Search PubMed⌕ Search

Biomedical subjects

Y Weiss

Publications and source records attributed to Y Weiss.

At least 19 recordsLinked to original sources
PubMed2006

Reporter gene recombination in juxtaglomerular granular and collecting duct cells by human renin promoter-Cre recombinase transgene.

To assess the feasibility of using the renin promoter for expressing Cre recombinase in juxtaglomerular (JG) cells only, we generated five independent transgenic mouse lines (designated hRen-Cre) expressing Cre recombinase under control of a 12.2-kb human renin promoter. In the kidneys of adult mice Cre mRNA (RT-PCR) was found in the renal cortex, with Cre protein (immunohistochemistry) being localized in afferent arterioles and to a lower degree in interlobular arteries. Cre mRNA levels were regulated in a renin-typical fashion by changes in oral salt intake, water restriction, or isoproterenol infusion, indicating the presence of key regulatory elements within 12.2 kb of the 5'-flanking region of the human renin gene. hRen-Cre mice were interbred with both the ROSA26-EGFP and ROSA26-lacZ reporter strains to assess renin promoter activity from Cre-mediated excision of a floxed stop cassette and subsequent enhanced green fluorescent protein (EGFP) and beta-galactosidase (beta-gal) detection. In adult mice, beta-gal staining and EGFP were observed in afferent arterioles and interlobular arteries, overlapping with Cre protein expression. In addition, intense beta-gal staining was found in cortical and medullary collecting ducts where Cre expression was minimal. In embryonic kidneys, beta-gal staining was detected in the developing collecting duct system beginning at embryonic day 12, showing substantial activity of the human renin promoter in the branching ureteric bud. Our data indicate that besides its well-known activity in JG cells and renal vessels the human renin promoter is transiently active in the collecting duct system during kidney development, complicating the use of this approach for JG cell-specific excision of floxed targets.

Animals↗
PubMed2001

Beyond junctions: nonlocal form constraints on motion interpretation.

Because of the aperture problem, local motion measurements must be combined across space. However, not all motions should be combined. Some arise from distinct objects and should be segregated, and some are due to occlusion and should be discounted because they are spurious. Humans have little difficulty ignoring spurious motions at occlusions and correctly integrating object motion, and are evidently making use of form information to do so. There is a large body of theoretical and empirical evidence supporting the importance of form processes involving junctions in the way motion is integrated. To assess the role of more complex form analysis, we manipulated nonlocal form cues that could be varied independently of local junctions. Using variants on diamond and plaid stimuli used in previous studies, we found that manipulations distant from the junctions themselves could cause large changes in motion interpretation. Nonlocal information often overrides the integration decisions that would be expected from local cues. The mechanisms implicated appear to involve surface segmentation, amodal completion, and depth ordering.

Cues↗
PubMed2001

Correctness of belief propagation in Gaussian graphical models of arbitrary topology.

Graphical models, such as Bayesian networks and Markov random fields, represent statistical dependencies of variables by a graph. Local "belief propagation" rules of the sort proposed by Pearl (1988) are guaranteed to converge to the correct posterior probabilities in singly connected graphs. Recently, good performance has been obtained by using these same rules on graphs with loops, a method we refer to as loopy belief propagation. Perhaps the most dramatic instance is the near Shannon-limit performance of "Turbo codes," whose decoding algorithm is equivalent to loopy propagation. Except for the case of graphs with a single loop, there has been little theoretical understanding of loopy propagation. Here we analyze belief propagation in networks with arbitrary topologies when the nodes in the graph describe jointly gaussian random variables. We give an analytical formula relating the true posterior probabilities with those calculated using loopy propagation. We give sufficient conditions for convergence and show that when belief propagation converges, it gives the correct posterior means for all graph topologies, not just networks with a single loop. These results motivate using the powerful belief propagation algorithm in a broader class of networks and help clarify the empirical performance results.

Journal Article↗
PubMed2001

Management of varicocele in military obligatory service: Israel Defense Forces Medical Corps policy.

Varicocele is a well-known and highly prevalent medical problem in young obligatory service recruits. Still, there are many questions regarding its management. Is there a clear relation between varicocele and infertility? Can early varicocelectomy in young soldiers prevent future infertility? Is there a role for varicocelectomy in pain relief in physically active soldiers? And finally, what are the pros and cons of the open surgical, laparoscopic, or radiographic techniques in this specific population? Answering these questions should help military physicians in varicocele patients' care. It should also help decision makers to build cost-effective and evidence-based health policy. In this article, we review the literature regarding the controversies in the management of varicocele in young adults and delineate the current policy of the Israel Defense Forces Medical Corps.

Age Factors↗
PubMed2000

Diagnosis of abdominal tuberculosis by transabdominal ultrasound-guided needle biopsy.

Laparotomy and laparoscopy have been used for biopsy of pelvic masses in the differential diagnosis between abdominal tuberculosis and ovarian cancer. We suggest the use of transabdominal needle biopsy under ultrasound guidance in such cases. Two women developed abdominal distention, one of whom had been receiving medical treatment for known tuberculosis. In both cases, ultrasonography showed a pelvic mass and ascites associated with high levels of CA 125. A transabdominal ultrasonographically-guided biopsy of the masses with a trucut needle established their tuberculous origin. The transabdominal sonographic needle biopsy is a reliable diagnostic procedure in the differential diagnosis between abdominal tuberculosis and ovarian malignancy. This minimally invasive procedure saves the patient with tuberculosis from unnecessary laparotomy.

Adult↗
PubMed2000

Adventures with gelatinous ellipses--constraints on models of human motion analysis.

An ellipse rotating rigidly about its center may appear to rotate rigidly or to deform nonrigidly so that it appears gelatinous. We use this ambiguous stimulus to study how motion information is propagated across space. We find that features that are quite far from the contour of the ellipse may have a strong influence on the percept of the ellipse, provided they move in a way consistent with the motion of the ellipse. We show that the percept cannot be accounted for by computational models that pool constraints over a local area only, or by models that propagate information along contours, or by models that indiscriminately propagate information across space. However, the percept can be accounted for by a class of models that assume smoothness in a layered representation.

Algorithms↗
PubMed2000

Correctness of local probability in graphical models with loops.

Graphical models, such as Bayesian networks and Markov networks, represent joint distributions over a set of variables by means of a graph. When the graph is singly connected, local propagation rules of the sort proposed by Pearl (1988) are guaranteed to converge to the correct posterior probabilities. Recently a number of researchers have empirically demonstrated good performance of these same local propagation schemes on graphs with loops, but a theoretical understanding of this performance has yet to be achieved. For graphical models with a single loop, we derive an analytical relationship between the probabilities computed using local propagation and the correct marginals. Using this relationship we show a category of graphical models with loops for which local propagation gives rise to provably optimal maximum a posteriori assignments (although the computed marginals will be incorrect). We also show how nodes can use local information in the messages they receive in order to correct their computed marginals. We discuss how these results can be extended to graphical models with multiple loops and show simulation results suggesting that some properties of propagation on single-loop graphs may hold for a larger class of graphs. Specifically we discuss the implication of our results for understanding a class of recently proposed error-correcting codes known as turbo codes.

Bayes Theorem↗
PubMed1997

Match quality, new information, and marital dissolution.

"This article investigates the role of surprises in marital dissolution [in the United States]. Surprises consists of changes in the predicted earning capacity of either spouse. Data from the National Longitudinal Study of the High School Class of 1972 is used. We find that an unexpected increase in the husband's earning capacity reduces the divorce hazard, while an unexpected increase in the wife's earning capacity raises the divorce hazard. Couples sort into marriage according to characteristics that are likely to enhance the stability of the marriage. The divorce hazard is initially increasing with the duration of marriage, and the presence of children and high levels of property stabilizes the marriage."

Americas↗
PubMed1997

Impaired glucose-induced insulin response in transgenic mice overexpressing the L-phosphofructokinase gene.

The selective impairment of glucose-induced insulin secretion in NIDDM can be attributed to defects in the glucose-signaling system. An alteration in the activity of phosphofructokinase (PFK), a key enzyme in the glycolytic pathway, may play a role in the abnormal glucose-induced insulin secretion. In this study, we evaluated insulin secretion in transgenic (Tg) mice overexpressing the liver-type subunit of phosphofructokinase (PFKL). Three independently derived Tg-PFKL lines showed random and postprandial hyperglycemia with diminished acute insulin response following intravenous glucose tolerance load. Isolated islets of Tg-PFKL mice exhibited a shift to the right of the glucose insulin dose curve. However, the maximal insulin secretory capacity, as well as the potentiation effect by arginine, were retained. PFK activity in Tg-PFKL islets was increased by 30-70%, because of the overexpression of PFKL. Conceivably, a selective overexpression of the PFKL isoform in Tg-PFKL mice altered the enzymatic properties of the tetrameric PFK and thereby affected glucose metabolism. A similar phenomenon was previously observed in transfected PC12-PFKL cells. The data show that overexpression of PFKL in transgenic mice was associated with diminished glucose-induced insulin response and suggest a mechanism to explain the role of beta-cell PFK activity in glucose-induced insulin secretion.

Age Factors↗
PubMed1997

Alveolar macrophages fat stain in early diagnosis of fat embolism syndrome.

The aim of this study was to assess the contribution of bronchoalveolar lavage (BAL) in the diagnosis of fat embolism syndrome (FES). The presence of fat droplets in alveolar macrophages was addressed in 13 trauma patients with bone fractures and 10 non-trauma patients with acute respiratory distress syndrome (ARDS). The control group was composed of 5 anesthesized patients with ischemic heart disease, immediately prior to cardiac surgery. Two patients with suggestive clinical and laboratory signs of FES had 40% and 24% fat-containing alveolar cells, respectively. The trauma patients without signs of FES displayed a wide variation in the percentage of fat-containing macrophages (from 3% to 95%). Most of the patients with ARDS who were receiving lipid emulsion as part of their parenteral nutrition, had a high percentage (> 85%) of fat-containing macrophages. Patients with normal lungs had no fat-containing macrophages. Our findings suggest that BAL Oil Red O-positive macrophages are frequently observed in trauma patients irrespective of the presence of FES. Therefore, estimation of the percentage of fat-containing macrophages from BAL is an unreliable marker of FES.

Adult↗
PubMed1996

[Epidural analgesia for postoperative pain in infants and children].

Until recently it was thought that children do not suffer as much from postoperative pain as adults. Coupled with the fear of administering systemic opiates to young children, this meant that babies were often left "to cry it out." Lately it has been acknowledged that children and even babies not only feel pain, but similar to adults, suffer from the physiologic consequences of the untreated stress response. It has also been shown that preventing this response improves the postoperative period in babies after undergoing cardiac surgery. Regional analgesia is commonly used to provide postoperative pain control in adults and children. Following minor lower abdominal surgery, pain relief is often provided by caudal analgesia or specific nerve blocks. Epidural and spinal anesthesia are also gaining popularity for young children and even babies. We describe 3 cases of continuous epidural analgesia in babies, and review other methods for postoperative pain relief. These cases are representative of the many which we have treated over the past 2 years. We use epidural analgesia in children who undergo major thoracic, abdominal, pelvic and major lower limb surgery, and are expected to suffer significant postoperative pain for more than 24 hours. We have not encountered any major complications or inadvertent dural punctures. We judiciously monitor these children, especially their respiratory function, as long as they receive epidural narcotics.

Adult↗
PubMed1996

Positive end-expiratory pressure-induced hemodynamic changes are reflected in the arterial pressure waveform.

OBJECTIVE: To examine whether the hemodynamic changes due to mechanical ventilation with positive end-expiratory pressure (PEEP) can be assessed by the respiratory-induced variations in the arterial pressure waveform during normovolemia and experimental acute ventricular failure. DESIGN: Prospective, controlled experimental study. SETTING: Institutional experimental laboratory. SUBJECTS: Adult mongrel dogs. INTERVENTIONS: Experimental acute ventricular failure was induced by the infusion of pentobarbital (a cardiodepressant) and methoxamine (a vasoconstrictor), combined with volume loading. Both the control and acute ventricular failure groups were subjected to ventilation with incremental levels of PEEP up to 20 cm H2O. MEASUREMENTS AND MAIN RESULTS: Cardiac function was evaluated by cardiac output and left and right ventricular change in pressure over time (dP/dt) measurements. Arterial pressure waveform analysis was performed by measuring the systolic pressure variation, which is the difference between the maximal and minimal systolic blood pressure values during one mechanical breath. The components of the systolic pressure variation, namely, dUp and dDown, which are the increase and decrease in the systolic pressure during the mechanical breath relative to the systolic pressure during apnea, were also measured at each PEEP level. PEEP caused significant reduction of cardiac output in normovolemic dogs, and was associated with significant increases in systolic pressure variation and dDown. Acute ventricular failure decreased the variations in the systolic pressure and caused the dDown component to disappear. The application of PEEP did not affect cardiac output in dogs with acute ventricular failure, nor did it change systolic pressure variation and the dDown. CONCLUSIONS: Analysis of arterial pressure waveforms during mechanical ventilation reflected the decrease in cardiac output in dogs with normal cardiac function subjected to incremental PEEP. In dogs with acute ventricular failure in which PEEP did not affect cardiac output, the systolic pressure variation was similarly unaffected by PEEP. In the absence of cardiac output measurement during mechanical ventilation with PEEP, the analysis of the respiratory variations in the arterial pressure waveform may be useful in assessing changes in cardiac output.

Animals↗
PubMed1995

Prevention of diabetes-associated embryopathy by overexpression of the free radical scavenger copper zinc superoxide dismutase in transgenic mouse embryos.

OBJECTIVES: It has recently been suggested that oxygen free radicals are involved in the high incidence of fetal dysmorphogenesis that is associated with diabetic pregnancies. The purpose of the current investigation was to study the effect of copper zinc superoxide dismutase, a free radical scavenging enzyme, on the prevention of diabetes-associated embryopathy in mice. STUDY DESIGN: Mice used in this study were either transgenic, bearing the human copper zinc superoxide dismutase gene, or nontransgenic controls. Diabetes was generated by streptozotocin administration on days 6 and 7 of gestation. Hyperglycemia developed on day 8 and was maintained through day 10 (critical period of organogenesis). On day 10 fetuses were examined for external anomalies, and their crown-rump lengths and deoxyribonucleic acid content were determined. RESULTS: Induction of maternal diabetes produced a significant reduction in mean crown-rump length of control embryos (4.48 +/- 0.7 mm vs 3.65 +/- 0.6 mm, p = 0.0001), whereas transgenic embryos were not affected (4.72 +/- 0.6 mm vs 4.45 +/- 0.8 mm, p > 0.05). After induction of diabetes fetal loss and malformation rates were significantly higher in control embryos (6.0% vs 23.8% and 8.4% vs 16.5%, respectively). Transgenic embryos were practically unaffected by diabetes and showed fetal loss and malformation rates of 5.9% and 4.4%, respectively, after induction of diabetes. CONCLUSIONS: Elevated levels of copper zinc superoxide dismutase, a key enzyme in the metabolism of free oxygen radicals, elicit a protective effect against diabetes-associated embryopathy.

Analysis of Variance↗
PubMed1995

Aortic distensibility in normotensive, untreated and treated hypertensive patients.

BACKGROUND: Compared with normotensive subjects, untreated hypertensive patients show a decrease of their aortic distensibility. Whether antihypertensive treatment, by reducing blood pressure and changing functional and/or structural abnormalities of the arterial wall, may prevent or reverse the arterial damage due to the accelerated ageing process remains unclear. The objective of the present study was to determine, using a cross-sectional approach, whether aortic distensibility as measured by pulse wave velocity, in treated hypertensive patients whose diastolic blood pressure had been normalised for several months, was significantly improved over that of untreated hypertensive patients. METHODS: Carotid femoral pulse wave velocity was measured in 124 normotensive subjects and 388 hypertensive patients. The latter group included 164 treated patients with well controlled diastolic blood pressure and 224 untreated hypertensive subjects. The three groups did not differ in other cardiovascular risk factors. RESULTS: In each group there was a significant relationship between age and pulse wave velocity. When compared with untreated hypertensives, treated hypertensives with well controlled diastolic blood pressure had significantly lower blood pressure and pulse wave velocity according to age. However, although diastolic blood pressure of well controlled hypertensives was not significantly different from that of normotensive subjects, the aortic distensibility of the controlled hypertensives remained reduced showing two characteristics: a faster increase in pulse wave velocity with age and a negative relationship with HDL-cholesterol. CONCLUSION: These results suggest that long-term antihypertensive treatment and control of blood pressure using only diastolic blood pressure criteria may not fully reverse arterial alteration associated with hypertensive vascular disease.

Adolescent↗