Habitat associations and communities of breeding birds in the highlands of south-west Jordan

Abstract

Habitat associations and communities of breeding birds were studied for the first time in a semi-arid region in the southern highlands of Jordan. Birds were censused and habitat variables estimated in different habitat types, ranging from steppe to open, Mediterranean-type woodland. The variation of abundance of several species was explained adequately with multiple regressions of up to five habitat variables. A distinct bird community was identified by using principal component analysis on the highland plateau (e.g. Short-toed Lark, Isabelline Wheatear), in steppe habitats modified by dry farming methods. The plateau was identified as a transition zone of Palaeoxeric/Turkestanian and Mediterranean faunal types. The remainding cluster included species of diverse origins (Palaearctic, Mediterranean, Saharo-Sindian, Afrotropical and others). It was subdivided into three bird assemblages with preferences for following habitat types: Mediterranean-type open woodlands (e.g. Syrian Serin), dwarf shrub formations of higher altitudes (e.g. Spectacled Warbler), dwarf shrub formations, including clearings and the edge of woodlands at lower altitudes (e.g. Scrub Warbler).     

Downregulation of connexin40 and increased prevalence of atrial arrhythmias in transgenic mice with cardiac-restricted overexpression of tumor necrosis factor

Atrial arrhythmias, primarily atrial fibrillation, have been independently associated with structural remodeling and with inflammation. We hypothesized that sustained inflammatory signaling by tumor necrosis factor (TNF) would lead to alterations both in underlying atrial myocardial structure and in atrial electrical conduction. We performed ECG recording, intracardiac electrophysiology studies, epicardial mapping, and connexin immunohistochemical analyses on transgenic mice with targeted overexpression of TNF in the cardiac compartment (MHCsTNF) and on wild-type (WT) control mice (age 8-16 wk). Atrial and ventricular conduction abnormalities were always evident on ECG in MHCsTNF mice, including a shortened atrioventricular interval with a wide QRS duration secondary to junctional rhythm. Supraventricular arrhythmias were observed in five of eight MHCsTNF mice, whereas none of the mice demonstrated ventricular arrhythmias. No arrhythmias were observed in WT mice. Left ventricular conduction velocity during apical pacing was similar between the two mouse groups. Connexin40 was significantly downregulated in MHCsTNF mice. In contrast, connexin43 density was not significantly altered in MHCsTNF mice, but rather dispersed away from the intercalated disks. In conclusion, sustained inflammatory signaling contributed to atrial structural remodeling and downregulation of connexin40 that was associated with an increased prevalence of atrial arrhythmias.     

Effects of chronic instrumentation on fetal growth

Chronically-instrumented fetal sheep are a commonly used animal model for the study of fetal growth and metabolism. In the current study, we wanted to test the hypothesis that instrumentation alone would alter fetal growth patterns. Thirty-two animals in three groups were used: (i) non-instrumented animals (n = 10); (ii) instrumented with catheters in the maternal and fetal femoral artery and vein and electromagnetic flow probes on the main uterine arteries (n = 10): (iii) animals instrumented as group 2, but with the addition of a doppler flow probe on the common umbilical artery and a common umbilical vein catheter (n = 12). Animals in group 2 and 3 were monitored until 137 to 140 days of gestation, at which time they were sacrificed for fetal morphometric measurements. Instrumentation significantly (P less than 0.05) decreased fetal body weight, length, and thymus weights. Liver-to-body ratios increased (P less than 0.05) in both surgically-instrumented groups. The addition of the umbilical artery doppler flow probe and an umbilical venous catheter did not lead to any further alterations in fetal growth. The current study demonstrates that surgical instrumentation alone can lead to significant alterations in fetal growth.     

Renal extraction of glutamine from plasma and whole blood: studies in dogs and rats

The change in plasma and blood cell pools of L-glutamine during a single pass through the kidney was studied in dogs and rats. It was shown that the glutamine content of blood cells does not change following one passage through the renal vascular bed in normal or acidotic dogs. Furthermore, an infusion of L-glutamine elevating by 10-fold the plasma concentration of this amino acid only minimally changed the blood cells' glutamine content. Therefore within the time frame of acute experiments, the dog blood cells can be assumed to be impermeable to glutamine in vivo. Accordingly, renal glutamine extraction can be measured using either whole blood or plasma arteriovenous difference in this species. However, the latter value is larger and therefore can be measured more accurately. In normal rats, no net renal glutamine extraction is measured. In contrast, a considerable renal glutamine uptake occurs in acidotic rats, 23% of the extracted glutamine coming from the blood cell pool. A load of glutamine in vivo significantly elevates both the plasma and the blood cell concentration. It is concluded (i) that the renal extraction of glutamine is best estimated using plasma arteriovenous difference in the dog, especially when the renal extraction is small; (ii) that whole blood measurements should be obtained in the rat.     

Cocaine and single ventricle: a population study.

A recent case report by Shepard et al. (Teratology 43:113-117, 1991) suggested that single ventricle may result from maternal cocaine ingestion by inducing coronary occlusion in the developing fetal heart. We used data from the Atlanta Birth Defects Case-Control Study and the Metropolitan Atlanta Congenital Defects Program (MACDP) to investigate the role of maternal cocaine ingestion in the induction of single ventricles. We identified through the MACDP 58 case infants with a single ventricle, 27 who were study subjects in the Atlanta Birth Defects Case-Control Study, and 31 who were not. We conducted a case-control study with the 27 Atlanta Birth Defects Case Control Study infants, frequency-matched to control infants by race, hospital of birth, and calendar quarter of birth. None of the 27 case infants were exposed to cocaine during early pregnancy, but 7 (0.43%) of the control infants were exposed during early pregnancy. Using MACDP data, we conducted an analysis of trends for prevalence of single ventricle in the metropolitan area. No upward trend in single ventricle was detected for 1968 through 1990. Our data suggest that even if maternal cocaine ingestion during pregnancy is a cause of single ventricle, most cases appear to be unrelated to this exposure.