24-h evaporative and sensible heat losses in relation to ambient humidity at 24 degrees C in clothed human subjects

The effect of ambient humidity on the energy expenditure of clothed subjects was investigated. Fifty-six healthy men and women, weighing about 65 kg, spent 24 h in a large human calorimeter at 24 degrees C and performed either of two fixed activity programmes. The ambient humidity varied between experiments from 3 to 11 g m-3. The sensible heat output did not vary significantly with humidity but the evaporative heat loss decreased by about 1.5 W for each g m-3 increase in humidity.     

Multiplicity in polyp count and extracolonic manifestations in 40 Dutch patients with MYH associated polyposis coli (MAP)

Objective: To investigate the contribution of MYH associated polyposis coli (MAP) among polyposis families in the Netherlands, and the prevalence of colonic and extracolonic manifestations in MAP patients. Methods: 170 patients with polyposis coli, who previously tested negative for APC mutations, were screened by denaturing gradient gel electrophoresis and direct sequencing to identify MYH germline mutations. Results: Homozygous and compound heterozygous MYH mutations were identified in 40 patients (24%). No difference was found in the percentage of biallelic mutation carriers between patients with 10–99 polyps or 100–1000 polyps (29% in both groups). Colorectal cancer was found in 26 of the 40 patients with MAP (65%) within the age range 21 to 67 years (median 45). Complete endoscopic reports were available for 16 MAP patients and revealed five cases with gastro-duodenal polyps (31%), one of whom also presented with a duodenal carcinoma. Breast cancer occurred in 18% of female MAP patients, significantly more than expected from national statistics (standardised morbidity ratio = 3.75). Conclusions: Polyp numbers in MAP patients were equally associated with the attenuated and classical polyposis coli phenotypes. Two thirds of the MAP patients had colorectal cancer, 95% of whom were older than 35 years, and one third of a subset of patients had upper gastrointestinal lesions. Endoscopic screening of the whole intestine should be carried out every two years for all MAP patients, starting from age 25–30 years. The frequent occurrence of additional extraintestinal manifestations, such as breast cancer among female MAP patients, should be thoroughly investigated.     

Mosaicism of the CAG repeat sequence in the Huntington disease gene in a pair of monozygotic twins

We report on a pair of monozygotic twins belonging to a family segregating Huntington disease (HD). In routine DNA analysis of blood cells, they displayed three alleles of the CAG repeat sequence in the HD gene. Two different cell lines, carrying the normal allele together with either an expanded allele with 47 CAGs or an intermediate allele with 37 CAGs, were detected in blood and buccal epithelium from both twins. To our knowledge, this is the first case described of HD gene CAG repeat length mosaicism in blood cells. Haplotype analysis established that the 37 CAG allele most likely arose by contraction of the maternal 47 CAG allele. The contraction must have taken place postzygotically, possibly at a very early stage of development, and probably before separation of the twins. One of the twins has presented symptoms of HD for 4 years; his skin fibroblasts and hair roots carried only the cell line with the 47 CAG repeat allele. The other twin, who is without symptoms at present, displayed mosaicism in skin fibroblasts and hair roots. If the proportion of the two cell lines in the brain of each twin resembles that of their hair roots (another tissue originating from the ectoderm), the mosaicism in the unaffected twin would mean that only a part of his brain cells carried the expanded allele, which could explain why he, in contrast to his brother, has no symptoms at this time.     

Effect of age on behavioral and enzymatic changes during thiamin deficiency

Open field behavior and whole brain enzymatic activities were determined during thiamin deficiency in two strains of young, as well as in aged mice. In young CD-1 mice, thiamin deficiency reduced total distance traveled and vertical movements after 7 days and the decline was more than 50% by day 9. The behavioral deficit was highly correlated to decreases in 2-oxoglutarate dehydrogenase activity (KGDH). The open field behavior of Balb/c mice was about 40% less than in CD-1 mice and responded in a qualitatively different manner to thiamin deficiency. The activity of the Balb/c mice increased and then decreased with thiamin deficiency. The activity of 3 month old mice peaked on day 6 (126% of initial score), whereas 10 and 30 month mice showed a much greater increase (about 175% of initial scores), but on day 7. Although the activity of the thiamin dependent enzyme transketolase (TK) was affected similarly at all ages, the activity of KGDH in the aged brain was more sensitive to thiamin deficiency than in the young; KGDH activity declined 41%, 57% or 74% at 3, 10, or 30 months, respectively. Thus, the current mouse model is an attractive one to study the interaction of thiamin deficiency with aging.     

Methodological implications of the post activation depression of the soleus H-reflex in man

Summary A long lasting inhibition (> 8 s) of the soleus Hoffmann reflex (H-reflex) was evoked by a preceding soleus H-reflex, by a brief voluntary ankle flexor or extensor muscle contraction or by a tap applied to the Achilles tendon. The time course of this long lasting inhibition was similar in all these cases, suggesting that the same spinal mechanism is involved. Furthermore, it was shown that the post-activation depression may interfere with the determination of inhibitory or facilitatory effects on the H-reflex. It is stressed that when the onset of inhibitory or facilitatory effects on the soleus H-reflex is to be determined in relation to start of an ankle movement, either very long stimulus intervals (> 8 s) must be used, or the onset must be determined in relation to a reference value of the soleus H-reflex, which may be influenced by the long lasting inhibitory effect, but not yet by the succeeding muscle contraction.     

H-reflexes are less depressed following muscle stretch in spastic spinal cord injured patients than in healthy subjects

The size of the soleus H-reflex was measured after a slow (17 deg/s) passive stretch of ankle plantarflex ors and compared to its control size without muscle stretch in ten neurologically healthy subjects and in six spastic spinal-cord-injured patients. Two seconds after the end of the stretch, the size of the H-reflex was reduced to about 30% of its pre-stretch size in the healthy sub jects. The depression remained for 10–15 s. In the spastic, spinal-cord-injured patients, stretch caused significantly less reduction in the size of the H-reflex. The H-reflex also regained its pre-stretch size much faster than in healthy subjects. We suggest that the smaller depression of the H-reflex observed in spastic patients may be involved in the pathophysiology of spasticity.     

Maxi K+ channels co-localised with CFTR in the apical membrane of an exocrine gland acinus: possible involvement in secretion

The primary secretion formed in various exocrine glands has a [K+] 2-5 times that of plasma. In this study we measured the transepithelial flux of 36Cl-, 22Na+ and 42K+ across the frog skin and applied the single-channel patch-clamp technique to the apical membrane of frog skin gland acini to investigate the pathway taken by K+ secreted by the glands. Transepithelial K+ secretion was active and was driven by a larger force than the secretion of Na+. When driving Na+ through the epithelium by clamping the transepithelial potential to 100 mV (apical solution reference), blockers of cellular secretion (apical 5-nitro-2-(3-phenylpropylamino)benzoate or basolateral quinine or furosemide) decreased K+ secretion but left Na+ secretion unaffected. We conclude that K+ follows a transcellular pathway across the epithelium. Patch-clamp analysis of the apical membrane of microdissected gland acini revealed a population of voltage- and calcium-activated K+ channels of the maxi K+ type. In cell-attached patches these channels were activated by membrane potential depolarisation or exposure to prostaglandin E2 and had a permeability of 3.6 +/- 0.3 x 10(-13) cm3 s-1, giving a calculated conductance of 170 pS with 125 mM K+ on both sides of the membrane. In inside-out patches the channels were activated by increasing intracellular [Ca2+] from 10(-7) to 10(-6) M and were blocked by Ba2+ added to the cytoplasmic side. Exposure of inside-out patches containing the maxi K+ channel to ATP on the inside activated cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channels, confirming that both channels are co-localised to the apical membrane. We interpret these findings in terms of a model where transepithelial NaCl secretion can be supported in part by an apical K+ conductance.