Biomedical subjects

R Lamberts

Publications and source records attributed to R Lamberts.

At least 19 recordsLinked to original sources

PubMed1992

[Type-2B multiple endocrine neoplasms with diffuse liver metastases as the cause of chronic diarrhea].

During examination before surgical correction of pes valgus a 20-year-old man reported having 3-5 pasty, foul smelling diarrhoeic motions per day for the past 3 years. He was noted to have rather thick lips and Marfan-like body build. Erythrocyte sedimentation rate was 18/34 mm, serum activity of GOT 22.5 U/l, GPT 35.7 U/l. Faecal weight was increased to 640 g/d, fat content to 12 g/d. Serum levels of the carcinoembryonic antigen (2494 ng/ml; normal: < 2.5) and of calcitonin (1,619,760 pg/ml; normal < 100) were elevated. Gastroscopy, partial coloscopy, colon-contrast imaging, ultrasonography and computed tomography of the neck and abdomen, as well as magnetic nuclear imaging of the neck were all normal. But laparoscopy revealed the liver to be infiltrated by small whitish nodules which immunohistologically proved to be metastases of a C-cell carcinoma. Total thyroidectomy was performed and the diagnosis of a C-cell carcinoma of the thyroid confirmed intra-operatively. After the operation the diarrhoea was stopped with codeine (9 mg/d). In case of tumour progression, therapy with octreotide, a somatostatin analogue, will be carried out. The concomitant occurrence of C-cell carcinoma, Marfan-like body build, thick lips and skeletal changes is typical of multiple endocrine neoplasia type 2B, which is caused by a chromosomal defect.

Adult↗

PubMed1992

Inter-relationship between serum gastrin levels, gastric mucosal histology and gastric endocrine cell growth.

The development of gastric enterochromaffin-like (ECL)-cell hyperplasia in humans may be associated with extreme hypergastrinaemia, as occurs in Zollinger-Ellison syndrome (ZES) and pernicious anaemia (type A gastritis). More recently, endocrine cell hyperplasia has been found in all forms of chronic atrophic gastritis and even in cases of focal atrophy. Serum gastrin levels, non-antral gastric endocrine (argyrophil) cell growth, and the severity and type of concomitant gastritis were monitored in 66 unoperated and 8 antrectomized patients with poorly responsive peptic ulcer or reflux oesophagitis during up to 5 years' treatment with high-dose omeprazole, 40 mg daily. A small subgroup of patients (23%) had serum gastrin concentrations of more than four times the normal upper limit. These patients also had hyperplasia of the gastric argyrophil cells. More importantly, the same subgroup of patients had high-grade (atrophic) gastritis. Micronodular hyperplasia of argyrophil cells was significantly more frequent in biopsies showing atrophic gastritis (48%) than in biopsies showing only superficial gastritis (3.6%). It is concluded that, as previously demonstrated in untreated patients with gastric ulcer, the argyrophil cell hyperplasia observed during high-dose omeprazole therapy is related to the progression of chronic atrophic gastritis rather than to serum gastrin levels.

Biopsy↗

PubMed1992

Budd-Chiari syndrome as the primary manifestation of a fibrolamellar hepatocellular carcinoma.

An 18-year-old female patient was admitted with ascites, right upper abdominal tenderness and peripheral edema. Angiography showed complete occlusion of the vena cava inferior up to the level of the right atrium. By open heart surgery, masses of thrombotic material were pulled out of the v. cava inferior/vv. iliacae which histologically contained tumor cell populations consistent with a hepatocellular carcinoma. Celiacography showed a highly vascularized tumor in the right hepatic lobe. Histologically, it proved to be fibrolamellar subtype hepatocellular carcinoma.

Adolescent↗

PubMed1991

Somatostatin cells in rat antral mucosa: qualitative and quantitative ultrastructural analyses in different states of gastric acid secretion.

In the gastrointestinal tract somatostatin is localized in endocrine cells and in neurons. The antral somatostatin (D-) cell shares features of both cell types. The activity of the antral D-cell is regulated by intragastric pH. Therefore different states of gastric acidity were induced experimentally in order to study D-cell morphology at the electron microscopical level. The morphological findings were related to measurements of plasma and tissue concentrations of the peptide. The D-cell is characterized by extensive membrane interdigitations with neighbouring cells. Changes in the activity of antral D-cells are reflected by an increase in cytoplasmic secretory granule density and a shift of secretory granules towards basal cell processes. Direct endocrine cell contacts at the level of the perikarya were rarely observed. The intracellular distribution of secretory granules suggests that cell communication is more likely to take place at the level of the strongly immunoreactive cytoplasmic processes. No evidence for endocrine or exocrine (luminar) secretion was observed morphologically. This is in agreement with the concept of paracrine secretion of the antral D-cell.

Animals↗

PubMed1991

Lysosomal storage of glycogen as a sequel of alpha-glucosidase inhibition by the absorbed deoxynojirimycin derivative emiglitate (BAYo1248). A drug-induced pattern of hepatic glycogen storage mimicking Pompe's disease (glycogenosis type II).

Effects of the two absorbable alpha-glucosidase inhibitors miglitol (BAYm1099) and emiglitate (BAYo1248) on hepatic and muscular glycogen concentrations were investigated in the rat after 3, 7, and 28 days. Both compounds were (orally) administered at very high doses (5-50-500 mg/kg b.wt.). In a second experiment, glycogen storage after oral administration of acarbose (1000 mg/kg b.wt.) was studied after 7 days. In a third protocol, hepatic glycogen concentrations were investigated in the fed rat after 7 days of either inhibitor at the respective highest dosage. In fasted rats, emiglitate induced a significant, dose-dependent increase of hepatic glycogen concentrations, which--at the dose of 500 mg/kg b.wt.--were present after 3, 7, and 28 days, but resulted in a significant increase of the liver weight after 28 days only. Light and electron microscopy proved that the increase in hepatic glycogen was due to lysosomal storage of glycogen only. Emiglitate in the amount of 5 mg/kg b.wt. did not induce significant changes either of glycogen concentrations or at the EM-level. While emiglitate also increased hepatic glycogen at a dosage of 50 mg/kg b.wt., miglitol led to significant storage of hepatic glycogen after 3, 7, or 28 days at the highest dose only. With miglitol (500 mg/kg b.wt.), only insignificant lysosomal storage of glycogen could be detected by electron and light microscopy, and liver weight was essentially unaffected. Both compounds displayed a dose-dependent tendency towards higher glycogen concentrations in the soleus muscle, which was significant with the highest dosage of either inhibitor. At an oral dose of o.i.d. 1000 mg/kg b.wt., the almost unabsorbable alpha-glucosidase inhibitor acarbose induced significantly increased glycogen concentrations both in the liver and in the soleus muscle after 7 days. With respect to an enormous enlargement of the lysosomes (EM) and in the absence of cytoplasmatic alpha-glycogen, this accumulation of glycogen must be attributed to lysosomal storage. In fed rats, all alpha-glucosidase inhibitors investigated significantly decreased postprandial hepatic glycogen concentrations (emiglitate greater than miglitol greater than acarbose), thereby reflecting the modulation of absorption. It is concluded that in the rat acarbose at approximately 1000 x ED50 may penetrate the intestinal mucosa at amounts significant enough to induce lysosomal storage of glycogen. Miglitol may cause some hepatocellular, lysosomal glycogen storage at a dose of 500 mg/kg b.wt., but no glycogen storage could be proven up to 100 x ED50 over 28 days.(ABSTRACT TRUNCATED AT 400 WORDS)

1-Deoxynojirimycin↗

PubMed1991

Antral Helicobacter pylori-like organisms in different states of gastric acid secretion.

The frequency of Helicobacter pylori (H.p.) infestation in antral mucosa and the presence of gastritis were investigated in different states of gastric acid secretion. Biopsies were stained by the Warthin-Starry technique and hematoxylin-eosin. Antral H.p. was found in similar frequencies in Zollinger-Ellison syndrome (n = 17; profound acid hypersecretion, associated with duodenal ulcer disease in most cases) and the same number of age-matched controls (35% in each group) whereas H.p. could be detected in 31 out of 33 duodenal ulcer patients (94%). The incidence of H.p. infestation in H2-blocker refractory reflux oesophagitis was low (24%). Treatment of peptic lesions with omeprazole (drug-induced hypochlorhydria) led to a reduction or disappearance of H.p. in 7 out of 10 H.p.-positive patients whereas none of 19 primarily H.p.-negative patients became infected with H.p. during prolonged omeprazole therapy. It is concluded that (1) development of duodenal ulcers (as in gastrinomas) does not necessarily require H.p., and (2) at least in some patients H.p. is reduced in antral mucosa by omeprazole.

Adolescent↗

PubMed1991

Is hypergastrinaemia dangerous to man?

Achlorhydria has been discussed as a possibly dangerous consequence of therapeutic inhibition of gastric acid secretion since the introduction of H2-receptor antagonists. The risk of long-term hypergastrinaemia has only been considered for about 5 years. The reason for this was the demonstration that gastric carcinoids (ECLomas) observed after life-long treatment of rats with the proton pump inhibitor omeprazole could also be produced in rats by other methods leading to long-lasting profound hypergastrinaemia. Such methods were the 80% resection of the oxyntic mucosa or feeding of ranitidine (2000 mg/day) for 2 years. The endocrine tumours corresponded to the gastric carcinoids found in patients with long-lasting hypergastrinaemia due to pernicious anaemia or with a gastrinoma as part of the MEN I syndrome. Neither in animals nor in man could other endocrine tumours or adenocarcinomas of the gastrointestinal tract be related to hypergastrinaemia. Epidemiologic data do not support gastrin dependence of adenocarcinoma of the stomach or the colon. Experimental findings of gastrin effects on tumour growth in vivo and in vitro have been contradictory and may be explained by the presence of gastrin receptors on tumour cells and the role of gastrin as an autocrine growth factor in some of these tumours. Since acid blockade by proton pump inhibitors or H2-receptor blockers dose-dependently increase serum gastrin levels, patients with ranitidine-resistant peptic ulceration receiving long-term treatment with high-dose omeprazole have been followed up with serial gastric biopsy specimens for up to 5 years. Complete healing, moderate hypergastrinaemia, and a slight hyperplasia but no dysplasia of the ECL cells in the oxyntic mucosa have been observed, which seemed to be correlated to chronic gastritis progressing over the years. Despite these negative findings excessive hypergastrinaemia by overdosage of potent drugs for inhibition of gastric secretion should be avoided and monitoring of plasma gastrin levels is recommended in case of long-term treatment.

Achlorhydria↗

PubMed1990

[Infectious mononucleosis: hemolysis by autoantibodies against triosephosphate isomerase].

Generalized adenopathy and splenomegaly developed in an 18-year-old youth after a severe tonsillitis followed by headache, tiredness and weight loss for several weeks. Infectious mononucleosis (acute Epstein-Barr virus infection) was confirmed by the demonstration of virus-specific antibodies. A reticulocytosis (24%), decreased haptoglobin concentration (0.6 mg/dl) and increased lactate dehydrogenase activity (657 U/l) indicated marked haemolysis. The bone marrow showed increased erythropoiesis with abnormal maturation. Antibodies against triosephosphate isomerase and against blood group marker "i" were demonstrated in the patient's serum. Antibodies against triosephosphate isomerase from the patient's serum were purified by affinity-chromatography. They strongly reacted with the patient's erythrocytes and under complement activation induced an increased 51Cr liberation from marked erythrocytes. No corresponding effect of anti-i-antibodies was noted at 37 degrees C. With the fall in antibodies against triosephosphate isomerase the haemolysis receded and the patient became free of symptoms after 7 weeks.

Adolescent↗

PubMed1990

Light and electron microscopical immunocytochemical localization of pancreastatin-like immunoreactivity in porcine tissues.

Pancreastatin is a 49 amino acid comprising peptide isolated from porcine pancreas that is derived by proteolytic processing from chromogranin A. Using an antibody against the synthetic C-terminal fragment pancreastatin (33-49), we examined the light and electron microscopical immunocytochemical localization of this peptide in porcine tissues. Pancreastatin-like immunoreactivity (PLI) was found in pancreatic somatostatin-, insulin- and glucagon cells in varying intensities; pancreatic polypeptide cells were always negative. At the electron microscopical (EM) level the immunoreactivity was confined to the electron dense core of the secretory granules in the case of somatostatin and insulin cells or to the less electron dense "halo" of the glucagon granules. In the antrum PLI positive cells represented gastrin (G), somatostatin (D) and enterochromaffin (EC) cells, in the duodenum in addition to EC- and G-cells a small number of PLI positive cells showed a positive immunoreaction for glucagon-like peptide (GLP) I and secretin in serial sections. Both norepinephrine and epinephrine containing cells of the adrenal medulla exhibited a strong reaction for PLI. In the pituitary several cell populations stained with varying intensities, including gonadotrophs and thyrotrophys. PLI is present in a distinct and characteristic subpopulation of neuroendocrine cells in various organs. The subcellular localization may indicate a function in the granular concentration, packaging and storage of peptides and amines in the brain-gut endocrine system.

Adrenal Medulla↗

PubMed1990

Investigation of the origin of the impedance cardiogram by means of exchange transfusion with stroma free haemoglobin solution in the dog.

PURPOSE OF INVESTIGATION - To determine the contribution of variations in orientation of erythrocytes (orientation effect) to the heart synchronous variations in thoracic impedance in impedance cardiography. DESIGN - The blood of four dogs was gradually replaced by stroma free haemoglobin solution, causing a decrease in resistivity and orientation effect. The decrease in orientation effect was used to determine the contribution of the orientation effect using an extended form of the "parallel conductor" model of the thorax (parallel connection of a tissue admittance Yt and a blood conductance Gb). SUBJECTS - Four adult splenectomised mongrel dogs. MEASUREMENTS and RESULTS - Packed cell volume and resistivity at body temperature of every volume of circulating fluid removed was measured. Real and imaginary parts of the transthoracic impedance and the modulus of the heart synchronous impedance variations were measured just before each exchange. The parallel conductor model was extended to account for the influence on Gb of packed cell volume and orientation of erythrocytes. Applying this extended model, the average variations in Gb at a packed cell volume of 40% were estimated to be 7.46%:3.03% due to volume variations, 4.43% due to orientation effect. After further extending the model to account for the influence of small changes in blood pressure and heart rate, the average volume variations were estimated to range from 2.8% to 3.3% and the average orientation effect from 4.1% to 4.7% at a packed cell volume of 40%. CONCLUSION - Resistivity of the blood is far from constant and the contributions of variations in blood conductivity and volume to the heart synchronous thoracic impedance are of comparable magnitude. The contribution of the volume variations is the sum of the volume variations in the contributing intrathoracic vessels. The effects of variations in orientation are added up in proportion to the relative volumes of the contributing vessels. The extensions of the parallel conductor model brought out all physiological factors determining the heart synchronous thoracic impedance variations: pulse pressures and flows, mean pressures and flows, compliances of all contributing blood vessels, packed cell volume and heart rate, as well as the relevant properties of blood: the relations between volume, flow and orientation effect and the change in orientation effect during decelerating flow.

Animals↗

PubMed1990

Efficacy and safety of omeprazole in the long-term treatment of peptic ulcer and reflux oesophagitis resistant to ranitidine.

A total of 143 patients with peptic ulceration of the duodenum, stomach and oesophagus who did not respond to 3 or more months of high-dose treatment with ranitidine, 450 mg or more daily, were treated with oral omeprazole, 40 mg daily. In 94% of the patients, ulcers healed within 2-8 weeks. After healing, 133 patients underwent long-term maintenance treatment with omeprazole, 40 mg daily, for 1-5 years (continuing). During maintenance therapy with omeprazole, no endoscopically verified relapses occurred, and no drug-related adverse effects were seen. There were no significant changes in routine laboratory tests in any patient, including 27 with concomitant liver cirrhosis. Basal serum gastrin levels, which were already elevated by the previous high-dose ranitidine treatment, rose to 4 times normal levels after 4 months of treatment with omeprazole. Thereafter, no further increases in basal serum gastrin levels were observed, even after 5 years of administration. The volume density of argyrophilic cells in the oxyntic mucosa increased during omeprazole treatment, but no dysplasia of the gastric enterochromaffin-like cells was seen. In conclusion, omeprazole was highly effective in healing ranitidine-resistant peptic ulcers, and subsequent maintenance therapy with omeprazole, 40 mg daily, was found to be effective and safe over the period observed.

Drug Resistance↗

PubMed1989

[Relapsing polychondritis].

For three months a 17-year-old boy had been suffering from laryngitis, pharyngitis and conjunctivitis, weight loss, nocturnal sweating and signs of changing cranial-nerve involvement (dizziness, nausea, nystagmus). The diagnosis of recurrent polychondritis was made only when, in addition to a definite inspiratory stridor there also developed a painful swelling of the left ear cartilage and a saddle nose due to loss of the cartilaginous portion of the nasal skeleton. Histological examination of the inflamed ear cartilage confirmed the diagnosis. After treatment with prednisone (100 mg daily, gradually reduced to 25 mg) and azathioprine (100 mg daily, increased to 150 mg after three weeks), there was clinical improvement, but the airway resistance (R = 6.2 cm H2O.s/l) rose further, requiring tracheostoma twelve months after onset of symptoms.

Adolescent↗

PubMed1989

Quantitative studies of gastric endocrine cells in patients receiving long-term treatment with omeprazole.

A total of 36 patients with chronic gastric or oesophageal peptic ulceration (including 6 with antrectomy), resistant to high-dose ranitidine treatment for at least 3 months, were successfully treated with omeprazole 20-60 mg/day, for periods up to 3 years. Fasting serum gastrin levels were monitored at regular intervals during therapy and multiple gastric mucosal biopsies were taken during gastroscopy every 3-6 months. Gastrin levels increased significantly during the first 6 months of therapy from a mean of 81.5 to 206 pg/ml; a slight decrease was observed thereafter. There was no significant increase in the volume density of argyrophilic cells in the oxyntic mucosa. No clusters of endocrine cells were found in the oxyntic mucosa and no change of G-cell volume density occurred in the antral mucosa under therapy. Omeprazole therapy did not result in any changes in gastrin levels or oxyntic argyrophilic cells in the antrectomized patients. It is concluded that the moderate hypergastrinaemia observed during long-term omeprazole treatment in man does not induce hyperplasia of argyrophilic cells in the oxyntic mucosa.

Biopsy↗

PubMed1988

Therapy with omeprazole in patients with peptic ulcerations resistant to extended high-dose ranitidine treatment.

94 patients with peptic ulcerations of duodenum, stomach, and esophagus, who did not respond to 3 or more months high-dose (450 or 600 mg) treatment with ranitidine, were treated orally with 40 mg omeprazole daily. After healing all patients were offered long-term maintenance therapy with the same dose for 5 years. In 75 patients the peptic ulcerations healed within 4 weeks, in 13 patients within 8 weeks, and in 3 patients only after an increase to 60 mg omeprazole daily. In 3 patients the ulcers did not heal. So far 83 patients have entered long-term maintenance therapy. 59 of these patients are on the drug between 1 and 4 years. During maintenance therapy with 40 mg omeprazole no relapses have occurred up to now as demonstrated by endoscopy and no drug-related adverse effects were observed. Routine laboratory tests remained without significant changes in all patients including 18 patients with concomitant liver cirrhosis. Serum gastrin levels were already elevated during the initial high-dose ranitidine treatment (106 +/- 15.4 pg/ml). 4 weeks after the start of omeprazole treatment serum gastrin levels rose to 4 times normal levels (195 +/- 28 pg/ml). Thereafter, no further increase in serum gastrin was observed even up to 4 years of continuous observation. It is therefore concluded that omeprazole is highly effective in healing ranitidine-resistant peptic ulcerations and that omeprazole maintenance therapy with 40 mg omeprazole is safe during the time observed and highly effective in the prevention of ulcer recurrence.

Adult↗

PubMed1988

Long-term omeprazole treatment in man: effects on gastric endocrine cell populations.

36 patients with chronic gastric or oesophageal peptic ulceration (including 6 with antrectomy), resistant to high-dose ranitidine treatment for at least 3 months, were successfully treated with 40-60 mg of omeprazole daily for periods between 1 and 2 years. Fasting serum gastrin levels were monitored at regular intervals during therapy and multiple gastric mucosal biopsies were taken during gastroscopy every 3-6 months. Gastrin levels increased significantly during the first 6 months of therapy from a medium level of 81.5 to 206 pg/ml, a slight decrease was seen thereafter. In 10 patients investigated before the start of the treatment and after 1 and 2 years, the volume density of argyrophilic cells in the oxyntic mucosa increased from 0.43 +/- 0.08 to 0.91 +/- 0.14% during the first year; this change was statistically significant. No further increase was observed thereafter. No such difference could be demonstrated between a larger group of 18 patients investigated before and after 1 year of treatment with omeprazole (0.806 +/- 0.1 vs. 0.93 +/- 0.08%) and between a larger group of 22 untreated patients and 17 patients treated for 17-24 months with omeprazole (0.73 +/- 0.1 vs. 0.86 +/- 0.09%). The volume density of argyrophilic cells found in 8 patients with gastrinoma amounted to 1.37 +/- 0.22%. No clusters of endocrine cells were found in omeprazole-treated patients. The D cell volume density in the antral mucosa decreased significantly during the first months of treatment, but steadily increased thereafter to reach pretreatment values after 17 months. There was no change in G cell volume density under therapy. No changes in gastrin levels or oxyntic argyrophilic cells were observed in the antrectomized patients. It is concluded that the hyperplasia of argyrophilic cells observed in some patients during long-term omeprazole treatment is mediated by hypergastrinaemia.

Female↗

PubMed1988

Pancreastatin: molecular and immunocytochemical characterization of a novel peptide in porcine and human tissues.

Pancreastatin, a novel 49-amino acid peptide isolated from porcine pancreas, shows over 70% sequence homology to the central part of bovine and human chromogranin-A. Using an N-terminal and C-terminal synthetic peptide, we developed two sensitive and specific RIAs for the detection of pancreastatin-like immunoreactivity (PLI) in porcine and human tissue extracts. PLI was present throughout the gastrointestinal tract and in most endocrine and neuronal tissues. Highest concentrations were measured in the pituitary, adrenal gland, and pancreas (1200-4000 pmol/g), similar to the distribution of chromogranin-A. PLI was also detected in human endocrine tumors, with large quantities in some carcinoids (up to 14 nmol/g). HPLC revealed that extracts from porcine pituitary and pancreas contained small pancreastatin-like peptides, whereas in adrenal medulla large chromogranin-A-like molecular forms predominated. Human endocrine tumors showed a different pattern, with intermediate forms distinct from chromogranin-A and pancreastatin. Biochemical analysis was confirmed by immunocytochemistry localizing PLI in pancreatic islets, adrenal medulla, pituitary, duodenum, and human endocrine tumors. Pancreastatin is present in a variety of gastrointestinal, endocrine, and neuronal tissues and may represent a novel peptide of unknown physiological function, derived from chromogranin-A by proteolytic cleavage.

Amino Acid Sequence↗

PubMed1987

Investigation of the parallel conductor model of impedance cardiography by means of exchange transfusion with stroma free haemoglobin solution in the dog.

To test one of the assumptions underlying the calculation of stroke volume--namely, that the transthoracic impedance consists of a parallel connection of a tissue impedance and a blood resistance--experiments were carried out on four dogs in which blood was gradually replaced by a stroma free haemoglobin solution, with the purpose of changing the blood resistance while leaving the tissue impedance unchanged. This was accomplished by exchange transfusion in such a way that the volume of the circulating fluid remained constant and the distribution of fluid volume between the fluid compartments was not altered. During the exchange transfusions the mean decrease in resistivity of the circulating fluid was 54%. The packed cell volume and resistivity of every volume of removed circulating fluid were measured. Just before each exchange the real and imaginary parts of the transthoracic impedance were measured. The packed cell volume decreased exponentially with the number of exchanges. This indicates that the circulating fluid volume remained constant during the exchange transfusion. From the packed cell volumes an estimate of the circulating fluid volume was made. Because of the parallel connection all calculations were based on the use of admittance, which is the reciprocal value of impedance. The real and imaginary parts of the transthoracic admittance were calculated from the measured values of the real and imaginary parts of the transthoracic impedance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Fixation, fine structure, and immunostaining for neuropeptides: perfusion versus immersion of the neuroendocrine hypothalamus.

The effects of various fixatives and fixation methods on ultrastructural morphology and the immunocytochemical localization of beta-endorphin were examined in rat brain. The mediobasal hypothalamus was preserved by vascular perfusion and/or immersion in nine different fixatives. We tested several combinations of paraformaldehyde, glutaraldehyde, acrolein, and picric acid in various isosmolar buffers. Vibratome sections were stained for beta-endorphin employing the peroxidase-antiperoxidase technique, or processed directly for electron microscopy. The ultrastructural quality of a given region was attributed to its location with respect to the blood-brain barrier, the method of fixation, and the concentrations of some of the fixative components. Immersion fixation gave better results and reduced extracellular space in the median eminence (outside the blood-brain barrier) and areas close to the hypothalamic surface. Positive immunostaining of beta-endorphin perikarya occurred only in tissue fixed with periodate-lysine-paraformaldehyde. Light to moderate fiber staining was also present in some paraformaldehyde-glutaraldehyde-acrolein combinations. However, a glutaraldehyde concentration of 1% or higher abolished all positive staining for beta-endorphin. These results emphasize the necessity of optimizing fixation for ultrastructure and for immunocytochemical staining of each individual antigen. The choice of the best fixation method depends not only on the intracellular location of the antigen but also on the relationship between hypothalamic tissue compartments and the blood-brain barrier.

Animals↗