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Biomedical subjects

V Vitek

Publications and source records attributed to V Vitek.

At least 19 recordsLinked to original sources
PubMed2000

Analytic environment-dependent tight-binding bond integrals: application to MoSi2.

We present the first derivation of explicit analytic expressions for the environmental dependence of the sigma, pi, and delta bond integrals within the orthogonal two-center tight-binding approximation by using the recently developed bond-order potential theory to invert the nonorthogonality matrix. We illustrate the power of this new formalism by showing that it not only captures the transferability of the bond integrals between elemental bcc Mo and Si and binary C11(b) MoSi2 but also predicts the absence of any discontinuity between first and second nearest neighbors for the ddsigma bond integral even though large discontinuities exist for ppsigma, pppi, and ddpi.

Journal Article↗
PubMed1987

Thyroid hormone alterations in patients with shock and injury.

Serum concentrations of total T3 and T4, free T4, rT3, TSH, TBG and cortisol were measured on arrival in hospital in 33 adult injured patients, 26 of whom were received directly from the accident. Serum cortisol levels and all thyroid indices, except TBG, were altered substantially by injury. Compared with values from 57 healthy volunteers, statistically significant (P less than 0.01) decreases were found in the mean serum free and total T4 concentrations and the rT3 level. Similarly significant (P less than 0.001) increases were seen in the mean serum T3, TSH and cortisol concentrations. Repeated assessment of thyroid function in six patients suggested a biphasic response to injury by TSH, T3 and rT3. The first phase was of short duration (1-2 h). Serum levels of TSH and T3 were above normal, and rT3 was decreased. These data suggest participation by the thyroid in the 'fight-or-flight' response to life-threatening stress. The second phase was fully established 6-18 h after injury and was characterized by reductions in serum TSH, T3 and total and free T4 and a rise in rT3. This pattern persisted throughout the 2-week period of measurement. Thus, as in other critical illnesses, the 'low T3' syndrome is common in severely injured patients. However, changes in thyroid hormone metabolism after injury are of greater intensity and longer duration.

Adult↗
PubMed1984

Relationship of thyroid hormone patterns to survival in canine hemorrhagic shock.

6 of 13 dogs subjected to 1 h of hemorrhagic shock (BP = 45-50 mm Hg) died during the first convalescent day. Nonsurvivors had lower baseline plasma concentrations of total and free T4 and T3, as well as rT3, and higher T3 uptake values. During shock, dogs that died had significantly lower plasma levels of total and free T4 and T3 and higher T3 uptake. In general, intergroup differences were accentuated during resuscitation. After volume replenishment, indices of thyroid function had stabilized or improved in survivors, but were still deteriorating in dogs that ultimately died. There were no consistent hemodynamic differences between the two groups. Thus, parameters of thyroid metabolism appear to be good prognostic indicators in canine hemorrhagic shock.

Animals↗
PubMed1983

Thyroid hormone responses in hemorrhagic shock: study in dogs and preliminary findings in humans.

One hour of hemorrhagic shock in the dog produces alterations in thyroid hormone metabolism far exceeding those seen after elective surgery or thermal injury. The changes in plasma thyroid hormone levels cannot be fully explained by carrier protein loss. Plasma concentrations of total thyroxine (T4) and triiodothyronine (T3) were significantly decreased after only 20 minutes of shock, continued to decrease throughout shock and resuscitation, and remained depressed for several days thereafter. Both hormones reached nadirs during volume replacement of 42% and 17% of baseline, respectively. The total T4 level normalized by the fifth postshock day, but the T3 concentration was still depressed on the ninth day. Plasma albumin, the principal canine thyroid hormone carrier, was significantly reduced 20 minutes after hemorrhage and remained low throughout convalescence. Concentrations of free T4 and T3 decreased during shock, but not as much as the total T4 and T3 concentrations. Reverse T3 levels, corrected for albumin loss, and T3 uptake values were increased during shock and resuscitation. Similar alterations in circulating thyroid hormone concentrations were seen in three patients with major traumatic injury and/or shock. The thyroid hormone changes in shock may represent another example of the "euthyroid sick syndrome."

Adult↗
PubMed1982

Aggravating effect of alcohol on admission serum insulin patterns of patients with trauma and in a state of shock.

The effect of alcohol upon admission serum insulin levels was studied in 114 injured patients with mean blood alcohol levels of 130 +/- 71 milligrams per deciliter, ranging from 10 to 350. These data were compared with those of 133 similar patients with no measurable blood alcohol levels and with those of 47 healthy volunteers. Whereas marked hyperglycemia caused by trauma or shock was unaffected by alcohol ingestion, insulin levels were more depressed in patients with blood alcohol levels 29.5 +/- 15.3 microunits per milliliter versus 37.8 +/- 36.7 microunits per milliliter, p less than 0.025. In fatally injured patients with measurable alcohol concentrations, insulin and glucose levels were markedly different from those for the corresponding surviving patients, p less than 0.001 and less than 0.01, respectively, with particularly large differences in the insulin-glucose ratio, p less than 0.001. The spontaneous reappearance of the insulin response to hyperglycemia was dependent upon the elapsed time and the severity of injury. Regardless of the blood alcohol concentrations, in patients admitted within two hours, there was no correlation between the levels of insulin and glucose. In patients admitted within two to eight hours, a significant correlation was found only in those with no detectable alcohol blood levels, p less than 0.001. In addition, a remarkable similarity of mean different admission times. These findings suggest that, in alcohol intoxication, recovery of insulin secretions suppressed by acute trauma is delayed; metabolism of alcohol in acute trauma is probably reduced.

Accidents, Traffic↗
PubMed1979

The unexpected increase of serum insulin levels in patients soon after trauma.

Serum insulin values elevated above the normal fasting range, i.e., 19.0-43.4 microU/ml (mean 27.9 +/- 6.4) were found on admission in 18.2% of patients with various forms of acute injury. Concomitant mean serum glucose level was 184 +/- 59 mg/100 ml compared with 81 +/- 6 mg/100 ml found in overnight fasting normal subjects. In this group of patients, the mean and the highest insulin elevations above the control mean value were 170% (85 microU/ml) and 940% (290 microU/ml) respectively. In individuals admitted directly from the scene of an accident, the mean insulin increase was significantly smaller (95%; p less than 0.01) than in patients transferred from other hospitals-203% (68 microU/ml ) in contrast to 940% (290 microU/ml) found in the transfer subgroup. Mean serum glucose concentrations in both subgroups differed similarly (p less than 0.02). The magnitude of the insulin increase did not correlate with severity or type of injury but showed a strong dependence on the time elapsed following trauma. Strong hyperinsulinemia appears to be less detrimental to survival than severe hypoinsulinemia manifested with a very low insulin-to-glucose ratio. Since both forms of insulinemia may occur under similar clinical conditions, early routine determinations of serum insulin levels are recommended in order to introduce effective therapeutic measures.

Adolescent↗
PubMed1978

Obesity and thyroid function. 3. Relationship between some indicators of thyroid function and the energy metabolism of striated muscle in obese women.

1. In a group of 23 obese women the relations between some indicators of thyroid function (thyroxine-binding globuline--T4BG, triiodothyronine-binding globuline--T3BG, Achilles tendon reflex--ART) on the one hand and activities of enzymes of the energy metabolism (hexokinase--HK, triose phosphate dehydrogenase--TPDH, lactate dehydrogenase--LDH, glycerol-3-phosphate dehydrogenase--GPDH, citrate synthease--CS, malate dehydrogenase--MDH, hydroxyacyl--COA dehydrogenase) in the quadriceps femoris muscle on the other hand were investigated. 2. Correlations were found between T4BG and TPDH, LDH and GPDH activities, between T3BG and TPDH and GPDH activities and between the value of the Achilles tendon reflex and TPDH activity. Functionally these enzymes activities are associated with glycolysis and hydrogen transport from cytoplasmatic NADH2. No correlations were found between enzymes of the aerobic metabolism incl. enzymes of fatty acid oxidation and indicators of thyroid function. 3. The results indicate a relationship between thyroid function and enzymes involved in glycolysis and hydrogen transport from cytoplasmatic NADH2. They do not suggest, however, the unequivocal conclusion that in obese women with reduced thyroid function there is a generally reduced energy supplying metabolism in skeletal muscle.

Achilles Tendon↗
PubMed1977

Urinary cyclic AMP and post-traumatic acute renal failure.

Consecutive daily urinary excretion of cyclic AMP has been investigated in 16 patients with severe trauma or illness, five of whom developed acute renal failure (ARF). Fluctuations in the nucleotide excretion exceeded the range found in 20 healthy volunteers (1.26-14.74, mean 7.13+/-1.18 vs. 2.04-10.10, mean 5.07+/-2.21 micronmol/24 h). This resulted in a 41% increase of cAMP excretion in the group with normal renal function (P less than 0.003) with the highest individual increase of 87%. The excretion usually reached its peak by 24 h after trauma and its lowest value by the third day, (first day vs. third day; 7.82+/-4.23 vs. 3.96+/-2.58 micronmol/24 h, P less than 0.05 for a group of 11 patients), while creatinine clearance remained normal. In four patients with severe ARF, the mean urine volume was above control value but the cAMP excretion was reduced to 3.9 to 14.4% and in one patient with a mild ARF to 60.6%. Creatinine excretion of the group was less reduced than that of cAMP (41.2% vs. 19.6%, resp.). cAMP excretion declined proportionally with diminishing creatinine clearance. In the category of 33-65 ml/min it decreased by 33.4% to 3.39 micronmol+/-1.16 micronmol/24 h. cAMP/creatinine ratio proved to be a less sensitive indicator than cAMP/24 h. Daily output of cAMP and creatinine correlated highly with diuresis in ARF patients, controls (always P less than 0.001) and less in patients with normal renal function (P less than 0.02). Urinary cAMP appears to be a very sensitive and early indicator of the onset of ARF and subsequent recovery. This warrants its further study.

Acute Kidney Injury↗