[Effect of subglottic air insufflation on subglottic pressure during swallowing]. / Efecto de la insuflación de aire subglótico sobre la presión subglótica durante la deglución.

OBJECTIVE: To determine whether there are differences between subglottic pressure during swallowing with and without air insufflation via a subglottic catheter in tracheostomized patients. DESIGN: A prospective, randomized cross-over study was made. SETTING: Adult Intensive Care Units. PARTICIPANTS: Patients requiring mechanical ventilation and tracheostomy with a subglottic catheter, and with tolerance to deflation of the balloon and a speaking valve placed over the opening of the tracheostomy tube. INTERVENTIONS: Subglottic pressure was measured during swallowing of a thickened solution with and without the delivery of airflow through the subglottic catheter. MAIN VARIABLE: Subglottic pressure during swallowing. RESULTS: Twelve out of 14 patients showed higher subglottic pressure values during swallowing with air insufflation. Two patients showed no differences between both conditions. Median (Med) values of subglottic pressure for the first, second and third swallow were 5, 4 and 4.5 cmH2O (Med 4.5 cmH2O) without air insufflation, and 8, 5.5 and 7.5 cmH2O (Med 5.5 cmH2O) with air insufflation, respectively (Wilcoxon, Z=-3.078; p=.002). CONCLUSION: In a group of tracheostomized patients, air insufflation via a subglottic catheter increased subglottic pressure levels measured during swallowing.

[Towards an early differential diagnosis in autism spectrum disorders and fragile X syndrome. A systematic review]. / Hacia un diagnóstico diferencial temprano en el trastorno del espectro autista y el síndrome de X frágil. Una revisión sistemática.

INTRODUCTION: Nearly 60% of those diagnosed with fragile X syndrome show comorbidity with autism. Thus, there are similarities and differences between both conditions that lead to very different clinical manifestations. However, an early differential diagnosis may help professionals to detect deficits and enhance strengths to apply the best suitable intervention. The purpose of this scoping review was to provide a comprehensive overview of the relation and the differences between autism and fragile X syndrome to orientate diagnosis and intervention. MATERIALS AND METHODS: The research for articles was carried out in PsycInfo, Medline, SCOPUS and Web of Science, including scientific articles published from 2010 to 2020 and children aged 0-6 years. The scoping review followed the PRISMA-ScR criteria. RESULTS: 22 studies were selected. Results were reviewed in terms of structural and morphological changes and cognitive, communicative, social-emotional and sensory-motor skills. CONCLUSIONS: Different growing cerebral patterns are observed in both conditions. Besides, there are early signs from the different developmental areas studied that show comorbidity or allow early differentiation. However, attentional function or repetitive mannerisms, among others, need further research.

TITLE: Hacia un diagnóstico diferencial temprano en el trastorno del espectro autista y el síndrome de X frágil. Una revisión sistemática.Introducción. Aproximadamente el 60% de las personas con síndrome de X frágil también reciben un diagnóstico de trastorno del espectro autista. Entre estos trastornos existen tantas semejanzas como diferencias, que provocan cuadros clínicos distintos, por lo que es importante el diagnóstico diferencial temprano, de cara a conocer los déficits y fortalezas de cada niño y ajustar el tipo de intervención lo mejor posible. El presente estudio tiene como objetivo realizar una aproximación al conocimiento de la relación y las diferencias de ambas condiciones, y contribuir al diagnóstico diferencial y la posterior intervención. Materiales y métodos. Siguiendo el protocolo PRISMA-ScR, se realizaron búsquedas en las bases de datos de PsycInfo, Medline, SCOPUS y Web of Science, incluyendo los artículos científicos empíricos centrados en la etapa de los 0 a los 6 años desde 2010 a 2020. Resultados. Se seleccionaron 22 estudios en los que se trata el desarrollo inicial de estos dos trastornos y su confluencia. Los resultados se reagruparon en función de cambios morfológico-estructurales, y de las áreas cognitivas, comunicativas, socioemocionales y sensoriomotoras. Conclusiones. A nivel morfológico-estructural, parecen existir ciertos patrones de crecimiento cerebral diferenciadores entre estos trastornos. Asimismo, existen ciertas señales de alarma en las distintas áreas del desarrollo que son indicativas de comorbilidad o permiten la discriminación entre patologías, y existe cierto debate en torno a algunas de ellas, como el nivel atencional o los manierismos repetitivos.

Preliminary evaluation of cerebral 18F-DOPA PET/CT in the differential diagnosis of brain lesions in inconclusive MR.

AIM: To evaluate the utility of brain 18F-DOPA PET/CT in the differential diagnosis of brain lesions with inconclusive MRI. MATERIAL AND METHODS: Twelve patients were studied, with a total of 16 lesions, without definitive diagnosis after brain MRI. A double acquisition PET/CT brain scan was acquired at 20 and 90min. Visual and semiquantitative assessment was performed with SUVmax calculation of the lesions and calculation of the T/S Ratio (tumor/contralateral striatum) and T/N Ratio (contralateral healthy tumor/parenchyma) for each time. RESULTS: Based on the visual assessment scale and using T/S ratio ≥1 and T/N ratio ≥1.3 to determine malignancy, the values of sensitivity (S), specificity (E) and positive predictive value (PPV) were: visual assessment (S 100%, E 33.3%, VPP 71.4%), T/S Ratio (S 90%, E 100%, VPP 100%) and T/N Ratio (S 100%, E 16.6%, VPP 66.6 %). No lesion showed an increase in SUVmax in late acquisition. 18F-DOPA PET/CT modified treatment in 75% of the patients. CONCLUSION: 18F-DOPA PET/CT is a useful tool in the study of brain lesions with inconclusive MRI. Late imaging (dual-point) has no added value in the final diagnosis. FDOPA has an impact on patient management modifying therapeutic behavior.

H2A.Z overexpression suppresses senescence and chemosensitivity in pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most intractable and devastating malignant tumors. Epigenetic modifications such as DNA methylation and histone modification regulate tumor initiation and progression. However, the contribution of histone variants in PDAC is unknown. Here, we demonstrated that the histone variant H2A.Z is highly expressed in PDAC cell lines and PDAC patients and that its overexpression correlates with poor prognosis. Moreover, all three H2A.Z isoforms (H2A.Z.1, H2A.Z.2.1, and H2A.Z.2.2) are highly expressed in PDAC cell lines and PDAC patients. Knockdown of these H2A.Z isoforms in PDAC cell lines induces a senescent phenotype, cell cycle arrest in phase G2/M, increased expression of cyclin-dependent kinase inhibitor CDKN2A/p16, SA-ß-galactosidase activity and interleukin 8 production. Transcriptome analysis of H2A.Z-depleted PDAC cells showed altered gene expression in fatty acid biosynthesis pathways and those that regulate cell cycle and DNA damage repair. Importantly, depletion of H2A.Z isoforms reduces the tumor size in a mouse xenograft model in vivo and sensitizes PDAC cells to gemcitabine. Overexpression of H2A.Z.1 and H2A.Z.2.1 more than H2A.Z.2.2 partially restores the oncogenic phenotype. Therefore, our data suggest that overexpression of H2A.Z isoforms enables cells to overcome the oncoprotective barrier associated with senescence, favoring PDAC tumor grow and chemoresistance. These results make H2A.Z a potential candidate as a diagnostic biomarker and therapeutic target for PDAC.

[Impact of a short stay unit in a tertiary hospital]. / Impacto de una unidad de corta estancia en un hospital de tercer nivel.

OBJECTIVE: To analyze the health care activity indicators of a short-stay unit (SSU) and compare them with those of other services in a Conventional Hospital. MATERIAL AND METHODS: A descriptive, retrospective study was conducted of the patients admitted to SSU during 2003-2007. Number of admissions, mean stay (MS), mortality and destination were analyzed. Mean stay and number of admissions of the main diagnosis-related groups (DRGs) in the SSU were compared with other services of conventional hospitalization. RESULTS: A total of 15.3% of the patients who came to the Emergency Service were admitted to the SSU. Mean stay was significantly lower in the SSU than in the rest of the hospital (year 2003, SSU 3.2 days, rest of the hospital 10.2 days; year 2007, SSU 3.3 days, rest of the hospital 8.6 days). The 4 most common DRGs (71.3% of all those admitted to the SSU) were COPD, respiratory infection/bronchitis, simple pneumonia/pleuritis and heart failure/shock. Mean stay for the 4 DRGs in the SSU was significantly lower (p<0.01) than in Internal Medicine, Pneumology and Cardiology (heart failure/shock). CONCLUSIONS: The SSU handles its most prevalent diseases with greater agility compared to other conventional hospitalization services.

Valoración preliminar de la 18F-DOPA PET/TC cerebral en el diagnóstico diferencial de lesiones cerebrales con RM no concluyente.

AIM: To evaluate the utility of brain 18F-DOPA PET/CT in the differential diagnosis of brain lesions with inconclusive MRI. MATERIAL AND METHODS: Twelve patients were studied, with a total of 16 lesions, without definitive diagnosis after brain MRI. A double acquisition PET/CT brain scan was acquired at 20 and 90 minutes. Visual and semiquantitative assessment was performed with SUVmax calculation of the lesions and calculation of the T/S ratio (tumor/contralateral striatum) and T/N ratio (tumor/contralateral healthy parenchyma) for each time. RESULTS: Based on the visual assessment scale and using T/S ratio ≥ 1 and T/N ratio ≥ 1.3 to determine malignancy, the values of sensitivity (S), specificity (E) and positive predictive value (PPV) were: visual assessment (S 100%, E 33.3%, VPP 71.4%), T/S ratio (S 90%, E 100%, VPP 100%) and T/N ratio (S 100%, E 16.6%, VPP 66.6%). No lesion showed an increase in SUVmax in late acquisition. 18F-DOPA PET/CT modified treatment in 75% of the patients. CONCLUSION: 18F-DOPA PET/CT is a useful tool in the study of brain lesions with inconclusive MRI. Late imaging (dual-point) has no added value in the final diagnosis. F-DOPA has an impact on patient management modifying therapeutic behavior.

[Congenital duodenal obstruction: comparison of two corrective methods]. / Obstrucción duodenal congénita: comparación de dos métodos correctivos.

INTRODUCTION: There are few studies on congenital duodenal obstruction. The poor peristalsis of the proximal duodenum that causes functional obstruction is a well known problem that occurs in the immediate postoperative period. The optimum technique to address the problem is still controversial. OBJECTIVE: To compare the results obtained using two different surgical techniques to resolve congenital duodenal obstruction. PATIENTS AND METHODS: A five-year retrospective review of the neonates who underwent surgery for duodenal obstruction was undertaken. Two different surgical techniques were used: the Kimura operation and Heinecke-Mikulicz enteroplasty. The clinical characteristics, operative time, onset of oral feeding, hospital stay, complications and mortality were analyzed. The results of both groups were compared. RESULTS: Forty-one patients were included; 27 were operated on with the Kimura technique and 14 underwent Heinecke-Mikulicz duodenoplasty.Thirty-five patients had duodenal atresia (86%) and 6 (14%) an annular pancreas. All of them had post-Vater's papilla obstruction and 8 (20%) had trisomy 21. The clinical characteristics of both groups were similar. No significant difference was found in the operative time, onset of oral feeding and hospital stay. Eight patients in each group developed septicemia (30% in the Kimura group vs. 57% in the Heinecke-Mikulicz group, p = 0.16) and one patient in each group died (4% in the Kimura group vs.7% in the Heinecke-Mikulicz group, p = 0.78). CONCLUSION: The Kimura duodenal-duodenal anastomosis and Heinecke-Mikulicz duodenoplasty seem to be useful procedures to resolve congenital duodenal obstruction.

Rendimiento y validación del puntaje NoSAS en la evaluación inicial del síndrome de apnea/hipopnea del sueño / Performance and validation of NoSAS score in sleep apnea-hypopnea syndrome initial assessment

Introducción: El método de referencia para diagnosticar el síndrome de apnea-hipopnea obstructiva del sueño (SAHOS) es la polisomnografía, esta no es diagnóstica en otros trastornos respiratorios del sueño, por lo que es necesario la implementación de puntajes predictivos para diferenciar aquellos pacientes que tienen más riesgos de padecer SAHOS y necesiten de una polisomnografía. El objetivo de este estudio fue validar el puntaje NoSAS y la escala de Berlín frente a la polisomnografía tipo 1 en pacientes con sospecha de SAHOS. Materiales y métodos: Estudio de pruebas diagnósticas. A 264 pacientes se les realizó una polisomnografía basal, la aplicación del puntaje NoSAS y la escala de Berlín; luego, se hizo el análisis de las pruebas diagnósticas y se calculó el rendimiento de cada una en relación con el índice de apnea hipopnea (IAH). Resultados: La sensibilidad del puntaje NoSAS para un IAH ≥ 20 fue 88,57% con intervalo de confianza (IC) 95% 80,4-96,74; especificidad 56,70 %; IC 95% 49,47-63,93 y valor predictivo negativo (VPN) de 93,22, IC 95% 91,70- 99,82. Para la escala de Berlín, la sensibilidad fue de 81,43%, IC 95% 71,60-91,25; especificidad de 58,76%, IC 95% 51,58-65,95 y VPN 89,76%, IC 95% 89,08-98,32. Conclusión: Se demostró que el puntaje NoSAS y la escala de Berlín tienen una buena sensibilidad para descartar a las personas con un menor riesgo de SAHOS. Un paciente clasificado de bajo riesgo probablemente está sano o tiene bajo riesgo para SAHOS moderado a severo y no requeriría de una polisomnografía inicial.

Introduction: The gold standard for diagnosing obstructive sleep apnea-hypopnea syndrome (OSAHS) is the polysomnography, and it is not a diagnostic tool for another sleep breathing disorders, so that it is necessary to implement predictive scores to differentiate those patients who have more risk of suffering OSAHS, therefore they need a polysomnography. The aim to this study was to validate the NoSAS score and Berlin scale in relation to the polysomnography type 1, in patients who have the clinical suspicion of OSAHS. Material and methods: Diagnostic tests study. 264 patients underwent polysomnography, and the NoSAS score and Berlin scale were applied to them. After that, the diagnostic tests analysis was done and the performance of each one of them was calculated in relation to the apnea- hypopnea index (AHI). Results: The sensitivity of the NoSAS score for an AHI ≥ 20 was 88.57%, confidence interval (CI) 95% (80.4-96.74), specificity 56.70 %, CI 95% (49.47-63.93), and the negative predictive value (NPV) was 93.22, CI 95% (91.70-99.82). For Berlin scale the sensitivity was 81.43%, CI 95% (71.60-91.25), specificity 58.76%, CI 95% (51.58-65.95) and NPV 89.76%, CI 95% (89.08-98.32). Conclusions: It was shown that NoSAS score and Berlin scale have a good sensitivity to rule out people who have less OSAHS risk. A patient classified as low risk, probably is healthy or at low risk for moderate to severe OSAHS and would not require an initial polysomnography.

Urinary excretion of nitrate, N-nitrosoproline, 3-methyladenine, and 7-methylguanine in a Colombian population at high risk for stomach cancer.

Urinary excretion levels of nitrate and N-nitrosoproline were determined in 160 individuals in a Colombian population at high risk for gastric cancer. In 156 of these subjects urinary levels of 3-methyladenine and 7-methylguanine were determined. Gastric biopsy specimens were obtained from 118 individuals and were histologically characterized according to pathological criteria into the following groups: normal, superficial gastritis, chronic atrophic gastritis, chronic atrophic gastritis with intestinal metaplasia, and dysplastic. The histological changes were correlated with the four variables listed above. There were no significant differences in the excretion of nitrate, N-nitrosoproline, 3-methyladenine, or 7-methylguanine in subjects with different pathological changes. A statistically significant correlation was present between nitrate and N-nitrosoproline excretion in the total population group (r = 0.297, P = 0.0001). A highly significant correlation (r = 0.56, P = 0.0002) was noted for urinary nitrate and N-nitrosoproline excretion in individuals with intestinal metaplasia and dysplasia. An increase in the urinary excretion of 3-methyladenine and 7-methylguanine was associated with tobacco smoking in the total population group.

Morphological and histochemical studies on the collagen in neurinomas, neurofibromas, and fibromas.

The collagen in neurinomas, neurofibromas was studied by optical and electron microscopy. Neurinomas were shown to be composed mainly of thin argyrophilic, weakly birefringent fibers formed by thin collagen fibrils. Fibromas presented only thick, non-argyrophilic, strongly birefringent fibers composed of thick collagen fibrils. Neurofibromas showed populations of the two above-mentioned types of fibers occupying different areas of their parenchyma. These results suggest that the collagen of neurinomas is mainly of type III, while fibromas present collagen type I, and neurofibromas are composed of both types of collagen.

Relation between interstitial myocardial collagen and the degree of clinical impairment in Chagas' disease.

Cardiac performance is negatively associated with interstitial collagen in Chagas' cardiomyopathy. The magnitude of dysfunction is related to the degree of collagen, and this association seems to exhibit a threshold above it if definite cardiac deterioration occurs.

Mutagenic activity of gastric juice.

Gastric juice samples from patients of a rural area of the Colombian Andes at high risk to gastric cancer were tested for mutagenesis with Salmonella typhimurium strains TA100 and TA1538. Direct mutagenic effect was found in samples with detectable amounts of nitrite. This effect was not accountable by nitrite alone. Nitrite-negative samples from the same area and samples from the low-risk area of Cali were negative using the same mutagenesis assay.

Sodium intake and gastric cancer.

To test the hypothesis that excessive intake of sodium chloride is a factor in gastric carcinogenesis, urinary excretion of sodium and creatinine was measured in Colombian subjects. Age, sex, weight, and height regression slopes for creatinine excretion were more similar in Colombia than in other countries. Sodium/creatinine (S/C) ratios correlated with 24-h urinary excretion of sodium revealed higher sodium excretion in populations with higher gastric cancer rates. The S/C ratios were not affected by circadial rhythms, making it possible to use single urine samples to investigate interpopulation differences in sodium excretion.

Estrogen and progesterone modulation of eosinophilic infiltration of the rat uterine cervix.

Ripening of the rat cervix involves widespread collagenolysis that follows an eosinophilic leukocyte infiltration. The hormonal control of these events is not well understood. The aims of this study were to investigate the mechanism through which progesterone (P) and 17beta-estradiol (E(2)) modulate eosinophilic invasion and to determine if this event is protein synthesis mediated. Cervical eosinophilic invasion was measured in intact rats during the second half of pregnancy and compared with values from ovariectomized (O) pseudopregnant (PSP) rats treated with P and E(2) in doses that mimicked the levels of pregnancy. Other O-PSP rats were treated with an E(2) antagonist (tamoxifen) and the antiprogestin RU-486. To study the role of protein synthesis in eosinophilic invasion of the cervix, rats were treated with actinomycin-D (an inhibitor of mRNA synthesis), and animals were sacrificed on D21 or D22 to evaluate eosinophilic invasion. Rats treated with E(2) showed high levels of infiltration and tamoxifen blocked this E(2) effect. On the other hand, P antagonized the stimulatory effects of E(2) on eosinophilic invasion, however when the P and E(2) treated rats were injected with RU-486 the inhibitory effect of P was reversed. In intact pregnant rats a sharp rise in eosinophilic infiltration was detected on D23, 20 h after the fall of serum P. Finally, E(2) treated rats injected with actinomycin-D had no invasion of eosinophils. In conclusion, the estrogen-triggered eosinophil invasion is affected by the classic estrogen receptor antagonist tamoxifen and by the mRNA synthesis blocker actinomycin-D suggesting a genomic action of E(2). Furthermore, the estrogen effect is blocked by P and this inhibition is reversed by RU-486.

Occurrence of Crassulacean acid metabolism in Cissus trifoliata L. (Vitaceae).

Evidence for the operation of CAM in the deciduous climber, Cissus trifoliata L., was obtained in field and laboratory studies. Under natural conditions, diurnal oscillations of titratable acidity and colorimetric measurements of night CO2 fixation, determined for a period of two and a half years, suggested that acid accumulation was related to plant water status, assessed through the daily courses of stomatal resistance and xylem water potential during dry and rainy seasons. These findings were confirmed by gas exchange studies under controlled conditions which showed that the plant fixed all its CO2 during the day when it was well irrigated; as water stress increased, dark CO2 uptake gradually replaced fixation during the day until the plant only performed dark fixation. In severe water stress, even the rate of the latter process decreased until leaves fell.

Volume fraction of dense-core granules correlates strongly with survival in disseminated (stage IV) neuroendocrine cell carcinomas of the lung of the well differentiated and small cell subtypes.

In order to verify whether ultrastructural quantitative morphological indices of neuroendocrine cell carcinoma of the lung may help to predict survival in disseminated disease (Stage IV), 21 biopsy specimens were studied. Volume density of mitochondria and dense-core granules was assessed by a conventional point-counting procedure. Survival in months after biopsy was considered the dependent variable of age and of the morphometric parameters, in a multivariate linear regression analysis. The significance level was set at 5%. Survival was positively correlated (p = 0.011, multiple r = 0.686) with volume fraction of dense-core granules (p = 0.0025) and negatively correlated with volume fraction of mitochondria (p = 0.035), and also with age (p = 0.034). Our data indicate that survival is strongly dependent on the degree of neuroendocrine differentiation and of metabolic activity of tumour cells and that improved prognostic accuracy is provided by the use of quantitative analyses as compared with the conventional subtyping of malignant pulmonary neuroendocrine neoplasms.

School readiness among urban children with asthma.

BACKGROUND: Children with chronic illnesses, including asthma, are at risk for school problems. Developmental problems, however, may begin before school entry, and the developmental status of preschool children with asthma has not been evaluated. OBJECTIVE: To test the hypothesis that urban preschool children with asthma have lower parent-reported developmental scores compared with children without asthma. METHODS: A comprehensive survey of children beginning kindergarten in 1998 in the urban school system in Rochester, NY, collected parent reports of demographic, medical, and developmental data. We compared children with asthma with and without limitation of activity to children without asthma for motor, language, socioemotional, and school readiness skills and the need for extra help with learning. Linear and logistic regression were used to determine associations between asthma and developmental outcomes. RESULTS: Among the 1058 children in this sample, 9% had asthma, including 5% with asthma with limitation of activity. After adjustment for multiple potential confounding variables, the children with asthma with limitation had lower scores on school readiness skills compared with children without asthma (2.0 vs 2.5, P <.001). Further, the parents of children with asthma with limitation were substantially more likely (P <.05) to describe them as needing extra help with learning (74% vs 56%; odds ratio, 3.2; 95% confidence interval, 1.5--7.8). CONCLUSIONS: Urban preschool children with significant asthma had poorer parent-reported school readiness skills and a greater need for extra help with learning compared with children without asthma. This finding suggests that developmental problems for children with asthma may begin before school entry.

The role of the collagenous and elastic system fibers in modulating bronchoconstriction.

The distribution and conformational changes of the fibers of the collagenous and elastic systems in guinea pig airways after a contractile agonist challenge are described. We observed a distinct pattern of behavior within the mucosal fibers during bronchoconstriction. Part of the fibers of the two systems tend to follow the epithelial invaginations towards the airway lumen, while the remaining ones seem to be attached to the internal smooth muscle. These layers of fibers in the mucosa are interconnected to one another and to the adventitial network by slender fibers. We suggest that the configuration and behavior of these fibers during bronchoconstriction may contribute to airway reopening after the contractile stimulus has ceased. The possible role of this mechanism in the pathophysiology of human asthma is discussed.

Dating of fibrotic lesions by the Picrosirius-polarization method. An application using the lesions of Lechiguana (bovine focal proliferative fibrogranulomatous panniculitis).

This work was designed to verify if a simple quantitative procedure to estimate the state of collagen aggregation is useful in describing the natural history of a fibrous process. For this purpose sixteen cases of Lechiguana lesion were used. Histochemical evaluation of the collagen content and its state of aggregation was done by the Picrosirius-polarization method. Morphometric studies were done by means of a point-counting procedure, which allowed the determination of the areal fraction of thin and thick collagenous fibers within Lechiguana lesions collected at different times of clinical evolution (14 days through 8 months). Early lesions are characterized by thin collagenous fibers. This population of slender fibers decreases later on, when thick fibers become more prevalent. Curve fitting procedures were employed using the state of collagen aggregation as the dependent variable and time as the independent variable. The best fitting was obtained by linear and exponential functions. Statistical analysis indicates that the quantitative study of the degree of collagen organization allows an adequate determination of the time course of Lechiguana lesions. We concluded that simple determinations of collagen aggregation provide numerical data that may be useful to build mathematical models relating time of evolution of the disease to fibrosis.

Effect of aqueous and nonaqueous fixatives on the quantitative estimation of collagen-proteoglycan interaction in tissue sections.

The present study was designed to assess the influence of aqueous and nonaqueous fixatives on the quantitative estimation of collagen-proteoglycan interaction in tissue sections. Tissues containing different collagen types and distinct sulfated proteoglycan classes were isolated from pig costal cartilage, human skin, and the inner muscular layer of dog small intestine and fixed using aqueous or nonaqueous methods. The results showed that the best fixation method was exposure to paraformaldehyde gas. When using aqueous fixatives, proteoglycans were lost to different degrees among the various tissues analyzed, reflecting differences in chemical properties of proteoglycan classes and/or in their interactions with other matrix components such as collagen.