Carbamoylation of glomerular and tubular proteins in patients with kidney failure: a potential mechanism of ongoing renal damage.

BACKGROUND: Cyanate formed spontaneously from urea carbamoylates non-protonated amino groups of protein, irreversibly altering function, charge and structure. Carbamoylated proteins in renal tissue have not been examined hitherto. OBJECTIVES: To identify homocitrulline (epsilon-amino-carbamoyl-lysine), a result of in vivo carbamoylation by urea-derived cyanate, from patients with renal disease or in newly transplanted kidneys by immunohistochemistry. To evaluate enzymatic activity of carbamoylated and non-carbamoylated matrix metalloproteinase-2 and correlate this with renal tissue carbamoylated in vivo. DESIGN: Anti-homocitrulline antibody is specific for homocitrulline and was used to identify carbamoylation of epsilon-amino-lysine in renal biopsies from patients with elevated BUN, with isolated proteinuria, and as controls, from normal donors at time of transplantation. Enzymatic activity of matrix metalloproteinase-2 carbamoylated in vitro was evaluated. RESULTS: Homocitrulline was present in glomerular basement membrane (8/10), mesangium (8/10), tubular epithelium and cytoplasm (7/10) and Bowman's capsule (1/10) in patients with elevated BUN. The discordant patterns of glomerular and tubular localization of homocitrulline versus immune complexes indicated that the carbamoylated proteins were not a component of immune deposits but were modified proteins in renal tissue. No homocitrulline was found in transplanted kidneys (14/15) or in proteinuric patients (2/2). Enzymatic activity of both human and rat matrix metalloproteinase-2 was strongly inhibited in a dose-dependent fashion when incubated with cyanate. CONCLUSIONS: In situ carbamoylation in proteins occurred in kidneys of patients with renal dysfunction but not in normal newly transplanted kidneys. Decreased enzymatic activity of carbamoylated enzymes may alter specific renal regulatory mechanisms. Carbamoylated proteins with altered function and charge may represent a previously underestimated mechanism in renal pathophysiology.

Assuring quality in laboratory testing at the point of care.

The science of laboratory medicine has undergone much change during recent years. Despite more recent emphasis on quality improvement, there has not been sufficient attention paid to effective quality management of new approaches to laboratory testing such as point of care testing. It is important that appropriate resources be allocated to quality management, so that waste is minimized and that resources which are expended may be demonstrated to affect the quality of patient care in a positive way. Older quality management tools such as process quality control and proficiency testing are vital to the success of point of care testing programs, however, new ways of looking at the use of these tools are required. Newer approaches such as electronic quality control of point of care devices and an expanded role of total quality management strategies will enhance rather than supplant the more traditional quality improvement mechanisms.

Solitary spinal cord sarcoidosis without other manifestations of systemic sarcoidosis.

We report a biopsy-proven case of sarcoidosis limited to the spinal cord and responsive to treatment with oral corticosteroids. Involvement of the spinal cord by systemic sarcoidosis is uncommon and is associated with several unusual pathological and radiological characteristics that may contribute to its misdiagnosis and subsequent mismanagement. The importance of these unusual characteristics is greatly amplified in solitary spinal cord sarcoidosis because there are no systemic findings to suggest a sarcoid etiology.

Further observations on the etiology of pre-eclampsia: mobilization of toxic cadmium-metallothionein into the serum during pregnancy.

Cadmium-metallothionein, mobilized from the liver, might be the toxic serum factor associated with pre-eclampsia. We base this on four documented concepts. First, during pregnancy, maternal physiology adjusts to assure the fetus of the proper amounts of nutrients necessary for growth. Our focus is on zinc and progesterone. Second, because zinc and cadmium are similar, they compete for binding sites. Our focus is on the storage protein metallothionein. Third, the manifestations of cadmium toxicity closely mimic the manifestations of toxemia (i.e. hypertension, proteinuria, edema). Our focus is on cadmium-induced endovasculitis. Fourth is the concept that metallothionein-bound cadmium can be mobilized from the liver into the serum during pregnancy as it follows the mobilization of metallothionein-bound zinc. Our focus is on the extreme toxicity of extracellular cadmium-metallothionein. We correlate these four concepts into a rational theory on the etiology of toxemia, and we suggest a method of proof.

Solitary focal demyelination in the brain as a paraneoplastic disorder.

Solitary focal demyelination (SFD) in the brain is an uncommon and poorly understood disorder of uncertain etiology that may represent an intermediate entity between multiple sclerosis and acute disseminated encephalomyelitis. In a few reported cases of SFD, the patient was briefly noted to have a nonneurological malignancy. We studied two patients who had solitary focal lesions in the brain. Utilizing magnetic resonance imaging and tissue biopsy, we found the characteristics of the brain lesions in these two patients to be those of SFD. In our combined experience over the past 10 years, we have encountered no similar brain lesions at our medical center. We found it remarkable that both of these patients also had malignancy outside of the nervous system. One had a seminoma, and the other a lymphoma. We conclude that some cases of SFD in the brain may occur as a paraneoplastic disorder associated with nonneurological malignancies.

College of American Pathologists Conference XXVIII on alternate site testing: introduction.

The College of American Pathologists Conference XXVIII, Alternate Site Testing Conference: Venturing Beyond the Boundaries of the Clinical Laboratory, was held from January 29 through February 1, 1995. This open format consensus conference gathered together individuals with many different points of view on the topic of hospital laboratory testing in noncentralized laboratories. The goals of the conference were to establish a basis for common beliefs about alternate site testing, to discover where consensus existed, and to establish future directions for consensus development and resolution of disputes in this sometimes contentious and confusing area of laboratory medicine. Attainment of the goals was attempted through a variety of conference activities, including plenary addresses, poster sessions, and, most importantly, through open-forum breakout sessions. During the breakout sessions all conference attendees were invited to contribute ideas toward the development of consensus about critical issues surrounding alternate site testing. Although it is clear that much work remains to be done if we are to learn how to use alternate site testing strategies to the best advantage, an important beginning has been made. The stage has been set as we continue to provide high-quality laboratory testing in an era that demands both fast turnaround time and optimal cost effectiveness.

The mobile laboratory in alternative site testing.

The establishment of mobile or portable laboratories as one strategy for delivery of laboratory services at alternative sites is evaluated. The mobile laboratory may be used to replace centralized laboratory testing in areas of critical need, such as critical care areas of the hospital in which relatively large numbers of tests are needed quickly. Other possible areas of use include outpatient clinics and other outreach settings in which care of the patient may be hastened by the availability of laboratory data on a real-time basis. In such areas where a need is established, mobile laboratory testing may be performed economically and may enhance the position of the medical technologist as a hands-on clinical caregiver.

Background--setting the stage for alternate-site laboratory testing.

Market forces and service demands are driving a segment of laboratory testing away from centralized laboratories and closer to the patient's bedside. Placed into a historical perspective, this should be neither surprising nor distressing. Terminology is being clarified and professional societies are beginning to take the lead in molding these testing strategies into appropriate tools for advancing excellent patient care.

Quality control and quality management of alternate-site testing.

Quality is an important attribute of clinical laboratory results; however, methods for defining acceptable quality may not be entirely agreed upon. In addition, confusion over quality is added when laboratory testing is moved to alternate sites. As quality parameters are designed for novel laboratory delivery systems, it will be best to use novel approaches that build on already well-defined principles of laboratory quality management.

Urea-derived cyanate forms epsilon-amino-carbamoyl-lysine (homocitrulline) in leukocyte proteins in patients with end-stage renal disease on peritoneal dialysis.

Carbamoylated proteins have been located by using a site-specific polyclonal antihomocitrulline antibody and a fluorescent secondary antibody in leukocytes from patients with end-stage renal disease who were undergoing maintenance continuous ambulatory peritoneal dialysis. A covalent reaction with urea-derived cyanate and the epsilon-amino group of lysine forms homocitrulline residues in carbamoylated proteins. Isocyanic acid, the reactive form of cyanate, is spontaneously formed from urea in aqueous solution at physiologic pH and temperature. In washed, fixed monolayers of cells, an intracellular fluorescent antigen-antibody complex was located throughout the cytoplasm of polymorphonuclear neutrophils (PMNs) and monocytes from 11 patients with blood urea nitrogen (BUN) levels ranging from 32 to 102 mg/dl who were undergoing dialysis for 2 to 135 months. A punctate fluorescence present in the cell surface proteins of living cells demonstrated that lysine residues in the external domain of proteins were carbamoylated, forming homocitrulline. In contrast, we found a perinuclear fluorescence in PMNs in normal subjects with no history of renal insufficiency and BUN levels of 6 to 19 mg/dl. This suggests that homocitrulline is located in carbamoylated proteins within the perinuclear membrane, a structural organelle continuous with the endoplasmic reticulum. It appears that continuous exposure to urea-derived cyanate in low levels results in increasing carbamoylation of stable proteins over the PMN's lifetime. When normal PMNs were exposed to 120 mmol/L cyanate ion in vitro for 10 to 30 minutes, the ability of PMNs to release microbicidal superoxide was strongly inhibited. Thus protein carbamoylation may provide a regulatory mechanism. The altered function of PMNs in renal disease may be due in part to the posttranslational modification of proteins by urea-derived cyanate.

Increased absorption of and sensitivity to cadmium during late pregnancy: is there a relationship between markedly decreased maternal cadmium binding protein (metallothionein) and pregnancy-induced hypertension?

Laboratory animals have a unique sensitivity to cadmium toxicity in late pregnancy. This acute toxicity is not seen in non-pregnant, early pregnant, or lactating animals. Furthermore, during late pregnancy, laboratory animals absorb and retain substantially more cadmium from their diets than they do in the non-pregnant state. Both of these observations parallel the fact that a fivefold late gestational drop of maternal metallothionein (a metal-binding protein believed to detoxify cadmium) has been demonstrated in pregnant animals. Additional factors such as nutritional status and age affect cadmium absorption. As we have discussed previously, cadmium toxicity and toxemia of pregnancy have many common features including hypertension, proteinuria, edema, vasospasm and endovasculitis. Because of the above, we propose that cadmium plays a role in the etiology of toxemia.

Zinc, cadmium, metallothionein, and progesterone: do they participate in the etiology of pregnancy induced hypertension?

Cadmium, a toxic heavy metal, has been incriminated in the etiology of essential hypertension. Zinc, an essential micronutrient necessary for growth, competes with cadmium for binding sites in biochemical processes; zinc deficiency states (i.e. pregnancy and low protein diet) might expose an individual to increased risk of cadmium toxicity. The increased sensitivity to cadmium during pregnancy could also be related to the effect of progesterone on zinc and cadmium metabolism through the actions of metallothionein (MT). MT is a low molecular weight protein believed to function in cadmium detoxification. Several studies in lab animals have documented a late gestation drop of maternal MT levels. This was thought to be due to rising progesterone levels. If there is also a late gestation drop in human maternal MT, then the propensity toward maternal cadmium toxicity would be enhanced. Therefore, we propose that when a zinc deficient woman becomes pregnant and is exposed to both the nutritional demands of the fetus and to the influence of progesterone, she will be likely to develop the manifestations of cadmium toxicity (i.e. hypertension, proteinuria, edema, etc.).

Elevated serum bromide in patients taking lithium carbonate.

Serum bromide levels were determined for 20 patients receiving lithium carbonate for manic depressive illness. Bromides averaged 17.06 +/- 8.15 mg/dl, which exceeded the control average of 3.22 +/- 3.2 mg/dl. Elevated serum bromide in patients taking lithium may reflect altered renal function.

Fatal subscapular staphylococcal abscess.

A previously healthy 19-year-old man had a Staphylococcus aureus subscapular abscess after trauma to the shoulder, leading to sepsis, pneumonia, and death. Subscapular abscesses are infrequently described and might represent diagnostic difficulty to the clinician as well as to the unwary autopsy pathologist.

Intrathoracic lipomas in children.

An asymptomatic 8-year-old boy had had a large intrathoracic tumor for five years. When noninvasive technics proved fruitless in establishing a diagnosis, surgical removal was elected. A large posterior mediastinal lipoma was discovered. This is the 15th intrathoracic lipoma reported in the pediatric age group.