A scanning electron microscopic and photon absorptiometric study of the development, prolongation, and pattern of recovery from lactation-induced osteopenia in rats

Measurements by scanning electron microscopy (SEM) of femoral hemisections confirmed and amplified results by single-photon absorptiometry that had shown a marked increase in lactation osteopenia in rats fed a low-calcium diet (LCD, 0.04% Ca) as compared with a medium-(adequate) calcium diet (ACD, 0.4% Ca). SEM of bones from rats at the end of lactation on either diet showed a large loss of trabecular bone, increased porosity of endosteal surfaces, and cortical thinning. These changes were much more striking in LCD rats than in ACD rats. Backscattered electron imaging of cross sections of the femora revealed marked cortical thinning at midshaft after lactation, especially in rats on the LCD; this method also showed a marked increase in newly formed, less dense diaphyseal bone on the endosteal surface when dietary calcium had been made available to the LCD rats after lactation ceased. Unlike the rats fed the ACD after lactation, the rats continued on the LCD for the first 3 weeks postlactation failed to recover bone mineral, even though there was a marked decrease in resorbing surfaces of the femora as revealed by morphologic examination. When the diet was changed from the LCD to the ACD for the second 3 weeks postlactation (week 4-6), the bone mineral increased substantially. Overall, these results demonstrate the marked loss of bone during lactation, especially severe in rats fed a low-calcium diet, and the rapid postlactational recovery of bone when adequate dietary calcium was made available, even if the recovery had been delayed for the first 3 weeks by feeding a diet very low in calcium.     

How often can the clinical diagnosis of exanthema subitum be confirmed with the HHV-6 serology test

Three years ago a newly recognized human herpes virus (HHV-6) was identified to be the causative agent for exanthem subitum (roseola infantum). So far this diagnosis was suggested chiefly by excluding other infections and the presence of a typical course of the disease. To find out how often the clinical diagnosis can be confirmed serologically, we asked five pediatricians in private practice as well as residents of the out-patient and infant departments of our hospital to obtain paired heparinized blood samples of any child suspicious for exanthem subitum. 36 children with clinically suspected exanthem subitum and a mean age of 14.2 (5-71) months were included in this prospective study. Indirect immunofluorescence was used to detect IgG and IgM antibodies to HHV-6. In 22 children (61%) the clinical diagnosis was confirmed serologically. IgM antibody was found in only 16 of these 22 children. In 8 patients the results were ambiguous. Three had in the same time a doubtful seroconversion to other viruses of the herpes group (HSV twice; EBV once), in four children there was an insufficient rise in IgG antibodies without presence of an IgM response, and once we found a very high HHV-6 specific antibody titre (greater than 1:80) in both serum samples. In 6 children neither a seroconversion nor a rise in HHV-6 antibody titre were found. Retrospectively, only three of these children had a clinical course really typical for exanthem subitum. We conclude that in most cases the clinical diagnosis of exanthem subitum will be confirmed by serological examination.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synaptic physiology of horizontal connections in the cat's visual cortex.

Horizontal connections are a principal component of intrinsic cortical circuitry. They arise mainly from pyramidal cells and course parallel to the brain's surface for distances as long as 8 mm, linking columns with shared orientation preference and allowing cells to integrate visual information from outside their receptive fields. We examined the synaptic physiology of the horizontal pathway in slices of the cat's striate cortex and found that activating lateral fibers produced both excitation and inhibition. We recorded the postsynaptic responses of identified pyramidal cells in layer 2 + 3 of area 17 to electrical shocks applied at three sites: in the home column of the impaled neuron either in layer 2 + 3 or 4, or at a lateral distance of 0.9-3 mm in layer 2 + 3. Within the home column, suprathreshold stimuli produced compound EPSPs with action potentials, followed by fast, GABAAergic IPSPs and a slower, GABABergic IPSP. For the distant stimulating site, the threshold response was an EPSP. Stronger shocks frequently evoked a disynaptic, GABAAergic IPSP that truncated the EPSP and could dominate the postsynaptic response. At the resting potential, the horizontally evoked EPSP was too small to elicit spikes. With depolarization of the membrane, however, it grew several hundred-fold. This amplification was blocked by N-(2,6-dimethylphenylcarbamoylmethyl)triethylammonium bromide (QX-314), but not by 2-amino-5-phosphonovalerate (APV), indicating that it was mediated by Na+ channels, rather than by NMDA receptors. We propose that the horizontal connections provide the means for stimuli outside the receptive field to modulate activity elicited within its confines. The voltage-dependent enhancement of the laterally evoked EPSP may explain why stimulating the surround by itself fails to drive cells but can facilitate their response to stimuli within the receptive field. The ability to initiate disynaptic inhibition from lateral sites shows that recruiting appropriate groups of horizontal fibers can also have a suppressive effect. Thus, the effect of horizontal input is state dependent, with the size and sign of the laterally evoked response changing according to the balance of converging inputs.     

A framework for evaluating image segmentation algorithms.

The purpose of this paper is to describe a framework for evaluating image segmentation algorithms. Image segmentation consists of object recognition and delineation. For evaluating segmentation methods, three factors-precision (reliability), accuracy (validity), and efficiency (viability)-need to be considered for both recognition and delineation. To assess precision, we need to choose a figure of merit, repeat segmentation considering all sources of variation, and determine variations in figure of merit via statistical analysis. It is impossible usually to establish true segmentation. Hence, to assess accuracy, we need to choose a surrogate of true segmentation and proceed as for precision. In determining accuracy, it may be important to consider different 'landmark' areas of the structure to be segmented depending on the application. To assess efficiency, both the computational and the user time required for algorithm training and for algorithm execution should be measured and analyzed. Precision, accuracy, and efficiency factors have an influence on one another. It is difficult to improve one factor without affecting others. Segmentation methods must be compared based on all three factors, as illustrated in an example wherein two methods are compared in a particular application domain. The weight given to each factor depends on application.     

Calciphylaxis – a topical overview

'Calciphylaxis', a calcification syndrome associated with ischaemic cutaneous necrosis, is acquired naturally in humans in disease states. It is a life and limb-threatening complication, usually observed in patients with renal disease and secondary hyperparathyroidism, but known to occur in the absence of renal or parathyroid disease. The reported mortality rate, which ranges from 60-80%, relates to wound infection, sepsis and organ failure. It is a small-vessel vasculopathy, which is estimated to occur in about 4% of haemodialysis patients. Clinically, violaceous, reticulate areas of cutaneous necrosis and eschar may be evident, particularly in the extremities. In addition to the clinical picture, a raised calcium phosphorous product, an elevated parathyroid hormone level, radiographic evidence of vessel and soft-tissue calcification and the finding of mural calcification affecting small arteries and arterioles on histopathology help to confirm the diagnosis of this entity which generally has a poor prognosis. A high index of suspicion and an active multidisciplinary management approach, with rigorous attention to wound care and prevention of sepsis, are vital in the management of these patients. In this overview, we discuss the pathophysiology, clinical features and associations, risk factors, diagnosis and management issues relating to calciphylaxis.     

A profile of homicides on the streets and in the homes of New York City.

Although prior research has found that homes containing firearms and illicit drug and ethanol users are more likely to be the scene of a homicide than homes that do not contain these elements, the authors studied homicides on the streets as well as in homes so as to assess the role of firearms, cocaine, and ethanol in both settings. Using the files of the Chief Medical Examiner, the authors reviewed all 4,468 homicides occurring in New York City in 1990 and 1991. The most frequent places of occurrence were the streets and other outdoor places (49.6 percent) and the victims'' homes (19.3 percent). Firearms were the cause of death for 49.6 percent of homicides in the home and 80.3 percent of those on the streets. Use of cocaine and ethanol was found more frequently among victims killed on the streets than those killed at home. In addition, victims killed on the streets were more likely to be male, ages 15-24 years, and African American. Further research in regard to prevention and intervention strategies is needed, keeping in mind the different patterns of homicide on the streets compared with those occurring in other settings.