soon as possible after a sexual assault has occurred. From the forensic point of view it becomes pertinent to determine whether or not nonoxinol 9 would have an adverse effect on the high-molecular weight deoxyribonucleic acid (DNA) in vaginal swabs and thereby impact RFLP results. The study demonstrates that nonoxinol 9 does not have a negative effect on the ability to produce RFLP patterns. Therefore, the early administration of the topical anti-HIV agent nonoxinol 9 has to be considered as an important step in the medical treatment of sexual assault victims.

Calcium-free reperfusion prevents mitochondrial calcium accumulation but exacerbates injury.

Excessive accumulation of intracellular calcium has been proposed as a mediator of cell injury during ischemia and reperfusion. To test whether restriction of extracellular calcium might ameliorate hepatic injury following hypothermic ischemic preservation, isolated perfused rat livers were reperfused with a medium with normal extracellular calcium (mM-Ca) or no added calcium (microM-Ca) following 26 hr preservation at 4 degrees C. During reperfusion mitochondria from mM-Ca livers accumulated calcium and respiratory activity declined. Although mitochondrial calcium accumulation was prevented by microM-Ca reperfusion, damage to respiratory activity was exacerbated. Edema formation and loss of gluconeogenesis were similarly exacerbated in microM-Ca. This accelerated damage was not reversed by subsequent restoration of calcium. These results demonstrate that rather than ameliorating cell injury, calcium deprivation during reperfusion exacerbates damage to mitochondrial and cellular functions. Thus, cellular or mitochondrial calcium accumulation does not appear to be a sine qua non for hepatocyte injury during reperfusion following hypothermic ischemia.

Responses to dehydration and rehydration during heat exposure in young and older men.

Body temperature, plasma responses, and subjective ratings of thirst and hotness were studied in 5 older men (OM, 61-67 yr) and 6 younger men (YM, 21-29 yr) during 180-min thermal dehydration and subsequent 60-min rehydration (45 degrees C, 25% relative humidity). Rectal temperature (Tre) increased more rapidly and to a greater magnitude in OM, while average total body sweat rates and chest sweat rates were not significantly different. During dehydration, both OM and YM lost similar body weight (1.52 +/- 0.11 vs. 1.55 +/- 0.22%, mean +/- SE). However, in OM, plasma volume (Pv) decreased (-11.3 +/- 2.8 vs. -4.9 +/- 2.9%), and plasma osmolality (Posm) increased to a greater extent (+5.0 +/- 0.32 vs. 1.1 +/- 0.24 mosmol/kg) compared with YM. On rehydration, OM and YM similarly replaced water debt (46.6 +/- 4.9 vs. 49.0 +/- 3.0%). Within 30 min of drinking, YM had restored Pv and Posm, whereas OM showed slower responses, restoring Posm after 60 min and Pv only after a subsequent 30 min at 25 degrees C. Despite a higher Tre and greater change in Pv and Posm, OM rated themselves less thirsty and not significantly hotter than YM. These findings suggest that aging results in decreased ability to maintain Tre during heat stress and that the mechanisms comprise a combination of alterations in body fluid distribution and perception.

Screening for cryptorchid boys risking sterility and results of long-term buserelin treatment after successful orchiopexy.

This long-term prospective follow-up study showed that in cryptorchid patients a significant correlation exists between the number of germ cells at the time of orchiopexy (prepuberty) and the spermiogram, and thus a biopsy has a prognostic value. Fifty percent of our patients had a germ cell count of less than 0.1 per tubule and belong to the risk group for sterility. Successful surgery could not induce a significant increase of germ cells in the risk group, although it does prevent secondary testicular damage. Patients with cryptorchidism developed after birth have significantly better chances of fertility than those with primary cryptorchidism. The priming effect of testosterone in the first months of life is important for male fertility. In patients belonging to the risk group treated with buserelin, a significant age-dependent increase in germ cell count occurred.

Delayed menarche in swimmers in relation to age at onset of training and athletic performance.

Competitive swimmers have been considered to be different from other female athletes in that their mean age at menarche is similar to that of nonathletes. However, it was hypothesized that if the delayed menarche observed in athletes of other sports is caused by prepubertal training, then swimmers should also exhibit delayed menarche as the majority of swimmers begin training prior to puberty. Furthermore, if early prepubertal training is the important factor in delaying menarche, then it was hypothesized that a relationship between performance and age at menarche in swimming is unlikely to exist. Thus, 345 competitive female swimmers and 549 control subjects completed questionnaires concerning general health, athletic training history, and age at menarche. Results indicated that, as a population, the mean age at menarche of the swimmers (13.4 yr) was significantly later than the controls (13.0 yr). When swimmers and controls were compared on an age-group basis, it was found that the difference in age at menarche was due to the data obtained from the older and more highly competitive swimmers. Assigning swimmers to different competitive levels or by performance in specific swimming events (50- or 100-yd freestyle; 45.7- or 91.4-m, respectively) indicated a significantly later age at menarche for the more competitive swimmers. Thus, there is evidence that the age at menarche and subsequent athletic performance in swimming are related; the later menarche observed in swimmers appears to be associated with factors that select for superior performance.