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Biomedical subjects

J C van der Linden

Publications and source records attributed to J C van der Linden.

At least 19 recordsLinked to original sources
PubMed2006

Status epilepticus caused by a myxoedema coma.

The case of a 63-year-old woman who presented with status epilepticus, coma and hypoventilation is reported. A primary neurological cause was considered. Hypothermia led to further investigations and a diagnosis of severe hypothyroidism. The neurological complications of hyperthyriodism include alteration in mental status with slowness, decreased concentration and lethargy, headache, cranial nerve palsies, dysarthria, hoarseness, myopathy, neuropathy, reflex changes, ataxia, and psychotic episodes. Our patient suffered from a rare consequence of severe hypothyroidism presenting with status epilepticus and she died despite treatment. To our knowledge this is the second patient to be reported with myxoedema coma with this kind of presentation. Despite therapeutic options, there is a high mortality rate.

Atrophy↗
PubMed2005

Incidence of axillary recurrence in 113 sentinel node negative breast cancer patients: a 3-year follow-up study.

BACKGROUNDS/AIMS: This study evaluates the 3-year follow-up period and recurrence rate in patients with a negative sentinel node biopsy (SNB) without an additional axillary dissection (ALND). METHODS: Between January 2000 and March 2002, 197 patients with an invasive breast cancer and clinically negative axillary nodes underwent a sentinel node biopsy. One hundred and thirteen patients were included in our study. The follow-up consisted of clinical examination every 3 months in the first year, followed by every 6 months after the first year. A mammography was obtained annually. Attention was paid to loco-regional recurrence, including axillary recurrence, and distant metastases. RESULTS: The mean duration of follow-up was 37.5 months (range 24-54). In this period, one patient was diagnosed with an axillary recurrence and one patient developed a supraclavicular lymph node metastasis. Two patients developed a second primary breast cancer in the contralateral breast. No patients were diagnosed with distant metastasis. CONCLUSION: These 3 year follow-up results suggest that SNB is a procedure with a low clinical recurrence rate, which can replace, when strict criteria are met, ALND if the sentinel node is negative.

Adult↗
PubMed2004

Detecting and tracking local changes in the tibiae of individual rats: a novel method to analyse longitudinal in vivo micro-CT data.

In this study we present the analysis of in vivo micro-CT scans using a new method based on image registration that accurately evaluates longitudinal micro-CT studies. We tested if detailed changes in the bone architecture could be detected and tracked in individual animals. A prototype in vivo micro-CT scanner (Skyscan 1076) was developed in which tibiae of rats that are lying on a bed under gas anaesthesia were scanned. For this study, three female Wistar rats were used: a sham-operated rat, an ovariectomised (OVX) rat and one rat that served as a reproducibility control. The reproducibility control rat was scanned twice in 1 day. The other animals were scanned at week 0, just before surgery, at week 4 and at week 14 after surgery. Architectural changes over time were detected by overlaying two data sets made at different time points using an algorithm that uses mutual information for optimal registration. The scans were segmented into binary data sets using a local thresholding algorithm. The reproducibility test showed small errors of less than 3% in bone volume measurements and errors less than 0.5% in measurements of trabecular thickness. The sham-operated rat showed no changes in total bone volume, though thinning and eventual loss of some small trabeculae could be detected, which could be related to the age of the animal. The OVX rat lost much trabecular bone volume, especially in the metaphysis (60% at week 4, 75% at week 14). The remaining trabeculae slowly increased in thickness. Following the different scans in time showed the forming of new trabecular structures. Additionally, small longitudinal growth at the growth plate could be detected after the first 4 weeks. Further, the OVX rat showed extensive modelling at the proximal endosteal lateral cortex. We have shown a new method that can detect and track changes in the local bone architecture and individual trabeculae in time, in an individual living animal. This method enables longitudinal in vivo micro-CT studies and has the potential to greatly contribute to experimental rat or mouse studies on pharmacological intervention and transgenic models.

Animals↗
PubMed2004

Bisphosphonate treatment affects trabecular bone apparent modulus through micro-architecture rather than matrix properties.

Bisphosphonates are emerging as an important treatment for osteoporosis. But whether the reduced fracture risk associated with bisphosphonate treatment is due to increased bone mass, improved trabecular architecture and/or increased secondary mineralization of the calcified matrix remains unclear. We examined the effects of bisphosphonates on both the trabecular architecture and matrix properties of canine trabecular bone. Thirty-six beagles were divided into a control group and two treatment groups, one receiving risedronate and the other alendronate at 5-6 times the clinical dose for osteoporosis treatment. After one year, the dogs were killed, and samples from the first lumbar vertebrae were examined using a combination of micro-computed tomography, finite element modeling, and mechanical testing. By combining these methods, we examined the treatment effects on the calcified matrix and trabecular architecture independently. Conventional histomorphometry and microdamage data were obtained from the second and third lumbar vertebrae of the same dogs [Bone 28 (2001) 524]. Bisphosphonate treatment resulted in an increased apparent Young's modulus, decreased bone turnover, increased calcified matrix density, and increased microdamage. We could not detect any change in the effective Young's modulus of the calcified matrix in the bisphosphonate treated groups. The observed increase in apparent Young's modulus was due to increased bone mass and altered trabecular architecture rather than changes in the calcified matrix modulus. We hypothesize that the expected increase in the Young's modulus of the calcified matrix due to the increased calcified matrix density was counteracted by the accumulation of microdamage.

Alendronate↗
PubMed2004

Altered tissue properties induce changes in cancellous bone architecture in aging and diseases.

The mechanical properties of cancellous bone depend on its architecture and the tissue properties of the mineralized matrix. The architecture is continuously adapted to external loads. In this paper, it was assumed that changes in tissue properties leading to changes in tissue deformation can induce adaptation of the architecture. We asked whether changes in cancellous bone architecture with aging and in e.g. early osteoarthrosis can be explained from changes in tissue properties. This was investigated using computer models in which the cancellous architecture was adapted to external loads. Bone tissue with deformations below a certain threshold was resorbed, deformations above another threshold induced formation. Deformations between these two boundaries, in the 'lazy zone', did not induce bone adaptation. The effects of changes in bone tissue stiffness on bone mass, global stiffness and architecture were investigated. The bone gain (40-60%) resulting from a 50% decrease in tissue stiffness (simulating diseased tissue) was much larger than the bone loss (2-30%) resulting from a 50% increase in tissue stiffness (simulating highly mineralized, old tissue). The adaptation induced by a decrease in tissue stiffness resulted in an almost constant stiffness in the main load bearing direction, but the transversal stiffness decreased. An increased tissue stiffness resulted in a higher stiffness in the main direction and overcompensation in the transversal directions: the global stiffness could become even smaller than the stiffness of the original model. Concluding, we showed that changes in trabecular bone in aging and diseases can be partly explained from changes in tissue properties.

Adaptation, Physiological↗
PubMed2003

A simulation model at trabecular level to predict effects of antiresorptive treatment after menopause.

Antiresorptive drugs are widely used to prevent osteoporotic fractures in men and women. Large clinical trials have shown vertebral fracture risk reductions up to 50%, resulting from relatively small increases of 3-8% in bone mineral density (BMD). We developed a computer model that mimics bone turnover in human vertebral cancellous bone during menopause and antiresorptive treatment. This model links cell activity in trabeculae to changes in bone volume and mechanical properties. We asked whether treatment started shortly after menopause is better than treatment started late after menopause. In order to answer this question we used the model to simulate menopause and 5 years of anti-resorptive treatment with two different agents: one incorporated in the tissue, one not incorporated. We found that late treatment can result in almost the same bone mass as early treatment, but early treatment is much better in conserving the strength and stiffness of the cancellous bone. The effect of the incorporation of drugs in the tissue (giving the drugs a long half-life) was small. After discontinuation of treatment, bone was lost slower, but after 20 years the difference between the incorporated and the not incorporated drug in stiffness and bone volume was below 3%. This kind of simulation model may be used to preclinically test new pharmaceuticals and treatment protocols and to predict long-term effects of treatment before patient data become available.

Adult↗
PubMed2001

Trabecular bone's mechanical properties are affected by its non-uniform mineral distribution.

The bone remodeling process takes place at the surface of trabeculae and results in a non-uniform mineral distribution. This will affect the mechanical properties of cancellous bone, because the properties of bone tissue depend on its mineral content. We investigated how large this effect is by simulating several non-uniform mineral distributions in 3D finite element models of human trabecular bone and calculating the apparent stiffness of these models. In the 'linear model' we assumed a linear relation between mineral content and Young's modulus of the tissue. In the 'exponential model' we included an empirical exponential relation in the model. When the linear model was used the mineral distribution slightly changed the apparent stiffness, the difference varied between an 8% decrease and a 4% increase compared to the uniform model with the same BMD. The exponential model resulted in up to 20% increased apparent stiffness in the main load-bearing direction. A thin less mineralized surface layer (28 microm) and highly mineralized interstitial bone (mimicking mineralization resulting from anti-resorptive treatment) resulted in the highest stiffness. This could explain large reductions in fracture risk resulting from small increases in BMD. The non-uniform mineral distribution could also explain why bone tissue stiffness determined using nano-indentation is usually higher than finite element (FE)-determined stiffness. We conclude that the non-uniform mineral distribution in trabeculae does affect the mechanical properties of cancellous bone and that the tissue stiffness determined using FE-modeling could be improved by including detailed information about mineral distribution in trabeculae in the models.

Adult↗
PubMed2001

A decreased subchondral trabecular bone tissue elastic modulus is associated with pre-arthritic cartilage damage.

In osteoarthritis, one postulate is that changes in the mechanical properties of the subchondral bone layer result in cartilage damage. The goal of this study was to examine changes in subchondral trabecular bone properties at the calcified tissue level in the early stages of cartilage damage. Finite element models were constructed from microCT scans of trabectilar bone from the proximal tibia of donors with mild cartilage damage and from normal donors. In the donors with cartilage damage, macroscopic damage was present only in the medial compartment. The effective tissue elastic moduli were determined using a combination of finite element models and mechanical testing. The bone tissue modulus was reduced by 60% in the medial condyle of the cases with cartilage damage compared to the control specimens. Neither the presence of cartilage damage nor the anatomic site (medial vs. lateral) affected the elastic modulus at the apparent level. The volume fraction of trabecular bone was higher in the medial compartment compared to the lateral compartment of tibiae with cartilage damage (but not the controls), suggesting that mechanical properties were preserved in part at the apparent level by an increase in the bone volume fraction. It seems likely that the normal equilibrium between cartilage properties, bone tissue properties and bone volume fraction is disrupted early in the development of osteoarthritis.

Aged↗
PubMed2001

Mechanical consequences of bone loss in cancellous bone.

The skeleton is continuously being renewed in the bone remodeling process. This prevents accumulation of damage and adapts the architecture to external loads. A side effect is a gradual decrease of bone mass, strength, and stiffness with age. We investigated the effects of bone loss on the load distribution and mechanical properties of cancellous bone using three-dimensional (3D) computer models. Several bone loss scenarios were simulated. Bone matrix was removed at locations of high strain, of low strain, and random throughout the architecture. Furthermore, resorption cavities and thinning of trabeculae were simulated. Removal of 7% of the bone mass at highly strained locations had deleterious effects on the mechanical properties, while up to 50% of the bone volume could be removed at locations of low strain. Thus, if remodeling would be initiated only at highly strained locations, where repair is likely needed, cancellous bone would be continuously at risk of fracture. Thinning of trabeculae resulted in relatively small decreases in stiffness; the same bone loss caused by resorption cavities caused large decreases in stiffness and high strain peaks at the bottom of the cavities. This explains that a reduction in the number and size of resorption cavities in antiresorptive drug treatment can result in large reductions in fracture risk, with small increases in bone mass. Strains in trabeculae surrounding a cavity increased by up to 1,000 microstrains, which could lead to bone apposition. These results give insight in the mechanical effects of bone remodeling and resorption at trabecular level.

Bone Remodeling↗
PubMed2000

PCR based high risk HPV testing is superior to neural network based screening for predicting incident CIN III in women with normal cytology and borderline changes.

BACKGROUND/AIMS: To improve the accuracy of conventional cytology in cervical cancer screening, high risk human papillomavirus (HPV) testing and neural network based screening have been developed. This study assessed the power of both techniques to detect women at risk of developing incident CIN III; that is, CIN III detected during the follow up of women with normal cytology and borderline nuclear changes. METHODS: A cohort of 2250 women, 34-54 years of age, who attended population based cervical cancer screening from 1988 to 1991 and had normal smears or borderline nuclear changes was followed. All smears were tested for high risk HPV and the smears were rescreened using neural network based screening. The value of neural network based screening for predicting incident CIN III during a mean follow up period of 6.4 years was compared with that of high risk HPV testing. In addition, morphological markers presumed to be related to HPV were correlated with HPV status. RESULTS: Thirteen (0.6%) women had incident CIN III. Both high risk HPV positivity and abnormal cytology were associated with an increased risk for incident CIN III (odds ratio, 240 and 22, respectively) and high risk HPV positivity was associated with abnormal cytology. The sensitivity of high risk HPV testing for predicting incident CIN III was much higher than that of neural network based screening (92% and 46%, respectively). None of the morphological markers assessed, including koilocytosis, was correlated with high risk HPV status. CONCLUSION: High risk HPV testing is superior to neural network based screening in identifying women at risk of developing CIN III. For women with normal cytology and borderline changes and a negative high risk HPV test, the screening interval can be considerably prolonged.

Adult↗
PubMed1999

[Condylomata acuminata: a rare symptom of ubiquitous human papilloma virus and not a sign of risky sex behavior].

In general, condylomata acuminata can be diagnosed and treated by the general practitioner. Condylomata are caused by certain types of human papillomavirus (HPV). According to their carcinogenicity HPVs are classified as high risk and low risk HPV. The benign condylomata are an infrequent sign of an infection with low risk HPV, while cervical cancer is a rare and late complication of an infection with high risk HPV. Because high and low risk HPV are different viruses, the risk of cervical cancer is not increased by condylomata. Anogenital HPVs are predominantly transmitted sexually. It is useful to discriminate between sexually transmitted diseases (STDs) that are ubiquitous, like infections with HPV or herpes simplex virus (HSV), and rare STDs like syphilis, gonorrhoea and HIV infection: infections with HPV and HSV are also common with unriskful sexual behaviour, while syphilis, gonorrhoea and HIV infection are almost exclusively associated with riskful sexual behaviour. It has been shown that double infections with HPV and Chlamydia trachomatis are not more frequent than may be expected by chance. The literature indicates that the presence of condylomata acuminata by itself is no reason to screen patients for other STDs.

Condylomata Acuminata↗
PubMed1999

Sonographically guided aspiration cytology of neck nodes for selection of treatment and follow-up in patients with N0 head and neck cancer.

BACKGROUND AND PURPOSE: The management of the clinically negative neck (NO) remains controversial because the incidence of occult metastases is high and the prognostic difference between elective treatment and a "wait and see" approach remains unclear. This study was undertaken to assess the role of sonographically guided aspiration cytology for the selection of the initial-management strategy for the neck and for the early detection of neck metastases during follow-up of patients with NO. METHODS: Seventy-seven clinically and cytologically confirmed NO patients, who underwent a transoral tumor excision and no neck treatment, were followed up for 1 to 4 years by both palpation and sonographically guided aspiration cytology. RESULTS: Fourteen patients (18%) had recurrent neck tumor; 10 (71%) of these necks were salvaged. Of the 14 neck failures, six were detected before being palpable and nine were detected within 7 months. Eleven of the 19 aspirated tumor-positive nodes had a minimal diameter smaller than 1 cm, and all four patients who eventually died had lymph node metastases larger than 14 mm. CONCLUSION: With sonographically guided aspiration cytology, the risk of missing occult metastases was 18%, which is less than expected after palpation only. Sonographically guided aspiration cytology is an effective technique for following up on the status of the neck after transoral tumor excision, and should be used at frequent intervals if no elective neck treatment is performed.

Adult↗
PubMed1998

[A painful inflammation of the thyroid].

Four women aged 30, 29, 52 and 43 years presented with what appeared to be subacute thyroiditis (De Quervain's thyroiditis). This disease is characterized by fatigue, a painful thyroid gland and thyrotoxic manifestations. The diagnosis is further based on a high erythrocyte sedimentation rate and low tracer uptake during thyroid scintigraphy. Only the first patient showed a typical course. In the second and third ones the painful thyroid was associated with nodular enlargement. Fine needle aspiration cytology was at first consistent with subacute thyroiditis but a repeated aspiration showed papillary carcinoma in the second and anaplastic carcinoma in the third patient. In the fourth one, subacute thyroiditis was accompanied by normochromic anaemia, a low serum albumin concentration and liver function disorders. She made a full recovery without treatment. Thyroid malignancies can mimic subacute thyroiditis. Persistent nodular enlargement of the thyroid is suspicious and requires careful investigation.

Adult↗
PubMed1997

Ontogeny of milky spots in the human greater omentum: an immunochemical study.

BACKGROUND: Milky spots in the human greater omentum are preformed specific accumulations of primarily macrophages within the stroma of the greater omentum. To obtain a better understanding of milky spots in the human greater omentum, the development and the earliest forms of milky spots in the human greater omentum were studied, with special attention to the macrophage population. METHODS: Specimens of human greater omentum were obtained from fetuses of 20 to 40 weeks gestation and one newborn three days old (n = 6). Using mature macrophages (RFD 7), activated macrophages (RFD 1), B-lymphocytes (CD 22), and T-lymphocytes (CD 2), and immunoperoxydase labeling, the percentage of these cells in developing milky spots and the development of milky spots were studied by light microscopy. A time-dependent increase in the percentage of positive staining cells and the size of clusters was analyzed using the non-parametric Spearman rank correlation test. RESULTS: Small accumulations of cells with about 50% monocytes/macrophages were present at 20 weeks of gestation. With increasing gestational age the number of clusters of cells increased significantly (P < 0.01) as well as their size (P < 0.01). Starting at 29 weeks, vascularized clusters of cells were seen; true milky spots were present at 35 weeks. A significant (P < 0.05) increase in the percentage of mature macrophages was found in developing milky spots, whereas no activated macrophages were seen. The percentage of B-lymphocytes and T-lymphocytes found in the clusters of cells and milky spots increased significantly (P < 0.05) but did not exceed 10% of the total number of cells. CONCLUSIONS: From our data it can be concluded that milky spots are specific structures in the greater omentum formed between the 20th and 35th week of gestation. Further, we concluded that immature cells (promonocytes) mature locally in developing milky spots.

Cell Aggregation↗
PubMed1996

PCR-based high-risk HPV test in cervical cancer screening gives objective risk assessment of women with cytomorphologically normal cervical smears.

Cervical-cancer screening programmes using cytomorphological criteria could be more efficient if the screening included objective individual risk factors for women with normal cytology, such as a test for high-risk human papillomavirus (HPV). The value of a PCR-based test for high-risk HPV types was studied in a cohort of 1622 women presenting in a routine triannual population-based screening programme. Women were included in the study when they had no previous history of cervical dysplasia; and their initial Pap smear was read as normal (Pap 1 or 2). The mean age of the women was 42 years (range 34-54 years) and mean follow-up time was 40 months (range 5-73 months). Women were referred for colposcopically directed biopsies if they had had 2 successive cervical smears read as Pap 3a (mild to moderate dyskaryosis) or one read as > or = Pap 3b (severe dyskaryosis). Women with histologically confirmed cervical intraepithelial neoplasia grade III (CIN III) were considered positive cases. All women were tested for 14 high-risk HPV genotypes. Of the 86 high-risk HPV-positive women, 6 developed CIN III, whereas only 1 of the 1536 HPV-negative women did. The women with normal Pap smears containing high-risk HPV genotypes were 116 times (95% CI, 13-990) more at risk of developing CIN III, in contrast to women without high-risk HPV. These results support the view that the interval between successive smears in cervical-cancer screening can be increased considerably for women with cytomorphologically normal and high-risk HPV-negative cervical smears as determined by PCR.

Adult↗
PubMed1996

Microsatellite instability in childhood rhabdomyosarcoma is locus specific and correlates with fractional allelic loss.

Replication errors (RERs) were initially identified in hereditary nonpolyposis colon cancer and other tumors of Lynch syndrome II. Mutations in genes involved in mismatch repair give rise to a mutator phenotype, resulting in RERs. The mutator phenotype is thought to predispose to malignant transformation. Here we show that in the embryonal form of childhood rhabdomyosarcoma, RERs also occur, but in contrast to hereditary nonpolyposis colon cancer, only a subset of the microsatellite loci analyzed show RERs. The occurrence of RERs is strongly correlated with increased fractional allelic loss (P < 0.001), suggesting that the occurrence of RERs is a secondary phenomenon in rhabdomyosarcoma. Coincidental loss of genes involved in mismatch repair, possibly due to their proximity to tumor suppressor genes involved in tumor progression of embryonal form of childhood rhabdomyosarcoma, could explain the observed phenomenon.

Alleles↗